Experimental study of development of strain and pore water pressure during liquefaction of saturated Lanzhou loess

Using a dynamic hollow cylinder apparatus WF12440 as the test platform,this paper firstly studied the loess saturation by the back pressure method.The developments of pore water pressure,axial strain,deviatoric stress-axial strain curve during liquefaction are then investigated.Testing results indicate that the back pressure method can be successfully used for loess saturation;and the pore water pressure coefficient could achieve 0.95 and more.Under the condition of isotropic consolidation,pore water pressure increased slowly at the beginning;after several cycles the pore water pressure increased rapidly until it reached the effective consolidation pressure.The deviatoric stress-axial strain curve developed with the increase of cycles;and plastic strain increased step by step.When the axial strain was less than 2%,the pore water pressure increased slowly;afterwards,its increase ratio was much larger,and a strain of 3% could appear at the initial liquefaction process.Before liquefaction of the loess,the mean effective stress under negative deviatoric stress is larger than that under the positive deviatoric stress.