REQUIREMENTS FOR ALL SUCCESSFUL DEEP FOUNDATION PROJECTS

Transcription

1 REQUIREMENTS FOR ALL SUCCESSFUL DEEP FOUNDATION PROJECTS 1 st Leg: Design 3 rd Leg: Inspection 2 nd Leg: Construction Slide 1 of 125

2 SELECTED REFERENCES YOU SHOULD HAVE IN YOUR LIBRARY Naval Facilities Command (NAVFAC) Soil Mechanics (DM7.01, 1986) EPRI EL-6800 Manual for Estimating Soil Properties for Foundation Design (Kulhawy & Mayne 1991) FHWA Manual on Subsurface Investigations (NHI , 2001) FHWA Evaluation of Soil & Rock Properties (IF , 2002) AVAILABLE ON COURSE WEBSITE! Slide 2 of 125

3 OBJECTIVES OF SUBSURFACE EXPLORATION Three (3) General Objectives for Subsurface Exploration: 1. Define Soil and Rock Stratigraphy and Structure within Proposed Construction Zone of Influence. 2. Obtain Groundwater Data. - Level at Time of Testing. - Seasonal Fluctuations. 3. Determine Engineering Properties of Subsurface Materials for Use in Foundation Design. - Collect samples for laboratory testing. - Determine insitu engineering properties. Photograph courtesy of Slide 3 of 125

4 GENERAL SUBSURFACE INVESTIGATION METHODS METHOD Abbrv. ASTM SAMPLING MAX. DEPTH (ft) Hand Auger Borings HAB D a D (06) Yes Typ (w/difficulty) Test/Excavation Pits TP None Yes Limits of equipment (Typ. 20 ft) Soil Test Borings STB D420-98(03) D a D (06) Yes ~ 300 ft (dependent of various factors) D420-98(2003) Standard Guide to Site Characterization for Engineering, Design, and Construction Purposes Green Near Surface : Red Near and Deep Slide 4 of 125

5 Requires Manual Labor. Typical Depths up to 6 to 8 ft. Standard Diameter: 3¼ in (Other Diameters Available). Allows for soil samples (disturbed) to be collected for classification and laboratory testing (if desired). HAND AUGER BORINGS (HAB) Typical HAB Cross-Section Figure courtesy of WPC Engineering Inc. Two Man Operation Photograph courtesy of Slide 5 of 125

6 TEST/EXCAVATION PITS (TP) Requires Appropriate Construction Equipment (e.g. backhoe). Typical Depths up to 20 ft (limited by equipment). Pit size determined by needs. Allows for soil samples (disturbed) to be collected for classification and laboratory testing (if desired). Allows for greater examination of insitu soils by geotechnical engineers and engineering technicians. Photographs courtesy of photos.orr.noaa.gov, & Slide 6 of 125

7 SOIL TEST BORING (STB) RIGS Failing Truck Mounted Rig CME750 All-Terrain Rig Photographs courtesy of FHWA NHI Course Subsurface Investigations Slide 7 of 125

8 SOIL TEST BORING (STB) RIGS MoDOT Track Mounted Rig Wireline Rig for Kaolin Mines Macon, GA Water Boring from Barge for Bridge Crossing Photographs courtesy of FHWA NHI Course Subsurface Investigations Slide 8 of 125

9 Continuous flight augers, added in 5-ft increments. Limited to non-caving soils and depths < 30 ft. Solid flight augers are removed prior to soil sampling, thus labor-intensive. Auger diameters from 4 in to 8 in. Front end has finger or fish-tail bit to loosen soil. Spoil collects around top of borehole. SOIL TEST BORINGS (STB) Solid Flight Augers Solid Auger and Drill Bit Text & Photographs courtesy of FHWA NHI Course Subsurface Investigations Slide 9 of 125

10 SOIL TEST BORINGS (STB) Solid Flight Augers Photographs courtesy of FHWA NHI Course Subsurface Investigations Slide 10 of 125

11 Continuous hollow flight augers, added in 5 ft increments. Hollow stem augers allow soil sampling without removal. Act as temporary casing to stabilize borehole. Center stem and plug are inserted down the hollow center during boring advance. HSA range from about 6 to 12 inch O.D. with 3 to 8 inch I.D. HSA generally limited to depths < 100 ft. HSA should not be used in loose silts and sands below the GWT. SOIL TEST BORINGS (STB) Hollow Stem Augers (HSA) Truck-Mounted Rig with Hollow-Stem Augers HSA outer and inner assembly with stepwise center bit Text & Photographs courtesy of FHWA NHI Course Subsurface Investigations Slide 11 of 125

12 SOIL TEST BORINGS (STB) Rotary Wash Borings Rotary wash techniques are best for borings extending below GWT. Rotary wash can achieve great depths > 300+ ft. Drilling bits: Drag bits for clays Roller bits for sand In rotary wash method, borehole is stabilized using either temporary steel casing or drilling fluid. Fluids include water, bentonite or polymer slurry, foam, or Revert that are re-circulated in tub or reservoir at surface. Truck Rig conducting rotary wash boring Text & Photographs courtesy of FHWA NHI Course Subsurface Investigations Slide 12 of 125

13 SOIL TEST BORINGS (STB) Rotary Wash Borings Schematic (Hvorslev 1948) Photographs courtesy of FHWA NHI Course Subsurface Investigations Slide 13 of 125

14 Bucket auger drills are used for obtaining large disturbed or undisturbed samples. Diameters range from 0.6 m (2 ft) to 1.2 m (4 ft). Increment of 0.3 m to 0.6 m depths (1 to 2 feet). Good for gravelly soils and cobbles. SOIL TEST BORINGS (STB) Bucket Auger Borings Same rigs used for constructing Drilled Shafts. Setup of rig for Bucket Auger Boring (ASTM D4700) Text and Figure courtesy of FHWA NHI Course Subsurface Investigations Slide 14 of 125

15 Disturbed Sampling (Most Common) Bulk samples (from auger cuttings or TP excavations). Bucket samples (borrow pits). Drive samples (e.g. split-spoon). Laboratory Tests: Grain size, Atterberg Limits, Specific Gravity, Organic Content, Hydraulic Conductivity (coarse grained), Shear Strength (coarse grained). Partially Undisturbed (ASTM D1587) Continuous Hydraulic Push. SOIL SAMPLING Split Spoon Sampler Undisturbed Sampling (ASTM D1587) Push Tubes (e.g. Shelby, Piston, Laval) Rotary & Push (e.g. Denison, Pitcher) Block Samples Laboratory Tests: Consolidation, Hydraulic Conductivity (cohesive), Shear Strength (cohesive) Thin Wall Samplers Text & Photographs courtesy of FHWA NHI Course Subsurface Investigations Slide 15 of 125

16 UNDISTURBED SAMPLES Sampling Disturbance Photoelasticity Studies Radiography (X-rays) of Tubes Photographs courtesy of FHWA NHI Course Subsurface Investigations Slide 16 of 125

