St and nda ar d Pen et r at i o n an d Co n e Pen et r at i o n Tes t s
Prof Pro f . J i e Han Han , Ph.D., Ph.D., PE The Unive ni vers rsit ity y of Kans Kansa as
Out utli line ne of Pre rese sent nta ati tion on • Introduction Pen et r at i o n Tes Tes t • St an d ar d Pe
• Co n e Pen et r at i o n Tes t valua ation ti on of o f Liqu Li que efact factio ion n • Evalu
Out utli line ne of Pre rese sent nta ati tion on • Introduction Pen et r at i o n Tes Tes t • St an d ar d Pe
• Co n e Pen et r at i o n Tes t valua ation ti on of o f Liqu Li que efact factio ion n • Evalu
Introduction
Ins nsit itu u Test Testin ing g Devi vice ces s
St an d ar d Pen et r at i o n Tes t (SPT)
St an d ar d Pen et r at i o n Tes t (SPT) Ad A d v ant an t ages ag es • L ong ong r ec o rd o f ex p erie rien c e vaila able bl e test test data data and corr corre elati lation on • Many avail • Per f o r m t h e t es t d u r i n g s o i l s am p l i n g u s i n g t h e splitspli t-spoo spoon n sample sampler r in expe xp ensiv ns ive e • Fast and ine
Disadvantages • Crude • Many varia variants nts No c o n t i n u o u s s o i l p r o f i l e
SPT Test Procedure • Drill a boring to the depth of the test • Insert the SPT sampler (split-spoon sampler) into the boring • Raise a 63.5kg (140lb) hammer to a distance of 760mm (30in) and allow it to fall. Repeat this process until the sampler has penetrated 450mm (18in). Record the number of hammer blows required for each 150mm (6in.) interval • Compute the N value by summing the blow counts for the last 300mm (12in) of penetration • Remove the SPT sampler and soil sample
Standard Penetration Test (SPT)
Standard Penetration Test (SPT)
Standard Penetration Test (SPT)
Standard Penetration Test (SPT)
Hollow Stem in Place (Widener)
Standard Penetration Test (Widener)
SPT with Automatic Hammer (Widener)
SPT with Automatic Hammer (KU)
Auger Pulled out (Widener)
Split Barrel (Widener)
Boring Log
Some Special SPT Terms
• Refusal - N>50 for any of the intervals or N>100
• W/H - weight of hammer • W/R - weight of rod
Corrected SPT N Value The measured N value may be corrected by considering a number of key factors: N 60 =
C E C B CSC R N 0.60
where N60 = SPT N value corrected for field procedures; CE = hammer efficiency; CB = borehole diameter correction; CS = sampler correction; CR = rod length correction;
Corrections to SPT N-value Effect
Variable
Overburden Stress Energy Ratio1 Borehole Diameter Sampling Method
CN
vo'
· · · · · · ·
Term
Safety Hammer Donut Hammer Automatic Hammer 65 to 115 mm 150 mm 200 mm Standard sampler Sampler without
Value (Pa/
0.5 vo')
but < 2
CE
0.6 to 0.85 0.3 to 0.6 0.85 to 1.0
CB
1.00 1.05 1.15
CS
1.0 1.1 to 1.3
CR
1.0 0.95 0.85 0.75 60 + 25 log D 50
Rod Length
· liner · · · ·
Particle Size
Median Grain Size (D50) of Sand in mm
CP
Aging
Time (t) in years since deposition
CA
1.2 + 0.05 log (t/100)
COCR
OCR0.2
Overconsolidation
10 m 6 4 3
OCR
to to to to
30 m 10 m 6m 4m
Corrected SPT (N1)60 Value The N value may also be corrected by considering the overburden stress at the location where the SPT is conducted:
