Study On The Stability Of High Cutting Slope Under Gradation Excavation And Rainfall Condition

In recent years,construction of infrastructure has been increasingly improved.When construct railroad,highway,water conservancy or other large projects,a large number of slopes are formed by excavating the earth in order not to be restricted by the topography of the site,and stability of slopes directly determines whether these large construction projects can be operated safely and stably.In the process of slope excavation,the unloading effect leads to the redistribution of stress,which reduces the stability of the slope.If a large amount of rainfall occurs in the process of slope excavation,the stability of the slope will be further reduced.Therefore,it is of great significance to study the stability of the slope under the rainfall condition and excavation.This paper is based on the project of long-term stability and monitoring technology of high and steep cutting slope in Xingquan Railway,the stability of slope excavation under rainfall conditions was studied by combining theoretical calculation,numerical simulation and field test methods,and the relevant parameters are selected for sensitivity study,and the following conclusions are obtained.1.Fristly,Physical parameters of the soil were determined by field tests and indoor tests,on this basis,permeability coefficient,soil-water characteristic curve,shear strength and other parameters were measured to provide support for the numerical simulation of slope excavation and rainfall.According to the results,the soil with small permeability coefficient belongs to the micro-permeable soil.With the increase of soil moisture content,the shear strength decreases gradually.2.Through Geo-studio geotechnical calculation software,the excavation process under natural and rainfall conditions of the slope was simulated,and analyzed the influence of rainfall on the stability of the slope excavation process.On this basis,studied the stability of slope under different excavation slope and step height.According to the analysis results,under the condition of rainfall,the horizontal displacement of the slope increases,the settlement of the slope top increases,and the rebound of the slope surface decreases.According to the sensitivity analysis results of parameters,the horizontal displacement of slope increases gradually with the increase of step height,while the vertical displacement basically remains unchanged.With the increase of excavation slope ratio,the horizontal displacement gradually increases,and the vertical displacement basically remains unchanged.3.The safety factor of slope were calculated by strength reduction method and limit balance method.According to the calculation results,safety factor calculated by strength reduction method is less than the results by limit balance method.In the natural state,the safety factor of slope basically does not depend on the excavation slope ratio,under the condition of rainfall,the slope safety factor decreases gradually with the increase of the step height,and decreases gradually with the increase of the excavation slope ratio.4.Analyzed the force,deformation and reinforcement effect of anti-slip piles by Fl AC^3D,and completed the rainfall seepage calculation by self-programmed FISH language,studied the effect of rainfall on anti-slip piles;on this basis,conducted sensitivity analysis of cross-sectional size,spacing,anchoring depth to determine the optimal support scheme.According to the calculation results,rainfall will lead to a significant increase in the stress and deformation of anti-slide pile.With the increase of section size,the supporting effect of anti-slide pile is strengthened.1.75m*2.75m is the optimal section size.With the increase of pile spacing,the supporting effect of anti-slide pile decreases,and it decreases obviously when it reaches 10m.With the increase of the length of the anchorage section,the supporting effect improves,but the improvement of the supporting effect slows down when the length exceeds13m.5.Force sensors were arranged on the vertical main bar of the anti-slide pile,to monitor the force of the anti-slide pile.Three anti-slide piles were selected for monitoring,and 16 force sensors were arranged on each pile.According to the test results,the force of the pile is basically consistent with the numerical simulation results.