FAMUFSU College of Engineering

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FAMU-FSU College of Engineering Department of
Civil Environmental Engineering Geotechnical
Design CEG 4801 Soil Strength By Kamal
Tawfiq, Ph.D., P.E. Summer 2009
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Normal Force N
? displacement
Direct Shear Test
Shearing Force T
Shear Resistance

• Repeat this test three times.
• Each time increase N
• - Record sn and tmax for each test
• Plot sn and tmax for each test
• Fit a straight line through the 3 points
• Find c and f

? T/A
Soil
sn1 N/A
tmax
?
?
?
Angle of Internal
Friction
t c s tan ?
tmax2
tmax3
tmax1
Cohesion c
sn
sn2
sn3
sn1
By Kamal Tawfiq, Ph.D., P.E.
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Load
Deformation
Axial Stress
Axial Stress
Unconfined Compression Test
By Kamal Tawfiq, Ph.D., P.E.
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Triaxial Compression Test
3- At Failure
2- Loading
1- Applying
Confining
Axial
s1
Stresses

stress
Ds
Deviator stress
Ds
f

s
s
Confining stress

2
Each Circle

s
s
s
s
One Test
2
q
s
s
Failure
2
Surface

Ds
s
f
Major
Principal Stress
s
Ds
1
Minor Principal Stress
deviator stress
2
Failure Surface
s2
s2
s1
s1
s1
By Kamal Tawfiq, Ph.D., P.E.
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