( N1 )60 = N 60
100kPa
σ 'z
Consistency and Undrained Shear Strength of Clay N value (blows/ft)
Consistency
Undrained shear strength, s u (tsf)
0 to 2 2 to 4 4 to 8 8 to 15 15 to 30 >30
Very soft Soft Medium Stiff Very stiff Hard
<1/8 1/8 to 1/4 1/4 to 1/2 1/2 to 1 1 to 2 >2
(Terzaghi and Peck, 1967)
Relative Density and Friction Angle of Sand vs. SPT N N value (blows/ft)
Density description
Dr (%)
0 to 4 4 to 10 10 to 30 30 to 50 >50
Very loose Loose Medium Dense Very dense
0 to 15 15 to 35 35 to 65 65 to 85 85 to 100
(Terzaghi and Peck, 1967)
<28 28 to 30 30 to 36 36 to 41 >41
Relative Density Dr vs. SPT N60 Cubrinovski and Ishihara (1999) proposed the following correlation for the relative density of granular soils
⎡ N 60 (0.23 + 0.06 / D50 ) Dr (%) = ⎢ 9 ⎣
1. 7
z’
⎛ 98 ⎞⎤ ⎜⎜ ' ⎟⎟⎥ ⎝ σ z ⎠⎦
= effective overburden stress in kPa
D50 = mean grain size in mm
0.5
Relative Density Dr vs. SPT N
Friction Angle vs. SPT N60
Friction Angle ’ vs. SPT N60 Kulhawy and Mayne (1990) proposed the following correlation for the effective friction angle of sands
φ ′ = tan
z’
−1
⎡ ⎤ N 60 ⎢12.2 + 20.3(σ ' / p )⎥ z a ⎦ ⎣
0.34
= effective overburden stress in kPa
pa = atmospheric pressure ( 100kPa)
Friction Angle vs. SPT (N1)60 Wolff (1989) proposed the following correlation for the effective friction angle of sands
φ ′ = 27.1 + 0.3 N 1 )60 − 0.00054( N 1 )60 2
( N 1)60 = corrected SPT N60
Undrained Shear Strength vs. SPT N Terzaghi and Peck (1967):
su / pa
≈ 0.06 N
Hara et al. (1974):
su / pa
≈ 0.29 N 0.72
Undrained Shear Strength vs. SPT N
OCR vs. SPT N for Clays
Elastic Modulus vs. SPT N Value
• Es
(5N60)x100kPa (sands with fines)
• Es
(10N60)x100kPa (clean NC sands)
• Es
(15N60)x100kPa (clean OC sands) (Kulhawy and Mayne, 1990)
cu = undrained strength Is One Number Enough??? T = unit weight DR = relative density IR = rigidity index T = unit weight ' = friction angle LI = liquefaction index OCR = overconsolidation ' = friction angle K0 = lateral stress state c' = cohesion intercept eo = void ratio eo = void ratio Vs = shear wave qa = bearing capacity E' = Young's modulus p' = preconsolidation Cc = compression index Vs = shear wave qb = pile end bearing SAND E' = Young's modulus fs = pile skin friction = dilatancy angle k = permeability qb = pile end bearing qa = bearing stress f = pile skin friction CLAY
N
Cone Penetration Test
Cone Penetration Test (CPT) [ASTM D3441]
• A common in-situ test method • Once known as the Dutch cone • Two types: - Mechanical cone - Electric cone
Casing
Connecting rod
Cone Penetration Test (CPT)
Cone
(a) Dutch cone
Filter to facilitate pore water pressure measurement
(b) Piezocone
Mechanical CPT
Electronic CPT
Cone Penetration Test (CPT)
Cone Penetration Test (CPT)
Cone Penetration Test (CPT)
Rig
Cone Tip
Cone Shaft
Saturation of Cone Tip
Pouring Water into Tip Connection
Screwing in Cone Tip
Assembled CPTU Probe
CPT with Cableless Rods
CPT Penetrating the Ground
Adding A Rod with Cable during CPT Test
