DIRECT SHEAR TEST FOR TEMPERATURE EFFECT ON SHEAR STRENGTH OF UNSATURATED CLAYEY SOILS

In order to systematically study the temperature effect on the engineering properties of clayey soils,laboratory test was conducted to evaluate the relations between temperature and shear strength of unsaturated remodeling soil samples.Among three common types of clayey soils in Nanjing with different mineral composition,direct shear tests of soil samples in different moisture content and dry density have been done in the range of 5~50℃.The results indicate that the following. (1)the cohesive force change mainly and linearly with the temperature. (2) the shear strength of clayey soils with higher content of hydrophilic mineral is more sensitive to temperature change. (3)the cohesive force decrease with the temperature rise,showing thermal-softening on strength. (4) for clayey soils with lower content of hydrophilic mineral,when the moisture content is lower(w17%),the shear strength shows the thermo-hardening phenomenon,however it shows the thermal-softening phenomenon when the moisture content is higher(w22%),and the temperature effect on shear strength is more obvious when the dry density of sample is higher.Moreover,the mechanism of thermal softening and hardening of unsaturated clayey soils is analyzed.