Experimental Study On The Engineering Characteristics Of Expansive Soil Under Wetting-drying Cycle

In order to study the effect of wetting-drying cycle of expansive soils this paper study on expansive soil. Through laboratory test such as uniaxial tensile test, direct shear test, no load swell test, a more comprehensive description of expansive soil’s strength and deformation variation characterristc after wetting-drying cycle has been achieved and the mechanisms which caused wetting-drying cycle effects and principles of the test results has been analyzed, the main conclusions seems as follows:1. By conducting the unloading swelling experiment of expansive soil, the expansion variation, contraction distortion of expansive soil under wetting-drying cycle has been studied, the relationship of swell-shrink rate and initial water content, dry density and desorption temperature has been established. Under a single variable conditions, swelling and shrinking index of expansive soils increases with the decrease of initial water content, increases with the increase dry density, and increases with the increase of dehumidifyinging temperature. With the increase of wetting-dying cycle, the relative expansion of the sample decreases, while the absolute expansion increases, and eventually tends to a stable value. The swelling and shrinkage deformation of expansive soil(relative expansion) is not fully reversible.2. The permeability characteristics of expansive soil under repeated wetting-dying cycle effects is studied by interior experiment. The variable head permeability test are carried on sample with different of wetting-drying cycle. Infiltration strength of expansive soils increases with the increase of wetting-dying cycle. Permeability coefficient also increases with the increase of wetting-dying cycle, increases with the increase of wetting-drying cycle amplitude, but decreases with the increase of dehumidifying temperatures.3. By uniaxial tensile test, the strength variation of expansive soil under wetting-drying cycle conditions has been researched, on this basis, the relationship between the tensile strength of expansive soil under wetting-drying cycle conditions with initial water content, dry density, wetting-dying cycle, circulating amplitude, and dehumidifying temperatures are explored.4. By carring out the direct shear tests, the relationship between the strength of expansive soil under wetting-dying cycle with initial moisture content, dry density, wetting-dying cycle, circulating amplitude, and dehumidifying temperatures. the strength attenuation formula on the shear strength and different test parameters are established. From the test results, it can be concluded that the strength of expansive soil under wetting-dying cycle decrease mainly in 1-3 cycles, and the times which the strength stabilitied decreases with the increasing of circulating amplitude. At the same initial moisture content and dry density, the relationship of strength parameters of expansive soil with the number of cycles of wetting-dying cycle, circulating amplitude, and dehumidifying temperatures are established.