Implementation of Pile Setup in the LRFD Design of Driven Piles in Louisiana

Transcription

1 Implementation of Pile Setup in the LRFD Design of Driven Piles in Louisiana Md. Nafiul Haque (Ph.D. Candidate) Murad Y. Abu-Farsakh, Ph.D., P.E. March 1, 2016 Louisiana Transportation Conference

2 OUTLINE Objectives Brief Background Methodology Results and Analysis Analytical Models LRFD Calibration 2

3 OBJECTIVES Evaluate the time-dependant increase in pile capacity (or setup) for piles driven into Louisiana soils through conducting repeated static and dynamic field testing with time on full-scale instrumented test piles. Study the effect of soil type/properties, pile size, and their interaction on pile setup phenomenon. Develop analytical model(s) to estimate pile setup with time using typical soil properties. Incorporate setup into LRFD design of driven pile in Louisiana (calibrate setup resistance factor, f setup ). 3

4 PILE SET-UP Pile resistance/capacity have been reported to usually increase with time, after end of pile driving (EOD). The increase in resistance/capacity after end of driving, is known as pile set-up. Set-up is observed both in cohesive (clayey) and non-cohesive (sandy-silty) soils. 4

5 Benefits of Incorporating Set-up in Design The implementation of pile set-up capacity in the design can result in significant cost savings through Shortening pile lengths Reducing pile cross-sectional area (using smaller-diameter/width piles) Smaller hammer to drive pile Reducing the number of piles Substantial cost will be saved for full project 5

6 MECHANISMS - Pile Set-Up Soil around the pile usually experiences plastic deformation and remolded during pile driving. Excess pore water pressure develops as the result of pile driving. After the completion of pile driving, a certain degree of excess pore water pressure dissipates at the soil-pile interface zone, usually resulting in an increase in pile resistance. Aging and Thixotropy also plays significant role in set-up. Fellenius, 2008 Result from Our Study 6

7 MECHANISMS - Pile Set-Up In cohesive soils, the induced excess pore water pressure may dissipate slowly due to low permeability and it takes days to dissipate. However, for noncohesive soils, the duration of dissipation of excess pore water pressure take several hours to several days due to high permeability. This dissipation phase plays the most significant role for the set-up phase / period or how long it will take for the completion of set-up. Clayey Soil Sandy Soil 7

8 EMPIRICAL MODELS The model that were developed earlier were mainly formed by regression analyses of limited data sets. The first model for pile set-up was proposed by Skov and Denver in Rt t R o = 1 + A log 10 t o R t : the ultimate pile capacity at time t after driving, R o : the ultimate pile capacity at time (Reference time) t o, A : a constant that depends on soil type and pile characteristics, t o : initial time (taken as the time to first restrike), Reference time 8

9 Resistance/Capacity Phase 1 A parameter R t Phase 2 R o Slope of the line, A Phase 3 t o log (t/t o ) t 9

10 Methodology Conduct Field Test Collect Data From Performed Old Set-up Studies Analyze Data For Individual Soil Layers Correlate Set-up of Individual Soil Layers with Soil Properties Develop Model LRFD Calibration 10

11 METHODOLOGY Field Projects Instrumented Test Piles (12 Test Piles) 1. Bayou Lacassine (3 Test Piles) 2. Bayou Zourie (1 Test Pile) 3. Bayou Bouef (1 Test Pile) 4. LA-1 (6 Test Piles) 5. Bayou Teche (1 Test Pile) 11

12 METHODOLOGY-FIELD PROJECTS 12

13 Depth (m) Depth (ft) SOIL INVESTIGATION Soil Type TN. SI. SA. BR. SA. SI. GR. & TN. SA GR. & TN. CL. SA. w/cl TN. SA. GR. Sandy CL. GR. SI. CL. GR. & BR. CL M.C.; L.L.; & P.I Liquid Limit Moisture Content Plasticity Index Particle Size Distribution (%) Clay Silt Sand Zhang and Tumay (1999) method S u (kpa) Coefficient of Probability of Consolidation (cmtip 2 /sec) Resistance, q t, (MPa) Soil Type(%) S u from UU PCPT Test-1 3 S u from CPT Minimum Test-2 6 Maximum Insitu 9 Test

