INVESTIGATING THE STRENGTH PARAMETERS OF UNSATURATED SOIL IN SEASONAL FROZEN AREAS UNDER LOW MATRIC SUCTION AND THEIR EFFECT ON OVERWINTERING DEEP FOUNDATION PITS.

In the current paper, we explore the effect of temperature changes in seasonal frozen areas on the strength parameters of unsaturated soil under low matric suction, as well as the impact of the parameters under different temperatures on an overwintering deep foundation pit in unsaturated soil under low matric suction. In particular, we take unsaturated silty clay in its original state as the research object and Global Digital Systems Ltd. (GDS) unsaturated silty soil as the triaxial tester to perform triaxial shear tests on unsaturated silty clay under several temperatures. The strength parameters obtained from the laboratory tests are then combined with Abaqus numerical simulations to analyze the stress and deformation of the overwintering deep foundation pit supporting structure in unsaturated soil within seasonal frozen areas. Experimental results under low matric suction demonstrate that temperature variations have a greater effect on the total cohesive force of unsaturated silty clay, yet their impact on the effective internal friction angle is relatively small. The influence of the frost heaving force produced by the freezing of the unsaturated soil on supporting structures is observed to be greater than the earth pressure during the freeze-thaw process. When the unsaturated soil is frozen, the horizontal frost heaving force of the retaining structure at the top and bottom of the foundation pit is relatively large. Furthermore, the selection of strength parameters for unsaturated soil during the freeze-thaw process has a great influence on the surrounding environment of the deep foundation pit, as well as the stress and the deformation of the supporting structure. Numerical simulations using strength parameters under different temperatures (20°C, - 15°C, 20°C -15°C--20°C) resulted in the following general trend for the horizontal displacement of the retaining structure, the horizontal force of the pile side and the displacement of the top of the deep foundation: simulation results of frozen soil parameters > simulation results of dynamic changes of parameters with temperature > simulation results of normal temperature soil parameters. [ABSTRACT FROM AUTHOR]