Conducting CPT Test on Truck
CPT Profile q t (MPa) 0
f s ub
) s r e t e m ( h t p e D
20
40
u b (kPa)
f s (kPa) 60
0
500
1000
-200
0
0
4
4
8
8
12
12
16
16
20
20
24
24
0
200 400 600 800
CPT Parameters
• Tip resistance, q t • Side resistance, f s • Pore water pressure, u b • Friction ratio, Rf = f s /q t x 100%
Tip Resistance, q t vs. q c qc
Area ratio A t = D2/4
d
A n = d 2/4 ub
D
an =d 2/D2 q t vs. q c q t =q c + u b (1 – an )
q
Seismic Piezocone Test
Obtains Four Independent Measurements with Depth:
Cone Tip Stress, qt Penetration Porewater Pressure, u Sleeve Friction, fs Arrival Time of Downhole Shear Wave, ts
Vs fs u2 u1
60o
Downhole Shear Wave Velocity
Anchoring System Automated Source Polarized Wave Downhole V
SCPTu at Amherst Test Site
Geoenvironmental Cone
Other Cone Tests
Determination of Soil Parameters
CPT vs. SPT Advantages: - Obtain more information (two parameters or more vs. one parameter) - Get a continuous and more consistent soil profiles
Disadvantages: - No soil sampling - Unreliable for soils containing large particles (such as: gravel)
CPT Soil Classification
Rf (%)
Type of soil
0 – 0.5
Loose gravel fill
0.5 – 2.0
Sands or gravels
2–5
Clay sand mixture and silts
>5
Clays, peat, etc.
CPT Soil Behavioral Classification
Soil Behavio r Type (Roberts on et al., 1986; Robertson & Campanell a, 1988) 1 – Sensitive fine grained 5 – Clayey silt to silty clay 9 – sand 2 – Organic material 6 – Sandy silt to silty sand 10 – Gravelly sand to sand 3 – Clay 7 – Silty sand to sandy silt 11 – Very stiff fine grained* 4 – Silty clay to clay 8 – Sand to silty sand 12 – Sand to clayey sand*
q c versus Dr
Relative Density of Sands
⎛ q c / 100kPa ⎞ ⎟ D r = ⎜ ⎜ 305Q OCR 0.18 ⎟ c ⎝ ⎠
100 kPa
σ
' z
x100%
Qc = compressibility factor (= 0.9 to 1.1)
Friction Angle for Uncemented Quartz Sand
q c versus ’ Friction angle of sand:
φ' ≈ tan
−1 ⎡
⎛ q c ⎞⎤ ⎢0.1 + 0.38 log ⎜⎜ ' ⎟⎟⎥ ⎢⎣ ⎝ σ z ⎠⎥⎦
(Kulhawy and Mayne, 1990)
q c versus Normalized cone tip Resistance, qc/pa
tc ’
of Sands
Relative Approximate φtc’ Density (degrees)
< 20
Very loose
< 30
20 to 40
Loose
30 to 35
40 to 120
Medium
35 to 40
120 to 200
Dense
40 to 45
> 200
Very dense
> 45
q c versus c u cu =
qc − σ vo N k
= cone factor σ vo = γz = total overburden pressure Nk
Lunne and Kelven (1981) Type of clay Normally consolidated Overconsolidated at shallow depths at deep depths
Cone factor 11 to 19 15 to 20 12 to 18
Preconsolidation Stress
Preconsolidation Stress
Preconsolidation Stress
Preconsolidation Stress and Undrained Shear Strength Preconsolidation stress: σ p' = 0.29qc
(Kulhawy and Mayne, 1990)
For low OCR clays with low to moderate PI: cu / σ p' = 0.23 ± 0.04
(Jamiolkowski, 1985)
Effective Cohesion
Coefficient of Consolidation, c h Teh and Houlsby (1991) proposed the following Formula to estimate c h : *
ch
=
T R
2
I r
t
T* = modified time factor for a given probe geometry and porous element location t = measured time R = radius of the probe Ir = rigidity index = G/s u
Modified Time Factors, T*
Degree of Consolidation U = 1 −
