Research On The Wetting-Drying Effect And Micro-Mechanism Of Expansive Soil

With the research object of expansive soil in Nanning, Guangxi and the aimof the wetting-drying effect and micro-mechanism of expansive soil under theeffect of atmosphere, combining on the observation date of expansive soil slopeof field engineering, the variable law of the strength and deformation ofexpansive soil under wetting and drying cycle are roundly disclosured and themicro-mechanism is analyzed by strength test, deformation test and microscopicview test in laboratory. The main research findings are as follows:1. According to the depth of atmospheric effect and the observation data ofthe moisture content of field engineering, the amplitude of wetting and dryingcycle is determined. Then the variable law of the strength of expansive soilunder wetting and drying cycle is discussed by conventional triaxial test andstraight scissors test, and the attenuation formula of strength is establishedcorrespondingly. Based it on, the relationship between strength and moisturecontent& circulate amplitude of expansive soil under wetting and drying cycleeffect is discussed subsequently.2. Based on the expansion test and shrinkage test, the variable law of thedeformation of expansive soil under wetting and drying cycle is discussed, and the corresponding formula of deformation is also created. Subsequently, therelationship between deformation index and moisture content of expansive soilunder wetting and drying cycle effect is discussed.3. The mercury intrusion porosimetry (MIP) test is applied to determine thepore size distribution curve of expansive soil during wetting and drying cycle,and the results are corrected. And the soil-water characteristic curves (SWCC)which obtained from the MIP test results that are corrected are computed, andthe change rule is also analyzed. Then the attenuation formula of matrix suctionduring wetting and drying cycle is studied, and the corresponding formula ofdeformation is also created. Finally, the wetting-drying effect mechanism ofexpansive soil is analyzed from the microstructure (matrix suction and crack).4. Based on the test results, the stability analysis of expansive soil slope isstudied. Then the necessity and feasibility of the theory for wetting and dryingcycle lamination of expansive soil slope is expounded.