Relationship between monotonic and cyclic behavior of saturated soft clay in undrained triaxial compression tests

Cyclic loading–induced deformation of soil is a common problem in engineering practice. In current practice, however, monotonic triaxial tests are more commonly used due to the availability of apparatus and ease of operation. Thus, it would be very useful and practical if monotonic triaxial tests could be used to evaluate the behavior of soil under cyclic loading. This study aims to find an explicit relationship between monotonic and cyclic behavior of saturated soft clay. Six monotonic and nine cyclic triaxial compression tests were conducted on undisturbed saturated soft clay under an undrained condition. The test results showed that the monotonic and cyclic tests shared the same stress–strain surface in a three-dimensional p′–q–ε a space (p′, effective mean principal stress; q, deviatoric stress; ε a , axial strain). It was also found that it is possible to evaluate the effective stress states of cyclic tests at two specific numbers of cycles, using corresponding monotonic tests. Based on these two findings, a simple procedure is proposed to predict the peak axial strain for the saturated soft clay under different cyclic loadings based on the monotonic tests and only one cyclic test, which was further verified against additional test data from the previous literature.