PILE LOAD CAPACITY USING STATIC AND DYNAMIC LOAD TEST ANUP KUMAR HALDER

Transcription

1 PILE LOAD CAPACITY USING STATIC AND DYNAMIC LOAD TEST By ANUP KUMAR HALDER A thesis submitted to the Department of Civil Engineering, Bangladesh University of Engineering and Technology, Dhaka, in partial fulfillment of the degree of MASTER OF SCIENCE IN CIVIL ENGINEERING (Geotechnical) BANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY APRIL, 2016

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3 CADIDIDATE'S DECLARATION It is hereby declared lpl this thesis or any part of it has not been sub,mitted elsewhere for the award ofany degree or diploma. 2,.nA* es+r. (Anup Kumar Halder) 111

4 ACKNOWLEDGEMENTS The author is obliged to his supervisor Dr. Mehedi Ahmed Ansary, Professor, Department of Civil Engineering, Bangladesh University of Engineering and Technology (BUET), for his inspiration, encouragement, continuous guidance, important suggestions throughout the various stages of this research. The author also expresses his profound gratitude to Dr. Abdul Muqtadir, Professor and Head, Department of Civil Engineering, BUET, Dhaka, for his valuable corrections and suggestions during writing of this thesis. The author gratefully acknowledges the constructive criticisms and valuable suggestions made by Dr. Abu Siddique, Professor, Department of Civil Engineering, BUET. Thanks are due to Dr. Md. Abu Taiyab, Professor, Civil Engineering Department, DUET, Gazipur for his review and comments. Special thanks are also due to Icon Engineers Services and Prosoil for providing data and technical assistance towards this thesis. Last but not the least the author gratefully acknowledges the patience and encouragement of his parents, spouse and daughter for supporting his endeavor of M. Sc. Engineering study in BUET. iv

5 ABSTRACT Piles are common for construction of deep foundation in Bangladesh. Confirming the pile capacity is a job for a geotechnical engineer. From the soil investigation data, piles can be designed but it need to be confirmed by static pile load test or dynamic pile load test. Generally, static pile load test is used to estimate pile capacity whereas dynamic pile load test is a relatively new method for the engineers of Bangladesh. This study presents an evaluation of ultimate pile load capacity by static and dynamic load test methods. To establish a comparison, a field experiment was conducted on two full scale driven precast piles. Both piles were tested using dynamic and static load test. For dynamic load test pile capacity was determined using CAPWAP (CAse Pile Wave Analysis Program). In case of static load test pile capacity was calculated using Davission, Butler and Hoy, British standard and BNBC (Bangladesh National Building Code) 1993 methods. The capacity of two test piles was also calculated using soil investigation data applying BNBC-2015 (Draft version), AASHTO method. For these two driven piles capacity calculations were also investigated following driving equations. The relationship among capacity of static load test, dynamic load test, predicted capacities (using BNBC-2015, BNBC SPT, AASHTO-2002, driving equations) were compared and correlation values were obtained. To generalize the study, ten cast-in-situ and fifteen precast test pile data were collected. In each case, soil investigation report of the particular site, pile properties, CAPWAP capacity was available for detailed study. From the collected data, it was found that predicted capacity of precast driven piles using BNBC-2015 static bearing capacity has a very good co-relation with CAPWAP capacity confirmed by dynamic load test. For BNBC-15 Static method, CAPWAP capacity=1.10x BNBC 2015 Static capacity (r 2 =0.81).However, pile capacity calculated using BNBC-2015 SPT method also showed good correlation compare with the CAPWAP capacity. In this method CAPWAP capacity=1.06x BNBC 2015 SPT capacity (r 2 =0.77). Similarly, cast-in-situ pile capacity matched fairly well with all the considered methods like: BNBC-2015 static bearing capacity, BNBC-2015 SPT, AASHTO-2002 comparing with the CAPWAP capacity. From this study three relations were established. They are CAPWAP capacity=1.15x BNBC 2015 Static capacity (r 2 =0.81), CAPWAP capacity=1.04x BNBC 2015 SPT capacity (r 2 =0.89) and CAPWAP capacity=0.91x AASHTO-2002 capacity (r 2 =0.92). Recommendation and conclusions were also made for piles of Bangladesh considering different alternative methods. v

6 TABLE OF CONTENTS Candidate's Declaration Acknowledgements Abstract Table of Contents List of Tables List of Figures Notations iii iv v vi ix x xii CHAPTER 1: INTRODUCTION General Background of the Study Objectives of the Study Organization of the Thesis 3 CHAPTER 2: LITERATURE REVIEW Introduction Ultimate Pile Capacity Driven Pile Capacity Using Static Formulae Cohesive soil Cohesion-less soil Driven Pile Capacity Using SPT Cohesive soil Cohesion-less soil Bored Pile Capacity Using Static Formulae Cohesive soil Cohesion-less soil Bored Pile Capacity Using SPT Values Cohesive soil 11 vi

7 2.6.2 Cohesion-less soil Bored Pile Capacity Based on AASHTO Pile Capacity During Driving Engineering News formula Gates formula Janbu formula Pile Capacity by Static Load Test Load test evaluation methods for axial compressive load Dynamic Analysis by Wave Equation The wave equation Smith s idealization Pile modes-internal spring Soil model external springs Basic equation Values of soil parameters Dynamic Load Test Test method Methods Of Interpretation For Dynamic Load Test CASE method CAPWAP method Summary 31 CHAPTER 3: INSTRUMENTATION AND TEST PROGRAM General 3.2 Capacity Estimation 3.3 Pile Load Tests 3.4 Pile Driving and Driving Record 3.5 Dynamic Load Test Arrangement 3.6 Static Load Test Arrangement vii

8 3.6.1 Loading sequnce Data Collection Summary 46 CHAPTER 4: RESULTS AND DISCUSSIONS General Pile Capacity of Precast Piles Using Driving Equations Pile Capacity Using PDA Test Results CAPWAP Analysis Pile Capacity From Pile Load Tes Pile Capacity Summary Comparison with Collected Data for Cast-In-Situ Piles Summary 59 CHAPTER 5: CONCLUSIONS General Concluding Remarks Recommendations 62 References 63 APPENDIX A: PILE DRIVING RECORDS OF TP-1 AND TP-2 67 APPENDIX B: CAPACITY CALCULATION USING DRIVING EQUATIONS 72 APPENDIX C: CAPACITY CALCULATION OF PRECAST PILES 76 APPENDIX D: CAPACITY CALCULATION OF BORED PILES 107 viii

9 LIST OF TABLES Table 2.1 Typical ϕs/ϕ and K/Ko values for the design of drilled Shaft 11 Table 2.2 Table 2.3 Recommended values of α and fsi for estimation of drilled shaft side resistance in cohesive soil, after Reese and O Neill (1988) Recommended values of unit end bearing for cohesion-less soil (Reese and O Neill, 1988) Table 2.4 Empirical values of Q,J and percent side adhesion 27 Table 2.5 Range of CASE damping values for different types of soil 30 Table 3.1 Load testing program for test piles 36 Table 3.2 Static load test program 40 Table 3.3 Typical loading sequence arrangement for pile load test 43 Table 3.4 Data summary for precast pile 45 Table 3.5 Data summary for cast-in-situ pile 46 Table 4.1 Beta value for pile integrity (Rausche and Goble, 1979) 48 Table 4.2 Capacity of piles using PDA 49 Table 4.3 Summary of dynamic test 52 Table 4.4 Test result summary 54 Table 4.5 Pile capacities from driving formulas 55 ix

10 LIST OF FIGURES Figure 2.1 Figure 2.2 Figure 2.3 Bearing capacity factor Nq for deep foundation (After Tomlinson, 1986) Adhesion factor α for drilled shaft (after Kulhawy and Jackson, 1989) Identification of Portions of drilled shafts neglected for estimation of drilled shaft side resistance in cohesive soil, after Reese and O neill (1988) Figure 2.4 Smith s spring model (Smith, 1960) 22 Figure 2.5 Load deformation relationships for internal springs 23 Figure 2.6 Load-deformation relationship of soil (after Lowery et al, 1969) 24 Figure 3.1 Flow diagram of the working process 33 Figure 3.2 Borehole log BH-1 34 Figure 3.3 Borehole log BH-2 35 Figure 3.4 Casting of pile at site for construction 36 Figure 3.5 Pile driving using drop hammer 37 Figure 3.6 Strain transducers and accelerometer bolted on the concrete piles 39 Figure 3.7 Pile driving analyser 39 Figure 3.8 Dynamic test arrangement for TP-1 40 Figure 3.9 Dynamic test arrangement for TP-2 40 Figure 3.10 Figure 3.11 Schematic diagram of typical arrangement of applying load in an axial compressive test Schematic diagram of data collection for precast and cast in situ piles Figure 4.1 Force and velocity record for TP-1 49 Figure 4.2 Force and velocity record for TP-2 50 Figure 4.3 CAPWAP Iteration force matched graph for TP-1 51 Figure 4.4 CAPWAP Iteration force matched graph for TP-2 51 Figure 4.5 Load settlement graph for Pile load test TP-1 52 x

11 Figure 4.6 Load settlement graph for pile load test TP-1 53 Figure 4.7 Load settlement graph for pile load test TP-2 54 Figure 4.8 Figure 4.9 Figure 4.10 Figure 4.11 Figure 4.12 Correlation between CAPWAP and BNBC 2015 (static bearing) pile capacity for precast pile Correlation between CAPWAP and BNBC 2015 (SPT) and pile capacity for precast pile Correlation between CAPWAP and BNBC-2015 (static bearing) capacity Correlation between CAPWAP capacity and BNBC-2015 SPT capacity for cast-in-situ pile Correlation between CAPWAP and AASHTO-2002 pile capacity for cast-in-situ piles xi

12 NOTATIONS A = Cross sectional area of pile A = End bearing area of pile A = Skin friction area (perimeter area) of pile B,D = Diameter or width of pile D = Diameter of pile at base D = Critical depth of soil layer E = Modulus of elasticity of pile material E = Modulus of elasticity of soil FS = Factor of safety H = Layer thickness K = Coefficient of earth pressure K = Coefficient of earth pressure at rest L = Length of pile N = Standard penetration test value (SPT) N = Corrected SPT value for field procedures N = Average SPT N value (N ) = Corrected SPT value for overburden pressure (for sandy soil) N, N, N = Bearing capacity factors OCR = Over consolidation ratio Q = Allowable load Q = End bearing at the base or tip of the pile Q = Load transferred to the soil at pile tip level Q = Skin friction or shaft friction or side shear Q = Ultimate bearing/load carrying capacity W = Weight of the pile c = Apparent cohesion of soil c = Un-drained cohesion of soil f = End bearing resistance on unit tip area of pile f = Skin frictional resistance on unit surface area of pile g = Gravitational acceleration q = Unconfined compressive strength xii

13 s = Un-drained shear strength; same as c z = Depth z = Thickness of any (i ) layer α = Adhesion factor β = Friction factor due to overburden γ, γ = Unit weight of the soil γ = Unit weight of water μ = Poisson s ratio of soil σ = Initial effective stress at mid-point of a soil layer σ = Increase in effective stress at mid-point of a soil layer due to increase in stress σ = Reference stress (100 kpa) for computation of pile settlement σ = The total vertical stress σ = Effective vertical stress σ = Effective vertical stress; same as σ ϕ = Apparent angle of internal fiction ϕ = Effective/drained angle of internal fiction xiii

14 CHAPTER 1 INTRODUCTION 1.1 General Piles are conventionally the best possible solution in case of soft soil for transferring structural load to the harder layers of soil strata. Generally, high safety factors are used to get assurance in pile design as there are many uncertainties arise from concreting for cast-in-situ piles and driving for precast piles. Pile load test shall be conducted to verify design capacity and thus ensure economical design. Generally, static pile load test provides best method for determining bearing capacity of pile but it is time consuming and expensive. Under this condition dynamic load test can be considered as an alternative of static load test. Since, the usage of static load test is very common and dynamic test is newly adopted in our country, comparison between the two tests is attempted in this project. 1.2 Background of the Study Soft soil is very common in the southern part of Bangladesh which is not suitable for construction of shallow foundation. Pile foundation provides the best possible solution to transfer load to the deeper harder layers of soil. In Bangladesh, the traditional practice is to construct cast in situ concrete piles. However, precast piles are also used in large numbers because of their various advantages over cast in situ piles; like: high quality of construction, idea of capacity during driving etc. Estimating pile capacity accurately is a difficult job even for the experienced geotechnical engineer. There are many conventional methods for calculating pile capacity but selection of each requires knowledge of soil properties as well as the limitation or applicability of any method in a regional boundary. Traditionally, pile capacity can be evaluated by using bore log of subsoil investigation report (Bowles, 1997) later it need to be confirmed by static load test. In the design process, test piles need to be tested using static pile load test before fixing the final length, capacity and cross section. It is a time consuming and expensive test for a construction project which requires extensive supervision. Moreover, the test has some problems like: transferring load to the pile due to frictional errors (Hoque et. 1

15 al, 1999). In addition, manual data collection system introduces human error possibilities. In this circumstances, a suitable alternative to static load test or cross checking options were necessary for foundation engineers. Researchers in Bangladesh showed keen interest regarding pile related issues. Khan (2002) has attempted to correlate ultimate pile capacity and settlement from static test data of twenty one precast RCC piles and twenty five RCC cast in situ piles. Similarly, Rahman (2008) verified axial load capacity of cast in situ piles with static load test in stiff Dhaka clay. Prediction of load deformation behavior of axially loaded piles in sand was also done by Morshed (1991). Rahman (2014) has studied performance of eight methods based on cone penetration test (CPT) for predicting the ultimate load carrying capacity of square precast RC concrete piles. Until now, no research work was done considering application of dynamic load test in Bangladesh. Pile dynamic analysis using wave equation requires very basic driving system, pile parameters and few standard soil properties. It uses measurement of strain and acceleration near the pile head when pile drives or restrikes with a pile driving hammer. These dynamic measurements can be used to evaluate performance of pile driving system, pile installation stress, pile integrity as well as static capacity. Test data can be further evaluated using signal matching techniques to determine relative soil resistance distribution and dynamic properties for use in wave equation analysis. A Pile Driving Analyzer (PDA) receives data during driving or restrike of pile through two pair of strain and acceleration transducers attached near the pile head. PDA instantly can determine pile stress, integrity, approximate static pile capacity and energy transmission to the pile. PDA data can be used for CAse Pile Wave Analysis Program (CAPWAP) analysis to determine refine static capacity, soil resistance distribution, soil quake and damping parameters for wave equation input (Rausche et al, 2000). Dynamic analysis need to check with static load test method simultaneously to ensure applicability. A firm relationship with static and dynamic load test method need to establish before using dynamic load test in the context of our country which is truly absent until now. 1.3 Objectives of the Study The objectives of the study are as follows: 2

16 i. To determine the ultimate compressive pile load capacity of precast driven pile using Pile Dynamic Analyzer (PDA). ii. iii. iv. To determine the ultimate compressive pile load capacity of precast pile using soil test data mainly, Standard Penetration Test (SPT) value and pile driving records. To determine the ultimate compressive pile capacity using Static Pile load test. To compare the pile load capacity obtained from different methods. 1.4 Organization of the Thesis The thesis is composed of five chapters. In Chapter One, background and objectives of the research is described. Chapter two contains the literature review where methods for calculating pile capacity using soil parameter are discussed. In this chapter pile load test both static and dynamic method along with dynamic formulas, wave equation, dynamic soil response, computational tools for wave equation, dynamic loading test etc. is also described here. Chapter three focus on the testing arrangement and program for data collections at site and laboratory. Chapter four contains results and discussion of collected data. The final Chapter contains conclusions and recommendations for further research. 3

