m Maleki - associate professor department of civil engineering bualisin university hamedan
m Bayat - MSc student department of civil engineering bualisin university hamedan

Critical state models for unsaturated soils have been proposed in recent years however the proposed models have been based on limited experimental data. In this paper a laboratory study for verifying influence of matric suction on the shear strength and mechanical behavior of a silty sand is presented . for thiw purpose a set of triaxial tests in saturated and unsaturated conditions have been carried out with the aim of considering the sucion effect and its chanes during fast rate of loading such as earthquake.

unsaturated soil, critical state, suction , volume change , constant water content triaxial test