14 Normalized Excess Pore Water Pressure ( u/ui) Normalized Excess Pore Water Pressure ( u/ui) Dissipation Tests to Calculate c v m m m m m m m m m m m 5.14 m 8.38 m 6.38 m m Time (sec) BL-TP Time (sec) BL-TP-3 Bayou Zourrie 14

15 METHODOLOGY-INSTRUMENTATION Sister bar Strain gauges Pressure cells Piezometers Multilevel Piezometers Clayey Sandy Clayey Sandy Sandy Clayey Soil Profile 15

16 Depth (ft) METHODOLOGY-INSTRUMENTATION OCR OCR from CPT OCR from Lab Tip Resistance, q t (MPa) Rf (%) Probability of Soil Type (%) " Always one pair of strain gauge was installed near top in order to calibrate the elastic G.L. modulus 8.0' Layer ' 28.0' 23 Sandy Clayey Clayey Clayey Layer ' Layer-3 5.0' Layer-4 5.0' Layer ' Layer-6 5.0' Layer-7 5.0' Layer-8 5.0' 12.0' B 14.0' B 10.0' B B B MP-1 MP-2 MP-3 B B B MP-4 MP-5 MP-6 B MP-7 MP-8 MP-9 One pair of strain gauge near tip in order to calculate the tip resistance 16

17 INSTRUMENTATION PLAN FOR TEST PILES 30" 30" G.L. G.L. 8.0' 8.0' Layer ' 28.0' Layer ' 28.0' Layer ' Layer-3 5.0' Layer-4 5.0' Layer ' Layer-6 5.0' Layer-7 5.0' Layer-8 5.0' TP-1 B B B Layer-2 4.0' Layer-3 8.0' MP-1 MP-2 MP ' B B B Layer-4 5.0' Layer-5 5.0' MP-4 MP-5 MP ' B B B Layer ' 10.0' MP-7 MP-8 MP-9 Layer ' 2.0' Layer-8 B B B MP-1 MP-2 MP-3 8.0' B B B MP-4 MP-5 MP ' B B B MP-7 MP-8 MP ' 7.0' TP-3 17

18 INSTRUMENTATION Sister bar strain gauges Sister bar strain gauges always installed in pairs- The average readings were taken in order to eliminate the effect bending stress during driving 18

19 INSTRUMENTATION Geokon Model 4820 Pressure cell Piezometer Geokon Model 4500S Pressure cell & Piezometer 19

20 INSTRUMENTATION Installed in predefined depth Before Pouring Concrete After Pouring Concrete 20

21 INSTRUMENTATION Saturated before driving Vacuum pump and peanut oil was used 21

22 INSTRUMENTATION Multilevel Piezometer Saturated before driving Installed with PVC pipe at predefined depth 22

23 INSTRUMENTATION All the wires were pulled out through a PVC pipe near the top of pile The wires were connected to a data logger system through a trench A data collection system composed of CR-1000, multiplexels and solar panel was there for six months 23

24 DRIVING AND LOAD TESTS Hammer PDA device Accelerometer and strain transducer 24

25 STATIC LOAD TESTS 25

26 BAYOU LACASSINE 26

27 BAYOU LACASSINE The project was located in Lake Charles, Louisiana The test piles were monitored for 6 months. 3 dynamic load tests and 5 static load tests were conducted. TP-1 TP-2 TP-3 27