17 CHAPTER 2 LITERATURE REVIEW 2.1 Introduction There are numerous equations available for evaluating the pile capacity for engineering professionals (Bowles, 1997). Based on soil classification, different equations have been evolved to predict the ultimate capacity of pile. For precast pile, capacity calculation is based on observing pile penetration per blow during driving. After the pile is installed in the desired soil strata, capacity can be ascertain by applying pile load test both static and dynamic. So, there is a scope to study pile capacity and compare or correlate among the methods. 2.2 Ultimate Pile Capacity The ultimate load capacity, Q, of a pile consists of two parts. One part is due to friction called skin friction or shaft friction or side shear, Q and the other is due to end bearing at the base or tip of the pile, Q The ultimate axial capacity (Q ) of piles shall be determined in accordance with the following for compression loading. Q = Q + Q W (2.1) Where, W is the weight of the pile. The skin friction, Q and end bearing Q can be calculated as: Q = A f (2.2) Q = A f (2.3) Where, A = skin friction area (perimeter area) of the pile = Perimeter Length f = skin frictional resistance on unit surface area of pile that depends on soil properties and loading conditions (drained or un-drained) A = end bearing area of the pile = Cross-sectional area of pile tip (bottom) f = end bearing resistance on unit tip area of pile, that depends on soil properties to a depth of 2B (B is the diameter for a circular pile section or length of sides for a square pile section) from the pile tip and loading conditions (drained or un- drained) 4

18 For a layered soil system containing n number of layers, end bearing resistance can be calculated considering soil properties of the layer at which the pile rests, and the skin friction resistance considers all the penetrating layers calculated as: Q = Z (Perimeter) (f ) (2.4) Where, Z represents the thickness of any i layer and (Perimeter) is the perimeter of the pile in that layer. The manner in which skin friction is transferred to the adjacent soil depends on the soil type. 2.3 Driven Pile Capacity using Static Formulae Cohesive soil The ultimate axial capacity of driven piles in cohesive soil may be calculated from static formula, given by Equations 2.2, 2.3 and 2.4, using a total stress method for undrained loading conditions, or an effective stress method for drained loading conditions. Appropriate values of adhesion factor (α) and coefficient of horizontal soil stress (k ) for cohesive soils that are consistent with soil condition and pile installation procedure may be used. The following α-method is used for calculating skin friction: The α-method that is based on total stress analysis and is normally used to estimate the short term load capacity of piles embedded in fine grained soils. In this method, a coefficient α is used to relate the un-drained shear strength c or s to the adhesive stress (f ) along the pile shaft. To calculate the skin friction of pile in cohesive soil, Tomlinson (1971) proposed this method. Q = αc A (2.5) American Petroleum Institute (API, 1984) provides the following values to find the skin friction in clay soils. α = 1.0 for clays with c 25 kn/m 2 α = 0.5 for clays with c 70 kn/m 2 α = 1 for clays with 25 kn/m2 < c < 70 kn/m 2 The end bearing in such a case is found by analogy with shallow foundations and is expressed by Mayerhof (1976) as: Q = (c ) (N ) A (2.6) 5

19 N is a bearing capacity factor and for deep foundation the value is usually 9. c is the undrained shear strength of soil at the base of the pile. The suffix b s are indicatives of base of pile. The general equation for N is, however, as follows (Skempton, 1951). N = (2.7) D represents the diameter of the pile at base and L is the total length of pile. The skin friction value, f = (c ) (N ) should not exceed 4.0 Mpa (Engeling and Reese, 1974) Cohesion-less soil The β -method is based on an effective stress analysis and is used to determine both the short term and long term pile load capacities. Burland (1973) developed this method of obtaining skin friction from effective stress on the shaft of pile. The friction along the pile shaft is found using Coulomb s friction law, where the friction stress is given by f = μσ = σ tanϕ. The lateral effective stress, σ is proportional to vertical effective stress, σ by a co-efficient, K. As such, f = Kσ tanϕ = βσ (2.8) Where, β = Ktanϕ = K tanϕ = (1 sinϕ ) OCR (2.9) ϕ is the effective angle of internal friction of soil and OCR is the over-consolidation ratio. For normally consolidated clay, β varies from 0.25 to The value of β decreases for a very long pile, as such a correction factor is used (Kaniraj, 1988) Correction factor for β = log 0.5 (2.10) The end bearing capacity is calculated by analogy with the bearing capacity of shallow footings and is determined from: f = (σ ) N (2.11) Where, N is a bearing capacity factor that depends on angle of internal friction ϕ of the soil at the base of the pile, as presented in Figure 2.1. Subscript b designates the parameters at the base soil. 6

20 Figure 2.1: Bearing capacity factor Nq for deep foundation (After Tomlinson, 1986) 2.4 Driven Pile Capacity Using SPT Cohesive soil Standard Penetration Test N-value is a measure of consistency of clay soil and indirectly the measure of cohesion. The skin friction of pile can thus be estimated from N-value. The following relation may be used for preliminary design of ultimate capacity of concrete piles in clay soil. According to Mayerhof (1976) For skin friction the relationship is as under. f = 1.8N (in kpa) 70 kpa (2.12) For end bearing, the relationship is as under. f = 45N (in kpa) 4000 kpa (2.13) Where, N is the average N-value over the pile shaft length and N is the N-value in the vicinity of pile tip. 7

21 2.4.2 Cohesion-less soil Standard Penetration Test N-value is a measure of relative density hence angles of internal friction of cohesion less soil. The skin friction of pile can thus be estimated from N-value. The following relation may be used for ultimate capacity of concrete piles in cohesion less soil and non-plastic silt. For skin friction the relationship is as under (Mayerhof, 1976) For sand: f = 2N (in kpa) 60 kpa (2.14) For non-plastic silt: f = 1.7N (in kpa) 60 kpa (2.15) For end bearing, the relationship is as under (Mayerhof, 1976) For sand: f = 40N (in kpa) 400N and kpa (2.16) For non-plastic silt: f = 30N (in kpa) 300N and kpa (2.17) Where, N is the average N-value over the pile shaft length and N is the N-value in the vicinity of pile tip. 2.5 Bored Pile Capacity Using Static Formulae Cohesive soil Skin friction resistance in cohesive soil may be determined using either the α-method or the β-method as described in the relevant section of driven piles. However, for clay soil, α-method has wide been used by the engineers. This method gives: f = αs (2.18) Where, f = Skin friction s = undrained shear strength of soil along the shaft 8

22 α = adhesion factor =0.55 for undrained shear strength 190 kpa (4000 psf) For higher values of s the value of α may be taken from Figure 2.2 as obtained from test data of previous investigators. Figure 2.2: Adhesion factor α for drilled shaft (after Kulhawy and Jackson, 1989) The skin friction resistance should be ignored in the upper 1.5 m of the shaft and along the bottom one diameter of straight shafts because of interaction with the end bearing. If end bearing is ignored for some reasons, the skin friction along the bottom one diameter may be considered. For belled shaft, skin friction along the surface of the bell and along the shaft for a distance of one shaft diameter above the top of bell should be ignored. For end bearing of cohesive soil, the following relations given by Equations 2.19 and 2.20 are recommended. f = N S 4000 kpa (2.19) Where, N = (2.20) 9

23 Where, f = End bearing stress S = undrained shear strength of soil along the shaft N = Bearing capacity factor L = Length of the pile (Depth to the bottom of the shaft) D = Diameter of the shaft base Cohesion less soil Skin friction resistance in cohesion less soil is usually determined using the β-method. The relevant equation is reproduced again: f = βσ (2.21) β = Ktanϕ (2.22) Where, f = Skin friction σ = Effective vertical stress at mid-point of soil layer K = Coefficient of lateral earth pressure ϕ = Soil shaft interface friction angle The values of K and ϕ can be obtained from the chart of Tables 2.1, from the soil friction angle, ϕ and preconstruction coefficient of lateral earth pressure K. However, K is very difficult to determine. An alternative is to compute β directly using the following empirical relation. β = (2.23) Where, Br = Reference width=1 ft = 0.3 m = 12 inch = 300 mm z = Depth from the ground surface to the mid-point of the strata 10

24 Table 2.1: Typical φ s /φ and K/K o values for the design of drilled shaft Construction method φ s /φ Construction method K/K o Open hole or temporary casing Slurry method minimal slurry cake Slurry method heavy slurry cake 1.0 Dry construction with minimal side wall disturbance and prompt concreting 1.0 Slurry construction good workmanship 0.8 Slurry construction poor workmanship Permanent casing 0.7 Casing under water 5/ /3 2.6 Bored Pile Capacity Using SPT Values Cohesive soil The following relations may be used for preliminary design of ultimate capacity of concrete bored piles in clay soils. According to Mayerhof (1976) For skin friction the relationship is as under. f = 1.2N (in kpa) 70 kpa (2.24) For end bearing, the relationship is as under. f = 25N (in kpa) 4000 kpa (2.25) Where, N is the average N-value over the pile shaft length and N is the N-value in the vicinity of pile tip Cohesionless soil Standard Penetration Test N-value is a measure of relative density hence angle of internal friction of cohesion less soil. The skin friction of pile can thus be estimated from N-value. The following relation may be used for ultimate capacity of concrete piles in cohesion less soil and non-plastic silt. For skin friction the relationship is as under (Mayerhof, 1976). For sand: f = 1.0 N (in kpa) 60 kpa (2.26) 11

25 For non-plastic silt: f = 0.9N (in kpa) 60 kpa (2.27) For end bearing, the relationship is as under (Mayerhof, 1976). For sand: f = 15N (in kpa) 150N and 4000 kpa (2.28) For non-plastic silt: f = 10N (in kpa) 100N and 4000 kpa (2.29) Where, N is the average N-value over the pile shaft length and N is the N-value in the vicinity of pile tip. 2.7 Bored Pile Capacity Based on AASHTO 2002 The ultimate axial capacity (Qult) of drilled shafts shall be determined in accordance with the following for compression: Qult=Qs+QT -W (2.30) Shaft in cohesive soils may be designed by total and effective stress methods of analysis, for un-drained and drained loading conditions, respectively. Shafts in cohesion-less soil shall be designed by effective stress methods of analysis for drained loading conditions. Side resistance in cohesive soil For shafts in cohesive soil located under un-drained loading conditions, the ultimate side resistance may be estimated using the following equation: Q s=πb αi S ui Δz i (2.31) The ultimate unit load transfer in side resistance at any depth f si is equal to the product of αi and Sui. Refer to Table 2.2 for guidance regarding selection of αi and limiting values of f si for excavated dry in open or cased holes in cohesive soil after Reese and O neill (1988). Environmental long term loading or construction factor may dictate that a depth greater than five feet should be ignored in estimating QS. Refer to Figure 2.3 for identification of portions of drilled shaft not considered in contributing to the complete 12

26 value of QS. For shaft in cohesive soil under drained loading conditions may be determined using the procedure in the next article. Where time dependent changes in soil shear strength may occur (e.g., swelling of expansive clay or down drag from a consolidating clay), effective stress method should be used to compute Q S in the zone where such changes may occur. Table 2.2: Recommended values of α and fsi for estimation of drilled shaft side resistance in cohesive soil, after Reese and O Neill (1988) Location of drilled shaft Value of α Limiting value of load transfer, fsi (ksf) From ground surface to depth along drilled shaft of 5ft* Bottom 1 diameter of the drilled shaft or 1 stem diameter above the top of the bell (if skin friction is being used) All other points along the sides of the drilled shaft *The depth of 5 ft may need adjustment if the drilled shaft is installed in expansive clay or if there is substantial ground line deflection from lateral loading Figure 2.3: Identification of Portions of drilled shafts neglected for estimation of drilled shaft side resistance in cohesive soil, after Reese and O neill (1988) 13

27 Side resistance in cohesion-less soil For shafts in cohesion-less soil or for effective stress analysis of shafts in cohesive soils under drained loading conditions, the ultimate side resistance of axially loaded drilled shafts may be estimated using the following equation: QS=πB γi'ziβiδzi (2.32) The βi may be determined using the following: βi= zi ; 1.2> βi>0.25 (2.33) The value of γ i' should be determined from measurements from undisturbed sample along the length of the shaft or from empirical correlations with SPT or other in-situ test methods. The ultimate unit load transfer in side resistance at any depth, fsi, is equal to the product of β i and σ vi. The limiting value of f si for shafts in cohesion-less soil is 4 ksf. Tip resistance in cohesive soil For axially loaded shafts in cohesive soil subjected to un-drained loading conditions, the ultimate tip resistance of drilled shafts may be estimated using the following: QT=qTAT=Nc Sut AT (2.34) q T=Unit end bearing A T=Cross section area of pile Sut=Un-drained shear strength Values of bearing capacity factor Nc may be determined using the following: Nc=6.0[1+0.2(D/Bi)];Nc 9 (2.35) The limiting value of unit end bearing (qt=ncsut) is 80ksf. The value of S ult should be determined from the results of in-situ and or laboratory testing of un-drained samples obtained within a depth of 2B below the tip of the shaft. If soil within 2B of the tip is of soft consistency the value of Nc should be reduced by one-third. Tip resistance in cohesion-less soil 14

28 There is a tendency for the sand to loosen slightly at the bottom of excavation due to relief of stress. Some densification of sand occurs below the base of a drilled shaft as settlement occurs. The load-settlement curve that have been obtained by experiment for the base of drilled shafts are consistent with the above concepts. The load continued to increase for some of the tests to a settlement of more than 15 percent of the diameter of the base. Such a large amount of settlement could not be tolerated for most structures; therefore, it was decided to limit the values of end bearing for drilled shafts in granular soil to that which could occur at a downward movement of the base of 5 percent of the diameter of the base. Table 2.3: Recommended values of unit end bearing for cohesion-less soil (Reese and O Neill, 1988) Range of value of NSPT (Uncorrected) Values of qb (Tsf) 0 to N Above Pile Capacity during Driving It has been observed that a pile exerting greater resistance against driving can sustain greater load. A number of formulae have been evolved to determine the load carrying capacity based on the principle that the energy supplied to the pile is utilized in useful work done in driving the pile and in other loses. These formulae are known as Dynamic formulae. The Engineering News formula is generally recognized to be one of the most popular dynamic formula (Agerschou, 1962). Chellis (1961) list more than 30 different formulae in his text book. Despite of their obvious deficiencies and unreliability the pile formulae enjoy a great popularity among practicing engineers because of the use of these formulae reduces the design of pile foundations to a very simple procedure Engineering News formula This formula was published by Wellington in Engineering News in 1888 and it was called Engineering News Record Formula (ENR). This is expressed as follows, P u = (2.36) 15

29 Pu =Ultimate capacity of pile e =Hammer efficiency W =Weight of ram h=height of all of ram s=amount of point penetration per blow Gates formula This method was the results of a research performed by Gates (1957). The basic assumption is that the resistance is directly proportional to the squared root of the net hammer energy. The relationship is presented by P =a e E (b log ) (2.37) P = Ultimate pile capacity (kn) Hammer efficiency, e =0.75 for drop hammer Manufactures hammer energy rating E =kn.m s= Point penetration per blow-set a=104.5 b=2.4 A suggested safety factor to be used is 3. In this formula, the following assumptions were made: a) Hammer and pile may be treated as impinging particles b) Hammer gives up its entire energy on impact. c) On impact the resistance increases in an elastic manner as the pile is displaced, remains constant for further displacement and then falls to zero in an elastic manner as the pile rebounds Janbu formula The Janbu formula as mentioned by Olson et al (1967). Pile resistance as measured during driving using this method shall be taken as 16

30 P = (2.38) Wr =Weight of ram Wp =Weight of pile s=pile set E=Modulus of elasticity e =Hammer efficiency E h=manufactures hammer energy rating L=Pile length Cd= (2.39) k u=c d (2.40) λ= It also based on some assumptions such as: a) There is frictional or other loss in the hammer system so that energy actually applied at impact is less than energy delivered. b) There is loss due to elastic compression of the pile. c) There is loss due to impact. Recommended factor of safety is 3 to Pile Capacity by Static Load Test Static load tests relied upon an accurate measure of a pile s ultimate resistance. Ultimate resistance is the maximum resistance mobilized by the positive shaft resistance and toe bearing in the soil. Static load testing involves loading the pile statically by placing increments of load and recording settlements as the load is applied following ASTM D1143. As the pile resistance may set up (resistance increased with time) or relax (resistance decrease with time), static load tests are often performed after some wait period so that equilibrium conditions are re-established.two principal types 17