17 INSITU TESTING METHODS METHOD Abbrv. ASTM SAMPLING MAX. DEPTH (ft) Dynamic Cone Penetrometer DCP D Yes (via HAB) 6 8 Typ. 20 (w/difficulty) Standard Penetration Test SPT D a Yes > 300 ft (dependent on boring method) Cone Penetration Test CPT D D No > 300 ft (typically ft max) Flat Plate Dilatometer DMT D No > 300 ft (typically ft max) Pressuremeter PMT D Vane Shear Test VST D Yes (via boring) Yes (via Boring) > 300 ft (dependent on boring) > 300 ft (dependent on boring) Green Near Surface : Red Near and Deep Slide 17 of 125

18 Labor Intensive (Can be done with one person, better with two). Several types in use: - Scala (1956) DYNAMIC CONE PENETROMETER (DCP) - Sowers (Sowers and Hedges, 1966) (Common in Southeast US) - Dual Mass (Army COE) Mainly used for residential construction and pavement subgrade evaluations. Conducted in conjunction with HAB s (therefore, soil samples can be collected). Depth limited by soil type. 6 8 ft typical, 20 ft maximum (if lucky). Figure courtesy of WPC Engineering Inc. Slide 18 of 125

19 INSITU TESTING METHODS Figure courtesy of FHWA NHI Course Subsurface Investigations Slide 19 of 125

20 STANDARD PENETRATION TEST (SPT) (ASTM D a) Marking of 6 inch Increments for SPT Test Photograph courtesy of physics.uwstout.edu Very common test worldwide Colonel Gow of Raymond Pile Co. Split-barrel sample driven in borehole. Conducted on 2½ to 5 ft depth intervals. ASTM D1586 guidelines Drop Hammer (140 lbs falling 30 inches) Three increments of 6 inches each; Sum last two increments = SPT N value" (blows/ft) Correlations available with all types of soil engineering properties. Disturbed Soil Samples Collected Text courtesy of FHWA NHI Course Subsurface Investigations Slide 20 of 125

21 STANDARD PENETRATION TEST (SPT) (ASTM D a) Split Spoon Dimensions (after ASTM D1586) Typical Setup Figures courtesy of J. David Rogers, Ph.D., P.E., University of Missouri-Rolla & FHWA NHI Course Slide 21 of 125

22 STANDARD PENETRATION TEST (SPT) (ASTM D a) Figure courtesy of FHWA NHI Course Subsurface Investigations Slide 22 of 125

23 STANDARD PENETRATION TEST (SPT) (ASTM D a) Figure courtesy of Slide 23 of 125

24 STANDARD PENETRATION TEST (SPT) Factors Affecting SPT (after Kulhawy & Mayne, 1990 & Table 8. FHWA IF ) Cause Inadequate Cleaning of Borehole Effects SPT not made in insitu soil, soil trapped, recovery reduced Influence on N Value Increases Failure to Maintain Adequate Head in Borehole Bottom of borehole may become quick Decreases Careless Measure of Drop Hammer Energy varies Increases Hammer Weight Inaccurate Hammer Energy varies Inc. or Dec. Hammer Strikes Drill Rod Collar Eccentrically Hammer Energy reduced Increases Lack of Hammer Free (ungreased sleeves, stiff rope, more than 2 turns on cathead, incomplete release of drop, etc.) Hammer Energy reduced Increases Sampler Driven Above Bottom of Casing Sampler driven in disturbed soil Inc. Greatly Careless Blow Count Recording Inaccurate Results Inc. or Dec. Use of Non-Standard Sampler Correlations with Std. Sampler Invalid Inc. or Dec. Coarse Gravel or Cobbles in soil Sampler becomes clogged or impeded Increases Use of Bent Drill Rods Inhibited transfer of energy to sampler Increases Slide 24 of 125

25 CARE & PRESERVATION OF SOIL SAMPLES Mark and Log samples upon retrieval (ID, type, number, depth, recovery, soil, moisture). Place jar samples in wood or cardboard box. Should be protected from extreme conditions (heat, freezing, drying). Sealed to minimize moisture loss Packed and protected against excessive vibrations and shock. Text and Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 25 of 125

26 STANDARD PENETRATION TEST (SPT) (ASTM D a) TEST RESULTS (i.e. BORING LOG) Shows the following: Soil Profile (determined from sampling and boring information) with respect to depth and/or elevation. Groundwater Table (GWT). SPT N Values. Laboratory Test Results (if available). ASTM D Standard Guide for Field Logging of Subsurface Explorations of Soil and Rock Boring Log courtesy of WPC Engineering Inc. Slide 26 of 125

27 CONE PENETRATION TEST (CPT) (ASTM D ) Electronic Steel Probes with 60 Apex Tip Hydraulic Push at 20 mm/s No Boring, No Samples, No Cuttings, No Spoil Continuous readings of stress, friction, pressure With Pore Pressure Measurements (CPTu) With Shear Wave Measurements (SCPT) Text and Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 27 of 125

28 CONE PENETRATION TEST (CPT) (ASTM D ) V s Shear Wave Velocity (V s ) f s Sleeve Friction (f s ) u 2 Penetration Porewater Pressure (U 2 ) q c Cone Tip Resistance (q c ) Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 28 of 125

29 CONE PENETRATION TEST (CPT) RIGS Figures courtesy of FHWA NHI Course Subsurface Investigations & WPC Engineering Inc. Slide 29 of 125

30 CONE PENETRATION TESTING (CPT) RESULTS q c f s u o, u 2 F R Soil Profile Very stiff fine grained (9) Clayey silt to silty clay (4) Clays, clay to silty clay (3) Clayey silt to silty clay (4) Silty sand to sandy silt (5) Silty sand to sandy silt (5) Clays, clay to silty clay (3) Clays, clay to silty clay (3) Silty sand to sandy silt (5) Clayey silt to silty clay (4) Clays, clay to silty clay (3) Silty sand to sandy silt (5) C le an sands to silty sands (6) Silty sand to sandy silt (5) Clays, clay to silty clay (3) Clayey silt to silty clay (4) Dep CPT Results courtesy of WPC Engineering Inc. Slide 30 of 125

31 CONE PENETRATION TESTING (CPT) Factors Affecting CPT Results Figure 9-2. FHWA NHI Course Subsurface Investigations V s f s U 2 q c Slide 31 of 125

32 FLAT PLATE DILATOMETER (DMT) (ASTM D (2007)) Direct push of stainless steel plate at 20-cm intervals; No borings; no cuttings. Introduced by Marchetti (1980). 18 o angled blade Pneumatic inflation of flexible steel membrane using nitrogen gas Two pressure readings taken (A and B) within about 1 minute A B Figures and Text courtesy of FHWA NHI Course Subsurface Investigations Slide 32 of 125

33 FLAT PLATE DILATOMETER (DMT) (ASTM D (2007)) Figure courtesy of FHWA NHI Course Subsurface Investigations Slide 33 of 125

