Effect Of Expansion Deformation On The Stability Of Expansive Soil Slope

Expansive soil is a kind of special clay,widely distributed in our country,it has the characteristics of swell when wetered and shrink when dried out,very sensitive to the change of the environment,the above properties of expansive soil has brought a lot of problems to the engineering construction,at the same time,it may also cause great economic losses.Since the late 1930 s,the engineering knowledge of expansive soil from the earliest judgment,identification,to testing,the theoretical study of expansive soil are also developed from the early strength theory to the unsaturated soil theory,especially in this century,due to the construction of the central line of the south-north water transfer project,the country has been in the "11th Five-Year Plan " and "12th Five-Year Plan " science and technology support projects,carried out large-scale experiments and theoretical research on expansive soil pipeline project,in the expansive soil slope failure mechanism,strength theory,swelling deformation of expansive soil and its stability analysis method and the treatment technology of expansive soil has obtained a lot of fruitful research results,which provide theoretical support for the construction of the central line of the south-north water transfer project.During the "11th Five-Year Plan" period,the Changjiang River Scientific Research Institute proposed two failure modes of expansive soil slope,"the shallow instability caused by the expansion deformation" and "the overall instability of the strength control of the fissure",and put forward the corresponding analysis method of slope stability for these two destruction modes.The shallow instability caused by expansion deformation introduces the expansion model into the finite element analysis program,which solves the problem that the conventional stability analysis method cannot consider the effect of expansion deformation on slope stability.This paper takes the central line of the south-north water transfer project and the diversion of water from Changjiang River to Huaihe River project as the engineering background.In order to study the law of expansion deformation and obtain its empirical formula,the effect of compaction and water content on expansion deformation is explored through the test of no-load expansion rate,the traditional test method of the test of the expansion ratio with loadings is improved,the purpose of controlling the final water content of the specimen is realized,the linear relationship between expansion deformation and the upper load is established by analyzing the experimental results,the linear fitting method is used,and the resulting water content,the initial water content,and the average stress-related deformation is summarized.Based on the traditional one-dimensional expansion model,based on the assumption that expansion strain is only related to the first stress invariant,the three-axis expansion test under the axis symmetrical stress condition is carried out,and the results of the three-axis expansion test are analyzed,and the linear relationship between volume strain and the average main stress logist is found,and the empirical formula of expansion deformation under the three-dimensional stress state is obtained.In order to understand the effect of expansion deformation on the permeability of expanded soil,this paper carried out the penetration test of the water head,and simulated the effect of wet and dry cycle on the permeability of expansion soil saturation by using the method of low temperature drying and pumping saturation of the oven.Finally,the ABAQUS finite element program is used to simulate the change of moisture field through the change of temperature field,and then the change of soil moisture content is simulated,and the slope stability after considering the expansion and deformation is analyzed The research shows that expansion deformation has a significant effect on slope stability and is one of the important factors to control the stability of expansive soil slope.