31 of test may be used for compression loading on piles - the constant rate of penetration (CRP) test and the maintained load (ML) test. Maintained load (ML) test will be used in this study. In the ML test the load is increased in stages to 1.5 times or twice the working load with time settlement curve recorded at each stage of loading and unloading. The general procedure is to apply static loads in increments of 25% of the anticipated design load. The ML test may also be taken to failure by progressively increasing the load in stages. In the ML test, the load test arrangements as specified in ASTM D1143 shall be followed. According to ASTM D1143 each load increment is maintained until the rate of settlement is not greater than 0.25 mm/hr or 2 hours is elapsed, whichever occurs first. After that the next load increment is applied. This procedure is followed for all increments of load. After the completion of loading if the test pile has not failed the total test load is removed any time after twelve hours if the butt settlement over one hour period is not greater than 0.25 mm otherwise the total test load is kept on the pile for 24 hours. After the required holding time, the test load is removed in decrement of 25% of the total test load with 1 hour between decrement. If failure occurs, jacking the pile is continued until the settlement equals 15% of the pile diameter or diagonal dimension Load test evaluation methods for axial compressive load A number of arbitrary or empirical methods are used to serve as criteria for determining the allowable and ultimate load carrying capacity from pile load test. Some are based on maximum permissible gross or net settlement as measured at the pile but while the others are based on the performance of the pile during the progress of testing Chellis (1961); Whitaker (1976); Poulos and Davis (1980); Fuller (1983). It is recommended to evaluate the load carrying capacity of piles and drilled shaft using any of the following methods along with the arbitrary methods: (a) Davission Offset Limit (b) British Standard Institution Criterion (c) Indian Standard Criteria (d) Butler-Hoy Criterion (e) Brinch-Hansen 90% Criterion 18

32 The recommended criteria to be used for evaluating the ultimate and allowable load carrying capacity of piles and drilled shaft are summarized below. (a) A very useful method of computing the ultimate failure load has been reported by Davisson (1972). This method is based on offset method that defines the failure load. The elastic shortening of the pile, considered as point bearing, free standing column, is computed and plotted on the load-settlement curve, with the elastic shortening line passing through the origin. The slope of the elastic shortening line is 20 o. An offset line is drawn parallel to the elastic line. The offset is usually 0.15 inch plus a quake factor, which is a function of pile tip diameter. For normal size piles, this factor is usually taken as 0.1D inch, where D is the diameter of pile in foot. The intersection of offset line with gross load-settlement curve determines the arbitrary ultimate failure load. Davisson method is too restrictive for drilled piles, unless the resistance is primarily friction. This method is recommended for driven precast piles. (b) Terzaghi (1942) reported that the ultimate load capacity of a pile may be considered as that load which causes a settlement equal to 10% of the pile diameter. However, this criterion is limited to a case where no definite failure point or trend is indicated by the load-settlement curves. This criterion has been incorporated in BS 8004 Code of Practice for Foundations which recommends that the ultimate load capacity of pile should be that which causes the pile to settle a depth of 10% of pile width or diameter. (c) The allowable load capacity of pile should be 50% of the final load, which causes the pile to settle a depth of 10% of pile width or diameter BS (d) Ultimate load capacity of pile is smaller of the following two IS: 2911 Part-4: (i) Load corresponding to a settlement equal to 10% of the pile diameter in the case of normal uniform diameter pile or 7.5% of base diameter in case of underreamed or large diameter cast in-situ pile. (ii) Load corresponding to a settlement of 12 mm. (e) Allowable load capacity of pile is smaller of the following IS: 2911 Part-4: (i) Two thirds of the final load at which the total settlement attains a value of 12 mm. 19

33 (ii) Half of the final load at which total settlement equal to 10% of the pile diameter in the case of normal uniform diameter pile or 7.5% of base diameter in case of under-reamed pile. (f) Butler and Hoy (1977) states that the intersection of tangent at initial straight portion of the load-settlement curve and the tangent at a slope point of 1.27 mm/ton determines the arbitrary ultimate failure load. (g) The Brinch Hansen (1963) proposed a definition for ultimate load capacity as that load for which the settlement is twice the settlement under 90 percent of the full test load. (h) Where failure occurs, the ultimate load may be taken to calculate the allowable load using a factor of safety of 2.0 to Dynamic Analysis by Wave Equation Pile driving could not accurately be analyzed by rigid-body mechanics led to the development of an analysis that utilizes wave theory. The wave equation analysis of pile driving has eliminated many shortcomings related with dynamic formulae by accurately simulating the hammer impacts and pile penetration process. The use of wave equation was considered by Isaacs (1931) and Glanville et al (1938); but not until the works of Smith (1960), that the methodology was fully developed The wave equation The wave equation may be derived from consideration of the internal forces and motion produced on a segment of a freely-suspended prismatic bar subject to and impact at one end. The resulting equation is = (2.41) Where D=longitudinal displacement of a point of the bar from its original position E=modulus of elasticity of bar ρ=density of bar material t=time x=direction of longitudinal axis 20

34 For a pile, the resistance of the surrounding soil must also be considered and the equation becomes = (±)R (2.42) Where R= soil-resistance term This equation may be solved for the appropriate initial and boundary conditions, to determine the relationship among displacement, time and position in the pile. From which the stress variation in the pile may be determined Smith s idealization Pile driving analyses are generally accomplished by modeling 1-D wave propagation in an elastic rod (pile). The methods routinely used are based on a lumped mass discretization of the pile with simplified rheological models of pile-soil interaction following the framework first proposed by Smith (1960). The Smith model simulates 1- D wave propagation in the pile idealized as in Figure 2.4 and consists of- 1. A ram, to which an initial velocity is imparted by the pile driver. 2. A cap-block 3. A pile cap. 4. A cushion block (cushioning material). 5. The pile. 6. The supporting soil. 21

35 Figure 2.4: Smith s spring model (Smith, 1960) The ram, cap block, pile cap, cushion block, and pile are represented by appropriate discrete weights and springs. The frictional resistance on the side of the pile is represented by a system of springs and dashpots (Figure 2.4), while the point resistance is represented by a single spring and dashpot. The characteristics of the components are considered subsequently. If the actual situation differs from that shown in Figure 2.4 that is, if the cushion block is not used or if an anvil is placed between ram and cap block the idealization of the system can of course be modified. 22

36 Pile modes-internal spring The ram, cap block, pile cap, and cushion block may be considered to consist of internal springs, although the ram and pile cap can often be treated as rigid bodies. The load, deformation behavior of these elements is most simply taken to be linear (Figure 2.5a) although the internal damping may also be consider (e.g., as shown in Figure 2.5b), for components such as the cap block and the cushion block. a) No internal Damping pile elements b) Internal damping cap block and cushion block Figure 2.5: Load deformation relationships for internal springs Soil model external springs Smith s model of the load-deformation characteristics of the soil, represented as external springs, subjected to static loading, is shown in Figure 2.6.The path OABCDEFG represents loading and unloading in side friction. For the point, only compressive loading is considered and the loading and unloading path is OABCF. The quantities defining this static behavior are Q and Ru where Q = quake, the maximum soil deformation that may occur elastically R u= ultimate soil resistance A load deformation diagram such as Figure 2.6 may be established separately for each spring, so that K (m)= ( ) ( ) (2.43) 23

37 Where K (m) is the spring constant during elastic deformation for external spring m. (c) Equivalent rheological model of soil Figure 2.6: Load-deformation relationship of soil (after Lowery et al, 1969) To allow for the effects of dynamic loading during driving in increasing the instantaneous resistance of the soil, the dynamic load-settlement behavior of the soil is taken to be that shown in Figure 2.6b, which is pointed out by Lowery et al (1969), corresponds to a Kelvin rheological model (Figure 2.6c). This dynamic behavior is characterized by a further parameter J, the damping constant. The dashpot in the model produces an additional resisting force proportional to the velocity of loading (V). 24

38 Basic equation In solving the wave equation numerically, Equation 2.44 could be expressed in finitedifferential form for each element, and then the resulting equations, incorporating the appropriate boundary conditions, could be solved simultaneously for each time-interval considered. This method is the conventional method for solving such equations and has been suggested by Soderberg (1962); it may also be applied to periodic dynamic loading of the pile. However, it has been shown by Smith (1960) that the finitedifference form of the wave equations and this form of expression of the wave equation has been adopted for pile-driving analysis. The basic equations are as follows: D(m,t)=D(m,t-1)+Δt V(m,t-1)......(2.44) C(m,t)=D(m,t)-D(m+1,t). (2.45) F(m,t)=C(m,t)K(m)...(2.46) R(m,t)=[D(m,t)-D (m,t)][k (m)[1+j(m)v(m,t- 1)]..(2.47) V(m,t)=V(m,t-1)+[F(m-1,t)+W(m)-R(m,t)]...(2.48) ( ) Where, m=element number t= time Δt = time interval C(m,t)= compression of internal spring m at time t D(m,t)= displacement of external spring m at time t Dˊ(m,t)=plastic displacement of external spring m at time t F(m,t)= force in internal spring m at time t g= acceleration caused by gravity J(m)= soil damping constant at element m K(m)= spring constant for internal spring m 25

39 K (m)= spring constant for external spring m R(m,t)= force exerted by external spring m on element m at time t V(m,t)= velocity of element m at time t W(m)= weight of element m Equation 2.48 applies for elastic pile elements for which internal damping is ignored. For elements such as the cap block and the cushion block, in which internal damping should be considered, the following equation should be used instead of equation F(m,t)= ( ) [ ( )]. C(m, t) [ ( )] Where e(m)=coefficient of restitution of internal spring m C(m,t)max= temporary maximum value of C(m,t) 1. K(m). C(m, t)max... (2.49) The above equation characterizes the path OABCDEO shown in the Figure 2.6b.For a pile cap or cushion block, no tensile forces can exist and hence only this part of the diagram applies. Intermittent unloading-loading is typified by path ABC, established by control of C(m,t) max in equation: The slope of the of lines AB, BC and DE depends on the value of e(m). Smith (1960) notes that Equation 2.47 produces no damping when D(m,t)- D (m,t) becomes zero, and suggests anal ternate equation to be used after D(m,t) first becomes equal to Q(m), where Q(m) is the quake for element m. R(m,t)=[D(m,t)-D (m,t)].k (m)+j(m).ru(m).v(m,t- 1)...(2.50) Where Ru(m) is the ultimate static soil-resistance of element m. Equation 2.44 to 2.48 are solved for each of the pile elements involved, m=1 to m=p (point), for a succession of time intervals starting when the hammer [W(1)] travelling with known velocity touches the first spring. The solution of these equations continues until the permanent set or plastic displacement of the soil at the point D (p,t) is a maximum Values of soil parameters The soil parameters required for the wave-equation analysis are the ultimate soil resistance, Ru; quake Q; and damping factor, J. 26

40 Ultimate soil resistance, Ru Various values of Ru are input into the computer program and the corresponding permanent set determine the relative proportions of shaft and base resistance. A reasonable estimate of these proportions may be made by made by estimating the static shaft and base resistance from the known or assumed soil properties. A somewhat higher ultimate resistance for a given driving resistance is obtained if some shaft resistance is considered, rather than only end-bearing. As rough guide where other information is not available, value of the percentage of shaft resistance suggested by Forhan and Reese (1964) are shown in Table 2.4. Table 2.4: Empirical values of Q, J and percent side adhesion Soil Q(in) J(p) (sec/ft) 27 Side Adhesion (% of Ru) Coarse sand Sand and gravel mixed Fine sand Sand and clay or loam, at least 50% of pile in sand Silt and fine sand underlain by hard strata Sand and gravel underlain by had strata Quake Values of Q have obtained empirically to date, and the single empirical values of Q for all elements of the pile suggested by Forhand and Reese (1964) are shown in Table 2.4.It is however possible to derive values of Q theoretically from pile settlement theory if the elastic soil parameters are known. On the basis of this theory, the value of Q varies along the pile, with the value at the pile tip being greater than the values along the shaft. Alternatively, Q could also be estimated from the soil-resistance curve employed by Seed and Reese (1957) and Coyle and Reese(1966). Damping factor, J Empirical correlations between J and soil type obtained by Forehand and Reese (1964) are shown in Table 2.4.The values in the Table are for the pile point [i.e., J (p)]. The average value for the sides of the pile J(m) have been found to be less than J(p), and for practical purposes, it has been suggested that

41 J(m)= J(p) (2.51) Where J(m)= Soil damping constant for sides of pile J(p)= Soil damping constant for pile point 2.11 Dynamic Load Test Various techniques for dynamic loading tests are now available. These tests are relatively cheap and quick to carry out compared with static loading tests. Information that can be obtained from a dynamic loading test includes: (a) Static load capacity of the pile, (b) Energy delivered by the pile driving hammer to the pile, (c) Maximum driving compressive stresses (tensile stress should be omitted), and (d) Location and extent of structural damage Test method The dynamic loading test is generally carried out by driving a prefabricated pile or by applying impact loading on a cast-in-place pile by a drop hammer. A standard procedure for carrying out a dynamic loading test is given in ASTM The equipment required for carrying out a dynamic pile loading test includes a driving hammer, strain transducers and accelerometers, together with appropriate data recording, processing and measuring equipment. The hammer should have a capacity large enough to cause sufficient pile movement such that the resistance of the pile can be fully mobilized. A guide tube assembly to ensure that the force is applied axially on the pile should be used. The strain transducers contain resistance foil gauges in a full bridge arrangement. The accelerometers consist of a quartz crystal which produces a voltage linearly proportional to the acceleration. A pair of strain transducers and accelerometers are fixed to opposite sides of the pile, either by drilling and bolting directly to the pile or by welding mounting blocks, and positioned at least two diameters or twice the length of the longest side of the pile section below the pile head to ensure a reasonably uniform stress field at the measuring elevation. It should be noted that change of cross-section of the pile due to connection may affect the proportionality of the signals and hence the quality of the data. An electronic theodolite 28

42 may also be used to record the displacements of the pile head during driving (ASTM D ).In the test, the strain and acceleration measured at the pile head for each blow are recorded. The signals from the instruments are transmitted to a data recording, filtering and displaying device to determine the variation of force and velocity with time Methods of Interpretation for Dynamic Load Test Two general types of analysis based on wave propagation theory, namely direct and indirect methods are available. Direct methods of analysis apply to measurements obtained directly from a (single) blow, whilst indirect methods of analysis are based on signal matching carried out on results obtained from one or several blows. Examples of direct methods of analysis include CASE, IMPEDANCE and TNO method, and indirect methods include CAPWAP, TNOWAVE and SIMBAT. CASE and CAPWAP analyses are used mainly for displacement piles, although in principle they can also be applied to cast-in-place piles. SIMBAT has been developed primarily for cast-in place piles, but it is equally applicable to displacement piles. In a typical analysis of dynamic loading test, the penetration resistance is assumed to be comprised of two parts, namely a static component, Rs, and a dynamic component, Rd. Two methods of analysis are described below CASE method This method assumes that the resistance of the soil is concentrated at the pile toe. In the analysis, the dynamic component is given by: Rd = jc Z vb..(2.52) Here jc = the CASE damping coefficient Z = impedance =Ep Ap/cw Ap = cross sectional area of the pile Ep = Young's modulus of the pile cw = wave speed through the pile vb = velocity of pile tip The appropriate jc is dependent on the type of soil at the pile toe and the actual pile dimensions. A range of jc values appropriate to different soil types was proposed by Rausche et al (1985) and has been further refined by Pile Dynamics Inc. (PDI, 1996). 29

43 Typical ranges of jc are given in Table 2.5 These represent the damping factors at pile toe and are correlated with dynamic and static loading tests. In practice, jc values can vary significantly, particularly in layered and complex ground conditions, causing potential errors in pile capacity prediction. For large piling projects where CASE method is to be used to ascertain the load-carrying capacity of piles, site-specific tests can be conducted to determine the appropriate damping factors by correlating the CASE results with static loading tests or results of CAPWAP analysis. Table 2.5: Range of CASE damping values for different types of soil Soil type at pile toe CASE damping Updated CASE damping (Rausche et al, 1985) (PDI, 1996) Clean sand Silty sand, sand silt Silt Silty clay, clayey silt Clay or higher CAPWAP method In a CAPWAP (CAse Pile Wave Analysis Program) analysis, the soil is represented by a series of elasto-plastic springs in parallel with a linear dashpot similar to that used in the wave equation analysis proposed by Smith (1960). The soil can also be modeled as a continuum when the pile is relatively short. CAPWAP measures the acceleration-time data as the input boundary condition. The program computes a force versus time curve which is compared with the recorded data. If there is a mismatch, the soil model is adjusted. This iterative procedure is repeated until a satisfactory match is achieved between the computed and measured force-time diagrams. The dynamic component of penetration resistance is given by Rd = js vp Rs (2.53) Where js = Smith damping coefficient vp = velocity of pile at each segment Rs = static component of penetration resistance Input parameters for the analysis include pile dimensions and properties, soil model parameters including the static pile capacity, Smith damping coefficient, js and soil quake (i.e. the amount of elastic deformation before yielding starts), and the signals 30

