Geotechnical Field Investigation Methods

Looking into the Ground

Trial pit, trench Disturbed sampling Undisturbed sampling Standard Penetration Test

Soil Sampling

Trial Pits and Trenches

Screw Sampler Piston Sampler

Auger Sampling with SPT rig

Piston Sampler

8

Field Investigation Methods

Standard Penetration Test (SPT) Cone Penetration Tests (CPT, CPTU) Pressuremeter Test (PMT) Dilatometer Test (DMT) Screw Plate - Plate Load Test (PLT) Vane Test (VST) Drilling Seismic tests

Field Investigation Methods

Swedish Weight Sounding, 1920

Field Investigation Methods

Standard Penetration Test

SPT Adjustment Approach

NCNN =1where CN = stress adjustment factor

' = effective overburden stress (t/ft2) N = SPT N-index (bl/ft) N1 = stress-adjusted N

and

20lg'lg1

'20lg77.0

=

=NCPeck et al. (1974)

=

r

vNC

'log25.11Seed (1976)

'r = a reference stress = 1 t/ft2 (100 KPa)

Friction Angle from SPT

CPT Test Equipment

Cone Penetration Test - CPT

CPT Point and Pore Pressure Cone

Comparison between CPT and SPT

0,00

0,25

0,50

0,75

1,00

1,25

0,001 0,01 0,1 1

PARTICLE SIZE, D50

q c/ N

Dry SandWet SandDry GravelRobertson & Campanella (1983)

Determining SPT Index

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.001 0.010 0.100 1.000

Mean Particle Size (mm)

qc/N

(M

Pa/B

low

s)

Robertson et al. (1983)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.00 0.50 1.00 1.50 2.00

Mean Particle Size (mm)

qc/N

(M

Pa/B

low

s)

S A N DFine Medium Coarse

Results of CPTU Test

Soil Classification from CPT Robertson and Campanella,1986

EslamiFellenius Profiling Chart

05

10

15

20

25

30

0 10 20 30Cone Stress, qt (MPa)

DEP

TH (

m)

0

5

10

15

20

25

30

0 100 200

Sleeve Friction (KPa)

DEP

TH (

m)

0

5

10

15

20

25

30

0 100 200 300 400

Pore Pressure (KPa)

DEP

TH (

m)

0

5

10

15

20

25

30

0.0 1.0 2.0 3.0 4.0

Friction Ratio (%)

DEP

TH (

m)

CLAY CLAYCLAY

SILT SILT SILT

SAND SAND SAND

Interpretation of CPTU Sounding

ESLAMI-FELLENIUS CHART

0.1

1

10

100

1 10 100 1,000

Sleeve Friction (KPa)

Con

e St

ress

, qE

(MPa

)5

1 2

3

4

Eslami-Fellenius Chart of Data

Vibro-compaction of Soils - CPT

tqE =25where E25 = secant modulus for a stress equal to about 25 % of ultimate stress = an empirical coefficient qt = cone stress

Soil Type Silt and sand 1.5

Compact sand 2.0

Dense sand 3.0

Sand and gravel 4.0

Determining E-Modulus CFEM, 1992

MttM Cqq =

Massarsch, 1994

Adjustment of Cone Resistance to Overburden Stress

5.0

=

m

rttM qq

Massarsch, 1994

Adjustment of Cone Resistance to Overburden Stress

( )321 0Kv

m

+=

Settlement Calculation Tangent Modulus Method

Stress Exponent Modulus Number

31

5.0)(r

tMqam

=

where m = modulus number for tangent modulus

a = an empirical modulus modifier,

which depends on soil type

qtM = stress-adjusted cone stress *)

r = reference stress = 100 KPa

Soil Type Modulus Modifier, a

Soft clay 3 Firm clay 5 Silt, organic soft 7 Silt, loose 12 Silt, compact 15 Silt, dense 20 Sand, silty loose 20 Sand, loose 22 Sand, compact 28 Sand, dense 35 Gravel, loose 35 Gravel, dense 45

*) Note, the adjustment requires an estimate of the overconsolidation ratio, OCR, and K0

Massarsch and Fellenius, 2001

Modulus Number, m from CPT

05

10

15

20

25

0 5 10Cone Stress, qt (MPa)

DEP

TH (

m)

0

5

10

15

20

25

0 10 20 30 40 50

Sleeve Friction, fs (KPa)

DEP

TH (

m)

0

5

10

15

20

25

0 500 1,000 1,500

Pore Pressure (KPa)

DEP

TH (

m)