28 Depth (m) Depth (ft) DYNAMIC LOAD TEST Total Side Resistance (kips) Driving EOD 1st Restrike (0.5 hour) 2nd Restrike (1 day) 3rd Restrike (217 day) 217 days Total Side Resistance (kn) TP-1 Total Side Resistance (kips) Driving EOD 1st Restrike (1 hour) 2nd Restrike (1 day) 3rd Restrike (181 day) Total Side Resistance (kn) TP days

29 Settlement (mm) Settlement (inch) STATIC LOAD TEST 0 Load (kips) Load (kips) st SLT (13 days) 2nd SLT (53 days) 3rd SLT (127 days) 4th SLT (148 days) 5th SLT (208 days) 1 st SLT 5 th SLT. 1st SLT (15 days) 2nd SLT (29 days) 3rd SLT (93 days) 4th SLT (129 days) 5th SLT (175 days) 1 st SLT 5 th SLT Load (kn) TP Load (kn) TP-3 29

30 Set-Up Plots for Bayou Lacassine Set-up for TP-1 Set-up for TP-3 30

31 Set-Up for TP-1 Events Time from EOD Total Resistanc e Increas e from EOD Side Resistan ce Increas e from EOD Tip Resistan ce Increas e from EOD Set-up factor for Total Resistan ce Days kips % kips % kips % (R t /R o ) TP-1 EOD st RST nd RST SLT SLT SLT SLT SLT rd RST

32 Results-Bayou Zourrie 32

33 Pile Resistance, QR (kn) Pile Resistance,QR (kips) Set-up Results for Bayou Zourrie Events Time Side Resistance Tip Resistance Total Resistance kips % kips % kips % Driven /602-1 st Dynamic Load Test 1 hr / nd Dynamic Load Test 1 day / st Static Load Test 14 days 2 nd Static Load Test 30 days 3 rd Dynamic Load Test 78 days / R 2 = Time, t (Days) 33

34 LA-1 TP-2 TP-3 TP-4 TP-5 34

35 LA-1 Time Side Resistance, R s Events Set-up Hour kips Ratio s (R s /R so ) EOD st DLT nd DLT rd DLT th DLT th DLT th DLT th DLT Static Test For BL R s /R so 1.7 times (In 6 months) BZ R s /R so 1.8 times (In 3 months) Very soft soil 35

36 Set-Up for Bayou Teche and Bayou Bouef Bayou Teche Bayou Bouef R s /R so 1.9 times (In 32 days) R s /R so 3.8 times (In 716 days-almost 2 years) 36

37 Pile Set-Up (Result of 12 Test Piles) The result is consistent with literature that set-up fits best with linear logarithmic of time 37

38 Percentage of Excess Pore Water Pressure Dissipation (%) Set-Up Process with Consolidation Behavior 0 2nd Restrike 1st SLT 2nd Restrike Installation of Load Frame 8.54 m deep m deep m deep m deep 3rd SLT 4th SLT 2nd SLT 5th SLT Time after EOD, t (Days) TP-1 Installation of Load Frame 8.54 m deep m deep m deep m deep Time after EOD, t (Days) TP-3 1st SLT 2nd SLT 3rd SLT 4th SLT 5th SLT Set-up continues for 127 days No set-up after 15 days 38

39 Set-Up Process with Consolidation Behavior By Layers Smaller amount of set-up or low rate of set-up as consolidation process finished earlier Higher amount or rate of set-up as consolidation process continued for longer period of time 39

40 Set-Up for Individual Soil Layers P = E x ξ x A Load-Strain Plot Tip Resistance Used to calculate the resistance of individual soil layers Modulus-Strain Plot Load Distribution Plot 40

41 Depth (m) Depth (m) Depth (ft) Depth (ft) CAPWAP ANALYSES Unit SIde Resistance (kpa) EOD BOR1 BOR2 BOR Unit Side Resistance (kpa) CAPWAP analyses for Bayou Zourrie Total Side Resistance (kips) EOD BOR1 BOR2 BOR Total Side Resistance (kn) CAPWAP analyses for LA-1 Test Pile 41

