Study On Stability Of Gravity Retaining Wall Of Expansive Soil Cut Slope Under Rainfall Condition

Rigid retaining wall is a kind of retaining structure commonly used in slope protection,which is widely used and the engineering technology is very mature.But in expansive soil areas,the rigid retaining wall supporting effect is not good,the reason is the current standard for retaining wall design and calculation,some only consider the lateral pressure of the filled soil and the variable load caused by soil lateral pressure,does not take into account the additional lateral expansion pressure caused by the expansive soil suction expansion,it is the stability of the rigid retaining wall in expansive soil areas caused great safety hidden trouble.In this paper,the force of rigid retaining wall of expansive soil cutting slope under rainfall condition is simulated and analyzed by means of numerical simulation,and the additional lateral expansion pressure obtained by numerical simulation is superimposed on the soil side pressure,and the stability of rigid retaining wall of expansive soil cutting slope under rainfall condition is further studied.The main research contents and conclusions of this paper are as follows:(1)This paper studies the engineering characteristics of expansive soil of S213 highway project in Ningming County,Guangxi Province.The hydraulic characteristic parameters of the expansive soil were obtained through the pressure plate test and the double-ring penetration test;the mechanical and deformation parameters of the expansive soil were obtained through the unloaded expansion rate test,the direct shear test and the GDS triaxial test;The curve relationship of each parameter with water content is fitted,and the relationship formula with water content is obtained,which provides the basic parameters of expansive soil for subsequent numerical simulation.(2)Seep module of the finite element software Geo-Studio was used to simulate the seepage of expansive soil cutting slope under rainfall conditions,and the spatial distribution of pore water pressure in expansive soil cutting slope at different times under rainfall conditions was obtained,and the seepage field and pore pressure changes in different depths of soil layers under different rainfall duration were analyzed.It is found that the influence depth of atmospheric rainfall on expansive soil cutting slope is about 0-2.5m.Especially in the surface area of 1m,due to weathering and fracture development,the influence is particularly obvious.The deep soil is not affected by short period of atmospheric rainfall.(3)The rainfall seepage results simulated by Geo-Studio were imported into the finite-difference software FLAC3D,and the expansion constitutive model was invoked to conduct numerical simulation of the rigid retaining wall of expansive soil cutting slope under rainfall conditions.It was found that atmospheric rainfall had a great influence on the lateral pressure of the rigid retaining wall in expansive soil area.The maximum additional lateral expansion pressure caused by rainfall reached 46.1kPa,and the affected area was mainly concentrated in the surface area of 2m.(4)The numerical simulation to get the additional lateral swelling pressure superposition to the soil lateral pressure,under the condition of rainfall further expansive soil cut slope stability of rigid retaining wall was analyzed,and found that the precipitation of anti sliding stability of the retaining wall and the stability is very significant,the influence of the generation of lateral swelling pressure can lead to the stability of the retaining wall coefficient drops rapidly,and significantly;If the retaining wall is not strengthened or the lateral expansion pressure behind the wall is dissipated,the rigid retaining wall normally designed according to the code can not maintain the stability of the slope and itself in the expansive soil area.