CIVE 554/650. Geotechnical Engineering. Rock. Soil. Water. Site Investigation Techniques. CIVE Knight 1. 1/8/2006 CIVE Knight 1

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1 CIVE 554/650 Site Investigation Techniques 1/8/2006 CIVE Knight 1 Geotechnical Engineering Soil Rock Water 1/8/2006 CIVE Knight 2 CIVE Knight 1

conductivity) Flow of water through soils 1/8/2006 CIVE 554 -

2 Key Soil Engineering Properties Compressibility Settlement Strength Ability to carry load Permeability (hydraulic conductivity) Flow of water through soils 1/8/2006 CIVE Knight 3 Settlement Failure 1/8/2006 CIVE Knight 4 CIVE Knight 2

Serviceability Requirements 1/8/2006 CIVE 554 - Knight 5

3 Serviceability Requirements 1/8/2006 CIVE Knight 5 Shear Failure 1/8/2006 CIVE Knight 6 CIVE Knight 3

Palace of Fine Arts, Mexico A strange case of Palace of Fine Arts in the Alameda area of Mexico City. Built sometime between 1900 and 1934, it was a magnificent and strongly built structure.

4 Palace of Fine Arts, Mexico A strange case of Palace of Fine Arts in the Alameda area of Mexico City. Built sometime between 1900 and 1934, it was a magnificent and strongly built structure. It was built on grade, level with the square and other buildings nearby. But because of loose sand permeated with water in the subsurface, the massive structure sunk 6 ft into the ground! (Luckily, it settled evenly minimizing structural damage.) Believe it or not, in the 1960's the building moved again. This time it moved 12 ft up! The weight of skyscrapers being built around the Palace had pushed the subsurface water and soil around sufficiently to raise the building. (Source: Why Buildings Fall Down, M. Levy and M. Salvadori, WW Norton & Company, 1992) 1/8/2006 CIVE Knight 7 Permeability 1/8/2006 CIVE Knight 8 CIVE Knight 4

5 Site Investigation (SI) Objective Obtain sufficient information to enable a safe and economic design to be made and to avoid any difficulties during construction 1/8/2006 CIVE Knight 9 SI Requirements Sequence, thickness and lateral extent of soil strata and where appropriate level of bedrock Obtain representative samples of soils (and rock) for identification and classification and relevant soil parameters Identify groundwater conditions Insitu tests to access appropriate soil and/or rock characteristics 1/8/2006 CIVE Knight 10 CIVE Knight 5

6 How Much Site Investigation? Cost ($) Cost of site investigation & testing Total project cost Cost of construction More extensive site investigation & testing program 1/8/2006 CIV E Knight 11 How Much Site Investigation? Cost ($) Minimum project cost Total project cost Optimum SI cost Cost of site investigation & testing More extensive site investigation & testing program 1/8/2006 CIV E Knight 12 CIVE Knight 6

7 Risks and Consequences What is the consequence of failure or changing ground conditions? What will it cost to fix? Are people life in danger? Economic and social costs? 1/8/2006 CIVE Knight 13 Soil Sampling Cohesionless Soils 1/8/2006 CIVE Knight 14 CIVE Knight 7

Test Pits 1/8/2006 CIVE 554 - Knight 15 Hand tools (a) posthole

8 Test Pits 1/8/2006 CIVE Knight 15 Hand tools (a) posthole auger; (b) helical auger 1/8/2006 CIVE Knight 16 CIVE Knight 8

cutting head on auger flight attached with bolt (courtesy of William B.

9 Drilling with continuous-flight augers (courtesy of Danny R. Anderson Consultants, El Paso, TX) 1/8/2006 CIVE Knight 17 Carbide-tipped cutting head on auger flight attached with bolt (courtesy of William B. Ellis, El Paso Engineering and Testing, Inc., El Paso, TX) 1/8/2006 CIVE Knight 18 CIVE Knight 9

10 Hollow-Stem Auger Components (after ASTM,2001) 1/8/2006 CIVE Knight 19 Wash boring 1/8/2006 CIVE Knight 20 CIVE Knight 10

