Experimental Research on Shear Strength of Subgrade Soil and Plasticity Index under Different Freeze-Thaw Cycles

Three different plasticity index subgrade soils are selected from seasonal frozen soil area. Triaxial compression test under different confining pressures are executed on the samples exposed to 0 to 7 times closed-system freeze-thaw cycles. The conclusion gotten is that to the same kind of soil under the same freeze-thaw cycles, the shear strength increases with confining pressure; Shear strength with the same confining pressure decreases with the number of freeze-thaw cycles; With the same confining pressure and the same freeze-thaw cycles, shear strength increases with the plasticity index. Exponential function is adopted for multiple nonlinear fitting on the test results. The relationship between shear strength and confining pressure, plasticity index, freeze-thaw cycles is obtained and shows a good correlation.