42 Depth (m) Soil Profile for Bayou Zourrie Depth (ft) Soil Type TN. SI. SA. BR. SA. SI. GR. & TN. SA GR. & TN. CL. SA. w/cl TN. SA. GR. Sandy CL. GR. SI. CL. GR. & BR. CL M.C.; L.L.; & P.I Liquid Limit Moisture Content Plasticity Index Particle Size Distribution (%) Clay Silt Sand Layer-1 Layer-2 Layer-3 Layer-4 Layer-5 Layer-6 S u (kpa) Coefficient of Probability of Consolidation (cmtip 2 /sec) Resistance, q t, (MPa) Soil Type(%) S u from UU PCPT Test-1 3 S u from CPT Minimum Test-2 6 Maximum Insitu 9 Test

43 Set-up Ratio of Side Resistance (f t /f o ) Set-Up in Clayey Soil layers Unit Side Resistance, f (kpa) Dissipation of Excess PWP (kpa) Unit Side Resistance, f (kpa) Excess PWP DLT SLT f t /f o = 0.26 log (t/t o ) + 1 R 2 = Time after EOD, t (Days) 20 Clayey Soil Layer of Bayou Lacassine Clayey Soil Layer of Bayou Lacassine Unit Side Resistance, f (ksf)2.20 DLT-Layer-1 SLT-Layer-1 DLT-Layer-6 SLT-Layer-6 DLT-Layer-7 SLT-Layer-7 f s /f so = 0.31 log (t/t o ) + 1 R 2 = 0.96 f s /f so = 0.37 log (t/t o ) + 1 R 2 = 0.70 f s /f so = 0.43 log (t/t o ) + 1 R 2 = Time, t (Days) Clayey Soil Layer of LA-1 site Time, t (Days) Unit Side Resistance, f (ksf)0.95 DLT-Layer-2 SLT-Layer-2 DLT-Layer-4 SLT-Layer-4 DLT-Layer-5 SLT-Layer-5 f s /f so = 0.40 log (t/t o ) + 1 R 2 = 0.99 f s /f so = 0.45 log (t/t o ) + 1 R 2 = 0.99 f s /f so = 0.51 log (t/t o ) + 1 R 2 = 0.96 Clayey Soil Layer of LA-1 site

44 Set-Up in Sandy Soil layers Unit Side Resistance, f (kpa) Unit Side Resistance, f (kpa) Sandy Soil Layer of Bayou Zourie Time, t (Days) Unit Side Resistance, f (ksf)2.80 DLT-Layer-2 SLT-Layer-2 SLT-Layer-5 SLT-Layer-5 DLT-Layer-8 f s /f so = 0.08 log (t/t o ) + 1 R 2 = 0.94 f s /f so = 0.07 log (t/t o ) + 1 R 2 = 0.76 f s /f so = 0.13 log (t/t o ) + 1 R 2 = Sandy Soil Layers of LA-1 site Sandy Soil Layer of Bayou Lacassine Time, t (Days) Unit Side Resistance, f (ksf)2.05 DLT-Layer-3 SLT-Layer-3 DLT-Layer-6 SLT-Layer-6 DLT-Layer-9 SLT-Layer-9 f s /f so = 0.20 log (t/t o ) + 1 R 2 = 0.97 f s /f so = 0.16 log (t/t o ) + 1 R 2 = 0.96 f s /f so = 0.12 log (t/t o ) + 1 R 2 = Sandy Soil Layers of LA-1 site 44

45 SUMMARY OF A 94 soil layers were first identified based on soil strata from 12 instrumented test piles. Clayey soil behavior was dominant in 70 soil layers. Sandy soil behavior was dominant in 24 soil layers. Set-up parameter A was back-calculated for all soil layers using unit side resistance (f s ). The maximum A for clayey soil layers was The average A for clayey soil layer was The maximum A for sandy soil layers was The average A for sandy soil layer was