34 FLAT PLATE DILATOMETER (DMT) (ASTM D (2007)) Calibrations: A, B (positive values) Readings: contact pressure "A" and expansion pressure "B" with depth Corrections for membrane stiffness in air: p 0 = 1.05(A + A) (B - B) p 1 =B - B DMT INDICES: I D = material index = (p 1 -p o )/(p o -u o ) E D = dilatometer modulus = 34.7(p 1 -p o ) K D = horizontal stress index = (p o -u o )/ vo A B Text courtesy of FHWA NHI Course Subsurface Investigations Slide 34 of 125

35 FLAT PLATE DILATOMETER (DMT) (ASTM D (2007)) Manual Reading System (Standard) Marchetti Device (ASCE JGE, March 1980; ASTM Geot. Testing J., June 1986) Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 35 of 125

36 FLAT PLATE DILATOMETER (DMT) (ASTM D (2007)) Computerized System (Standard) Figure courtesy of FHWA NHI Course Subsurface Investigations Slide 36 of 125

37 FLAT PLATE DILATOMETER (DMT) (ASTM D (2007)) Results Charleston, SC Project Soil Behavior Classification E D with Depth Raw Data & Calibrations DMT Results courtesy of WPC Engineering Inc. Slide 37 of 125

38 FLAT PLATE DILATOMETER (DMT) (ASTM D (2007)) Results - Piedmont Residuum, Charlotte, NC Depth (meters) Po P1 14 Clay Silt Pressure (kpa) Material Index I D Modulus E D (atm) Horiz. Index K D DMT Results courtesy of FHWA NHI Course Subsurface Investigations Slide 38 of 125

39 SPT-CPT-DMT COMPARISON From Local Project in Charleston, SC Area (2000) Also see Hajduk, E.L., Meng, J., Wright, W.B., and Zur, K.J. (2006). Dilatometer Experience in the Charleston, South Carolina Region, 2nd International Conference on the Flat Dilatometer, Washington, D.C. Slide 39 of 125

40 PRESSUREMETER TEST (PMT) (ASTM D ) Figure courtesy of FHWA NHI Course Subsurface Investigations Slide 40 of 125

41 PRESSUREMETER (PMT) (ASTM D ) Results Utah DOT Project Pressure (tsf) 3 2 Pressure (tsf) Volume Change (cc) Creep (cc/min) PMT Results courtesy of FHWA NHI Course Subsurface Investigations Slide 41 of 125

42 Performed at bottom of boring or by direct push placement of device Four-sided blade pushed into clays and silts to measure following: s uv (peak) = Peak Undrained Strength VANE SHEAR TEST (VST) (ASTM D ) s uv (remolded) = Remolded Strength (after 10 revolutions) Sensitivity, S t = s uv (peak)/s uv (remolded) Scandinavian Vanes Pictures and text courtesy of FHWA NHI Course Subsurface Investigations Slide 42 of 125

43 VANE SHEAR TEST (VST) (ASTM D ) Figure courtesy of FHWA NHI Course Subsurface Investigations Slide 43 of 125

44 VANE SHEAR TEST (VST) (ASTM D ) Vane Shear Devices Dutch Vane Equipment, Holland VST in Upstate NY Pictures courtesy of FHWA NHI Course Subsurface Investigations Slide 44 of 125

45 VANE SHEAR TEST (VST) (ASTM D ) Results - San Francisco Bay Mud, MUNI Metro Station Vane Strength, s uv (kpa) Sensitivity, S t Peak Remolded 5 Depth (meters) Depth (meters) VST Results courtesy of FHWA NHI Course Subsurface Investigations Slide 45 of 125

46 INSITU TEST METHOD ADVANTAGES/DISADVANTAGES Method Advantages Disadvantages DCP Quick Low cost Limited depth range Limited correlations of DCP values to soil properties. SPT Obtain Sample + Number Simple & rugged device at low cost Suitable in many soil types Can perform in weak rocks Available throughout the U.S. and worldwide. Many correlations with soil engineering properties exist Obtain Sample + Number Disturbed sample (index tests only) Crude number for analysis Not applicable in soft clays and silts High variability and uncertainty Many correlations with soil engineering properties exist Slide 46 of 125

47 INSITU TEST METHOD ADVANTAGES/DISADVANTAGES Method Advantages Disadvantages CPT DMT Fast and continuous profiling of strata. Economical and productive. Results not operator-dependent. Strong theoretical basis for interpretation. Particularly suited to soft soils. Simple and Robust Equipment. Repeatable and Operator- Independent. Quick and Economical. Theoretical Derivations for elastic modulus, strength, stress history. High capital investment Requires skilled operator for field use. Electronics must be calibrated & protected. No soil samples. Unsuited to gravelly soils and cobbles. Difficult to push in dense and hard materials. Primarily established on correlative relationships. Needs calibration for local geologies. Slide 47 of 125

48 INSITU TEST METHOD ADVANTAGES/DISADVANTAGES Method Advantages Disadvantages VST Assessment of undrained shear strength of clays. Simple test and equipment. Measure inplace sensitivity. Long history of use in practice, particularly embankments, foundations, & cuts. Limited to soft to stiff clays & silts with s uv < 200 kpa Slow & time-consuming Raw s uv needs empirical correction Can be affected by sand seams and lenses Slide 48 of 125

49 ROCK EXPLORATION Geophysical Methods Geologic Mapping (need qualified geologists) Drilling and Coring Exploration Test Pits UML Health and Social Sciences Building Lowell, MA June 14, 2011 Slide 49 of 125

50 ROCK EXPLORATION Drilling and Coring STB Refusal Auger refusal SPT refusal (> 50 blows per 1 inch penetration) Coring (ASTM D2113) Noncore Drilling Sinkhole in Limestone Terrain Orlando, FL Percussive Methods ASTM D Standard Practice for Rock Core Drilling and Sampling of Rock for Site Investigation Text and Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 50 of 125

51 ROCK EXPLORATION Percussive Drilling Air-Tracks Drilling for Dynamite Placement Penobscot, Maine Photograph courtesy of FHWA NHI Course Subsurface Investigations Slide 51 of 125

52 ROCK EXPLORATION Drilling Rotary Wash Drill Rig Tricone, Roller, Plug Bits Roller Bits Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 52 of 125

53 ROCK EXPLORATION Coring Diamond Bits. Best and hardest, producing high quality core. Fastest cutting rates. Expensive. Synthetic Bits. Less expensive. Generally good quality cores. Tungsten Carbide Bits. Least expensive. Slower coring rates. Diamond Diamond, Carbide Tungsten, Sawtooth Carbide Type Bits Photograph courtesy of Slide 53 of 125

54 Most rugged, least expensive. Consists of head section, core recovery tube, reamer shell, & cutting bit. Often used as starter when beginning core operations ROCK EXPLORATION Coring Single Tube Core Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 54 of 125

