Test Study on Strength Characteristics of Unsaturated Silt

A series of consolidation and drainage unsaturated triaxial tests on remolded samples were carried out at controlled matrix suction and confining pressure through automatic GDS triaxial apparatus. According to the shear strength of unsaturated silt, the results show the matrix suction has a little influence on effective angle of internal friction, while has great influence on failure modes and cohesion. With the increasing of matrix suction, stress-strain curves translate from hardening type to softening type, the effective angle of internal friction changes a little and is approximately equal to the effective angle of internal friction of saturated soil, cohesion is significantly improved. Matrix suction friction angle is not a constant, when the matrix suction is less than 100kPa, it decreases with matrix suction increasing, the rate of decrease reduces gradually; when matrix suction is greater than 100kPa, it tends to be a fixed value. The results are consistent to modified strength theory proposed by Fredlund.