11 (a) Standard split-spoon sampler; (b) spring core catcher 1/8/2006 CIVE Knight 21 Configuration of Standard Penetration Test (SPT) hammers (a) safety hammer; (b) donut hammer (after Seed et al., 1985) N value = number of blows (hits) it takes to drive a standard split spoon 300mm with a 623N hammer dropped a distance of 762mm (ASTM D1586) 1/8/2006 CIVE Knight 22 CIVE Knight 11

12 N- value Number of blows to drive a SPT sample 300mm. 1/8/2006 CIVE Knight 23 N 60 N = 60 Nn H nbn 60 S n N 60 = Field corrected Standard Penetration number N = Measured penetration number n H = Hammer efficiency n B = Correction for bore diameter n S = Sampler correction n R = Correction for rod length R 1/8/2006 CIVE Knight 24 CIVE Knight 12

13 Schmertmann s (1975) correlation between N 60, σ 0, and φ for granular soils 1/8/2006 CIVE Knight 25 Canadian Foundation Manual 1/8/2006 CIVE Knight 26 CIVE Knight 13

14 Allowable Bearing Pressure q allow ~ 10 N (kpa) 1/8/2006 CIVE Knight 27 Cohesionless Soils 1/8/2006 CIVE Knight 28 CIVE Knight 14

15 Cohesive Soils (TILL) 1/8/2006 CIVE Knight 29 Soil Sampling Cohesive Soils 1/8/2006 CIVE Knight 30 CIVE Knight 15

Sampling devices (b) thin-walled tube; (c) and (d) piston sampler 1/8/2006 CIVE 554 - Knight 31 Soil

density Cohesive Soils Atterberg Limits Hydrometer Specific gravity Consolidation (oedometer)

16 Sampling devices (b) thin-walled tube; (c) and (d) piston sampler 1/8/2006 CIVE Knight 31 Soil Tests Cohesionless Soils Grain size distribution Specific gravity Direct shear Permeability Relative density Cohesive Soils Atterberg Limits Hydrometer Specific gravity Consolidation (oedometer) Unconfined compression Triaxial test Strength permeability 1/8/2006 CIVE Knight 32 CIVE Knight 16

17 Limitation of Field Collected Samples Sample disturbance Removal of insitu field stress Sample unloaded especially important in very soft (weak) soils that have a high insitu void ratio NEED INSITU SOIL PROPERTIES as this is what structure will feel..in the field 1/8/2006 CIVE Knight 33 Measurement of Insitu Properties Ground Water Table Location 1/8/2006 CIVE Knight 34 CIVE Knight 17

Casagrande-type piezometer 1/8/2006 CIVE 554 - Knight 35 2004 Brooks/Cole Publishing / Thomson Learning Groundwater Table Measurement

18 Casagrande-type piezometer 1/8/2006 CIVE Knight Brooks/Cole Publishing / Thomson Learning Groundwater Table Measurement Casagrande-type piezometer (courtesy of N. Sivakugan, James Cook University, Australia) 1/8/2006 CIVE Knight 36 CIVE Knight 18

19 Groundwater Table Measurement Open stand pipe with sand pack Stand pipe must be large enough to prevent meniscus effects Ground water table is where the water pressure is equal to the atmospheric pressure P water = P atmoshpere GWT will vary over seasons and changes in atmospheric pressure. GWT measure wrt a bench mark this must be stable.. 1/8/2006 CIVE Knight 37 Measurement of Insitu Properties Soft Cohesive Soils 1/8/2006 CIVE Knight 38 CIVE Knight 19

Shear Circular Cylinder of Soil 1/8/2006 CIVE 554 - Knight 39 Geometry of field vane (after

20 Shear Circular Cylinder of Soil 1/8/2006 CIVE Knight 39 Geometry of field vane (after ASTM, 2001) Measures Undrained Strength (Cu or Su) 1/8/2006 CIVE Knight 40 CIVE Knight 20