55 ROCK EXPLORATION Coring Double Tube Core Inner Barrel Assembly Outer Barrel Assembly Double tube core barrel is the standard. Outer barrel rotates with cutting bit. Inner barrel is either fixed or swivel type (with bearings) that retains core sample. Core diameters generally range from 21 to 85 mm (0.85 to 3.35 inch). NX core: standard diameter = 54 mm (2.15 inches). ASTM C42: The diameter of cores for determining f c in load bearing structural members shall be at least 3.70 in. Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 55 of 125

56 DRILLED DEEP FOUNDATIONS ROCK EXPLORATION Coring Triple Tube Core Good for obtaining core samples in fractured rock and highly weathered rocks. Outer core barrel for initial cut and second barrel to cut finer size. Third barrel to retain cored samples. Reduces frictional heat that may damage samples. Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 56 of 125

57 ROCK EXPLORATION Coring Drilling Fluids Notes Rotary wash with water, foam, or drilling mud (bentonitic or polymeric slurries). Fluids reduce wear on drilling and coring bits by cooling. Fluids remove cuttings & rock flour. Re-circulate to filter fluids and to minimize impact on environment Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 57 of 125

58 Stabilizes boreholes Driven casing Drilled-in casing Dual wall reverse circulation method Use in areas with expected large losses in drilling fluid Inner section for sampling ROCK EXPLORATION Coring Casing Outer casing maintains fluids for drilling Drilled-In Dual Wall Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 58 of 125

59 ROCK EXPLORATION Core Recovery Core Runs taken in either 5- or 10-foot sections. Log the amount of material recovered. Core Recovery is percentage retained. RQD (Rock Quality Designation) is a modified core recovery. Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 59 of 125

60 ROCK EXPLORATION Core Recovery Cores should be stored in either wooden boxes or corrugated cardboard box. Box marked with boring number, depth of core run, type core, bit type, core recovery (CR), rock type, RQD, and other notes. Core operations should be documented: Loss of fluid Drilling rates Sudden drop in rods Poor recovery Loss of core Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 60 of 125

61 Routine: Core boxes Special: Plastic sleeves General: Avoid exposure to shock and vibration during handling and transport. Non-natural fractures may result from excessive movements, temperatures, and exposure to air. Store for future reference ROCK EXPLORATION Care & Preservation Text & Figures courtesy of FHWA NHI Course Subsurface Investigations Slide 61 of 125

62 GEOPHYSICAL METHODS MECHANICAL WAVES Seismic Refraction (SR) (courtesy of Also Available: Downhole Tests (DHT) Spectral Analysis of Surface Waves (SASW) Crosshole Tests (CHT) (FHWA NHI Figurer 5-25) Slide 62 of 125

63 GEOPHYSICAL METHODS ELECTROMAGNETIC WAVES Electrical Resistivity (ER) Survey Results (FHWA NHI Figurer 5-35) Electromagnetic (EM) Survey (FHWA NHI Figurer 5-35) Ground Penetrating Radar (GPR) (photographs courtesy of Other Methods: Magnetometer Surveys (MS) Resistivity Piezocone (RCPTu) Slide 63 of 125

64 ADVANTAGES OF GEOPHYSICS Nondestructive and/or non-invasive Fast and economical testing Theoretical basis for interpretation Applicable to soils and rocks GEOPHYSICAL METHODS GPR Results for UST (FHWA NHI Figure 5-33) MS Results for Oil Well Location (FHWA NHI Figure 5-37) DISADVANTAGES OF GEOPHYSICS No samples or direct physical penetration Models assumed for interpretation Affected by cemented layers or inclusions. Results influenced by water, clay, & depth. Slide 64 of 125

65 SUBSURFACE EXPLORATION PLANNING Subsurface Exploration Plan: Function of - Type and Critical Nature of Structure - Foundation Loads - Topographical Information - Site Geology (Soil and Rock Formations) - Location of Bedrock 1.5 m core to confirm >3 m core required for foundations on rock - Engineer s Experience - Project Requirements USACE EM There are no hard and fast rules stating the number and depth of samples for a particular geotechnical investigation. ASTM D420-98(2003) Standard Guide to Site Characterization for Engineering, Design, and Construction Purposes Consequences of Poor Subsurface Explorations (photographs courtesy of NHI 13231) Slide 65 of 125

66 SUBSURFACE EXPLORATION PLANNING IBC (2009) Section The scope of the soil investigation including the number and types of borings or soundings, the equipment used to drill and sample, the insitu testing equipment and the laboratory testing program shall be determined by a registered design professional. YOU WILL NEED 1 BORING TO 100 ft TO DETERMINE SEISMIC SITE CLASSIFICATION FOR IBC 2009 LET THE ENGINEER DECIDE! Are Soil Explorations as Costly as the Repair? (Photographs courtesy of Slide 66 of 125

67 Photograph courtesy of TTU Center for Multidisciplinary Research in Transportation ( The Massachusetts State Building Code (7 th Edition) 780 CMR FOUNDATION AND SOILS INVESTIGATIONS Borings, Sampling and Testing. The scope of the subsurface exploration, including the number and types of borings, soundings or test pits, the equipment used to drill and sample, the in-situ testing equipment and the laboratory testing program, shall be determined by a registered design professional. LET THE ENGINEER DECIDE! Slide 67 of 125

68 SUBSURFACE EXPLORATION PLANNING IBC (2009) Section (8 th Edition of MSBC) The scope of the soil investigation including the number and types of borings or soundings, the equipment used to drill and sample, the insitu testing equipment and the laboratory testing program shall be determined by a registered design professional. YOU WILL STILL NEED 1 BORING TO 100 ft TO DETERMINE SEISMIC SITE CLASSIFICATION FOR IBC 2009 AGAIN, LET THE ENGINEER DECIDE! 780 CMR (8 th MSBC) Section Investigations Required. Exceptions: The building official shall be permitted to waive the requirement for a geotechnical investigation: 1. Where satisfactory data from adjacent areas is available that demonstrates an investigation is not necessary to meet the requirements of this chapter or, 2. For unoccupied structures that do not pose a significant risk to public safety in the event of failure; or 3. For structures used for agricultural purposes. Slide 68 of 125

69 SUBSURFACE TEST LAYOUT GUIDELINES Structure FHWA USACE NAVFAC (NHI ) (Table 2-4 EM ) (DM7.01) Min. # Spacing Min. # Spacing Min. # Spacing Rigid Frame Structure 1 per 230m² 50 ft spacing Low-Load Warehouse Isolated Rigid Ftg < 2500ft² Isolated Rigid Ftg < 10,00ft² Corners O.C. 3 around Per. Houses Subdivisions 1 per 8000m² 200 to 400 ft Houses Individual Lots Bridge Piers 1 (< 30m wide) 2 (> 30m wide) 1 per lot 1 Retaining Walls 1 60 m Roads 2 Lane 60 m 1 per 150 CL Roads Multi Lane 1 per 75 CL Cuts and Embankments 1 60 m Culverts 1 60 to 120 m Levees 6 to 12 m high Levees 12 to 18 m high 230 m 150 m 100 to 200 ft Slide 69 of 125