ut − u0 ui − u 0
ut = pore pressure at time t ui = initial pore pressure at t=0 u0 = hydrostatic pore pressure U = 50%
t50
Dissipation of Porewater Pressure ui
u0
t50
Permeability of Soils
Hor oriz izon onta tall Coe Coeff ffic icie ient nt of o f Con Conso soli lida dati tion on
Ela lasti stic c Modu odulu lus s of Soil oils s Elasti lastic c modulus modu lus of o f sands sands::
E ≈ 2q c
(Schmertmann, 1970)
Soil Sand (normally consolidated) Sand (overconsolidated) Clayey sand Silty sand Soft clay
E (2 – 4) qc (6 – 30) qc (3 – 6) qc (1 – 2) qc (3 – 8) qc
Sh ear Wav e Vel o c i t y , Vs un dame ment nta al mea measure su reme ment nt in all soli so lids ds • Funda (ste st eel, conc co ncrete rete,, wood wo od,, soil so ils, s, rock ro cks) s) ni tia al sma sm allll -stra st rain in stif st iffn fne ess repr repre esent sente ed by by • Initi G0 = Vs 2 shea shear modulu mod ulus: s: (alia ali as Gd y n = Gm ax = G0)
A p p l i es t o all al l s t ati at i c & d y n ami am i c p r o b l ems em s at • Ap small small stra s trains ins ( s < 10-6) A p p l i ed t o u n d r ain ai n ed & d r ain ai n ed c ases as es • Ap r educt du ctio ion n fa f actor ct or for fo r re r eleva levant nt stra st rain in • Need re levels.
Analyses Based on CPT Results
f sc
ub
f s
Pile Toe Bearing Capacity Based on CPT Results Pile toe bearing capacity q t ’ = Ct (q t – u b ) Ct = toe bearing coefficient (Ct = 1.0) q t = CPT cone tip resistance u b = pore water pressure measured behind the cone point
Pile Side Friction Resistance Based on CPT Results Side friction resistance f s = Cs (q t – u b ) Side friction coefficient, Cs (Eslami & Fellenius, 1997) Soil Type
Range
Typical design value
Soft sensitive soils
0.0737 – 0.0864
0.08
Clay
0.0462 – 0.0556
0.05
Stiff clay / mixture of clay & silt
0.0206 – 0.0280
0.025
Mixture of silt and sand
0.0087 – 0.0134
0.01
Evaluation of Liquefaction
Notation for Description of Earthquake Location
Ground surface
Epicentral distance Epicenter Site or observer
Hypocentral distance
Focus or hypocenter
Earthquake Magnitude
Richter Local Magnitude, ML - the log10 of the maximum trace amplitude (in micrometer) recorded on a Wood-Anderson seismometer located 100km from the epicenter
Surface Wave Magnitude, Ms - based on the amplitude of Rayleigh waves with a period of 20 sec.
Body Wave Magnitude, mb - based on the amplitude of the first few cycles of p-waves
Japanese Meteorological Agency Magnitude, M JMA - based on the amplitude of long-period waves
Moment Magnitude, Mw - based on the seismic moment
Earthquake Magnitude
Earthquake Map
Sand Boiling during Seattle Earthquake
Failur Induced by Liquefaction (Loma Prieta earthquake, 1906)
Uniform Cyclic Shear Stress
τmax
τ cyc
= 0.65τ max = 0.65
amax g
σ v r d
Stress Reduction Factor
Cyclic Stress Ratio (CSR) Cyclic stress ratio (CSR) is defined as:
CSR =
τ cyc ' vo
σ
CSR versus (N1)60 for Clean Sands
Magnitude Correction Factors Magnitude, M
CSRM/CSRM=7.5
5¼
1.50
6
1.32
6¾
1.13
7½
1.00
8½
0.89
Effect of Fine Contents
CSR versus q c
