A series of triaxial compression tests

composed of isotropically and anisotropically consolidated undrained compression (ICU and ACU) tests and constant shear drained compression (CQD) tests

are carried out on undisturbed saturated loess by GDS apparatus. The results of ICU and ACU tests performed at the in-situ stress level show that the soils are of consistently strain-softening in the stress-strain relations. The steady-state line and the potential region of instability are obtained from ICU and ACU test results. A necessary condition for liquefaction is that the soil state initially lies in or is brought into the potential instability region; CQD tests demonstrate that the mobilized friction angle is far less than the steady-state angle and that the soil experiences undrained contractive failure suddenly at very small strains when its stress path during drained loading tries to cross the potential instability region; thus the proposed instability region is validated. Based on the location of the region of potential instability and the stress state of slope soil

a method of static liquefaction analysis is proposed for loess landslides caused by rise in groundwater table.