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Part 7. Geotechnical Characterization

C. Vipulanandan, Ph.D., P.E.Professor of Civil Engineering

Director of CIGMATDirector of THC-IT

Department of Civil and Environmental Engineering

University of HoustonHouston, Texas 77204-4003

I G M A TC

1994

Methods of Geotechnical Characterization

1.Soil & Rock Sampling

2. In situ Methods

3. Nondestructive MethodsElastic Waves, Resistivity

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In situ Tests: Why? When? Where?

1.Sampling is difficult in Soils: Soft Soils to Cemented SoilsRocks (Soft to Hard)

2. Contaminated Sites (ESI)

3. Continuous Profiling (soft spots, mixed profile)

4. Bottom of a borehole

5. Time and Cost

Penetrometers (Since 1846…)

TCP (from Tex-132-E)CPT (from ASTM D5778).SPT (from ASTM D1586)

Dynamic Drive/Soil to Rock

Static/SoftSoil

Dynamic/Sandy Soils ? in/100 blow

3

StandardPenetrationTest (SPT)

4

45%60%

95%

5

Drilling To Sample Depth

Drilling a soil boring using a flight auger

Drilling a soil boring using the rotary wash method

6

Performing the Standard Penetration Test

Connecting the split spoon to the drill rod

Driving the spoon with the safety hammer

Borehole ???

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SPT Correction N60

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9

10

11

12

Texas ConePenetration

(TCP)

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TxDOT Cone Penetrometer Test

TxDOT Cone (3 “ dia) Attaching TCP Cone to Drill Stem

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TxDOT Geotechnical Manual

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1994

UncementedClay Shale?

How to Identify?DHP

Side Friction?

End Bearing ?

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TCP (in/100 Blows) vs. Rock Strength

The relationship between TCP andunconfined compressive strength (qu) forthe uncemented clay shale rock can berepresented as follows:

CIGMAT Downhole Penetrometer (New)

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DHP Steel Case

Penetration Piston

DHP head

Protector Plate

Spring

Sliding Ring

DHP in the Field

DHPAdopter

Kelly Bar

Adaptor

Slurry

RingMoved

DHP

Kelly Bar

Adaptor

Going in

Slurry Filled Borehole

Pulled Out

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Sampler Tube

Downhole Penetrometer

Sampler Tube (3in diameter)

DHP in Rock and Soil

qu-qmax Relation

y = 9.0623xR2 = 0.914

0

200

400

600

800

1000

1200

1400

1600

0 20 40 60 80 100 120 140 160

qu(psi)

qm

ax(p

si)

Dallas Results

Houston Results

Lab Results

Lab Results

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Gold Spings for Soils and Soft Rocks

y = 85.705x

R2 = 0.9334

0

20

40

60

80

100

120

140

160

0 0.5 1 1.5 2

DHP Displacement (inch)

qu (

psi)

Green Spings for Soft Rocks

y = 108.92x

R2 = 0.5782

0

20

40

60

80

100

120

140

160

180

0 0.25 0.5 0.75 1 1.25 1.5

DHP Displacement (inch)

qu

(p

si)

Gold SpringsForSoils and Rocks

Green Spring

For

Soft Rocks

CONCLUSIONS

(1) SPT is a Popular method. Can be used with Caution.

(2) TCP is used in Texas and few other States. Further Verification is Needed.

(3) Down Hole Penetrometer Has the Potential for Field Applications (?)

I G M A TC

1994

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I G M A TC

1994