Earthquake-induced flow liquefaction in fines-containing sands under initial shear stress by lab tests and its implication in case histories

摘要

Volume change of sands in shearing is either contractive or dilative depending on relative positions to SSL (Steady State Line) on the void ratio versus effective stress state diagram. This strongly affects how sands tend to liquefy during earthquakes and behave thereafter under initial shear stresses loaded by sloping ground or nearby structures. Torsional simple shear undrained cyclic loading test results are addressed here to categorize liquefaction behavior of sand specimens with various relative densities and fines contents F-c so that the specimens are positioned on both sides of SSL under the effect of different initial shear stress. A flow-type failure on the contractive side of SSL is particularly focused, and how to evaluate its potential in terms of F-c under initial shear stress is discussed. Lastly, unprecedented liquefaction-induced flow failures recently occurred in very gentle slopes are addressed to discuss their basic mechanism and possible scenario in view of the findings in the laboratory tests.