70 SUBSURFACE TEST LAYOUT GUIDELINES SCDOT Geotechnical Design Manual (2010) Foundation Type Min. Geotechnical Site Investigation Reference Bridge Pile Foundation Minimum one testing location per bent 1 Table 4-1 Bridge Single Foundation Drilled Shaft Minimum one testing locations per foundation location Table 4-1 Bridge Multiple Foundation Drilled Shaft 2 Minimum two testing locations per bent location Table 4-1 Bridge Shallow Foundation Founded on Soil Minimum three testing locations per bent location Table 4-1 Bridge Shallow Foundation Founded on Rock Minimum two testing locations per bent location Table 4-1 Retaining Wall (within 150 of bridge abutment) Minimum one testing location at least every 75 ft Section Retaining Wall (within 150 of bridge abutment) Minimum one testing location at least every 75 ft Section Embankments Minimum one testing location at least every 500 ft Section Cut Excavations Minimum one test locations every 300 ft along cut area Section Culverts Minimum one testing each end of culvert and at every 100 ft of new crossline culvert 2 Section Sound Barrier Walls Dependant on shallow or deep foundation used 2 Section Misc. Structures (Light poles, overhead signs) Minimum of one test location per foundation location Section NOTES: 1. Spacing between testing locations may be increased, but shall be approved prior to field operations and shall include justification. Spacing may not exceed 100 ft. 2. See SCDOT Geotechnical Manual for additional details. Slide 70 of 125

71 SUBSURFACE TEST DEPTH GUIDELINES Structure Spread Footings Deep Foundations (Soil) Deep Foundations (Rock) Roadways FHWA (NHI ) L f 2B, Min. Depth = 2B L f 5B, Min. Depth = 4B 2B < L f < 5B, Extrapolate Min. Depth = 6m below anticipated foundation tip elevation Min. Depth = 3m, 3D, or 2B group below foundation tip Min. 2m USACE (Table 2-4 EM ) Min. Depth = 1½B (4.5m for houses or to unweathered rock) Min. Depth = 1½B of imaginary 2/3 expected pile depth Min. 3m below finished grade (0.75m into rock) Embankments/Culverts Min. 2x Embankment Height Height of Levee Cuts Min. 5m below cut elevation NOTE: B = Footing Width Slide 71 of 125

72 SUBSURFACE TEST DEPTH GUIDELINES SCDOT Geotechnical Design Manual (2010) Foundation Type Minimum Depth Reference Deep Foundation Bridge Shallow Foundation Retaining Walls Embankments Cut Excavations Culverts Borings shall extend below the anticipated pile or drilled shaft tip elevation a minimum of 20 ft or a minimum of 4 times the minimum pile group dimension, whichever is deeper. L 2B, Minimum test depth = 2B L 5B, Minimum test depth = 4B 2B L 5B, Minimum test depth = 3B At least 2X wall height beneath the anticipated bearing elevation or to auger refusal, whichever is shallower. At least 2X embankment height beneath the anticipated bearing elevation (i.e. to a depth sufficient to characterize settlement and stability issues) or to auger refusal, whichever is shallower. At least 25 feet below the anticipated bottom depth of the cut or to auger refusal, whichever is shallower. At least 2X the embankment height beneath the anticipated bearing elevation or in accordance with the bridge spread footing criteria, whichever is deeper (or auger refusal) Section Table 4-2 Section Section Section Section Sound Barrier Walls Dependant on shallow or deep foundation used 1 Section Misc. Structures (Light poles, overhead signs) Same depth criteria as specified for the bridge test locations for the same type of foundation. NOTES: 1. See SCDOT Geotechnical Manual for additional details. Section Slide 72 of 125

73 TEST LOCATION PLAN (EXAMPLE) Other Useful Data: - North Arrow - Topographic Information Shows test locations relative to site Symbol key differentiates between test types Project Information Scale Test Location Plan Example (Courtesy of WPC Inc.) Slide 73 of 125

74 SUBSURFACE TEST LAYOUT & DEPTH GUIDELINES Other Guidelines HUD Directive Rev 2 (1995) Shallow Foundations: 1 boring per 2,500 ft² Deep Foundations: 1 boring per 1,600 ft² Borings must be at least to the bottom of proposed footings and deep enough to locate bearing strata that will support the proposed structure. When rock is encountered, depth of drilling into rock shall be at least 5 feet or enough to establish rock quality regarding voids, fissures and strength, or whether it is a boulder. Hospital and Office Buildings (Sowers and Sowers, 1970) Boring Depth = 3(Number of Stories) 0.7 (for light steel or narrow concrete buildings) Boring Depth = 6(Number of Stories) 0.7 (for heavy steel or wide concrete buildings) Slide 74 of 125

75 SUBSURFACE TEST LAYOUT & DEPTH GUIDELINES Other Guidelines ASCE (1972) 1. Determine for planned foundation. 2. Determine ' o with Depth. 3. Determine Depth D 1 at which = 0.1q (q = applied footing load) 4. Determine Depth D 2 at which ' o = Minimum Depth is the smaller of D 1 and D 2. Figure Das FGE (2005) Slide 75 of 125

76 DATA COLLECTION, INTERPRETATION, & ANALYSIS TO GEOTECHNICAL SOLUTIONS FLOW CHART PRIOR INFORMATION Reconnaissance Topography Geology Hydrology Environment SITE EXPLORATION Geophysics Drilling and Coring Sampling In-situ Testing LABORATORY TESTING Index Properties Strength Stiffness/Compressibility Flow/Permeability THEORETICAL EVALUATIONS Constitutive Models Numerical Simulation Analytical Solutions INTERPRETED SOIL PARAMETERS Geostatic Stress State Strength: Drained & Undrained Cases Stiffness & Rate Effects Anisotropy, Dynamic Response, Rheology PRIOR EXPERIENCE Statistical Trends Empirical Correlations ANALYTICAL METHODS Elastic Theory Theorem of Plasticity Limit Equilibrium COLOR CODE: Blue: & Red: ENGINEERING ANALYSIS Judgment Hand Calculations Computer Simulations Chart Solutions Experience GEOTECHNICAL SOLUTION Safe Feasible Economical NUMERICAL METHODS Finite Elements Boundary Elements Discrete Elements Finite Difference From Paul W. Mayne, PhD, P.E., Professor, Civil Engineering, GT Slide 76 of 125

