Triaxial Test of Deformation and Strength Change of a Remolded Unsaturated Sand

With triaxial apparatus for unsaturated soil,the deformation and strength properties of remolded unsaturated sand are discussed.Three types of stress path tests using modified triaxial apparatus are conducted:an isotropic compression test with controlled suction,a triaxial shrinkage test with controlled net mean stress and a triaxial drained shear test with controlled suction and net cell pressure.The research shows that the net mean yield stress and deviatoric yield stress increase with suction,and the yield suction is not equal to the maximum suction experienced by the soil specimen under constant net mean stress.The stress-strain curves of undisturbed sand will change from strain softening to strain hardening with the increase of consolidation cell pressure.Brittles destroy will happen with high suction and high cell pressure.Strength envelopes in p-q plane of test with controlled suction and with controlled initial water contents is a line.The cohesion of unsaturated sand has a linear increase with the increase of suction within research suction range(50～200 kPa),but the friction angle is found to have little change with the change of suction.The swell-shrinking of unsaturated sand is distinct.It not only depends on the dry density and the confining pressures,but also relates to the suction closely.