0

5

10

15

20

25

0.0 0.5 1.0 1.5 2.0

Friction Ratio, fR (%)

DEP

TH (

m)

FILL

CLAYoverconsoli-dated due to building load

SILT and SAND

Results of CPTU

05

10

15

20

25

0 5 10 15 20Modulus Number, m)

DEP

TH (

m)

Oedometer test

0

5

10

15

20

25

0 1 2 3 4 5Cone Stress, qt (MPa)

DEP

TH (

m)

qt filtered

qt filtered and depth adjusted

Determination of Modulus Number

05

10

15

20

25

0 1 2 3 4 5Cone Stress, qt (MPa)

DEP

TH (

m)

0

5

10

15

20

25

0 25 50 75 100Modulus Number, m)

DEP

TH (

m)

qt measured

qt filtered

qt filtered and depth adjusted

0

5

10

15

20

25

0 5 10 15

Exponent "a"

From Oedometer Tests

From Filtered CPTU Data

Modulus Number, m from CPTU

05

10

15

20

25

30

35

40

0 1 2 3 4 5Cone Stress, qt (MPa)D

EPTH

(m

)0

5

10

15

20

25

30

35

40

0 20 40 60 80 100Modulus Number, m)

DEP

TH (

m)

qt measured

qt filtered

qt filtered anddepth adjusted

Massarsch and Fellenius, 2001

Modulus Number, m from CPTU

Determining Undrained Shear Strength

u = undrained shear strength qt = cone resistance corrected for pore water pressure on shoulder v = total overburden stress Nkt = a coefficient; 10 < Nkt < 20

kt

vtu Nq

=

Determining Density Index (Relative Density)

ID = density index CI = a coefficient; CI 0.41 KI = a coefficient; KI 2.75 qt = cone resistance corrected for pore

water pressure on shoulder r = reference stress = 100 KPa v = effective overburden stress

Ivr

tID K

qCI +='

ln

Relative Density from CPT Robertson, 1986

Density Index from CPT Baldi et al. , 1986

Friction Angle from CPT

= effective friction angle C = a coefficient; C = 0.37 (= 1/2.68) K = a coefficient; K = 0.1 q t = cone resistance corrected for pore

water pressure on shoulder v = effective overburden stress

KqCtg

v

t +='

lg'

Friction Angle from CPT

Interpretation of CPT and SPT

Dilatometer

Field Vane Test

Pressuremeter Test, PMT

Interpretation of PMT

Screw Plate Test

Plate Load Test

Soil-Rock Drilling

Rock Drilling

Rock Quality Designation, RQD

Seismic Refraction Test

SASW Falling Weight Test

54

!

ISSMGE TC 10 - SCPT Procedure to Measure Shear Wave Velocity

Seismic Cross-hole Test

Seismic Diagonal Testing

58

Seismic Down-hole Test

Determination of Wave Travel Time

Surface Wave Measurement

61

Medium dense sand

GV

P-wave: measurement in wave propagation direction S-wave: perpendicular to wave propagation direction

Shear Wave Propagation in Sand

62

0 0.05 0.1 0.15 0.2 0.25 2

1.5

1

0.5

0

0.5

Time,s

t = 0,033 s

Distance: 10 m

Distance: 15 m

Distance: 20 m

Distance: 25 m

Parti

cle

Velo

city

, mm

/s

f = 53 Hz

v = 0,5 mm/s

Interpretation of Vibration Measurement

63

Deformation vs - Time

Time

Displacement Amplitude

t

s

Interpretation of Vibration Measurement

64

Deformation, s

s = v / (2 f ) = 1,5 10-3 mm

Shear Wave Speed, Cs

Cs = L /t = 5 m / 0,033 sec = 151 m/s

Shear Modulus, Gmax (small strain)

Gmax = Cs2 = 41 MPa (Density, = 1,8 t/m3)

Interpretation of Vibration Measurement

65

Shear Strain,

= v /CS = 0,5 x 10-3 / 151= 3,3 x 10- 4 %

Shear Strain rate at 53 Hz

= 0,0011 % / min

Wave Length,

= Cs / f = 151 / 53 = 2,85 m

Modulus Reductions Factor, R for Determination of Static Modulus

66

Relationship Between G-, E- and M-Modulus

Elastic (Youngs) Modulus:

Confined Modulus:

Assuming = 0.3:

Samband mellan vgfart och deformationsmodul

68

Mmax = CP2

Gmax = CS2E = 2(1+ )G

M = 2(1 )(1 2 )G

M: Kompressionsmodul G: Skjuvmodul

E: Youngs modul : Poissons tal

: Totaldensiteten