77 c u = undrained strength T = unit weight I R = rigidity index ' = friction angle OCR = overconsolidation K 0 = lateral stress state e o = void ratio V s = shear wave E' = Young's modulus C c = compression index q b = pile end bearing f s = pile skin friction k = permeability q a = bearing stress STANDARD PENETRATION TEST CLAY N SAND D R = relative density T = unit weight LI = liquefaction index ' = friction angle c' = cohesion intercept e o = void ratio q a = bearing capacity p ' = preconsolidation V s = shear wave E' = Young's modulus = dilatancy angle q b = pile end bearing f s = pile skin friction What Do We Need? How Do We Get It? Courtesy of FHWA NHI Course Subsurface Investigations Slide 77 of 125

78 CORRECTIONS TO SPT N VALUE N measured = Raw SPT Value from Field Test (ASTM D a) N 60 = Corrected N values corresponding to 60% Energy Efficiency (i.e. The Energy Ratio (ER) = 60% (ASTM D ) Note: 30% < ER < 100% with average ER = 60% in the U.S. N 60 = C E C B C S C R N measured Factor Term Equipment Variable Correction SPT Corrections From Table 9 FHWA IF Energy Ratio C E = ER/60 Donut Hammer Safety Hammer Automatic Hammer Borehole Diameter C B 150 mm mm 200 mm Standard Sampler Sampling Method C S Non-Standard Sampler Rod Length C R 3 4 m 4 6 m 6 10 m > 10 m 0.5 to to to to For Guidance Only. Actual ER values should be measured per ASTM D4633 Slide 78 of 125

79 CORRECTIONS TO SPT N VALUE EXAMPLE OF DATA FROM SAME SITE Measured N-values Corrected N Depth (meters) ER = 34 (energy ratio) Depth (meters) Donut Safety Trend 14 Donut Saf ety Sequence Data from Robertson, et al. (1983), Courtesy of FHWA NHI Course Subsurface Investigations Slide 79 of 125

80 EQUIVALENT ELASTIC MODULUS Courtesy of FHWA NHI Course Subsurface Investigations Slide 80 of 125

81 EQUIVALENT ELASTIC MODULUS WITH STRAIN LEVEL Slide 81 of 125

82 NORMALIZED SPT N VALUE (N 1 ) 60 (N 1 ) 60 = N 60 values normalized to 1 atmosphere overburden stress. (N 1 ) 60 = C N N 60 Where: C N = (P a / ' vo ) n P a = Atmospheric Pressure (1 atm = 14.7 psi = 2116 psf = 1.06 tsf) ' vo = Insitu Vertical Effective Stress n = 1 (clays) and 0.5 to 0.6 (sands) Slide 82 of 125

83 CORRECTIONS TO CPT MEASUREMENTS (WITH U 2 ) Need to correct tip resistance (q c ) for pore U2 location. q c q t U 2 = U b Pore Pressure Measurement behind Tip Porous Element for U 2 Materials: Sintered Metals, Ceramics, Plastics (disposable) Saturation of Porous Elements: Water, Glycerine, Silicone Procedures: Vacuum for 24-hours, Pre-Saturated Elements, Prophylactic to maintain fluids Courtesy of FHWA IF Slide 83 of 125

84 WHAT DO WE NEED FOR GEOTECHNICAL DESIGN? 1. Geostratigraphy: - Layering - Soil Types - Depth to Strata 5. Stiffness and Moduli: - Elastic Modulus (E) - Shear Modulus (G) - Compression Index (C c ) 2. Total and Effective Soil Stresses: - Soil Unit Weight ( or sat = t ) - GWT Location (u) 3. Shear Strength: - Effective Friction Angle ( ') - Effective Cohesion Intercept (c') - Undrained Shear Strength (S u ) 6. Consistency: - Void Ratio (e) - Relative Density (D r ) 7. Flow Parameters: - Coefficient of Permeability (k) - Coefficient of Consolidation (c v, c h ) 4. Stress State: - Maximum Past Pressure ( vm ). - Overconsolidation Ratio (OCR) - Coefficient of Earth Pressure at Rest (K o ) Slide 84 of 125

85 INSITU TESTS APPLICABLE SOIL PROPERTIES Soil Property SPT CPT DMT Soil Classification USCS Behavior Behavior Groundwater Table Yes Yes Possible Effective Friction Angle ( ') (Sands) Yes Yes Yes Relative Density (D r ) (Sands) Yes Yes Yes Unit Weight ( ) Yes Yes Yes Undrained Shear Strength (S u ) Possible 1 Yes Yes Maximum Past Pressure ( ' vm or ' p ) Possible 1 Yes Yes Overconsolidation Ratio (OCR) Shear Wave Velocity (V s ) Yes (SCPTu) Yes (SDMT) Small Strain Shear Modulus (G max ) Yes (SCPTu) Yes (SDMT) Small Strain Young s Modulus (E max ) Yes (SCPTu) Yes (SDMT) E (Young s Modulus) Possible 1 Possible 1 Yes Coefficient of At-Rest Earth Pressure (K o ) Yes Yes IBC Site Classification Yes (N) Yes (V s, S u ) Yes (S u ) Yes NOTES: 1. Possible, but not recommended for use. After Table 10. FHWA IF Slide 85 of 125

86 COEFFICIENT OF VARIATION (V) FOR GEOTECHICAL PROPERTIES AND INSITU TESTS (after Duncan, 2000) Coefficient of Variation: A measure of dispersion of a probability distribution. Measured or Interpreted Parameter V (%) Unit Weight ( ) 3 to 7 Effective Friction Angle ( ') 2 to 13 Undrained Shear Strength (S u ) 13 to 40 Undrained Shear Ratio (S u / ' vo ) 5 to 15 SPT N Value 15 to 45 Electric CPT Tip Resistance (q t ) 5 to 15 after Table 52. FHWA IF Also see Chapter 8 Applying Judgment in Selecting Soil and Rock Properties for Design (FHWA IF ). Slide 86 of 125

87 SOIL BORINGS DETERMINATION OF SOIL STRATIGRAPHY Figure 9-1. FHWA NHI Course Subsurface Investigations Slide 87 of 125

88 CONE PENETRATION TEST (CPT) DETERMINATION OF SOIL STRATIGRAPHY CPT Soil Behavior Classification (Based on q t, FR or B q ) Figure 9-3. FHWA NHI Course Subsurface Investigations Slide 88 of 125

89 CONE PENETRATION TEST (CPT) DETERMINATION OF SOIL STRATIGRAPHY Slide 89 of 125

90 CONE PENETRATION TESTING (CPT) RESULTS Soil Profile q c f s u o, u 2 F R Very stiff fine grained (9) Clayey silt to silty clay (4) Clays, clay to silty clay (3) LAYER 1 LAYER 2 Clayey silt to silty clay (4) Silty sand to sandy silt (5) Silty sand to sandy silt (5) Clays, clay to silty clay (3) Clays, clay to silty clay (3) Silty sand to sandy silt (5) Clayey silt to silty clay (4) Clays, clay to silty clay (3) Silty sand to sandy silt (5) LAYER 3 LAYER 4 LAYER 5 C le an sands to silty sands (6) LAYER 6 Silty sand to sandy silt (5) Clays, clay to silty clay (3) Clayey silt to silty clay (4) LAYER 7 LAYER 8 68 Dep CPT Results courtesy of WPC Engineering Inc. Slide 90 of 125

