Hydro-mechanical model for small-strain stiffness of unsaturated soil

This study aims to investigate a novel method for predicting the small-strain stiffness of unsaturated soil. A hydro-mechanical model is proposed to estimate the small-strain stiffness of unsaturated soil with various matric suction and stress states. A series of saturated and unsaturated bender element tests are conducted, and the test results indicate that the small-strain stiffnesses of saturated and unsaturated soil have similar changing trends with the variation of the stress state. The small-strain stiffness of unsaturated soil is calculated by the proposed model based on the test results of saturated soil. The model has two parameters that have a physical meaning and can be measured by tests. Thus, combined with the mature prediction model and measurement method of saturated soil and the proposed hydro-mechanical model, the complex unsaturated bender element tests are unnecessary. The proposed model is anticipated to be of practical value for solving engineering problems during the determination of small-strain parameters in the design of pits and foundations.