Ring shear apparatus is well suited for researching shear strength properties of large shear displacement conditions.This paper systematically introduces the DTA-138ring shear apparatus newly imported by Beijing University of Technology

and tests were done to silty clay of Ip=12and clay of Ip=36by this apparatus.Test results indicate that:ring shear apparatus used in this study has good stability and high precision for both silty clay and clay

thus can guarantee the accuraty of the test results;shear speed at 0.1°/min

1

0°/min has no significant effect on peak strength and residual strength for both silty clay and clay;over-consolidated ratio has almost no effect on the peak strength and residual strength of silty clay and

residual strength of clay

while the peak strength of clay has the increasing trend as the over-consolidation ratio increased

the residual strength of clay is significantly lower than the residual strength of silty clay at the same test condition.