Field Vane Procedure 1/8/2006 CIVE 554 - Knight 41

21 Field Vane Procedure 1/8/2006 CIVE Knight 41 1/8/2006 CIVE Knight 42 CIVE Knight 21

22 Vanes and Rotation Rate The vanes have a rectangular shape and a height double their diameter, according to the recommendation included in the EUROCODE 7 (1977) and ASTM Standard Code (D 2573); in the latter one also vanes having a tapered end are allowed. The above mentioned codes prescribe that the rotation must be carried out at a rate of degrees/sec., that is (6 12 degrees/min). 1/8/2006 CIVE Knight 43 Rotation Rate Required rate never happens in the field unless it is mechanized. It is difficult to get driller to take one minute to do the test Make sure it is done consistently 1/8/2006 CIVE Knight 44 CIVE Knight 22

23 Determination of Su Undrained shear resistance at failure (Su) is calculated by the maximum torque required to cut the soil included into the cylinder obtained rotating the vane blades. The general formula, referred to rectangular vanes having height (H) and diameter (D), is: Su = T /((π D 3 /2) (H/D + a/2)) (1) where: T = maximum applied torque (deducted any friction). a = factor depending by the assumed shear stress distribution at the ends of the cylinder obtained rotating the vane blades and amounting to 2/3 for uniform shear stress. For rectangular vanes having H/D = 2, equation (1) is reduced to: Su = 6T / 7π D 3 = 0.273T / D 3 (2) The remoulded shear strength value is calculated using the above mentioned formula (2) introducing the value of the torque, free from any friction, measured after some vane rotation turns, that is when the soil offers a fast constant resistance. 1/8/2006 CIVE Knight 45 Undrained Strength & Effective Stress 1/8/2006 CIVE Knight 46 CIVE Knight 23

24 Field Vane Corrections S = λs u( corrected ) u ( field ) λ =correction factor 1/8/2006 CIVE Knight 47 Figure 2.18 Variation of λ with c u(vst) /σ 0 [see Eq. (2.31)] 1/8/2006 CIVE Knight 48 CIVE Knight 24

25 Variation of preconsolidation pressure with field vane shear strength (after Mayne and Mitchell, 1988) σ ' = 7.04 [ ] c S u ( field ) 1/8/2006 CIVE Knight 49 Variation of β with plasticity index (after Mayne and Mitchell, 1988) OCR = β S u ( field ) σ ' 1/8/2006 CIVE Knight 50 o CIVE Knight 25

26 Measurement of Insitu Properties SANDS and CLAY 1/8/2006 CIVE Knight 51 Mechanical friction-cone penetrometer (after ASTM, 2001) 1/8/2006 CIVE Knight 52 CIVE Knight 26

27 Electric friction-cone penetrometer (after ASTM, 2001) 1/8/2006 CIVE Knight 53 Friction Ratio (Fr) frictional resis tan ce Fr = = cone resis tan ce f q c c 1/8/2006 CIVE Knight 54 CIVE Knight 27

28 Penetrometer tests with friction measurement (after Ruiter, 1971) 1/8/2006 CIVE Knight 55 Variation of q c, σ 0, and D r for normally consolidated quartz sand (based on Baldi et al., 1982 and Robertson and Campanella, 1983) 1/8/2006 CIVE Knight 56 CIVE Knight 28

29 Variation of q c with σ 0 and φ in normally consolidated quartz sand (after Robertson and Campanella, 1983) 1/8/2006 CIVE Knight 57 Correlation between q c, F r, and the type of soil 1/8/2006 CIVE Knight 58 CIVE Knight 29

30 General range of variation of q c /N 60 for various types of soil (after Robertson and Campanella, 1983) 1/8/2006 CIVE Knight 59 Measurement of Insitu Properties Pressure Meters 1/8/2006 CIVE Knight 60 CIVE Knight 30

(a) Pressuremeter; (b) plot of pressure versus total cavity volume 1/8/2006 CIVE 554 -

31 (a) Pressuremeter; (b) plot of pressure versus total cavity volume 1/8/2006 CIVE Knight 61 Dilatometer and other equipment 1/8/2006 CIVE Knight 62 CIVE Knight 31

32 a) Schematic diagram of a flat-plate dilatometer; (b) dilatometer probe inserted into ground 1/8/2006 CIVE Knight 63 Dillatometer test result conducted at Porto Tolle, Italy (after Marchetti, 1980) 1/8/2006 CIVE Knight 64 CIVE Knight 32