91 FLAT PLATE DILATOMETER DETERMINATION OF SUBSURFACE DATA Material Index, I D p p 1 0 p u Clay Silt Sand Material Index (I D ) p 0 p 1 Courtesy of FHWA NHI Course Subsurface Investigations Slide 91 of 125

92 FLAT PLATE DILATOMETER DETERMINATION OF SUBSURFACE DATA Figure 43. FHWA IF Slide 92 of 125

93 SOIL PROFILE (EXAMPLE) Plan View (Boring Locations) Soil Profile (Cross-Section) Figure courtesy of FHWA Slide 93 of 125

94 SOIL PROFILE (EXAMPLE) Boring Location Plan Figure 45. FHWA IF Slide 94 of 125

95 SOIL PROFILE (EXAMPLE) Soil Profile Figure 46. FHWA IF Slide 95 of 125

96 EFFECTIVE FRICTION ANGLE ( ') FOR SANDS - SPT 55 Triaxial Database from Frozen Sand Samples Friction Angle, ' (deg) ' = [15.4(N 1 ) 60 ] Sand (SP and SP-SM) Sand Fill (SP to SM) SM (Piedmont) H&T (1996) Normalized (N 1 ) 60 Figure FHWA NHI Course Subsurface Investigations Slide 96 of 125

97 EFFECTIVE FRICTION ANGLE ( ') FOR SANDS - SPT Comparison of ' from SPT and Laboratory Tests Peidmont Residuum (GT Campus) Silty Sand (SM) 0 10 SPT N-values (bpf) Effective Friction Angle, ' (deg) Depth (feet) Depth (feet) SPT-N Triaxial Courtesy FHWA NHI Course Subsurface Investigations Slide 97 of 125

98 EFFECTIVE FRICTION ANGLE ( ') FOR SANDS - CPT 55 Friction Angle, ' (deg) ' = arctan[ log (q t / vo ')] Frankston Sand Ticino Sand Edgar Sand Hokksund Sand Lone Star Sand R&C (1983) Normalized Tip Stress, q t / vo ' Figure FHWA NHI Course Subsurface Investigations Slide 98 of 125

99 Shear Strength Parameter DRILLED DEEP FOUNDATIONS SOIL SHEAR STRENGTH CORRELATIONS FROM INSITU TESTING Insitu Testing Method SPT CPT DMT Effective Soil Friction Angle ( ) See Slide 24 arctan[ log(q t / vo )] log(k D )-2.1 log 2 K D See Slide 24 Robertson and Campanella (1983) Marchetti et al. (2001) ISSMGE TC 16 Report Undrained Shear Strength (S u ) NO ACCEPTABLE CORRELATIONS (q t - vo )/N kt (N kt = 15 for CHS) Aas et al. (1986) 0.22 vo (0.5K D ) 1.25 Marchetti et al. (2001) ISSMGE TC 16 Report NOTES: 1. (N 1 ) 60 = N 60 (P a / vo ) 0.5 for sands. P a = Atmospheric Pressure = 1 bar 1 tsf. 2. vo = Insitu Effective Overburden Pressure = Insitu Vertical Effective Stress. 3. vo = Total Overburden Pressure = Insitu Vertical Total Stress. Slide 100 of 125

100 SOIL SHEAR STRENGTH CORRELATIONS FROM INSITU TESTING Effective Soil Friction Angle ( ) summary from NCHRP Report 651 (2010) Equation Reference ' = *exp( (N 1 ) 60 ) ' = [20*(N 1 ) 60 ] for 3.5 (N 1 ) ' = *(N 1 ) (N 1 ) 2 60 ' = [15.4(N 1 ) 60 ] ' = [15(N 1 ) 60 ] for (N 1 ) 60 > 5 and 45 Peck, Hanson, & Thorton (1974) from Kulhawy & Mayne (1990) Hatanaka & Uchida (1996) Peck, Hanson, & Thorton (1974) from Wolff (1989) Mayne et a. (2001) based on Hatanaka & Uchida (1996) JRA (1996) Slide 101 of 125

101 SOIL ENGINEERING PROPERTY CORRELATIONS FROM INSITU TESTING (TABLE 1) Soil Density/Consistency N q t (MPa) t (pcf) V. Loose <30 Loose ( ) SANDS Medium Dense Dense Very Dense >50 > Very Soft COHESIVE SOILS Firm Stiff Very Stiff Hard >30 > after Fang et al. (1991) and EM NOTE: 1 MPa = tsf NA Slide 102 of 125

102 SOIL ENGINEERING PROPERTIES DETERMINATION Maximum Allowable Shear Strengths (SCDOT, 2010) Cannot be exceeded with laboratory testing AND written permission from SCDOT Slide 103 of 125

103 SOIL ENGINEERING PROPERTIES DETERMINATION Maximum Allowable Shear Strengths (SCDOT, 2010) Cannot be exceeded with laboratory testing AND written permission from SCDOT Slide 104 of 125

104 EXAMPLE INTERPRETATION SPT Given Data Provided: - Soil Stratigraphy - USCS Classification - Groundwater Table (@ Time of Testing) - SPT N Values (No Energy Measurements) - Drilling Method (HSA) - Date Started/Ended Slide 105 of 125

105 Depth (ft) DRILLED DEEP FOUNDATIONS EXAMPLE INTERPRETATION SPT Determination of N ave, t, and ' vo SAND - Silty SAND N ave = 17 use t = 115 pcf Sandy SILT N ave = 4 use t = 110 pcf Depth (ft) Clayey SILT (MH)/MARL N ave = 4 use t = 115 pcf B-7 N (bpf) ' vo (psf) t from Table 1 (Lecture Notes) Slide 106 of 125

106 DRILLED DEEP FOUNDATIONS EXAMPLE INTERPRETATION SPT Determination of Effective Friction Angle ( ') SAND - Silty SAND N ave = 17 use t = 115 pcf Calculate N ave for sand layer from 0 to 8 ft. Simple Way: Using Table 1 (Lecture Notes) Depth (ft) Sandy SILT N ave = 4 use t = 110 pcf N ave = 17, therefore ' 36 Formula Way: Use Mayne et al. (2001) ' = [15.4(N 1 ) 60 ] and (N 1 ) 60 = N 60 (P a / ' vo ) Clayey SILT (MH)/MARL N ave = 4 use t = 115 pcf B-7 N (bpf) Use N ave = 17, ' vo,ave = 460 psf, and P a = 2115 psf Therefore, (N 1 ) 60 = 17(2115/460) 0.5 = 36 Using equation ' = [15.4(N 1 ) 60 ] , ' = 44 USE ' = 36 Slide 107 of 125

