lecture 01 shear stress laboratory test...
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CIE3032 지반공학및실험 Lecture 01 shear strength 1
LECTURE 01
Shear stress
Laboratory test methods
CIE3032 지반공학및실험 Lecture 01 shear strength 2
Lecture outline
Laboratory test methods to measure shear strength of soils
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1. Direct Shear Test
Failure Surface
CIE3032 지반공학및실험 Lecture 01 shear strength 4
Tests for Shear Strength of Soils 1. Direct Shear Test
Failure Surface
v
h
vf = v
hf
hf
Initial State of Stress State of Stress at Failure
CIE3032 지반공학및실험 Lecture 01 shear strength 5
Tests for Shear Strength of Soils 1. Direct Shear Test
’ = 30
Initial Condition’v = 60 kPaK0 = 0.5c’ = 0
Test is performed in Drained condition.
Determine ’1 and ’3 at failureDetermine plane of major principal plane at failure(Assume that the failure plane is formed at an angle that follows the Mohr hypothesis)
CIE3032 지반공학및실험 Lecture 01 shear strength 6
Tests for Shear Strength of Soils 1. Direct Shear Test
Advantages•inexpensive, fast, and simple
Disadvantages•impossible to control drainage•deformation is strongly inhomogeneous
(deformations is concentrated in a zone in the center of the shear box) •uncontrolled rotation of principal planes•failure plane might not be the critical or weakest direction
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Tests for Shear Strength of Soils 2. Simple Shear Test
v
h
v
h
hv
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Tests for Shear Strength of Soils 3. Triaxial Test
CIE3032 지반공학및실험 Lecture 01 shear strength 9
Tests for Shear Strength of Soils 3. Triaxial Test
MeasurementsAxial stressConfining stressAxial strainVolumetric change (pore water) only for saturate soil specimens
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CD test
Types of Triaxial Test (TX)CD Consolidated – DrainedCU Consolidated – UndrainedUU Unconsolidated - Undrained
CIE3032 지반공학및실험 Lecture 01 shear strength 11
CD test
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CD test
CIE3032 지반공학및실험 Lecture 01 shear strength 13
CD test
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CD test
CIE3032 지반공학및실험 Lecture 01 shear strength 15
CD test
Estimate Initial Effective Vertical ’v and Horizontal Stress ’v
Apply in-situ ’v and ’h in the triaxial cell (Drained or Undrained?) Consolidation Stage
Apply additional ∆’v that corresponds to the actual loading.(Drained!)
- Saturated sand- Clay
- Loading is applied very slowly to the soft clay deposit.
- Long-term stability
문제점Clay Low Permeability Takes a lot of time to consolidate!
CIE3032 지반공학및실험 Lecture 01 shear strength 16
Stress path of CD
Kf Line
p
q
’v = ’ h
p = (’v + ’ h)/2q = (’v - ’ h)/2
Apply ∆’v =’v + ∆ / ’h =’h
p = ([’v + ∆] + [’ h])/2q = ([’v + ∆] - [’ h])/2