44 measured in the field. The output will be in the form of distribution of static unit shaft resistance against depth and base response, together with the static load-settlement relationship up to about 1.5times the working load. It should be noted that the analysis does not model the onset of pile failure correctly and care should be exercised when predicting deflections at loads close to the ultimate pile capacity. Results of CAPWAP analysis also provide a check of the CASE method assumptions since the ultimate load calculated from the CAPWAP analysis can be used to calculate the CASE damping coefficient. Sound engineering judgment is required in determining whether a satisfactory match has been achieved and whether the corresponding combination of variables is realistic Summary This chapter describes the methods to calculate the pile capacity. Two types of pile was discussed both precast and cast-in-situ type. Later each pile type was discussed based on the soil classification. In addition to that, pile capacity using driving formula was mentioned. To ascertain the predicted pile capacity load test was discussed. Based on the aforementioned literature the capacity of pile will be determined in this study. 31

45 CHAPTER 3 INSTRUMENTATION AND TEST PROGRAM 3.1 General The study location is at a construction site in Tangail. First, a detailed subsoil investigation was done, with the help of two bore holes namely BH-1 and BH-2 which was approximately 5m apart. Based on subsoil investigation precast rectangular piles were selected. In this site detailed study of two precast piles was carried out. In the preliminary design phase pile section 12 X12 (300X300 mm 2 ) and length 45ˊ-0 (13.71m) was fixed. Next these piles were cast at site and cured for twenty eight days. Mature piles were driven in two locations namely TP-1 (Test pile) and TP-2 (Test pile). Drop hammer of 3.5 Ton was used and maximum height of fall was 5'-0''. During driving the driving records were collected for calculating the pile capacity which was also attached at Appendix B. After 14 days of interval these piles were tested using Pile Dynamic Analyzer (PDA) Test. At the last two feet (from top) of each pile, transducers and strain gages were attached with the pile for estimating dynamic capacity by PDA. Later CAPWAP analysis was carried out using the signal matching techniques for evaluating refine capacity of piles. Later these piles were tested by static load test method as well. 3.2 Capacity Estimation The pile capacity will be calculated by using sub soil investigation report. Methods that are considered for this study are based on the draft versions of Bangladesh National Building Code (BNBC-2015), where pile capacity estimation technique is described both for driven and cast-in-situ piles. It has presented two methods: one is Static bearing capacity (Alpha-Beta method) and the other is SPT method. Generally, professional geotechnical expert uses American Association of State Highway and Transportation Officials guidelines (AASHTO, 2002), which is widely used in Bangladesh. For this study AASHTO-2002 method is also applied and results are compared with the BNBC During driving the precast piles, there is an option for using the driving equations. This has also been used for pile capacity estimation. Figure 3.1 summaries the working process of the study. 32

46 PILE CAPACITY BASED ON SOIL TEST REPORT DRIVING EQUATION DYNAMIC LOAD TEST (PDA) STATIC LOAD TEST 1. BNBC AASHTO ENGINEERS NEWS 2. GATES FORMULA 3. JANBU FORMULA CAPWAP ANALYSIS 1. DAVISSION METHOD 2. BNBC-93 GUIDELINE 3. BS 8004 (BRITISH STANDARD) 4. IS: 2911 (INDIAN STANDARD) 5. BUTLER & HOY 6. BRINCH HANSEN Figure 3.1: Flow diagram of the working process From the soil test report it was found that the soil is uniform in horizontal and vertical direction. Mainly soil type was non-cohesive (Silt followed by Sand) up to the depth of investigation. Considering the imposed building loading deep foundation was considered. Figure 3.2 and 3.3 shows the two test borehole logs. The test pile driving records are attached at Appendix A. 33

47 Borehole No-1 Method of boring-percussion Method Boring dia (mm)-100 Soil Classification- ASTM D-2487 & D-2488 Depth below EGL(m) Thickness (m) Description of soil strata SPT N- Value (Raw field data) Graphical representation of SPT N-value Brown, non plastic, SILT, ML, trace mica Gray, loose to medium dense, Silty SAND, SM, trace mica Figure 3.2: Borehole log BH-1 34

48 Borehole No-2 Method of boring-percussion Method Boring dia (mm)-100 Soil Classification- ASTM D-2487 & D-2488 Depth below EGL(m) Thickness (m) Description of soil strata SPT N- Value (Raw field data) Graphical representation of SPT N-value Brown, nonplastic, SILT, ML, trace mica Gray, loose to 10 medium dense, 17 Silty SAND, SM, 26 trace mica Figure 3.3: Borehole log BH-2 35

49 3.3 Pile Load Tests Based on the sub soil investigation, pile length was selected as 45ft with a section of 12''X12'' (300mmX300mm). Initial estimated capacity was 40 Ton following equation of Schmertmann (1970). Table 3.1 shows the static and dynamic load testing program. Table 3.1: Load testing program for test piles Sl. No. Purpose of test Name of the test Number of tests 1. Dynamic Pile Capacity PDA followed by CAPWAP analysis 2 2. Static Pile Capacity Static Load Test 2 Figure 3.4: Casting of pile at site for construction 3.4 Pile Driving and Keeping Driving Record Piles are generally marked every one feet of interval and which is visible from the data observer during record keeping. In a proper formatted data sheet pile penetration and 36

50 hammer blow need to be recorded for per feet of penetration of pile. Data sheet provides necessary information like: pile section, length, casting date, pile identification mark, capacity of pile, hammer weight, drop height of hammer, blows required for a fixed penetration depth, refusal etc. From the driving of the two piles initial capacity can be calculated using available driving formulas like Engineering News, Gate etc. Figure 3.5 shows the driving of pile using a drop hammer. Figure 3.5: Pile driving using drop hammer 3.5 Dynamic Load Test Arrangement A typical dynamic testing system consists of a minimum of two strain transducers and two accelerometers bolted to diametrically two opposite sides of the pile to monitor strain and acceleration and account for non-uniform impacts and bending. The use of 37

51 two diametrically opposite mounted strain transducers is essential for a valid test. Generally, strain transducers and accelerometers are attached two to three diameters below the pile head. Figure 3.6 to Figure 3.9 illustrate the typical pile preparation procedures required for dynamic testing. In Figure 3.6 a concrete pile is being prepared for gage attachment by drilling. Pile preparation and gage attachment typically requires 10 to 20 minutes per pile. After the gages are attached, the driving process continues following usual procedures. The individual cables from each gage are combined into single main cable which in turn relays the signals from each hammer blow to the data acquisition system on the ground. The data acquisition system, such as the Pile Driving Analyzer shown in the Figure 3.7 receives and converts the strain and acceleration signals to force and velocity records versus time. The force is computed from the measured strain times the product of the pile elastic modulus, and cross sectional area. The velocity is obtained by integrating the measured acceleration record. During driving, the Pile Driving Analyzer performs integrations and all other required computations to analyze the dynamic records for transferred energy, driving stress, structural integrity, and pile capacity. Numerical results for dynamic quantities are electronically stored in a file which can be later used to produce graphical and numeric summary outputs. In this system, force and velocity records are also viewed on a graphic LCD computer screen during pile driving to evaluate data quality, soil resistance distribution, and pile integrity. Complete force and velocity versus time records from each gage are also digitally stored for later reprocessing and analysis by CAPWAP. During pile driving in the field, the Pile Driving Analyzer uses the Case Method capacity equations for estimating the ultimate static pile capacity. Case Method capacity results are calculated in real time from the measured force and velocity records obtained for each hammer blow. Correlating Case Method capacity results with pile penetration resistance information is another means of establishing the driving criteria. The CAPWAP analysis method is a more rigorous numerical analysis procedure that uses the measured force and velocity records (PDA data) from one hammer blow. The CAPWAP program uses the dynamic measurement data along with wave equation and soil modelling to calculate the ultimate static pile capacity, the relative soil resistance distribution, the dynamic soil properties of quake and damping, and the driving stresses 38

52 throughout the pile. CAPWAP capacity results are considered a more accurate assessment of the ultimate static pile capacity (Likins et al, 1996). Figure 3.6: Strain transducers and accelerometer bolted on the concrete piles Figure 3.7: Pile driving analyser 39

53 Figure 3.8: Dynamic test arrangement for TP-1 Figure 3.9: Dynamic test arrangement for TP Static Load Test Arrangement Maintain load (ML) method with standard loading procedure has been followed under complying ASTM D1143 and load applied by hydraulic ram against Kent ledge. ASTM D1143 recommends several alternative systems for applying compressive load to the pile, and measuring movements. Table 3.2 presents load testing details. Table 3.2: Static load test program Criteria Design Load Target test load Type of pile Dimension Method of installation Attributes 40 Ton 2.5 X Design load=100 Ton Reinforced concrete pre-cast pile 300mmX300mm (12 X12 ) Impact hammering 40

54 Driving equipment Hammer detail Criteria Attributes Skid mounted pile driver Drop hammer Hammer weight=3.5 Ton Drop height=5 Ft (max) Compressive loads are applied by hydraulic jacking against a weighted platform. The primary means of measuring the load applied to the pile should be with a calibrated load cell. The jack load should also be recorded from a calibrated pressure gauge. Axial pile movements are usually measured by dial gages that measure the movement between the pile head and an independently supported reference beam. Figure 3.10: Schematic diagram of typical arrangement of applying load in an axial compressive test 41

55 The steps are to be followed is given below: Arrangement of instrument and calibration. Preparation of mass of heavy material, termed Kentledge is placed on platform. Installation of reference beam Finish pile top for seating hydraulic jack, installation of pile collar, placement of jack, dial gauges and strain gauges and reading. Taking safety measures Loading sequence Detailed loading procedure is presented in ASTM D1143 for Maintained load (ML) test. The general procedure is to apply static loads in increments of 25% of the anticipated design load (BNBC-2015). According to ASTM D1143 each load increment is maintained until the rate of settlement is not greater than 0.25mm/hr or 2hr is elapsed, whichever occurs first. This procedure is applied for all increment of load. After completion of loading if the test pile has not failed the total test load is removed any time after twelve hours if the butt settlement over one hour period is not greater than 0.25mm otherwise the total test load is kept on the pile for 24 hours. After the required holding time, the test load is removed in decrement of 25% of the total test load with 1 hour between decrement. If failure occurs, jacking the pile is continued until the settlement equals 15% of the pile diameter or diagonal dimension. 42

56 Table 3.3: Typical loading sequence arrangement for pile load test. Design Load (kip)=80 Design Load (kg)=40,000 Test Load(kg)=100,000 Diameter of ram (cm)=24.13 Area of ram (cm 2 )= Regression equation: Y actual(kg/ cm 2 )=1.019X(kg/ cm 2 ) Loading steps % of Design Load Load (kg) Theoretical Required Pressure (kg/ cm 2 ) Required Corrected Pressure (kg/ cm 2 ) Observed Pressure (kg/ cm 2 ) Load (kg) As planned % of Design Load Holding Time Reading Intervals 1 st increment 25 10, , A/B 10 min 2 nd increment 50 20, , A/B 10 min 3 rd increment 75 30, , A/B 10 min 4 th increment , , A/B 10 min 5 th increment , , A/B 10 min 6 th increment , , A/B 10 min 7 th increment , , A/B 10 min 8 th increment , , A/B 10 min 9 th increment , , A/B 10 min 10 th increment , , C D 1 st decrement , , min 10 min 2 nd decrement , , min 10 min 3 rd decrement , , min 10 min 4 th decrement hr 10 min Notes: Holding time: A= Any time, if the rate of settlement is less than 0.25 mm/hr B= Max 2 hr if the rate of settlement is greater than 0.25 mm/hr C= Any time after 12 hr if the butt settlement is not greater than 0.25mm in 1 hr but otherwise 24 hr Reading time: D= At interval 10 min for 1 st 1 hr for next 10 hr, 2hr for next 12 hr When pile fails: If the pile fails at any load the pile will be jacked up to 15% of pile diagonal/diameter of settlement. 43

57 3.7 Data Collection Data was collected for both precast and cast-in-situ piles were done following the flow diagram. DATA COLLECTION SOIL TEST REPORT PILE DETAILS DYNAMIC LOAD TEST (PDA) CAPACITY CALCULATION 1. BNBC-2015 (SPT) 2. BNBC-2015 (STATIC BEARING) 3. AASHTO-2002 CAPWAP ANALYSIS COMPARE & CORELATE Figure 3.11: Schematic diagram of data collection for precast and cast in situ piles. Precast pile Two piles were tested for both dynamic and static load test at Tangail site. All the soil investigation report, static load test, dynamic load test data were collected for these two piles. Total fifteen precast pile data (pile length and cross section), soil investigation report, dynamic load test data were collected from Public Works Department (PWD). The Table 3.4 shows the collected data and predicted pile capacity based on different method. 44

58 SL No Project name Nursing College, Pabna Nursing College, Pabna Sadar Hospital, Manikganj Sadar Hospital, Manikganj Sadar Hospital, Manikganj Sadar Hospital, Manikganj Teachers Training College, Shariatpur Teachers Training College, Shariatpur Bangabandhu Textile Institute, Tangail Bangabandhu Textile Institute, Tangail Table 3.4: Data summary for precast pile Length (m) Pile data Section (m x m) X X X X X X X X 0.35 Pile capacity calculated (kn) Collected capacity CAPWAP (kn) Pile ID BNBC-2015 Static Beari SPT ng P-26 (H-07) P-04 (G-07) PC-4 P PC-8B P PC-5 P PC-4 P TP TP X 0.3 P X 0.3 P Keraniganj Sub Jail X 0.3 TP Cox s bazar Medical College X 0.3 TP Cox s bazar X 0.3 TP Medical College X 0.3 TP Teachers Training College, Barguna Source: Icon Engineering services Cast-in situ pile X 0.35 P Recently, Padma multipurpose bridge project service area-2, Mogbazar flyover project and few other projects used dynamic load test. For cast-in situ piles total ten dynamic load test, soil investigation report and pile data (pile length and cross section) were 45

59 collected for capacity calculation. Table 3.5 presents the collected data and capacity calculation based on different method. SL No Project Name Walton Office, Basundhara, Dhaka * Titas Railway Bridge, Akhaura * Padma Bridge, Naodoba, Zazira, Shariatpur * Mogbazar Fly over, Dhaka* Mogbazar Fly over, Dhaka* Mogbazar Fly over, Dhaka* Dhaka Road research Lab( P1) # Dhaka Road research Lab(P2) # Zinzira-Nawabganj Bridge (LRP,P3) # Zinzira-Nawabganj Bridge (LRP,P4) # Table 3.5: Data summary for cast-in-situ pile Pile Data Diameter (m) Source: * Icon Engineering services, # Prosoil 3.8 Summary Len gth (m) Pile capacity calculated (kn) BNBC BNBC Static bearin AASHT SPT g O-2002 Collected Capacity CAPWAP (kn) The test program focuses on two test pile which will provide adequate information regarding pile capacity. After load test confirmation both static and dynamic will allow the opportunity to compare with the predicted capacity by different methods in detail. Later data collection of soil test report, pile details and CAPWAP capacity will be done for both precast and cast in situ piles. Pile capacity prediction by different method will be done using the collected data which will be compared with CAPWAP capacity. 46

