Pore pressure development during non-uniform cyclic loading

Results of non-uniform cyclic triaxial tests on Monterey #0 sand are presented. Two series of tests are performed in which the number and magnitude of stress cycles are unchanged but the order in which the cycles are applied varies. Results of these tests show that pore pressure generation depends upon the order as well as the magnitude of the non-uniform stress cycles. To account for this dependence, a pore pressure generation model which accounts for the influence of cyclic shear stress ratio upon the shape of the pore pressure generation curve is developed. Pore pressures calculated using the stress ratio dependent model show good agreement with laboratory test results except when some of the applied stress cycles are below the threshold stress level causing liquefaction in uniform cyclic loading.