Settlement of silty sand deposits following liquefaction during earthquakes

The procedure for the evaluation of settlement of silty sand deposits following liquefaction is examined by the data obtained using a large triaxial test apparatus. Multiple series of irregularly excited undrained loading tests were conducted on Toyoura sand as well as on other soils with different grain compositions containing silts. Saturated and isotropically consolidated soil specimens were axially loaded undrained, using some acceleration time histories obtained in 1995 Kobe earthquake as inputs for irregular excitation time histories. The specimens were drained after application of varying amplitudes of axial stress, and the resulting volume change was measured. Based on the results of such tests, the relation between factor of safety against liquefaction and maximum shear strain, and the relation between post-liquefaction volumetric strain and maximum shear strain are examined, and the relations between factor of safety and post-liquefaction volumetric strain for different soils with various contents of silts are deduced. Based on the relations obtained as above, the procedure for the evaluation of the post-liquefaction settlement of silty sand deposits is proposed.