Because initial static shear stress exists in a sloped ground

soil is more possible to be liquefied and largely deformed than the level ground when subjected to a strong earthquake. So it is necessary to study the effects of initial static shear stress on the liquefaction and large deformation of liquefied soil. A series of cyclic torsional shear tests examine the saturated silts. The single amplitude shear strain exceeds 50% in the tests. The testing results show that the pore pressure of the specimens can reach the effective confining pressure under the combined effect of initial and cyclic shear stresses

namely the effective stress equals zero. Moreover

it is found that the cumulative strain increases gently during initial stage

and grows greatly later. Two types of large deformation of saturated silt can be distinguished: the cyclic liquefaction and the cumulative strain. At the same time

it is shown that

the cyclic shear strength decreases with the increasing of initial static shear stress ratio until initial static shear stress ratio reaches cyclic shear stress ratio

and starts to increase thereafter.