46 EMPIRICAL MODEL 46

47 Steps Followed for Model Preparation Identify potential soil properties Find the correlation between soil properties and A parameter Develop the model with SAS Perform F test and t test to find the significance of the model as well the independent parameters Perform detail statistical analyses (Goodness of fit, COV, Correlation among the parameters, P seudo R 2 etc) Validate the model with non-instrumented pile (These were not used to develop the model) Verify the model with published case studies 47

48 Undrained Shear Strength (S u ) Plasticity Index (PI) Over consolidation ratio (OCR) Coefficient of consolidation (c v ) Overburden pressure/depth Pile size/width (r) Sensitivity (S t ) Corrected Cone Tip Resistance (q t ) 48

49 EMPIRICAL MODELS Level-1 Including Undrained Shear Strength (S u ) Plasticity Index (PI) Level-2 Including Undrained Shear Strength (S u ) Plasticity Index (PI) Coefficient of Consolidation (c v ) Level-3 Including Undrained Shear Strength (S u ) Plasticity Index (PI) Coefficient of Consolidation (c v ) Sensitivity (S t ) 49

50 Clayey soil with high S u exhibited low set-up Clayey soil with low S u exhibited high set-up Clayey soil with low PI exhibited low set-up Clayey soil with high PI exhibited high set-up 50

51 Clayey soil with high c v exhibited low set-up Clayey soil with low c v exhibited high set-up OC clay exhibited low set-up NC clay exhibited high set-up 51

52 High sensitive clay exhibited higher set-up Low sensitive clay exhibited lower set-up 52

53 No strong correlation was observed in between depth and pile size with r 53

54 Final Developed Models A = 0.79 S u 1tsf PI A=f (PI, S u ) A = S u 1tsf log PI C v 0.01 in2 hour A=f (PI, S u, C v ) A = S u 1tsf log PI 100 C v 0.01 in2 hour S t A=f (PI, S u, C v, S t ) 54

55 EMPIRICAL MODEL Implementation Procedure 1. Define the soil layers along the length of the pile 2. Calculate the subsurface soil properties (i.e., S u, PI, OCR, c v, S t, q t ) 3. Evaluate f so of each soil layer from 1 st restrike (1 hr to 1 day). 4. Use the developed model to calculate f s at desired time (for clay) f s fso = 1 + [ 0.79 PI ] log t Su to 1 tsf R si (set-up) = f si (set-up ) x A si 5. Use a constant value of A = 0.15 set-up parameter (for sand) f s fso = log t to 6. R s (set-up) = R s1 (set-up) + R s2 (set-up) +..+ R sn (set-up) 55

56 LRFD CALIBRATION

57 LRFD CALIBRATION The limit state equation is g (R, Q) = R Q After considering set-up the above Equation can be rewritten as g (R, Q) = (R 14 +R set-up ) Q The limit state equation becomes ϕ 14 R 14 + ϕ set-up R set-up = γ DL Q DL + γ LL Q LL 57

58 LRFD CALIBRATION For Φ 14 By Abu-Farsakh et al. (2009) Resistance Factor (f14) and Efficiency Factor (f/l) for Louisiana Soil Design Method Monte Carlo FOSM FORM Simulation f 14 f14/l f 14 f 14 /l f 14 f 14 /l a-tomlinson Recommended Static method method and Nordlund method Schmertmann f 14 Direct CPT method LCPC/LCP De Ruiter and Beringen CPT average Dynamic CAPWAP (EOD) measurement CAPWAP (14 days BOR)

59 LRFD CALIBRATION *Set-up was predicted with the developed models. *Set-up was calculated or LRFD was calibrated for the resistance after 14 days for four different times days days days days (a) Comparison of (R 30 - R 14 ) for Level-1 (b) Comparison of (R 45 - R 14 ) for Level-1