60 CHAPTER 4 RESULTS AND DISCUSSIONS 4.1 General In this study, the main focus is to determine compressive load capacity of piles using different existing methods of pile capacity estimation and compare with dynamic and static load test. In this chapter pile capacity calculation was done based on BNBC- 2015(Static bearing capacity and SPT methods) and AASHTO For selected two precast test pile capacity was predicted and later compared with CAPWAP and static load test. Later part of the study uses collected data for capacity prediction and correlate with CAPWAP capacity for precast and cast in situ piles. 4.2 Pile Capacity of Precast Piles Using Driving Equations Using pile driving record the capacity was calculated for two testing piles. In this test drop hammer weight was 3.5 ton. Piles were marked per 0.3m (1'-0'') interval and lifted by one point lifting at 4.5m from the top. After fixing the pile with the tripod stand the hammer dropped from height varying from 0.6m (2'-0'') to max 1.52m (5'-0''). From the driving chart it was evident that the pile section penetrated up to 4.57m (15'-0'') by selfweight. Next each penetration of 0.3m (1'-0'') required 12 to 37 numbers of blows. Engineers News Formula, Janbu and Gates formula was used for capacity calculation. In the Engineering News formula efficiency of drop hammer value 0.75 was considered according to Bowles (1997). Resistance under working load was calculated using equation In this formula only weight of ram, point penetration per blow, height of ram need to be considered. Engineering News and Janbu equations are based on impulse momentum principles with various assumptions. The calculations of pile capacity based on the driving formulas are attached in the Appendix-C. 4.3 Pile Capacity Using PDA Test Results Dynamic testing on the piles was conducted by striking the piles by several blows. During testing of pile, complete dynamic measurements were obtained for each hammer blow delivered to the pile. The input of a weave equation analysis consists of information about the soil, pile, hammer, cushions, and any other devices which participates in the transfer of energy from hammer to soil. 47

61 In this test re-strike method was applied on driven pile. Before testing the upper portion of pile 150mm to 225mm (6'' to 9'') was recast and a smooth top was prepared for maintain level for hammer impact over pile top properly. Weight of the hammer was 1600kg. The sensor both strains gages and accelerometers were placed 0.6m (2'-0'') below the pile top. Height of fall was 1m. For analysis pile segment was divided into six segments. Ply wood was used as cushion material in two layers each was 16mm thick. Elastic modulus of pile material was considered MPa. Wave speed and specific weight of concrete was 3500 m/s and 24.5 kn/m 3 consecutively. Soil parameters like quake skin, quake toe, damping skin, damping toe was used as the default values provided by PDA. In Figure 4.1 hammer blows were given to TP-1 and all the records were measured. Capacity found at the field PDA is represented by Rsu=1346 kn and Rmx=1408kN. The degree of convergence between the force and velocity records is expressed by the BTA (Beta value) integrity value as a percentage of the approximate reduce cross sectional area. Pile integrity, BTA, value reading 100% indicate no damage was present. Table 4.1: Beta value for pile integrity (Rausche and Goble, 1979). Beta value Pile condition 100% OK 60% -80% Slightly damage 60% Damage 48

62 Figure: 4.1: Force and velocity record for TP-1. For TP-2 hammer blows were given and data was collected. Pile integrity BTA is 73% which indicate pile defect i.e. reduction of cross section area. Capacity found at the field PDA is represented by Rsu=1317 kn and Rmx=569kN. The data record of force and velocity presented in the Figure 4.2. The PDA measures the total (static and dynamic) resistance acting on the pile. Table 4.2 shows the pile capacity using PDA. Table 4.2: Capacity of piles using PDA. Capacity (kn) TP-1(P-24) TP-2(P-141) Rsu Rmx

63 Figure 4.2: Force and velocity record for TP CAPWAP Analysis CAPWAP (CAse Pile Wave Analysis Program) is a signal matching procedure based on pile top force and velocity measurements during hammer impact, extracts static and dynamic soil resistance parameters for pile shaft and toe. It refines the raw data of PDA by signal matching procedure through iteration. In Figure 4.3 and 4.4 shows CAPWAP force wave matching was done for TP-1 and TP-2. A reasonable matching was done in shaft, toe resistance, total resistance and soil unloading behaviour starting from zone 1 to 4. A large separation between force and velocity record in Figure 4.5 suggests a large shaft resistance on the pile. From the analysis the shaft resistance was found kn and toe resistance kn which support the point. 50

64 Figure 4.3: CAPWAP Iteration force matched graph for TP-1 A rigorous CAPWAP analysis of the data acquired from the PDA, confirmed that the pile had achieved an activated CAPWAP capacity of KN. In Figure 4.5 showed a reasonable match of force wave. Though both zone 2 and zone 3 disagrees slightly regarding matching. The resulting model will fairly estimate static pile capacity, soil resistance distribution, soil quake and damping characteristics. Figure 4.4: CAPWAP Iteration force matched graph for TP-2 From the Figure 4.5 it was found that a minimum separation occurred between the force and velocity records between time O, or the time of impact and time 2L/c. Hence this record indicated a minimum shaft and tow resistance on the pile. A rigorous 51

65 CAPWAP analysis of the data acquired from the PDA, confirmed that the pile had achieved an activated CAPWAP capacity of kn. There is a 45.11% reduction of pile impedance at around 4.0m below the sensors which indicates a major defect. Figure 4.5: Investigation of pile damage and beta factor Type of Testing Table 4.3: Summary of dynamic test Test pile ID TP-1 TP-2 52 Restrike Blow Number 5 4 Pile Length (m) Le (m) Lp (m) Max Comp. stress (MPa) Set (DFN) (mm) CAPWAP Capacity Shaft (kn) Toe (kn) Total (kn)

66 4.5 Pile Capacity from Pile Load Test Static pile capacity was determined in the TP-1 and TP-2 piles. Design load was 40 ton and the target load was 2.5 times the design load i.e. 100 ton. Using the test settlement under working load, adequacy of bearing capacity will be ensured. Maintained load test were performed to accomplish the above objectives. In case of TP-1 loading was done in ten consecutive steps which produce settlement 8.9 mm at a final loading of 99,975 kg for 12 hour. The unloading causes a 3.57 mm permanent settlement. One cycle of loading and unloading was done for the load test. During the test the settlement was within the capacity of the pile which suggests the pile capacity is more than the design load arrangement. After the test the Davission offset method applied which shows no point of failure. Other methods were applied for calculating the pile capacity. 0 Load (MT) Pile settlement (mm) Davission offset line, out of range Figure 4.6: Load settlement graph for pile load test TP-1 In case of TP-2 one cycle of loading was done up to design load and unload was done. Later pile load was increased up to the test load previously set. At load 90,318 kg load settlement was 37.96mm. After the unloading it experience mm permanent set. 53

67 0 Load (MT) 5 Pile settlement (mm) Davission offset line Figure 4.7: Load settlement graph for pile load test TP-2 For TP-1 ultimate capacity pile is more than 1000 kn and for TP-2 capacity was derived using different methods. The capacity trend of static load test is similar to the CAPWAP analysis. The pile load test summary is given below for the two piles in Table 4.4. Pile ID Davission Offset TP-1 Out of range Out of range TP-2 81 Ton (807 kn) Table 4.4: Test result summary Capacity Ton (kn) BS 8004 IS: 2911 Butler and Hoy 88.5 Ton (881 kn) Brinch Hansen Out of range Out of range Out of range 78 Ton (777 kn) 79 Ton (787 kn) +90 Ton (896 kn) Table 4.5 presents the pile capacity for two piles in different methods. From the Table 4.4 shows that pile capacity using Janbu formula provides higher capacity for both piles. 54

68 Table 4.5: Pile capacities from driving formulas Formulas used Total resistance TP-1(kN) Total resistance TP-2(kN) Engineering News Janbu Gates CAPWAP(Dynamic) Static (Average) However, Engineers News formula provides the least capacity value. Gates formula provides closer values comparing with the CAPWAP dynamic analysis. However, driving formulas fail to provide information of pile condition during driving. Static pile load test resembles with the CAPWAP capacity for the two piles though the capacity differs maximum 40%. 4.6 Pile Capacity Summary Fifteen dynamic test data of precast pile were collected. In the data predicted pile capacity, CAPWAP analysis was available. By observing the collected data the following comments were made. 1. There is good co-relation exist with the BNBC-15 methods with the CAPWAP capacity, which is shown in Figure 4.8 and 4.9. For BNBC-15 Static method an equation was developed as CAPWAP capacity =1.10X BNBC 2015 Static capacity and r 2 =0.81. For the case of BNBC SPT the equation was developed as CAPWAP capacity=1.06x BNBC 2015 SPT capacity and r 2 = Generally, BNBC-2015 Static capacity method under predict precast pile capacities most of the times (87%) comparing with the CAPWAP capacity. 3. CAPWAP analysis suggests that due to layer change in same vicinity pile capacity can be different. That is also reflected in the calculation of BNBC-2015 static bearing method. 55

69 4. CAPWAP analysis shows exact precast piles capacity considering the integrity of pile, as well as soil damping, driving and other relevant issues. If during driving the pile is injured it shows the integrity by beta value. Predicted pile capacity can very considering these variable which is beyond the scope of traditional equations based on soil parameter CAPWAP capacity= 1.10xBNBC2015 Static Capacity r² = 0.81 CAPWAP capacity (kn) BNBC-2015 Static bearing capacity(kn) Figure 4.8: Correlation between CAPWAP and BNBC 2015 (static bearing) pile capacity for precast pile 56

70 CAPWAP capacity = 1.06x BNBC 2015 SPT capacity r² = CAPWAP capacity (kn) BNBC-2015 SPT capacity(kn) Figure 4.9: Correlation between CAPWAP and BNBC 2015 (SPT) and pile capacity for precast pile 4.7 Comparison with Collected Data for Cast-In-Situ Piles Data of ten cast-in-situ piles were collected. In the data predicted pile capacity, CAPWAP analysis was also available. Following observations were found 1. In case of cast-in-situ piles the predicted capacity generally agrees with the CAPWAP capacity. 2. There is very good co-relation exist between BNBC-2015 static bearing capacity of pile with the CAPWAP capacity for these cast-in-situ piles. The equation was developed as CAPWAP capacity=1.15x BNBC static capacity and r 2 =0.81 which is shown in Figure

71 10000 CAPWAP capacity = 1.15x BNBC 2015 Static bearing capacity r² = CAPWAP capacity (kn) BNBC-2015 Static bearing capacity(kn) Figure 4.10: Correlation between CAPWAP and BNBC-2015 (static bearing) capacity. 3. The co-relation between BNBC-2015 SPT cast-in-situ pile and CAPWAP is developed as CAPWAP capacity=1.04x BNBC SPT capacity and r 2 =0.89 which is shown by Figure The co-relation between AASHTO-2002 cast-in-situ pile and CAPWAP is developed as CAPWAP capacity=0.91x AASHTO 2002 capacity and r 2 =0.92 which is presented by Figure

72 CAPWAP capacity (kn) CAPWAP capacity = 1.04x BNBC 2015 SPTcapacity r² = BNBC-2015 SPT capacity(kn) Figure 4.11: Correlation between CAPWAP capacity and BNBC-2015 SPT capacity for cast-in-situ pile CAPWAP capacity (kn) CAPWAP capacity = 0.91x AASHTO 2002 capacity r² = AASHTO capacity(kn) Figure 4.12: Correlation between CAPWAP and AASHTO-2002 pile capacity for cast-in-situ piles. 4.8 Summary There is a very good co-relationship exist with static pile load test and dynamic load test which is evident in this case. In a mega project where pile number is huge it is very 59

73 difficult to carry out the static load test frequently due to shortage of money or time. Application of dynamic test may be appropriate in those conditions. In the upcoming BNBC-2015 the static bearing capacity method and SPT methods are presented as a guideline for calculating both precast and cast-in-situ piles. Geotechnical experts over the years are familiar with the AASHTO-2002 method for practicing real life work. Considering both soil test report and CAPWAP analysis co-relationships were established for precast and cast-in-situ piles. Further study is necessary in this regard to validate proposed equations of BNBC During the study it was found that beta value is a very good indicator for pile integrity. In case of cast-in-situ piles it shows the casting quality and in case of precast pile it suggests the pile condition after driving. This is an excellent tool need to be utilized properly by our professionals. 60

74 CHAPTER 5 CONCLUSIONS 5.1 General The aim of the study was to determine the ultimate pile load capacity using Pile Dynamic Analyzer (PDA) along with static load test which is very common in our country. For the two test pile (precast) this was done together with the driving equations, BNBC-2015 guideline and AASHTO Later for fifteen precast pile and ten cast-in-situ pile CAPWAP analysis, BNBC-2015 capacity, AASHTO-2002 capacity was also used to summarized and establish co-relations. 5.2 Concluding Remarks Pile capacity was calculated for two test piles (TP-1 and TP-2) of this study using driving record. In each method the capacity of two piles are close. It suggests that soil variation in those two piles were not considered in driving equations. Each driving equation shows same pair of pile capacity values derived from Engineer s News, Janbu and Gates formula. However, inconsistency of capacity was observed. Results suggest that these methods should not be applied due to large inconsistency in capacity prediction. Capacity from static pile load test and dynamic load test for the two piles are close. In case of capacity obtained from BNBC-2015 guidelines and AASHTO-2002 fails to match with TP-2 but aggress well with TP-1. From dynamic load test it was found that beta factor for TP-1 was 100% and beta factor for TP-2 was 73%. This suggests TP-2 has major defects. It can be concluded that predicted pile capacity can vary widely if piles were not properly casted (in case of cast-in-situ pile) or driven (in case of precast pile) maintaining quality. In case of collected sample data analysis of soil test report, Dynamic Load Test, BNBC-2015 and AASHTO-2002 very useful co-relationships has been established. It can be improved by further study. 61

75 5.3 Recommendations From the lessons of the present study, the recommendations for future study may be summarized as follows: In this study, only the capacity of piles was estimated and compared but the effect of soil set-up (change of soil strength and adhesion) was not considered. Thus considering the effect of soil set-up modified pile capacity can be studied. This can be done by assessing a pile capacity after a time interval using dynamic load test. In our country selection of pile hammer depends on the availability of hammer. Proper selection of hammer or study is necessary for driving a pile without damaging it. This can be ensured by using PDA data of energy transfer ratio, pile stress and other indicator for optimize the appropriate diesel hammer. Application of drop hammer should be restricted for important projects. Attention should be given to beta values from the PDA during driving and take note any possible damage on the driving record. That will reduce the chance of overdriving of piles. There is no study for selection of damping factor and quake value for Bangladesh for CAPWAP analysis. Only prescribed guideline is used for signal matching. There is a scope to develop site specific factors for Bangladesh. Though dynamic analysis is already use in our country there is no guideline in BNBC There should be a guideline along with standard to use it efficiently. 62

76 REFERENCES Agerschou, H.A. (1962). Analysis of the Engineering News Pile Formula. J.S.M.F.D., ASCE, 88, SM5:1-11. American Society of State Highway and Transportation Officials (AASHTO-2002). Standard Specifications for Highway Bridges, Division 2, Washington, D.C. API (1984), Recommended Practice for Planning Designing and Construction Fixed Offshore Platforms, 14 th Edn. APIRP2A, American Petroleum Institute, Dallas, TX. ASTM D (Reapproved 1994). Standard Test Method for Piles under Static Axial Compression Load, Annual Book of ASTM Standards, Vol Soil & Rock; ASTM D a, Standard Test Method for Penetration Test (SPT) and Split-Barrel Sampling of Soils, Annual Book of ASTM Standards, Vol Soil & Rock; ASTM D (2006), Standard Practice for Thin-walled Tube Sampling of Soils for Geotechnical Purposes, American Society for Testing and Materials, ASTM International, West Conshohocken, PA , United States. ASTM D , Standard Test Method for High Strain Testing of Piles. Bowles, E.J. (1997). Foundation analysis and design, 5th Edition, The Mcgraw Hill Inc. Brinch Hansen, J. (1963). Discussion, Hyperbolic stress-strain response. Cohesive soils, Journal of Soil Mechanics and Foundations Division, ASCE, 89(SM4), BSI, (1986). British Standard Code of Practice for Foundations (BS 8004: 1986). British Standards Institution, London, 149 p. Burland, J.B. (1973). Shaft Friction of Piles in Clay- A Simple Fundamental Approach. Ground Eng., vol.6 no.3, May: Butler, H.D. and Hoy, H.E. (1977). The Texas Quick Load Method for Foundation Load Testing User s Manual, FHWA-IP-77-8, FHWA, Wash.,D.C, 53pp. 63

