Experimental Study Of The Effect Of Temperature On Shear Behavior Of Clays

With the increasing construction of energy-related infrastructure such as nuclear waste treatment,high-voltage cables,energy underground structures,high-temperature subsea pipelines,and energy tunnels,the analysis and design of related structures need to consider the impact of temperature on the structure and surrounding soil,but the related research is not deep enough,and it is worth to further study the temperature effect of clay.In this paper,the temperature-controlled triaxial apparatus was used to study the shear characteristics of two clays under thermal-mechanical coupling.Different temperature-stress loading path combinations were considered in the test,and the effects of factors such as effective stress,temperature path,and temperature increase on the shear characteristics of clay were analyzed.The response of shear strength,stress path and dilatancy of clay to temperature was studied.The main conclusions of this article are as follows:(1)The degree of influence of temperature on the shear behavior of soil is related to the type of soil.Compared with silty clay,the temperature effect of shear characteristics of clay is more obvious.(2)The higher the temperature,the more obvious the strain softening characteristic of the partial stress-strain curve in the consolidation of undrained shear of clay.After increasing the temperature by 40℃ and 60℃,the peak undrained shear strength increased by 32.1%and 52.2%,respectively,and the excess pore water pressure decreased by 5.1%and 9.4%,respectively.The increase in shear strength is not entirely the result of decrease in the pore water pressure and increase in the effective stress.(3)In consolidation and drainage shearing at different temperatures,the direction of clay plastic strain increment changes with temperature,and the dilatancy factor at the same stress ratio increases with increasing temperature.The volume of clay decreases continuously with the progress of shear,and no dilatancy occurs.The softening characteristics of the stress-strain curve at high temperature are mainly related to the additional structural strength caused by temperature,which is different from the dilatancy mechanism of strong over-consolidated soil.At the same time,an expression considering the influence of temperature on the dilatancy properties of cohesive soil is suggested.(4)The shear behavior of the clay are related to the temperature-stress path.The undrained strength of the sample under the conditions of temperature rise then consolidation is lower than that of the sample under temperature rise after consolidation.(5)Similar to the mechanical plastic volumetric strain,the plastic volumetric strain generated during temperature cycling will also cause the soil to harden.After one week of temperature cycling,the undrained strength of the clay was significantly improved compared to room temperature.