107 Soil Profile DRILLED DEEP FOUNDATIONS EXAMPLE INTERPRETATION CPT Given Data q t (tsf) f s (tsf) U o, U 2 (tsf) FR Depth (ft) Slide 108 of 125

108 Soil Profile DRILLED DEEP FOUNDATIONS EXAMPLE INTERPRETATION CPT Soil Layers q t (tsf) f s (tsf) U o, U 2 (tsf) FR 7ft Depth (ft) SAND 9ft SANDY SILT 17ft SILTY CLAY (MARL) Slide 109 of 125

109 Depth (ft) DRILLED DEEP FOUNDATIONS EXAMPLE INTERPRETATION CPT Determination of q t,ave, t, and ' vo SAND - Silty SAND q t,ave 125 tsf use t = 115 pcf Sandy SILT q t,ave 22 tsf use t = 110 pcf Silty CLAY - CLAY q t,ave 26 tsf use t = 115 pcf C-7 q t (tsf) Depth (ft) t from Table 1 (Lecture Notes) ' vo (psf) Slide 110 of 125

110 Depth (ft) DRILLED DEEP FOUNDATIONS EXAMPLE INTERPRETATION CPT Determination of Effective Friction Angle ( ') SAND - Silty SAND q t,ave 125 tsf use t = 115 pcf Sandy SILT q t,ave 22 tsf use t = 110 pcf Silty CLAY - CLAY q t,ave 26 tsf use t = 115 pcf C-7 q t (tsf) Calculate q t,ave for sand layer from 0 to 7 ft Simple Way: Using Table 1 (Lecture Notes) q t,ave 125 tsf 12 MPa therefore ' 37 Formula Way: Using Robertson and Campanella (1983) formula. ' = arctan[ log(q t / ' vo )] Use q t,ave 12 MPa ( psf) & ' vo,ave = 405 psf for layer. Using equation, ' = 49 USE ' 37 Slide 111 of 125

111 Depth (ft) DRILLED DEEP FOUNDATIONS EXAMPLE INTERPRETATION CPT Determination of Undrained Shear Strength (S u ) SAND - Silty SAND q t,ave 125 tsf use t = 115 pcf Sandy SILT q t,ave 22 tsf use t = 110 pcf Silty CLAY - CLAY q t,ave 26 tsf use t = 115 pcf C-7 q t (tsf) Calculate q t,ave for Sandy Silt from 7 to 17 ft Calculate q t,ave for Silty Clay from 17 to 24 ft Formula Way: use Aas et al. (1986) S u = (q t - vo )/N kt N kt = 15 for CHS (Lecture Slides) Sandy SILT Layer Use q t,ave 22 tsf & vo,ave = 1355 psf S u = 2850 psf Silty CLAY Layer Use q t,ave 26 tsf & vo,ave = 2310 psf S u = 3300 psf Slide 112 of 125

112 EXAMPLE INTERPRETATION SPT & CPT Comparison of Soil Engineering Properties SPT CPT 0 5 SAND - Silty SAND N ave = 17 use t = 115 pcf 0 5 SAND - Silty SAND q t,ave 125 tsf use t = 115 pcf Sand Layer Properties Method t (pcf) ' ( ) Depth (ft) Sandy SILT N ave = 4 use t = 110 pcf Depth (ft) Sandy SILT q t,ave 22 tsf use t = 110 pcf SPT - Table SPT - Formula NA Clayey SILT (MH)/MARL N ave = 4 use t = 115 pcf Silty CLAY - CLAY q t,ave 26 tsf use t = 115 pcf CPT - Table CPT - Formula NA B-7 N (bpf) C-7 q t (tsf) Two Tests ~ 15 ft Apart Slide 113 of 125

113 INDEX PROPERTIES OF INTACT ROCK Specific Gravity of Solids (G s ) Unit Weight ( ) Porosity (n) Ultrasonic Velocities (V p and V s ) Compressive Strength (q u ) Tensile Strength (T 0 ) Elastic Modulus, E R (at 50% of q u ) Courtesy of FHWA NHI Course Subsurface Investigations Slide 114 of 125

114 SPECIFIC GRAVITY OF ROCK MINERALS galena pyrite barite olivine dolomite calcite chlorite feldspar quartz serpentine gypsum halite Specific Gravities of Rock Mi Common Minerals Average G s = Reference Value (fresh water) Specific Gravity of Solids, G s Courtesy of FHWA NHI Course Subsurface Investigations Slide 115 of 125

115 DRILLED DEEP FOUNDATIONS UNIT WEIGHTS OF ROCKS Saturated Unit Weight, T (kn/m 3 ) Dolostone Granite Graywacke Limestone Mudstone Siltstone Sandstone Tuff sat = water [ G s (1-n) + n] Porosity, n G s = Courtesy of FHWA NHI Course Subsurface Investigations Slide 116 of 125

116 ULTRASONIC VELOCITIES OF ROCKS 5000 Seismic Velocities for Intact Rock Materials Shear Wave, Vs (m/s) Compression Wave, V p (m/s) Limestone Chalk Marble Schist Tuff Slate Anhydrite Grandiorite Diorite Gabbro Granite Dunite Basalt Dolostone Mudstone Siltstone Courtesy of FHWA NHI Course Subsurface Investigations Slide 117 of 125

117 STRENGTH OF INTACT ROCKS Compressive Strength, u = q u (Direct) Tensile Strength, *T 0 (Indirect) Brazilian Strength, T 0 Shear Strength, Across the intact rock Along the planar surface (joints) Courtesy of FHWA NHI Course Subsurface Investigations Slide 118 of 125

118 LAB DATA ON INTACT ROCKS (GOODMAN, 1989) q u T 0 E R Ratio Ratio Intact Rock Material (MPa) (MPa) (MPa) (-) q u /T 0 E R/ /q u Baraboo Quartzite Bedf ord Limestone Berea Sandstone Cedar City Tonalite Cher okee Marble Dwor shak Dam Gneiss Flaming Gorge Shale Hackensack Siltstone John Day Basalt Lockport Dolomite Micaceous Shale Navaj o Sandstone Nevada Basalt Nevada Granite Nevada Tuff Oneota Dolomite Palisades Diabase Pikes Peak Granite Quartz Mica Schist Solenhof en Limestone Taconic Mar ble Tavernalle Limestone Statistical Results: Mean = S.Dev. = Note: 1 MPa = tsf = psi Courtesy of FHWA NHI Course Subsurface Investigations Slide 119 of 125

119 CLASSIFICATION FOR ROCK MATERIAL STRENGTH Courtesy of FHWA NHI Course Subsurface Investigations Slide 120 of 125

120 ROCK MASS CLASSIFICATIONS RQD - Early form of rating rock mass Geomechanics System - Rock Mass Rating (RMR) by Bieniawski (1984, 1989) Q-System - Norwegian Geotechnical Institute (Barton, et al. 1974) Geological Strength Index, GSI (Hoek, et al., 1995) Courtesy of FHWA NHI Course Subsurface Investigations Slide 121 of 125