60 LRFD CALIBRATION (c) Comparison of (R 60 - R 14 ) for Level-1 Summary Statistics R m /R p R p /R m Time Mean (λ R ) σ COV Mean (d) Comparison of (R 90 - R 14 ) for Level-1

61 Probability Density Function and Histogram R 30 - R 14 R 45 - R 14 R 60 - R 14 R 90 - R 14 61

62 LRFD CALIBRATION Reliability Calibration Methods: FOSM closed form solution ϕ setup = γ D.L. + γ L.L. Ҡ ϕ 14 α (1 + Ҡ) λ D.L. + λ L.L Ҡ λ R14 (γ ϕ D.L. + γ L.L. Ҡ) R setup 14 α = R 14 Q D.L. + Q L.L Ҡ = Q L.L. Q D.L. = FORM iterative procedure Monte Carlo Simulation (MCS) Method iterative procedure 62

63 CALIBRATION RESULTS R 30 - R 14 R 45 - R R 60 - R 14 R 90 - R

64 CALIBRATION RESULTS β T = 2.33 FOSM FORM MC Recommended Days Days Days Days Kam Ng (2013) Yang & Liang (2006) Overall Recommended = f setup = 0.35 D Q D L Q L f 14 R 14 f setup R setup 64

65 CONCLUSIONS Set-up study was conducted on 12 instrumented test piles of 5 different sites. Set-up was mainly exhibited by side resistance. The tip resistance was almost constant. Set-up was mainly attribute to the consolidation behavior. Amount of set-up and set-up rate increased significantly during consolidation phase. Very small amount of set-up was observed during aging period. Horizontal effective stress increased significantly during the consolidation period. Once the consolidation period was over, the amount of increase became slower. Set-up for individual soil layers was calculated with the aid of strain gauge. The set-up rate A for clayey soil layers was 0.31 and for sandy soil layers it was

66 Three models were developed A = 0.79 A = A = S u 1tsf S u 1tsf S u 1tsf PI PI log C v 0.01 in2 hour 0.44 PI 100 S t log CONCLUSIONS C v 0.01 in2 hour A= f(pi, S u ) [Lab Test] A= f(pi, S u, C v ) [Lab Test] A= f(pi, S u, C v, S t ) [Lab Test] Set-up rate can be processed to predict total set-up resistance. The recommended set-up factor is 0.35 for LRFD design. 66

67 Chen, Q., Haque, Md. N., Abu-Farsakh, M., and Fernandez, B. A. (2014). Field investigation of pile setup in mixed soil. Geotechnical Testing Journal, Vol. 37(2), pp Haque, Md. N., Abu-Farsakh, M., Chen, Q., and Zhang, Z. (2014). A case study on instrumenting and testing full scale test piles for evaluating set-up phenomenon. Journal of the Transportation Research Board No 2462, National Research Council, Washington, D.C., pp Haque, Md. N., Abu-Farsakh, M., Zhang, Z. and Okeil, A. (2016). Estimate pile set-up for individual soil layers and develop a model to estimate the increase in unit side resistance with time based on PCPT data. Journal of the Transportation Research Board, National Research Council, Washington, D.C. (In Press). Haque, Md. N., Chen, Q., Abu-Farsakh, M., and Tsai, C. (2014). Effects of pile size on set-up behavior of cohesive soils. In Proceedings of Geo-Congress- 2014: Geo-Characterization and Modeling for Sustainability, Technical Papers GSP 234, pp Haque, Md. N., Abu-Farsakh, M., and Chen, Q. (2015). Pile set-up for individual soil layers along instrumented test piles in clayey soil. In Proceedings of the 15 th Pan-American Conference on Soil Mechanics and Geotechnical Engineering (From fundamentals to applications in Geotechnics), November 15-18, Argentina, pp

68 ACKNOWLEDGEMENT LADOTD Geotechnical Department Louisiana Transportation Research Center (LTRC) 68