33 Chart for determination of soil description and unit weight (after Schmertmann, 1986) Note: 1 t/m 3 = 9.81 kn/m 3 1/8/2006 CIVE Knight 65 Rock Sampling 1/8/2006 CIVE Knight 66 CIVE Knight 33

34 Rock coring (a) single-tube core barrel; (b) double-tube core barrel 1/8/2006 CIVE Knight 67 Casing and Core Sizes 1/8/2006 CIVE Knight 68 CIVE Knight 34

35 Rock Drilling Core Recovery = length core recovered x100 length of drill run Rock Quality Designation (RQD) Total length of core pieces100mm or longer RQD = length of drill run 1/8/2006 CIVE Knight 69 RQD 1/8/2006 CIVE Knight 70 CIVE Knight 35

Expect the Unexpected 1/8/2006 CIVE 554 - Knight 71 Peck, Hanson and Thornburn Foundation

36 Expect the Unexpected 1/8/2006 CIVE Knight 71 Peck, Hanson and Thornburn Foundation Engineering (Second Edition) 1974 Wiley & Son 1/8/2006 CIVE Knight 72 CIVE Knight 36

BASED ON LIMITED BOREHOLE DATA 1/8/2006 CIVE 554 - Knight 73

37 Expect the Unexpected Waste fill Clay Sand Gravel/cobble seams Boulders Changing ground conditions Organics DESIGN BASED ON LIMITED BOREHOLE DATA 1/8/2006 CIVE Knight 73 Expect the Unexpected 1/8/2006 CIVE Knight 74 CIVE Knight 37

38 Expect the Unexpected 1/8/2006 CIVE Knight 75 Expect the Unexpected Sand deposits discovered during hand carving slabs of clay during construction of Chicago subway system Origin of formation unknown 1/8/2006 CIVE Knight 76 CIVE Knight 38

moraine Markham, ON 1/8/2006 CIVE 554 - Knight 77 Expect the

39 Expect the Unexpected Permeability profile glacial deposit Chicopee, Mass USA (Terzaghi, 1929) Similar problem Oakridge moraine Markham, ON 1/8/2006 CIVE Knight 77 Expect the Unexpected 1/8/2006 CIVE Knight 78 CIVE Knight 39

40 Expect the Unexpected 1/8/2006 CIVE Knight 79 Expect the Unexpected 1/8/2006 CIVE Knight 80 CIVE Knight 40

41 New York City 1/8/2006 CIVE Knight 81 UW Field Test Site 1/8/2006 CIVE Knight 82 CIVE Knight 41

42 Test Pit Locations Site trailer Plan View 180 ft 8 in dia. HDPE pipe B Pipe Entrance A A West face East face excavation locations Pipe Exit B Cross Section 1/8/2006 CIVE Knight 83 Clay and Sand Bore limit Slurry 1/8/2006 CIVE Knight 84 CIVE Knight 42

Typical Soil Stratigraphy Clayey SILT Clay lens SILT SAND 1/8/2006 CIVE 554 - Knight 85 Subsurface

with some sand SAND with trace gravel, silt and clay SILT with varying sand content trace gravel

43 Typical Soil Stratigraphy Clayey SILT Clay lens SILT SAND 1/8/2006 CIVE Knight 85 Subsurface Soils Grain Size Distribution 100 clay lens Percent Passing Clayey SILT with some sand SAND with trace gravel, silt and clay SILT with varying sand content trace gravel and clay Particle Size (mm) 1/8/2006 CIVE Knight 86 CIVE Knight 43

$Expect the Unexpected Open fractures$

44 Expect the Unexpected Open fractures 1/8/2006 CIVE Knight 87 CIVE Knight 44

UNIT-I SOIL EXPLORATION

UNIT-I SOIL EXPLORATION SIDDHARTH GROUP OF INSTITUTIONS :: PUTTUR Siddharth Nagar, Narayanavanam Road 517583 QUESTION BANK (DESCRIPTIVE) Subject with Code : Geotechnical Engineering - II (16CE127) Year & Sem: III-B.Tech & II-Sem