77 Chellis R.D. (1961). Pile Foundations. Second Edition, McGraw-Hill Book Company, New York, Coyle, H. M. & Reese, L.C.(1966). Load Transfer for Axially Loaded Piles in Clay. J.S.M.F.D., ASCE, vol. 92, SM2:1-26. Davisson, M.T. (1972). High Capacity Piles, Proceedings, Soil Mechanics Lecture Series on Innovations in Foundation Construction. American Society of Civil Engineers, ASCE, Illinois Section, Chicago, Engeling, D. and Reese, L.C. (1974). Behaviour of Three Instrumented Drilled Shafts Under Short Term Axial Loading, Research Report No 176-3, Project , conducted for the Texas Highway Department, in cooperation with the U.S. Department of Transportation, Federal Highway Administration, Center for Highway Research, The University of Texas at Austin, 116 pages. Forehand, P. W. & Reese, J.L. (1964). Prediction of Pile Capacity by the Wave Equation. J.S.M.F.D., ASCE, vol. 90, SM2:1-25. Fuller, F.M. (1983). Engineering of Pile Installations, McGraw-Hill, New York, 286. Gates, M. (1957). Empirical Formula for Predicting Pile Bearing Capacity, Civil Engineering, ASCE, vol. 27, no. 3, March, pp Glanville, W. H., Grime, G., Fox, E.N, & Davies, W.W. (1938). An Investigation of the Stresses in Reinforced Concrete Piles during Driving. Br. Bldg. Res. Bd., tech. paper no. 20, D.S.I.R. Hoque, Siddiquee, M.S.A., and Ameen, S.F. (1999). Improvements in Instrumentation of Static Pile Load Test, Journal of Civil Engineering, The Institution of Engineers, Bangladesh Vol. CE 27, No.1, Housing and Building Research Institute (HBRI) & Bangladesh Standards and Testing Institution (BSTl), (2015). Draft final of Bangladesh National Building Code (BNBC), Dhaka, Bangladesh IS-2911, (1985). Code of Practice for Design and Construction of Pile Foundations- Load Test on Piles, Bureau of Indian Standards, New Delhi. Isaacs, D.V. (1931). Reinforced Concrete Pile Formulae. Trans. Instn. Engrs. Aust., 12:

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80 APPENDIX A PILE DRIVING RECORDS OF TP-1 AND TP-2 67

81 PILE DRIVING RECORD OF TP-1 Name of the project: Bangabondhu Textile Engineering College Tangail, (Boys hostel) Location of the project: Kalihati Tangail Pile length: 45ft (13.71m) Pile section: 12 X12 (300 mm X300mm) Weight of hammer: 3.5 Ton Hammer Type: Drop hammer Table B1: Pile driving data of TP-1 Pile id no Depth driven (ft) Height of fall (ft) Number of blows Remarks TP Pile penetrated due to selfweight only.

82 Pile id no Depth driven (ft) Height of fall (ft) Number of blows Remarks

83 PILE DRIVING RECORD OF TP-2 Name of the project: Bangabondhu Textile Engineering College Tangail, (Boys hostel) Location of the project: Kalihati Tangail Pile length: 45ft (13.71m) Pile section: 12 X12 (300 mm X300mm) Weight of hammer: 3.5 Ton Hammer Type: Drop hammer Table B2: Pile driving data of TP-2 Pile id no Depth driven (ft) Height of fall (ft) Number of blows Remarks TP Pile penetrated due to selfweight only.

84 Pile id no Depth driven (ft) Height of fall (ft) Number of blows Remarks TP

85 APPENDIX B CAPACITY CALCULATION OF TWO TEST PILES USING DRIVING EQUATIONS 72

86 1.A) ENGINEERING NEWS FORMULA (TP-1) Weight of ram, Wh = 3.5 Ton Number of blows for last one feet of penetration = 40 Nos Penetration of pile under last blow of hammer, s = 0.30 in Height of fall of ram, H = 5 ft Resistance under working load, R = Wh.H/(s+1) = Ton = 134 kn FS=6 Ultimate capacity = 804 kn 1.B) ENGINEERING NEWS FORMULA (TP-2) Weight of ram, Wh = 3.5 Ton Number of blows for last one feet of penetration = 37 Nos Penetration of pile under last blow of hammer, s = 0.32 in Height of fall of ram, H = 5 ft Resistance under working load, R = Wh.H/(s+1) = Ton = 132 kn Ultimate capacity = 792 kn 2.A) JANBU FORMULA (TP-1) Pile area, A = 144 sqin Length of pile, L = 45 ft Weight of pile, Wp = 6.75 kip Compressive strength of concrete, f'c = 3500 psi Modulus of elasticity of concrete, Ec = = psi = 3402 Ksi AE = Kip cd = (Wp/Wr) = 0.75 FS=6 73

87 For drop hammer, eh = 0.75 Weight of hammer = 7.00 kip Height of fall = 5.00 ft Eh = ft-lb s = 0.30 λ = ehehl/aes2 = 3.86 ku = Cd(1+ (1+(λ/Cd)) = 2.61 Pu = eheh/kus = Kip = kn Fs = B) JANBU FORMULA (TP-2) Pile area, A = 144 sqin Length of pile, L = 45 ft Weight of pile, Wp = 6.75 kip Compressive strength of concrete, f'c = 3500 psi Modulus of elasticity of concrete,ec = = psi = 3402 Ksi AE = Kip cd = (Wp/Wr) = 0.75 For drop hammer, eh = 0.75 Weight of hammer = 7.00 kip Height of fall = 5.00 ft Eh = ft-lb s = 0.32 λ = ehehl/aes2 = 3.30 ku = Cd(1+ (1+(λ/Cd)) 74

88 = 2.49 Pu = eheh/kus = Kip = kn Fs = A) GATES FORMULA (TP-1) Pu = a (eheh(b-logs) s a b FPS in 27 1 Hammer wt = 7 kip Drop of hammer = 5 ft Eh = 35 kip-ft eh = 0.75 s = 0.30 in/blow SF = 3 Pu = Kip = kn 3.B) GATES FORMULA (TP-2) Pu = a (eheh(b-logs) s a b FPS in 27 1 Hammer wt = 7 kip Drop of hammer = 5 ft Eh = 35 kip-ft eh = 0.75 s = 0.32 in/blow SF = 3 Pu = Kip = kn 75

89 APPENDIX C CAPACITY CALCULATION OF PRECAST PILES (BNBC 2015 STATIC FORMULA AND SPT METHOD) 76

90 SL No : 1 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Pabna Pile ID : P-26(H -07) Pile sec : 0.3mX0.3m Length : 21.34m Soil Profile and properties Soil Depth (m) SPT ϕ sil Clay silt Clay silt Clay silt Avg Angle of internal friction ϕ = 29 Friction factor β= 0.10 Confirm from chart Unit wt of soil γ= kn/m 3 Bore Hole Data of BH-5 Unit skin friction f = kpa (Equation 2.8) Skin friction Q = 400 kn (Equation 2.2) Bearing capacity factor N = 28 (L/d=71) Effective vertical stress σ = kpa= kpa Unit end bearing f = 4886 kn/m 2 (Equation 2.11) End bearing Q = 468 kn (Equation 2.3) Weight of pile W= 46 kn Total ultimate capacity Q ult = 857 kn (Equation 2.1) 77

91 SL No : 2 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Pabna Pile ID : P-04(G -07) Pile sec : 0.3mX0.3m Length : 22.5m Soil Profile and properties Bore Hole Data of BH-6 Soil Depth (m) SPT φ ML Cu (kpa) CL ML CL SM α Angle of friction ϕ = 29 (Avg) Friction factor β= 0.11 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = 17.45kPa(1-4.5m), 36.39kPa(6-2m),3.71kPa(12-5m),67.03kPa( m) (Equation 2.8) and f s=α c u Skin friction Q = 833 kn (Equation 2.2) Bearing capacity N = 65 (L/d=75) Effective stress σ = kpa=168 kpa Unit end bearing f = kn/m 2 (Equation 2.11) End bearing Q = 986 kn (Equation 2.3) Weight of pile W= 49 kn Total ultimate capacity Q ult = 1770 kn (Equation 2.1) 78

92 SL No : 3 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Manikgonj Pile ID : PC-4 P-4 Pile sec : 0.3mX0.3m Length : 13.72m Soil Profile and properties Bore Hole Data of BH-1 Soil Depth (m) SPT ϕ Silt SM Avg Angle of internal friction ϕ = 26 Friction factor β= 0.11 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = kpa (Equation 2.8) Skin friction Q = 178 kn (Equation 2.2) Bearing capacity factor N = 47 (L/d=46) Effective vertical stress σ = kpa=117 kpa Unit end bearing f = 5519 kn/m 2 (Equation 2.11) End bearing Q = 497 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q ult = 645 kn (Equation 2.1) 79

93 SL No : 4 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Manikgonj Pile ID : PC-8B P-134 Pile sec : 0.3mX0.3m Length : 13.72m Soil Profile and properties Bore Hole Data of BH-2 Soil Depth (m) SPT ϕ Silt Sand Avg Angle of internal friction ϕ = 26 Friction factor β= 0.11 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = kpa (Equation 2.8) Skin friction Q = 178 kn (Equation 2.2) Bearing capacity factor N = 45 (L/d=46) Effective vertical stress σ = kpa=117 kpa Unit end bearing f = 5285 kn/m 2 (Equation 2.11) End bearing Q = 497 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q ult = 624 kn (Equation 2.1) 80

94 SL No : 5 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Manikgonj Pile ID : PC-5 P-67 Pile sec : 0.3mX0.3m Length : 13.72m Soil Profile and properties Soil Depth (m) SPT φ Bore Hole Data of BH ML SM Avg Angle of internal friction ϕ = 25 Friction factor β= 0.11 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = kpa (1-6m),11.74 Kpa (Equation 2.8) Skin friction Q = 233 kn (Equation 2.2) Bearing capacity factor N = 48 (L/d=46) Effective vertical stress σ = kpa=117 kpa Unit end bearing f = 5637 kn/m 2 (Equation 2.11) End bearing Q = 507 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q ult = 710 kn (Equation 2.1) 81

95 SL No : 6 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Manikgonj Pile ID : PC-4 P-218 Pile sec : 0.3mX0.3m Length : 13.72m Soil Profile and properties Soil Depth (m) SP T φ Bore Hole Data of BH Silt (MH) Sand (SM) Avg Angle of internal friction ϕ = 26 Friction factor β= 0.11 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = Kpa (Equation 2.8) Skin friction Q = 178 kn (Equation 2.2) Bearing capacity factor N = 43 (L/d=46) Effective vertical stress σ = kpa=117 kpa Unit end bearing f = 5050 kn/m 2 (Equation 2.11) End bearing Q = 454 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q ult = 603 kn (Equation 2.1) 82

96 SL No : 7 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Shariat Pile ID : TP -02 Pile sec : 0.35mX0.35m Length : 16.16m Soil Profile and properties Bore Hole Data of BH-1 Soil Depth (m) SPT φ ML SM Avg Angle of internal friction ϕ = 29 Friction factor β= 0.11 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = Kpa (Equation 2.8) Skin friction Q = 283 kn (Equation 2.2) Bearing capacity factor N = 36 (L/d=46) Effective vertical stress σ = kpa=136 kpa Unit end bearing f = 4885 kn/m 2 (Equation 2.11) End bearing Q = 598 kn (Equation 2.3) Weight of pile W= 48 kn Total ultimate capacity Q ult = 834 kn (Equation 2.1) 83

97 SL No : 8 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Shariat Pile ID : TP -4 Pile sec : 0.35mX0.35m Length : 16.16m Soil Profile and properties Soil Depth (m) SPT φ Bore Hole Data of BH ML SM Avg Angle of internal friction ϕ = 29 Friction factor β= 0.11 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = Kpa (Equation 2.8) Skin friction Q = 283 kn (Equation 2.2) Bearing capacity factor N = 38 (L/d=46) Effective vertical stress σ = kpa=136 kpa Unit end bearing f = 5157 kn/m 2 (Equation 2.11) End bearing Q = 632 kn (Equation 2.3) Weight of pile W= 48 kn Total ultimate capacity Q ult = 867 kn (Equation 2.1) 84

98 SL No : 9 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Tangail Pile ID : P -24 Pile sec : 0.35mX0.35m Length : 16.16m Soil Profile and properties Soil Depth (m) SP T φ Bore Hole Data of BH Silt (ML) Sand (SM) Avg Angle of internal friction ϕ = 30 Friction factor β= 0.11 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = Kpa (Equation 2.8) Skin friction Q = 161 kn (Equation 2.2) Bearing capacity factor N = 90 Effective vertical stress σ = kpa=117 kpa Unit end bearing f = kn/m 2 (Equation 2.11) End bearing Q = 951 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q = 1083 kn (Equation 2.1) 85

99 SL No : 10 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Tangail Pile ID : P -141 Pile sec : 0.3mX0.3m Length : 13.7m Soil Profile and properties Soil Depth (m) SPT φ Bore Hole Data of BH-6 Silt (MH) Sand (SM) Avg Angle of internal friction ϕ = 29 Friction factor β= 0.1 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = Kpa (Equation 2.8) Skin friction Q = 161 kn (Equation 2.2) Bearing capacity factor N = 49 L/d=46 Effective vertical stress σ = kpa=117 kpa Unit end bearing f = 5747 kn/m 2 (Equation 2.11) End bearing Q = 517 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q ult = 649 kn (Equation 2.1) 86

100 SL No : 11 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Keranigonj Pile ID : TP -2 Pile sec : 0.3mX0.3m Length : 12m Soil Profile and properties Soil Depth (m) SPT φ Bore Hole Data of BH Silt Sand Avg Angle of internal friction ϕ = 30 Friction factor β= 0.1 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = Kpa (Equation 2.8) Skin friction Q = 161 kn (Equation 2.2) Bearing capacity factor N = 50 L/d=46 Effective vertical stress σ = kpa=117 kpa Unit end bearing f = 5864 kn/m 2 (Equation 2.11) End bearing Q = 528 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q ult = 659 kn (Equation 2.1) 87

101 SL No : 12 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Coxs Bazar Pile ID : TP -02 Pile sec : 0.3mX0.3m Length : 12m Soil Profile and properties Soil Depth (m) SPT φ Bore Hole Data of BH Sand Avg Angle of internal friction ϕ = 31 Friction factor β= 0.1 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = Kpa (Equation 2.8) Skin friction Q = 122 kn (Equation 2.2) Bearing capacity factor N = 126 L/d=40 Effective vertical stress σ = kpa=104 kpa Unit end bearing f = kn/m 2 (Equation 2.11) End bearing Q = 1186 kn (Equation 2.3) Weight of pile W= 26 kn Total ultimate capacity Q ult = 1282 kn (Equation 2.1) 88

102 SL No : 13 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Coxs Bazar Pile ID : TP -03 Pile sec : 0.3mX0.3m Length : 12m Soil Profile and properties Soil Depth (m) SPT φ Bore Hole Data of BH silt Sand Avg Angle of internal friction ϕ = 26 Friction factor β= 0.1 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = Kpa (Equation 2.8) Skin friction Q = 156 kn (Equation 2.2) Bearing capacity factor N = 90 L/d=45 Effective vertical stress σ = kpa=116 kpa Unit end bearing f = kn/m 2 (Equation 2.11) End bearing Q = 938 kn (Equation 2.3) Weight of pile W= 29 kn Total ultimate capacity Q = 1065 kn (Equation 2.1) 89

103 SL No : 14 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Coxs Bazar Pile ID : TP -05 Pile sec : 0.3mX0.3m Length : 12m Soil Profile and properties Soil Depth (m) SP T φ Bore Hole Data of BH-1 silt Sand Avg Angle of internal friction ϕ = 32 Friction factor β= 0.1 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = 3.37 Kpa (Equation 2.8) Skin friction Q = 45 kn (Equation 2.2) Bearing capacity factor N = 140 L/d=45 Effective vertical stress σ = kpa=116 kpa Unit end bearing f = kn/m 2 (Equation 2.11) End bearing Q = 1459 kn (Equation 2.3) Weight of pile W= 29 kn Total ultimate capacity Q ult = 1475 kn (Equation 2.1) 90

