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

摘要

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 parame-ters under different temperatures on an overwinter-ing 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 temper-atures. The strength parameters obtained from the la-boratory tests are then combined with Abaqus nu-merical simulations to analyze the stress and defor-mation of the overwintering deep foundation pit sup-porting 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 ofunsatu-rated silty clay, yet their impact on the effective in-ternal friction angle is relatively small. The influence of the frost heaving force produced by the freezing of the unsaturated soil on supporting structures is ob-served 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 re-taining structure at the top and bottom of the founda-tion pit is relatively large. Furthermore, the selection of strength parameters for unsaturated soil during the freeze-thaw process has a great influence on the sur-rounding environment of the deep foundation pit, as well as the stress and the deformation of the support-ing structure. Numerical simulations using strength parameters under different temperatures(20°C°C,-15°CC.20°CC--15°CC-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 topof the deep foun-dation: simulation results of frozen soil parameters>simulation results ofdynamic changes of parameters with temperature>simulation results of normal tem-perature soil parameters.