Study on effect of liquid limit on shear strength of undisturbed expansive soil in Nanyang

Abstract：In order to study the relationship between liquid limit and clay content of expansive soil and the effect of liquid limit on the friction angle of peak strength and residual strength friction angle of expansive soil, quick shear (including quick shear, saturated quick shear, saturated and consolidated quick shear) and repeated reversal direct shear tests were conducted on 26 kinds of undisturbed soil by using electric strain controlled direct shear apparatus and ShearTrac II repeated direct shear apparatus.The results showed that:there was a good linear positive correlation between the liquid limit and clay content in expansive soil;the order of peak strength in different states of samples was that saturated and consolidated quick shear strength > quick shear strength > saturated quick shear strength.The friction angle of peak strength decreased with increase of liquid limit, and the weaking effect of liquid limit on friction angle of the saturated quick shear was much stronger than that on the other two.When the liquid limit increased to 57%, the friction angle of saturated quick shear increased slightly, but not obviously, the order of these friction angles was same as that of peak strength.Under low normal stress, the residual strength stress and displacement curve's strain softening characteristic of saturated samples was weaker than natural samples', and the state of peak also would weaken or disappear.With the increase of liquid limit, the friction angle of residual strength decreased gradually in a polynomial manner.

Keyword：undisturbed expansive soil;liquid limit;quick shear test;repeated direct shear test;peak strength friction angle;residual strength friction angle;