104 SL No : 15 (Precast pile) Method : BNBC-2015 Static formula (α and β method) Site : Borguna Pile ID : P-106 Pile sec : 0.35mX0.35m Length : 16.7 : 16.7m Soil Profile and properties Soil Depth (m) Sand SPT φ Bore Hole Data of BH-1 Avg Angle of internal friction ϕ = 26 Friction factor β= 0.1 Confirm from chart Unit wt of soil γ= kn/m 3 Unit skin friction f = 3.93 Kpa (Equation 2.8) Skin friction Q = 77 kn (Equation 2.2) Bearing capacity factor N = 65 L/d=45 Effective vertical stress σ = kpa=140 kpa Unit end bearing f = 9084 kn/m 2 (Equation 2.11) End bearing Q = 1113 kn (Equation 2.3) Weight of pile W= 49 kn Total ultimate capacity Q ult = 1141 kn (Equation 2.1) 91

105 SL No : 1 (Precast pile) Method : BNBC-2015 SPT Based Site : Pabna Pile ID : P-26(H -07) Pile sec : 0.3mX0.3m Length : 21.34m Soil Profile and properties Soil Depth (m) SPT silt Clay silt Clay silt Clay silt Bore Hole Data of BH-5 Average N-value N = 10 N-value at pile tip N = 13 Unit skin friction f = 17 kpa 60 kpa (Equation 2.15) Unit end bearing f = kpa 5200 kpa kpa (Equation 2.17) = 5200 kpa Skin friction Q = 435 kn (Equation 2.2) End bearing Q = 468 kn (Equation 2.3) Weight of pile W= 46 kn Total ultimate capacity Q ult = 857 kn (Equation 2.1) 92

106 SL No : 2 (Precast pile) Method : BNBC-2015 SPT Based Site : Pabna Pile ID : P-04(G -07) Pile sec : 0.3mX0.3m Length : 22.5m Soil Profile and properties Soil Depth (m) SPT N silt Clay silt Clay Sand Bore Hole Data of BH-6 Average N-value N = As per table N-value at pile tip N = 25 Unit skin friction f = 5. kpa (0-4.5m);13.68 kpa (4.5m-12m),31.45 kpa ( m),25.2 kpa ( m),37.40 kpa (21m-End) (Equation 2.15&2.12) Unit end bearing f = = kpa kpa kpa kpa (Equation 2.17) Skin friction Q = 535kN (Equation 2.2) End bearing Q = 900 kn (Equation 2.3) Weight of pile W= 49 kn Total capacity Q ult = 1386 kn (Equation 2.1) 93

107 SL No : 3 (Precast pile) Method : BNBC-2015 SPT Based Site : Manikgonj Pile ID : PC-4 P-4 Pile sec : 0.3mX0.3m Length : 13.72m Soil Profile and properties Bore Hole Data of BH-1 Soil Depth (m) SPT N 60 Silt Sand Average N-value N = As per table N-value at pile tip N = 17 Unit skin friction f = 3.6 kpa (1-7.5m);30 kpa (9m- 13.5m) (Equation 2.12 & 2.14) Unit end bearing f = = kpa 6800 kpa kpa 6800 kpa (Equation 2.17) Skin friction Q = 194 kn (Equation 2.2) End bearing Q = 612 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q ult = 777 kn (Equation 2.1) 94

108 SL No : 4 (Precast pile) Method : BNBC-2015 SPT Based Site : Manikgonj Pile ID : PC-8B P-134 Pile sec : 0.3mX0.3m Length : 13.72m Soil Profile and properties Bore Hole Data of BH-2 Soil Depth (m) SPT N Silt Sand Average N-value N = As per table N-value at pile tip N = 17 Unit skin friction f = 4.08 kpa (silt);25.50 kpa (sand) (Equation 2.15 & 2.14) Unit end bearing f = = kpa 6800 kpa kpa 6800 kpa (Equation 2.16) Skin friction Q = 220 kn (Equation 2.2) End bearing Q = 612 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q ult = 803 kn (Equation 2.1) 95

109 SL No : 5 (Precast pile) Method : BNBC-2015 SPT Based Site : Manikgonj Pile ID : PC-5 P-67 Pile sec : 0.3mX0.3m Length : 13.72m Soil Profile and properties Bore Hole Data of BH-2 Soil Depth (m) SPT N Silt Sand Average N-value N = As per table N-value at pile tip N = 18 Unit skin friction f = 2.98 kpa (silt);21.60 kpa (sand) (Equation 2.15 & 2.14) Unit end bearing f = = kpa 7200 kpa kpa 7200 kpa (Equation 2.16) Skin friction Q = 222 kn (Equation 2.2) End bearing Q = 648 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q ult = 840 kn (Equation 2.1) 96

110 SL No : 6 (Precast pile) Method : BNBC-2015 SPT Based Site : Manikgonj Pile ID : PC-4 P-218 Pile sec : 0.3mX0.3m Length : 13.72m Soil Profile and properties Bore Hole Data of BH-4 Soil Depth (m) SPT N Silt Sand Average N-value N = As per table N-value at pile tip N = 17 Unit skin friction f = 5.10 kpa (silt);25.50 kpa (sand) (Equation 2.15 & 2.14) Unit end bearing f = = kpa 6800 kpa kpa 6800 kpa (Equation 2.16) Skin friction Q = 229 kn (Equation 2.2) End bearing Q = 612 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q ult = 812 kn (Equation 2.1) 97

111 SL No : 7 (Precast pile) Method : BNBC-2015 SPT Based Site : Shariat Pile ID : TP -02 Pile sec : 0.35mX0.35m Length : 16.16m Soil Profile and properties Bore Hole Data of BH-1 Soil Depth (m) SPT N Silt Silty Sand Average N-value N = As per table N-value at pile tip N = 14 Unit skin friction f = kpa (silt);29.67 kpa (sand) (Equation 2.15 & 2.14) Unit end bearing f = = kpa 4200 kpa kpa 4200 kpa (Equation 2.16) Skin friction Q = 470 kn (Equation 2.2) End bearing Q = 515 kn (Equation 2.3) Weight of pile W= 48 kn Total ultimate capacity Q ult = 937 kn (Equation 2.1) 98

112 SL No : 8 (Precast pile) Method : BNBC-2015 SPT Based Site : Shariat Pile ID : TP -4 Pile sec : 0.35mX0.35m Length : 16.16m Soil Profile and properties Bore Hole Data of BH-2 Soil Depth (m) SPT N ML SM Average N-value N = As per table N-value at pile tip N = 15 Unit skin friction f = 8.84 kpa (silt);33.33 kpa (sand) (Equation 2.15 & 2.14) Unit end bearing f = = kpa 4500 kpa kpa 4500 kpa (Equation 2.16) Skin friction Q = 404 kn (Equation 2.2) End bearing Q = 551 kn (Equation 2.3) Weight of pile W= 48 kn Total ultimate capacity Q ult = 907 kn (Equation 2.1) 99

113 SL No : 9 (Precast pile) Method : BNBC-2015 SPT Based Site : Tangail Pile ID : P -24 Pile sec : 0.35mX0.35m Length : 16.16m Soil Profile and properties Bore Hole Data of BH-1 Soil Depth (m) SPT N Silt Sand Average N-value N = As per table N-value at pile tip N = 25 Unit skin friction f = kpa (Equation 2.15) Unit end bearing f = = kpa kpa kpa kpa (Equation 2.16) Skin friction Q = 353 kn (Equation 2.2) End bearing Q = 900 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q ult = 1224 kn (Equation 2.1) 100

114 SL No : 10 (Precast pile) Method : BNBC-2015 SPT Based Site : Tangail Pile ID : P -141 Pile sec : 0.3mX0.3m Length : 13.7m Soil Profile and properties Bore Hole Data of BH-6 Soil Depth (m) SPT N Silt Sand Average N-value N = As per table N-value at pile tip N = 13 Unit skin friction f = kpa (silt), kpa(sand) (Equation 2.15 & 2.14) Unit end bearing f = = kpa 5200 kpa kpa 5200 kpa (Equation 2.16) Skin friction Q = 336 kn (Equation 2.2) End bearing Q = 468 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q ult = 774 kn (Equation 2.1) 101

115 SL No : 11 (Precast pile) Method : BNBC-2015 SPT Based Site : Keranigonj Pile ID : TP -2 Pile sec : 0.3mX0.3m Length : 12m Soil Profile and properties Bore Hole Data of BH-2 Soil Depth (m) SPT N Silt Sand Average N-value N = As per table N-value at pile tip N = 20 Unit skin friction f = kpa (silt), kpa(sand) (Equation 2.15 & 2.14) Unit end bearing f = = kpa 8000 kpa kpa 8000 kpa (Equation 2.16) Skin friction Q = 344 kn (Equation 2.2) End bearing Q = 720 kn (Equation 2.3) Weight of pile W= 30 kn Total ultimate capacity Q ult = 1034 kn (Equation 2.1) 102

116 SL No : 12 (Precast pile) Method : BNBC-2015 SPT Based Site : Coxs Bazar Pile ID : TP -02 Pile sec : 0.3mX0.3m Length : 12m Soil Profile and properties Bore Hole Data of BH-2 Soil Depth (m) SPT N Sand Average N-value N = As per table N-value at pile tip N = 26 Unit skin friction f = kpa(sand) (Equation 2.14) Unit end bearing f = = kpa kpa kpa kpa (Equation 2.16) Skin friction Q = 400 kn (Equation 2.2) End bearing Q = 936 kn (Equation 2.3) Weight of pile W= 26 kn Total ultimate capacity Q ult = 1310 kn (Equation 2.1) 103

117 SL No : 13 (Precast pile) Method : BNBC-2015 SPT Based Site : Coxs Bazar Pile ID : TP -03 Pile sec : 0.3mX0.3m Length : 12m Soil Profile and properties Bore Hole Data of BH-34 Soil Depth (m) SPT N Silt Sand Average N-value N = As per table N-value at pile tip N = 24 Unit skin friction f = 5.10kPa (silt),22.40 kpa(sand) (Equation 2.14 & 2.15) Unit end bearing f = = kpa 9600 kpa kpa 9600 kpa (Equation 2.16) Skin friction Q = 198 kn (Equation 2.2) End bearing Q = 864 kn (Equation 2.3) Weight of pile W= 26 kn Total ultimate capacity Q ult = 1036 kn (Equation 2.1) 104

118 SL No : 14 (Precast pile) Method : BNBC-2015 SPT Based Site : Coxs Bazar Pile ID : TP -05 Pile sec : 0.3mX0.3m Length : 12m Soil Profile and properties Bore Hole Data of BH-1 Soil Depth (m) SPT N silt Sand Average N-value N = As per table N-value at pile tip N = 32 Unit skin friction f = 8.93kPa (silt),48.40 kpa(sand) (Equation 2.14 & 2.15) Unit end bearing f = = kpa kpa kpa kpa (Equation 2.16) Skin friction Q = 503 kn (Equation 2.2) End bearing Q = 990 kn (Equation 2.3) Weight of pile W= 29 kn Total ultimate capacity Q ult = 1464 kn (Equation 2.1) 105

119 SL No : 15 (Precast pile) Method : BNBC-2015 SPT Based Site : Borguna Pile ID : P-106 Pile sec : 0.35mX0.35m Length : 16.7m Soil Profile and properties Bore Hole Data of BH-1 Soil Depth (m) SPT N Silty Sand Average N-value N = As per table N-value at pile tip N = 17 Unit skin friction f = kpa(sand) (Equation 2.15) Unit end bearing f = = kpa 6800 kpa kpa 6800 kpa (Equation 2.16) Skin friction Q = 307 kn (Equation 2.2) End bearing Q = 833 kn (Equation 2.3) Weight of pile W= 49 kn Total ultimate capacity Q ult = 1091 kn (Equation 2.1) 106

120 APPENDIX D CAPACITY CALCULATION OF BORED PILES (BNBC 2015 AND AASHTO 2002 METHOD) 107

121 SL No : 1 (Bored pile) Method : BNBC-2015 SPT Based Site : Walton Office, Basundhara, Dhaka Pile ID : TP-01 Pile diameter : 0.5m Length : 28.5m Soil Profile and properties Soil Depth (m) SPT N Clay Sand Bore Hole Data of BH-2 Unit skin friction f = kpa(clay), kpa (Sand) (Equation 2.24 & 2.26) Skin friction Q = 767 kn (Equation 2.2) Unit end bearing f = = kpa 3750 kpa 4000 kpa 3750 kpa (Equation 2.28) End bearing Q = 736 kn (Equation 2.3) Weight of pile W= 134 kn Total capacity Q ult = 1503 kn (Equation 2.1) 108

122 SL No : 2 (Bored pile) Method : BNBC-2015 SPT Based Site : Titas Railway Bridge, Akhaura Pile ID : Pile No-19 Pile diameter : 1.2 m Length : 30.8m Soil Profile and properties Soil Depth (m) SPT N Silt Clay Silt Bore Hole Data of BH-2 Unit skin friction f = 0.9 kpa(sand), 2.40 kpa (Clay),16.08 kpa (Silt) (Equation 2.26,2.24 & 2.27) Skin friction Q = 1463 kn (Equation 2.2) Unit end bearing f = = 6673 kpa 3900 kpa 4000 kpa 3900 kpa (Equation 2.27) End bearing Q = 4409 kn (Equation 2.3) Weight of pile W= 836 kn Total capacity Q ult = 5036 kn (Equation 2.1) 109

123 SL No : 3 (Bored pile) Method : BNBC-2015 SPT Based Site : Padma Bridge, Naodoba, Zazira Pile ID : Bridge 01 Abutment 02 Pile diameter : 1.2 m Length : 29.5m Soil Profile and properties Bore Hole Data of BH-8 Soil Depth (m) SPT N Silty Sand Unit skin friction f = kpa (Equation 2.27) Skin friction Q = 1228 kn (Equation 2.2) Unit end bearing f = = 5900 kpa 2400 kpa 4000 kpa 2400 kpa (Equation 2.29) End bearing Q = 2713 kn (Equation 2.3) Weight of pile W= 800 kn Total capacity Q ult = 3141 kn (Equation 2.1) 110

124 SL No : 4 (Bored pile) Method : BNBC-2015 SPT Based Site : Mogbazar Fly over, Dhaka Pile ID : TP-2 Pile diameter : 1.2 m Length : 29.5m Soil Profile and properties Bore Hole Data of BH-43 Soil Depth (m) SP T 2 15 N 60 Clay Sand Unit skin friction f = kpa (Clay), kpa(silt) (Equation 2.24& 2.27) Skin friction Q = 3730 kn (Equation 2.2) Unit end bearing f = = 8112 kpa 3300 kpa 4000 kpa 3300 kpa (Equation 2.28) End bearing Q = 3730 kn (Equation 2.3) Weight of pile W= 800 kn Total capacity Q ult = 4911 kn (Equation 2.1) 111

125 SL No : 5 (Bored pile) Method : BNBC-2015 SPT Based Site : Mogbazar Fly over, Dhaka Pile ID : P-114 Pile diameter : 1.5 m Length : 44m Soil Soil Profile and properties Depth (m) SPT 2 15 N 60 Clay Sand Bore Hole Data of BH-43 Unit skin friction f = kpa (Clay), kpa(silt) (Equation 2.24& 2.27) Skin friction Q = 3985 kn (Equation 2.2) Unit end bearing f = = kpa 4050 kpa 4000 kpa 4000 kpa (Equation 2.28) End bearing Q = 7065 kn (Equation 2.3) Weight of pile W= 1865 kn Total capacity Q ult = 9185 kn (Equation 2.1) 112

126 SL No : 6 (Bored pile) Method : BNBC-2015 SPT Based Site : Mogbazar Fly over, Dhaka Pile ID : P-180 Pile diameter : 1.2 m Length : 44m Soil Soil Profile and properties Depth (m) SPT 2 15 N 60 Clay Sand Bore Hole Data of BH-43 Unit skin friction f = kpa (Clay), kpa(silt) (Equation 2.24& 2.27) Skin friction Q = 3188 kn (Equation 2.2) Unit end bearing f = = kpa 4050 kpa 4000 kpa 4000 kpa (Equation 2.28) End bearing Q = 4522 kn (Equation 2.3) Weight of pile W= 1194 kn Total capacity Q ult = 6516 kn (Equation 2.1) 113

