Study On Stability Of Saline Soil Subgrade Slope In Cold Region Under Rainfall

The Qinghai-Tibet Plateau is located in northwestern China and has a wide range of saline-alkali land and salt lakes.In the case of large changes in water content,saline soils have complex physical and chemical processes,expansion or contraction,and structural changes.Greater impact.Because of the large difference in solubility and hydrophilicity of different salt types in saline soil,in order to clarify the influence of the relationship between water content and shear strength of high salinity saline soil on the stability of saline soil roadbed slope.Mainly carry out the following aspects of research:Firstly,combined with the rainfall survey and the depth distribution of the on-site water content,the indoor test adapted to the environmental conditions was carried out.Direct shear tests were carried out on high-chlorine saline soil and high-sulfur and low-chlorine saline soilunder different water content conditions to obtain water content and shear strength.Parameter relationship function.The volumetric pressure plate instrument test was used to measure the change law of soil sample matrix suction with volumetric water content.On this basis,considering the influence of water content on the shear strength and deformation characteristics of saline soil,a formula for shear strength of saline soil was established.The effects of water content and Young's modulus are analyzed,and the numerical formula is used to take into account the Young's modulus formula of saline soil under the influence of water content.Secondly,based on GeoStudio,a stratified calculation model of the saline soil roadbed moisture content-strength parameters is set up,and the SEEP/W module in GeoStudio is used to set the characteristic points and characteristic sections at different depths of the roadbed slope to simulate the water content of different positions inside the roadbed The changing law.Finally,by combining the finite element analysis of saturated/unsaturated seepage with the limit equilibrium analysis of subgrade slope stability,Using the SEEP/W and SLOPE/W module in GeoStudio,the effects of rainfall intensity,rainfall duratio,rainfall type and other conditions on the stability of saline soil roadbed slope are calculated and analyzed.The results show:?1?when the water content increases by 3%based on the optimal water content,the cohesive force of soil sample CL-1 and soil sample CL-2 decreases by 94.3%and54.0%,respectively,compared with the optimal water content.The change in the friction angle is not large;When the optimal water content is reduced by 3%,the cohesive force of soil sample CL-1 and soil sample CL-2 is increased by 277.1%and 89.7%,respectively,compared with the optimal water content.The internal friction angle of CL-2 changes little,and the internal friction angle of CL-1 changes greatly,the internal friction angle changes from43.02°to 37.27°.?2?Propose a water motion equation applicable to saline soil,which is based on the matrix suction as the control variable.At the same time,,the shear strength expressions of high-salt saline soil affected by water content are obtained at three different water contents(w_opt-3%,w_opt,w_opt+3%).The effects of water content and Young's modulus are analyzed,and the numerical formula is used to take into account the Young's modulus formula of saline soil under the influence of water content.?3?The subgrade fillings are CL-1and CL-2 respectively.Under the same rainfall intensity,as the depth increases,the increase in soil volumetric water content decreases.The soil volumetric water content from the same place as the natural slope of the subgrade slope is affected by rainfall.In the early stage of rainfall,the order of influence of different rainfall types on soil volumetric water content is:forward type>average type>center type>backward type.In the later period of rainfall,the order of influence of different rainfall types on soil volumetric water content is:forward type>center type>average type>forward type.?4?The safety factor of the roadbed filled with CL-1is significantly changed compared with the roadbed filled with CL-2,mainly because the chloride is more hydrophilic than the sulfate,and the shear strength parameters are more affected by changes in moisture.As a result,the safety factor of the subgrade filled with CL-1is more significant than that of the subgrade filled with CL-2.Different rainfall types affect the slope safety factor during the rainfall process.The safety factors of different rainfall types in the early stages of rainfall are ranked as follows:forward type?average type?forward type?forward type,and different types of rainfall after the end of rainfall The effect on the safety factor of the slope is the same,that is,the final safety factor tends to a fixed value.?5?According to the types of slope instability caused by rainfall,corresponding protective measures are proposed for these diseases,including raising the subgrade,setting up waterproof partitions,and planting halophytes.