Study On Unsaturated Strength Characteristics Of Hefei Expansive Soil Under Controlled Suction

Most of the soils encountered in engineering practice are in unsaturated state.Compared with saturated soil,the existence of suction makes the properties of unsaturated soil more complex,and the application of saturated soil mechanics in engineering practice is deficient.Expansive soil is very sensitive to the change of water content and has obvious unsaturated characteristics.In this paper,the unsaturated characteristics of Hefei expansive soil are studied.The soil water characteristic curves of different dry density samples were measured by filter paper test,and the unsaturated triaxial test was carried out to study the unsaturated strength of expansive soil.Based on the experimental data,the unsaturated expansive soil slope model is constructed,and the seepage characteristics and stability of the unsaturated expansive soil slope are analyzed.The main work of this paper is as follows:(1)The test results show that the density is an important factor affecting the soil suction.In a certain range,the low-density samples with the same moisture content tend to have higher matrix suction;in this paper,the filter paper method test results use the logarithmic form to fit the shape is simple and the effect is good.(2)In order to study the influence of matrix suction on the unsaturated strength of soil,the unsaturated triaxial test under controlled suction was carried out.The test results show that the matrix suction has obvious influence on the cohesion of soil samples,but has little influence on the friction angle.With the increase of matrix suction,adsorption angle of matrix suction gradually decreases.The test data are fitted and analyzed,and the unsaturated strength formula of Hefei expansive soil is obtained.(3)A model of unsaturated slope was built to simulate the influence of fracture and precipitation intensity on expansive soil slope based on Geo-studio,.The results show that the existence of cracks is an important factor in the catastrophic change of expansive soil slope.With the increase of rainfall intensity,the seepage characteristics of the slope change and the stability gradually decreases;the influence of rainfall will be controlled by the seepage characteristics and rainfall intensity of the soil.