1. Geotechnical Site Characterization by Cone Penetration Testing
Paul W. Mayne, PhD, P.E.
Professor, Geosystems
Civil & Environmental Engineering
Mid-America
Earthquake Center
FHWA

2. Standard Penetration Test
Rotary-drilled
Borehole
Standard Penetration Test (SPT)
Procedures: ASTM D 1586
N = measured Number of Blows to drive sampler 300 mm into soil.

3. Representative SPT Profile

4. Corrections to SPT N-value
Effect
Variable
Term
Value
Overburden
Stress
svo' CN
(Pa/svo')0.5 but < 2
Energy
Ratio1
·        Safety Hammer
·        Donut Hammer
·        Automatic Hammer CE
0.6 to 0.85
0.3 to 0.6
0.85 to 1.0
Borehole Diameter
·        65 to 115 mm
·        150 mm
·        200 mm CB
1.00
1.05
1.15
Sampling
Method
·        Standard sampler
·        Sampler without liner CS
1.0
1.1 to 1.3
Rod
Length
·        10 m to 30 m
·        to 10 m
·        to 6 m
·        to 4 m CR
0.95
0.85
0.75
Particle
Size
Median Grain Size (D50) of Sand in mm CP
log D50
Aging
Time (t) in years since deposition CA
log (t/100)
Overconsolidation
OCR
COCR
OCR0.2
1 Obtain by energy measurement per ASTM D4633

5. Corrections to SPT N-value
Nmeasured = Raw SPT Resistance (ASTM D 1586).
N60 = (ER/60) Nmeasured = Energy-Corrected N Value where ER = energy ratio (ASTM D 4633). Note: 30% < ER < 100% with average ER = 60% in the U.S.
N60  CE CB CS CR Nmeas = Estimated corrected N
(N1)60 = CN N60 = Energy-Corrected SPT Value normalized to an effective overburden stress of one atmosphere: (N1)60 = (N60)/(vo’) with stress given in atm. (Note: 1 atm = 1 bar = 100 kPa = 1 tsf).

6. Cone Penetrometers Electronic Steel Probes with 60° Apex Tip
ASTM D 5778 Procedures
Hydraulic Push at 20 mm/s
No Boring, No Samples, No Cuttings, No Spoil
Continuous readings of stress, friction, pressure

7. Cone Penetration Tests (CPT)
Cone Trucks
Mobile 25-tonne rigs with
enclosed cabins to allow
testing under all weather
conditions

8. Corrections to CPT
Tip Stress correction for porewater pressures on unequal areas – Important in Intact Clays & Silts
Sleeve Friction correction for porewater pressures – Use equal end areas on friction sleeve
Baseline corrections – Obtain before & after sounding

9. Anchored Cone Rig Mud Island, Downtown Memphis, TN
6-tonne Geostar truck with 20-tonne hydraulic pushing system
No special license
Twin earth anchors
Has penetrated to depths over 32+ meters at sites in SC, AL, MO, TN, & AL

10. CPT Profile, Downhole Memphisfs ub qt

11. Comparison CPT and SPT Downtown Memphis

12. Seismic Piezocone Test
Obtains Four Independent
Measurements with Depth: Vs
Cone Tip Stress, qt
Penetration Porewater Pressure, u
Sleeve Friction, fs
Arrival Time of Downhole Shear
Wave, ts fs u1 u2
60o qc

13. Downhole Shear Wave Velocity
Anchoring System
Automated Source
Polarized Wave
Downhole Vs

14. Automated Seismic Source
Electronically-actuated
Self-contained
Left and right polarization
Modified beam uses fin to enhance shear wave generation
Successfully tested to depths of 20m
Capable of being used with traditional impulse hammer

15. Downhole Shear Waves Left Strike Right Strike CROSSOVER Method
Shear Wave at 8.15 m
Shear Wave at 9.20 m
CROSSCORRELATION
Maximum crosscorrelation at Dt = 6.75 ms
Shear wave velocity = 155 m/s
Time shift (ms)

16. Sod Farm, Charleston, SC

17. CPT Soil Behavioral Classification
Soil Behavior Type (Robertson et al., 1986; Robertson & Campanella, 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*
*Note: Overconsolidated or cemented

18. Sounding - Shelby County, TN

19. CPT-Related Websites
The Liquefaction Site (and CPT site):
Link page to manufacturers, suppliers, and CPT services:
Listing of available videos on CPT and other in-situ tests:
The book Cone Penetration Testing in Geotechnical Practice (Lunne, Robertson, & Powell, 1997):
Review:
Order: