Abstract:Under undrained conditions,the phenomena of strain softening occur when the loess taken from northern France is subjected to monotonic loading,while liquefaction or cyclic mobility phenomenon is observed under cyclic loading. The bounding surface model and the generalized plasticity model are used to predict this behaviour. It is shown that the accumulated rate of plastic strain under cyclic loading is slower than that in softening region under monotonic loading. The sensitivity of model parameters is discussed;and it is concluded that both the bounding surface model and the generalized plasticity model can describe the loess liquefaction satisfactorily,provided that appropriate parameters are defined.