Features of Liquefaction-Induced Damages
Seismic liquefaction occurs in loose sandy ground that is saturated with water. When pore water pressure rises during shaking, the effective stress decreases with time (1.4);
Shear modulus of sand decreases as the effective stress decreases. Shear strength of sand decreases with (effective stress) tanφ. Thus, sandy ground becomes softer with time.
In the extreme case, the effective stress becomes zero. Since the effective stress stands for the contact force at grain-to-grain contacts in sand, the zero effective stress suggests that there is no effective contact between grains. Hence, grains are actually floating in pore water without constraint from surrounding sand particles. Now sand is similar to mud water; grains are in suspension in water.
After complete loss of effective stress, sand has neither shear modulus nor shear strength, and consequently develops large deformation even under minor shear stress (Figs. 17.1 and 17.2).
KeywordsEffective Stress Pore Water Pressure Earth Pressure Excess Pore Water Pressure Sheet Pile
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