Soil Response to Repetitive Changes in Pore-Water Pressure under Deviatoric Loading
Abstract
Introduction
Previous Studies: Asymptotic States
Pore-Fluid Pressure Oscillation
Volumetric Asymptotic State: Terminal Void Ratio
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Shear Asymptotic State: Shakedown or Ratcheting?
Experimental Study
Tested Sand: Properties
Property | KAUST 20/30 sand | Observations (Verifications using index test data) |
---|---|---|
Particle diameter | ||
Roundness | Image analysis—Roundness . The average radius of curvature of surface features divided by the radius of the largest inscribed sphere | |
Coefficient of uniformity | ||
Specific gravity | ||
Maximum void ratio | Estimated maximum void ratio: (Youd 1973) | |
Minimum void ratio | Estimated minimum void ratio: (Cho et al. 2006) | |
Friction angle at constant volume shear | Angle of repose method: (Santamarina and Cho 2001) Inferred from roundness is (Cho et al. 2006) | |
Critical state line CSL in e- | Intercept of at 1 kPa | |
Slope of | ||
Shear wave velocity parameters | Corresponds to Hertzian-based power model | |
Note: and values for | ||
Estimated threshold strain for contact loss in monotonic loading | Based on contact-loss analysis: | |
Confining stress | ||
Mineral: and (assumed in analysis) |
Note: Measured values are compared against values predicted from index properties for self-consistent verification.
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Experimental Devices and Configuration
Sample Preparation
Loading Histories
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Specimen characteristics | Pressure cycles | CU—AC | |||||||||||||||
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Stress conditions | Void ratio e | Shear strain a | |||||||||||||||
Conditions before pressure cycles relative to critical state | Test No. | Void ratio after specimen preparation | B-value | [kPa] | [kPa] | [kPa] | b | b | Volume change tendency during final undrained shear | ||||||||
Contractive side | 1 | 0.7461 | 0.972 | 50 | 100 | 250 | 0.33 | 0.7065 | 0.7000 | 1.0 | 49 | 0.090 | 0.0150 | 0.0015 | 0 | Contractive | |
2 | 0.7390 | 0.981 | 50 | 110 | 250 | 0.36 | 0.7027 | 0.6960 | 0.95 | 43 | 0.113 | 0.0205 | 0.0013 | 0 | No CU-AC | ||
3 | 0.7419 | 0.976 | 50 | 125 | 250 | 0.40 | 0.7031 | 0.6878 | 1.0 | 22 | 0.234 | 0.0250 | 0.0060 | 0 | Contractive | ||
4 | 0.7208 | 0.977 | 50 | 140 | 250 | 0.45 | 0.6828 | 0.6621 | 0.85 | 19 | 0.410 | 0.0240 | 0.0080 | 0 | Dilative | ||
5 | 0.7092 | 0.976 | 50 | 150 | 250 | 0.50 | 0.6722 | 0.6448 | 0.88 | 19 | 0.775 | 0.0230 | 0.0160 | 0 | Dilative | ||
6 | 0.7180 | 0.981 | 75 | 225 | 375 | 0.50 | 0.6660 | 0.6361 | 0.79 | 13 | 0.800 | 0.0220 | 0 | 0 | Dilative | ||
Dilative side | 7 | 0.6958 | 0.984 | 25 | 75 | 125 | 0.50 | 0.6783 | 0.6598 | 1.0 | 26 | 0.625 | 0.0220 | 0.016 | 0 | Dilative | |
8 | 0.6138 | 0.950 | 50 | 55 | 250 | 0.26 | 0.5900 | 0.5915 | 0.9 | 1 | 0.003 | 0.0400 | 0.00003 | 0 | No CU-AC | ||
9 | 0.6171 | 0.952 | 50 | 85 | 250 | 0.30 | 0.6021 | 0.6032 | 1.0 | 1 | 0.002 | 0.0280 | 0 | 0 | No CU-AC | ||
10 | 0.6151 | 0.951 | 50 | 125 | 250 | 0.40 | 0.6015 | 0.6030 | 0.9 | 1 | 0.010 | 0.0150 | 0.0001 | 0 | No CU-AC | ||
11 | 0.6196 | 0.966 | 50 | 140 | 250 | 0.45 | 0.6025 | 0.6029 | 1.0 | 1 | 0.075 | 0.0200 | 0.0001 | 0 | Dilative | ||
12 | 0.6145 | 0.977 | 50 | 153 | 250 | 0.52 | 0.6000 | 0.6008 | 1.0 | 1 | 0.080 | 0.0200 | 0.0001 | 0 | Dilative | ||
13 | 0.6133 | 0.965 | 50 | 155 | 250 | 0.53 | 0.5965 | 0.6052 | 1.0 | 7 | 0.170 | 0.0150 | 0 | 0 | No CU-AC | ||
14 | 0.6200 | 0.967 | 50 | 160 | 250 | 0.56 | 0.6032 | 0.6415 | 1.0 | 24 | 0.200 | 0.0500 | 0 | No CU-AC |
Note: Fitting parameters correspond to models introduced in the text. = deviatoric stress; = cyclic pressure amplitude; = maximum mean stress at the end of depressurization cycle; = maximum stress obliquity ; = initial void ratio at ; = terminal void ratio at ; = model parameter; = characteristic number; = shear strain at the end of first cycle ; , , and = model parameters; and = ratcheting parameter.
Experimental Results
Study 1: Maximum Stress Obliquity
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Study 2: Confining Effective Stress
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Analysis of the Complete Dataset
Shear Deformation
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Volume Change
Void Ratio
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Discussion
Particle-Scale Deformation Mechanisms: Threshold Strain
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Shakedown or Ratcheting?
Minimum Volumetric Strain
Maximum Volumetric Strain
Terminal Void Ratio
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Potential Volume Change: Obliquity
Design Guidelines
Comparison between Pressure Cycles versus -Loading Cycles
Ratio between Horizontal-to-Vertical Plastic Strains
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