Deformation Failure Mode And Stability Analysis Of Waste Slag Slope After Rainfall Infiltration

The waste dump slope is a slope formed by the accumulation of waste materials during the construction of the project.In the process of slope accumulation,the waste slag with different shapes and uneven particles are naturally stacked and sorted under the action of gravity,and finally the accumulation slope with obvious particle size distribution characteristics and uneven internal structure is formed.To a certain extent,the internal structure of the waste slag accumulation body controls the slope stability,especially under the condition of heavy rainfall,the stability of the waste slag accumulation body is obviously reduced or even causes damage and failure,which threatens the safety of surrounding residents and engineering buildings,causes unexpected environmental events.Therefore,in recent years,the stability of waste slag slope and its environmental effects have become an important concern of construction departments.As a temporary equilibrium system composed of complex granular materials,the deformation and failure are obviously disturbed by the outside world,especially after the rainfall infiltration.And the deformation and failure mode and stability evaluation analysis method of the waste slag slope still need to be clarified.In this paper,the slope of the waste disposal area along the xujiada railway is taken as the research object,and the method of field investigation and data collection is used to summarize the slope structure characteristics and possible deformation and failure problems of the waste disposal slope.The mechanical parameters of the waste disposal are mastered through in-situ and indoor experiments.The three-dimensional discrete element method is used to study the typical deformation and failure process of the waste slag slope.On this basis,the physical model of the indoor waste slag slope is built,the transformation of the slope structure caused by rainfall and the deformation and failure law of the waste slag slope induced by rainfall are explored,and the numerical simulation of the deformation and failure of the waste slag slope after rainfall infiltration is completed by using the fluid solid coupling method.The research results of the structural characteristics and stability of the waste disposal site slope are as follows:(1)The terrain of the study area is low in the West and high in the East,and straight in the north and south,showing the characteristics of deep ditch and steep slope.According to the field investigation and statistics of the waste disposal area along the railway,the study shows that the waste disposal area belongs to the low mountain structural denudation landform.The waste disposal area along the railway mainly includes roadside terraces,hillsides and gullies on the original ground,and the damage objects are farmland,ditches,gullies and farmhouses.The waste slope surface is mainly in the shape of "flat steep gentle steep",and in space it is in the shape of "tongue" and "ellipse".(2)The complex physical and mechanical properties of waste slag slope are quite different,and its deformation and failure are affected by many factors such as slope structure and stacking site environment.The deformation and failure of the waste disposal site mainly include slope surface damage,including the damage of retaining and drainage structure,slag body crack,slope surface sliding,slope surface scouring,local collapse,etc.,and the large-scale deformation and failure is less.(3)The important deformation and failure law of the waste slag slope in the study area is the failure of the slope surface and the front edge of the platform.The slope surface is a shallow sliding failure,the front edge of the platform is a dense fracture development,and the waste slag body is cracked.In the shallow layer of slope,there is a fine aggregate zone with "ball" effect,so the debris on the surface is easy to slide.On this basis,the typical deformation failure of the waste slag slope is summarized,that is,the shallow sliding of the slope surface without clay,which is characterized by the fact that the sliding surface is located on the shallow surface of the slope surface and the sliding surface is similar to the plane.(4)The three-dimensional discrete element software is used to simulate the deformation and failure process of waste slag slope in Gulin station.The particles in the model are generated according to the shape of the sieve after classification and generalization.The results show that the deformation area of the waste slag slope develops from the surface to the inside,from the bottom to the top.The change mode of deformation discrimination interface is "step arc step".The debris on the slope surface first reaches the critical point of instability.When the deformation is unstable,the debris slides parallel to the slope surface layer by layer.(5)Indoor slope model experimental materials are collected in situ,and the model meets the similar index according to the grading accumulation of the actual waste slope.According to the relationship between clay and gravel content,appropriate amount of clay is laid on the surface of the model slope,and the original ground of the model is generalized into a plane according to the actual terrain.Using rainfall spray system to simulate rainfall,the slope structure changes under the condition of natural rainfall,and after natural air drying,the basic deformation and failure mechanism of the waste slag slope under the condition of rainfall infiltration is obtained by studying the failure process of the model slope.(6)In the test model,the stability of the waste slag slope has a significant inverse relationship with the size of the ground slope angle.In typical cases,there is no clay in the waste slag slope.After the upper gravel sliding,the middle and lower gravel appears small-scale sliding.The sliding process is rapid and the coordinated deformation is completed in a short time.For the waste dump slope containing clay,the infiltration of rainfall makes the clay diffuse in a large range in the slope.The infiltration range of clay is mainly concentrated in the surface layer of the slope,with small content in the deep layer.After the clay is air dried,it can bond the rubble.The difference of the bonding between the upper and lower layers results in the unique "cavity" at the front of the slope top platform when the slope slips,and the stability of the slope increases when the cavity disappears.(7)The fluid structure coupling function of 3D DEM software can simulate the deformation process of waste slag slope under the action of rainfall approximately.The clay particles on the surface of the waste slag are distributed in a large amount on the surface of the slope and a small amount on the lower part of the slope.The change of the interface can be divided into two stages in time and two parts in space.The surface gravel particles are more closely bonded than the lower layer,so the particle displacement of the lower layer is larger.After the displacement deformation area develops from the slope toe to the platform,the upper part of the displacement interface is in the shape of "cavity",and the lower part is still in the shape of "step arc step".The structural characteristics of the waste slag obtained from the indoor test and the numerical simulation test are similar to the deformation and failure process of the slope,so as to achieve the purpose of mutual verification.