127 SL No Method Site Pile ID Pile diameter Length : 7 (Bored pile) : BNBC-2015 SPT Based : Dhaka Road Research Lab : P1 : 1.2 m : 44m Soil Soil Profile and properties Depth (m) SPT N Clay Sand Bore Hole Data of BH-1 Unit skin friction f = kpa (Clay), kpa(silt) (Equation 2.24& 2.27) Skin friction Q = 3188 kn (Equation 2.2) Unit end bearing f = = 4725 kpa 2100 kpa 4000 kpa 2100 kpa (Equation 2.28) End bearing Q = 1648 kn (Equation 2.3) Weight of pile W= 424 kn Total capacity Q ult = 2280 kn (Equation 2.1) 114

128 SL No : 8 (Bored pile) Method : BNBC-2015 SPT Based Site : Dhaka Road Research Lab Pile ID : P2 Pile diameter : 1.2 m Length : 44m Soil Profile and properties Soil Depth (m) SPT N Clay Sand Bore Hole Data of BH-1 Unit skin friction f = kpa (Clay), kpa(silt) (Equation 2.24& 2.27) Skin friction Q = 1453 kn (Equation 2.2) Unit end bearing f = = kpa 3900 kpa 4000 kpa 3900 kpa (Equation 2.28) End bearing Q = 3062 kn (Equation 2.3) Weight of pile W= 528 kn Total capacity Q ult = 3987 kn (Equation 2.1) 115

129 SL No : 9 (Bored pile) Method : BNBC-2015 SPT Based Site : Zinzira-Nawabganj (Bridge LRP) Pile ID : P3 Pile diameter : 1 m Length : 23.7m Soil Profile and properties Soil Depth (m) SPT Clay Sand N Bore Hole Data of BH-1 Unit skin friction f = 7.40 kpa (Clay), kpa(silt) (Equation 2.24& 2.27) Skin friction Q = 1311 kn (Equation 2.2) Unit end bearing f = = 9599 kpa 4050 kpa 4000 kpa 4000 kpa (Equation 2.28) End bearing Q = 3140 kn (Equation 2.3) Weight of pile W= 446 kn Total capacity Q ult = 4005 kn (Equation 2.1) 116

130 SL No : 10 (Bored pile) Method : BNBC-2015 SPT Based Site : Zinzira-Nawabganj (Bridge LRP) Pile ID : P4 Pile diameter : 1 m Length : 23.7m Soil Profile and properties Soil Depth (m) SPT Clay Sand N 60 Bore Hole Data of BH-43 Unit skin friction f = 7.20 kpa (Clay), kpa(silt) (Equation 2.24& 2.27) Skin friction Q = 1369 kn (Equation 2.2) Unit end bearing f = = 8100 kpa 4050 kpa 4000 kpa 4000 kpa (Equation 2.28) End bearing Q = 4522 kn (Equation 2.3) Weight of pile W= 651 kn Total capacity Q ult = 5239 kn (Equation 2.1) 117

131 SL No : 1 (Bored pile) Method : α and β method (BNBC-2015) Site : Walton Office, Basundhara, Dhaka Pile ID : TP-01 Pile diameter : 0.5m Length : 28.5m Bore Hole Data of BH-2 Soil Profile and properties Soil Depth z SPT γ Su(kpa) (m) (m) Clay Sand Adhesion factor α= 0.55 (Table 2.2) Effective vertical stress σ = kpa ( mid soil layer) Friction factor for overburden β = 0.35 (Equation 2.23) Skin friction f = 1.00 kpa (Clay), kpa (Sand-1), (Sand-2) Total skin friction Q = 1275 kn (Equation 2.2) Unit end bearing f = kpa (Table 2.3) Tip resistance Q = 294 kn [Q = q b X Area of pile] Weight of pile W= 134 kn Total capacity Q = 1435 kn (Equation 2.1) 118

132 SL No : 2 (Bored pile) Method : α and β method (BNBC-2015) Site : Titas Railway Bridge, Akhaura Pile ID : Pile No-19 Pile diameter : 1.2 m Length : 30.8m Soil Profile and properties Soil Depth Su z SPT γ (m) kpa (m) Silt Clay Silt Bore Hole Data of BH-2 Adhesion factor α= 0.55 (Table 2.2) Effective vertical stress σ = kpa ( mid soil layer) Friction factor for overburden β= 1.20 (1-3m),0.41 (9-30.8m) (Equation 2.23) Skin friction f = kpa (1-3m), kpa(3-7.5m),55.48 kpa ( m) Total skin friction Q = 5020 kn (Equation 2.2) Unit end bearing f = 1620 kpa (Table 2.3) Tip resistance Q = 1831 kn [Q = q b X Area of pile] Weight of pile W= 835 kn Total capacity Q = 6016 kn (Equation 2.1) 119

133 SL No : 3 (Bored pile) Method : α and β method (BNBC-2015) Site : Padma Bridge, Naodoba, Zazira Pile ID : Bridge 01 Abutment 02 Pile diameter : 1.2 m Length : 29.5m Soil Profile and properties Soil Depth (m) SPT γ z (m) Silty 12 9 Sand Bore Hole Data of BH-8 Adhesion factor α= 0.55 (Table 2.2) Effective vertical stress σ = kpa ( mid soil layer) Friction factor for overburden β= 0.59 (Equation 2.23) Skin friction f = kpa Total skin friction Q = 3464 kn (Equation 2.2) Unit end bearing f = 1440 kpa (Table 2.3) Tip resistance Q = 1628 kn [Q = q b X Area of pile] Weight of pile W= 800 kn Total capacity Q ult = 4291 kn (Equation 2.1) 120

134 SL No : 4 (Bored pile) Method : α and β method (BNBC-2015) Site : Mogbazar Fly over, Dhaka Pile ID : TP-2 Pile diameter : 1.2 m Length : 29.5m Soil Profile and properties Bore Hole Data of BH-43 Soil Depth (m) SPT 2 15 γ Su kpa z (m) Clay Sand Adhesion factor α= 0.38 (Table 2.2) Effective vertical σ = kpa ( mid soil layer) stress Friction factor for β= 0.40 (Equation 2.23) overburden Skin friction f = kpa (Clay), (Sand) Total skin friction Q = 3512 kn (Equation 2.2) Unit end bearing f = 1320 kpa (Table 2.3) Tip resistance Q = 1492 kn [Q = q b X Area of pile] Weight of pile W= 800 kn Total capacity Q ult = 4204 kn (Equation 2.1) 121

135 SL No : 5 (Bored pile) Method : α and β method (BNBC-2015) Site : Mogbazar Fly over, Dhaka Pile ID : P-114 Pile diameter : 1.5 m Length : 44m Soil Soil Profile and properties Depth (m) SPT 2 15 γ Su (kpa) z (m) Clay Sand Bore Hole Data of BH-43 Adhesion factor α= 0.5 (Table 2.2) Effective vertical stress σ = kpa ( mid soil layer) Friction factor for β= 0.30 (Equation 2.23) overburden Skin friction f = kpa (Clay), (Sand) Total skin friction Q = 6911 kn (Equation 2.2) Unit end bearing f = 1620 kpa (Table 2.3) Tip resistance Q = 2861 kn [Q = q b X Area of pile] Weight of pile W= 1865 kn Total capacity Q ult = 7907 kn (Equation 2.1) 122

136 SL No : 6 (Bored pile) Method : α and β method (BNBC-2015) : Site : Mogbazar Fly over, Dhaka Pile ID : P-180 Pile diameter : 1.2 m Length : 44m Soil Profile and properties Bore Hole Data of BH-43 Soil Depth Su SPT γ (m) kpa z (m) 2 15 Clay Sand Adhesion factor α= 0.52 (Table 2.2) Effective vertical σ = kpa ( mid soil layer) stress Friction factor for β= 0.27 (Equation 2.23) overburden Skin friction f = kpa (Clay), (Sand) Total skin friction Q = 4780 kn (Equation 2.2) Unit end bearing f = 1620 kpa (Table 2.3) Tip resistance Q = 1831 kn [Q = q b X Area of pile] Weight of pile W= 1194 kn Total capacity Q ult = 5416 kn (Equation 2.1) 123

137 SL No Method Site Pile ID Pile diameter Length : 7 (Bored pile) : α and β method (BNBC-2015) : Dhaka Road Research Lab : P1 : 1.2 m : 44m Soil Profile and properties Bore Hole Data of BH-1 Soil Depth Su z SPT γ (m) kpa (m) Clay Sand Adhesion factor α= 0.52 (Table 2.2) Effective vertical stress σ = kpa ( mid soil layer) Friction factor for overburden β= 0.56 (Equation 2.23) Skin friction f = kpa (Clay), (Sand) Total skin friction Q = 2517 kn (Equation 2.2) Unit end bearing f = 840 kpa (Table 2.3) Tip resistance Q = 659 kn [Q = q b X Area of pile] Weight of pile W= 424 kn Total capacity Q ult = 2752 kn (Equation 2.1) 124

138 SL No Method Site Pile ID Pile diameter Length : 8 (Bored pile) : α and β method (BNBC-2015) : Dhaka Road Research Lab : P2 : 1.2 m : 44m Soil Profile and properties Soil Depth Su z SPT γ (m) kpa (m) Clay Sand Bore Hole Data of BH-1 Adhesion factor α= 0.55 (Table 2.2) Effective vertical stress σ = kpa ( mid soil layer) Friction factor for overburden β= 0.45 (Equation 2.23) Skin friction f = kpa (Clay), (Sand) Total skin friction Q = 2533 kn (Equation 2.2) Unit end bearing f = 1560 kpa (Table 2.3) Tip resistance Q = 1225 kn [Q = q b X Area of pile] Weight of pile W= 537 kn Total capacity Q ult = 3221 kn (Equation 2.1) 125

139 SL No Method Site Pile ID Pile diameter Length : 9 (Bored pile) : α and β method (BNBC-2015) : Zinzira-Nawabganj (Bridge LRP) : P3 : 1 m : 23.7m m Soil Profile and properties Soil Depth (m) SPT γ Su kpa z (m) Clay Sand Bore Hole Data of BH-1 Adhesion factor α= 0.7 (Table 2.2) Effective vertical stress σ = kpa ( mid soil layer) Friction factor for overburden β= 0.30 (Equation 2.23) Skin friction f = kpa (Clay), (Sand) Total skin friction Q = 2557 kn (Equation 2.2) Unit end bearing f = 1680 kpa (Table 2.3) Tip resistance Q = 1319 kn [Q = q b X Area of pile] Weight of pile W= 537 kn Total capacity Q ult = 3339 kn (Equation 2.1) 126

140 SL No : 10 (Bored pile) Method : α and β method (BNBC-2015) Site : Zinzira-Nawabganj (Bridge LRP) Pile ID : P4 Pile diameter : 1 m Length : 23.7m Soil Profile and properties Bore Hole Data of BH-1 Soil Depth (m) SPT γ Su kpa z (m) Clay Sand Adhesion factor α= 0.7 (Table 2.2) Effective vertical stress σ = kpa ( mid soil layer) Friction factor for overburden β= 0.50 (Equation 2.23) Skin friction f = kpa (Clay), (Sand) Total skin friction Q = 2354 kn (Equation 2.2) Unit end bearing f = 1200 kpa (Table 2.3) Tip resistance Q = 942 kn [Q = q b X Area of pile] Weight of pile W= 537 kn Total capacity Q ult = 2760 kn (Equation 2.1) 127

141 SL No : 1 (Bored pile) Method : AASHTO(2002) Site : Walton Office, Basundhara, Dhaka Pile ID : TP-01 Pile diameter : 0.5m Length : 28.5m Soil Soil Profile and properties SPT Zi (ft) γ' lb/cft γ'zi (ksf) Clay Sand βi Bore Hole Data of BH-2 Adhesion factor α= 0.55 (Table 2.2) Un-drained shear strength s = 1.31 ksf [N(avg)/5] Skin friction Q = = kip(clay) kip (Sand) kip (Equation 2.31 & 2.32) Unit end bearing q = ksf (Table 2.3) Tip resistance Q = kip Q = q X Area of pile Weight of pile W= kip Total capacity Q = kip (Equation 2.30) 2130 kn 128

142 SL No : 2 (Bored pile) Method : AASHTO(2002) Site : Titas Railway Bridge, Akhaura Pile ID : Pile No-19 Pile diameter : 1.2 m Length : 30.8m Soil Profile and properties Bore Hole Data of BH-2 Soil SPT Zi (ft) γ' lb/cft γ'zi (ksf) Silt Clay Silt βi Adhesion factor α= 0.55 (Table 2.2) Un-drained shear strength s = 0.4 ksf [N(avg)/5] Skin friction Q = = kip(clay) kip (Sand) kip (Equation 2.31 & 2.32) Unit end bearing q = ksf (Table 2.3) Tip resistance Q = kip Q = q X Area of pile Weight of pile W= kip Total capacity Q = kip (Equation 2.30) 4983 kn 129

143 SL No : 3 (Bored pile) Method : AASHTO(2002) Site : Padma Bridge, Naodoba, Zazira Pile ID : Bridge 01 Abutment 02 Pile diameter : 1.2 m Length : 29.5m Soil Profile and properties Bore Hole Data of BH-8 Soil SPT Zi γ' γ'zi (ft) lb/cft (ksf) βi Silty Sand Adhesion factor α = 0.55 (Table 2.2) Un-drained shear strength s = 0.4 ksf [N(avg)/5] Skin friction Q = kip (Equation 2.32) Unit end bearing q = ksf (Table 2.3) Tip resistance Q = kip Q = q X Area of pile Weight of pile W= kip Total capacity Q = kip (Equation 2.30) 4924 kn 130

144 SL No : 4 (Bored pile) Method : AASHTO(2002) Site : Mogbazar Fly over, Dhaka Pile ID : TP-2 Pile diameter : 1.2 m Length : 29.5m Soil Profile and properties Bore Hole Data of BH-43 Soil SPT Zi (ft) γ' lb/cft Clay γ'zi (ksf) βi Sand Adhesion factor α = 0.55 (Table 2.2) Un-drained shear strength s = 2.53 ksf [N(avg)/5] Skin friction Q = = kip (Clay)+892 kip (Sand) 1265 kip (Equation 2.31 & 2.32) Unit end bearing q = 27 ksf (Table 2.3) Tip resistance Q = 338 kip Q = q X Area of pile Weight of pile W= kip Total capacity Q = 1423 kip (Equation 2.30) 6328 kn 131

145 SL No : 5 (Bored pile) Method : AASHTO(2002) Site : Mogbazar Fly over, Dhaka Pile ID : P-114 Pile diameter : 1.5 m Length : 44m Soil Soil Profile and properties SPT Zi (ft) γ' lb/cft Clay γ'zi (ksf) βi Sand Bore Hole Data of BH-43 Adhesion factor α= 0.55 (Table 2.2) Un-drained shear strength s = 2.53 ksf [N(avg)/5] Skin friction Q = 574 kip (Clay)+1452 kip (Sand) (Equation 2.31 & 2.32) = 2026 kip Unit end bearing q = 29 ksf (Table 2.3) Tip resistance Q = 562 kip Q = q X Area of pile Weight of pile W= 130 kip Total capacity Q = 2458 kip (Equation 2.30) kn 132

146 SL No : 6 (Bored pile) Method : AASHTO(2002) Site : Mogbazar Fly over, Dhaka Pile ID : P-180 Pile diameter : 1.2 m Length : 44m Soil Profile and properties Bore Hole Data of BH-43 Soil SPT Zi (ft) γ' lb/cft γ'zi (ksf) Clay Sand βi Adhesion factor α = 0.55 (Table 2.2) Un-drained shear strength s = 2.53 ksf [N(avg)/5] Skin friction Q = kip (Clay)+1162 kip (Sand) (Equation 2.32) = 1621 kip Unit end bearing q = 29 ksf (Table 2.3) Tip resistance Q = 360 kip Q = q X Area of pile Weight of pile W= 180 kip Total capacity Q = 1801 kip (Equation 2.30) 8009 kn 133