Failure Mode And Stability Analysis Of Slope Dumped On Soft Layer

Waste dump is an important part of surface mining.For the dump slope dumped on weak layer,the instabilities of dump slope are easily caused by continuous increasing of the heap height or softening of soft layer affected by water immersion.In order to predict accurately and properly prevent the landslide disaster in the dump,it is necessary to study the failure mode and mechanism of the dump slope.Therefore,physical model test,numerical simulation and theoretical analysis of the slope dumped on soft layer are carried out in this paper.The failure mode and stability of the dump slope are studied,which is verified by engineering practice.The conclusions are as follows:(1)The results of bottom friction and centrifuge model tests show that the failure of slope dump on soft layer is progressive.The failure begins in the toe of the slope and gradually expands toward the deep part of the slope along the weak layer.In the rear part of the slope,the weak layer is upwardly and the top of the slope is downwardly extended,a through sliding surface is finally formed,then the entire slope slides.The failure cracks can be divided into two types: dislocation cracks,the cracks mainly with dislocation deformation and accompanied by horizontal separation,mainly distributed in the interior of the slope;tension cracks,the cracks with mainly horizontal separation and accompanied by the dislocation deformation,mainly distributed in the rear part of slope.(2)The finite element limit analysis method simulation results show that when the soft layer is located on the surface(model A),the failure mode of the slope is double wedge,failure of the slope begins at the lower part of the slope,and the lower passive wedge moves along the weak basement layer.Upper active wedge falls down and passive wedge continues to move,finally forming a platform in the middle of the slope.When the weak layer is below the surface(Model B),the failure mode of the slope is triple wedge,failure of the slope begins at the front edge of the slope,the leading edge wedge expands and rises,the middle block slides along the weak basement layer,the upper wedge slides down and pushs the middle block,and the middle block pushes the leading edge wedge to squeeze out,finally forming a platform in the middle of the slope.(3)The Sarma method calculation results show that the most dangerous slip surface is polyline type,and the failure mode is wedge failure.When the soft layer is located on the surface(Model A),the failure mode of the slope is double wedge;when the weak layer is located below the surface(Model B),the failure mode of the slope is triple wedge.The relationship between the safety factor of the slope and the depth of the basement soft layer,the dip of the basement soft layer,the cohesion of the basement weak layer,and the cohesion of deposition layer is approximately linear,and friction of the basement weak layer,the friction angle of the deposition layer,surcharge height,the horizontal acceleration is similar to the quadratic polynomial.(4)Combined with on-site investigations,numerical simulations,model tests,and theoretical analysis,it was verified that when the soft layer is located at the surface,the failure mode of the dump slope is double wedge.At the same time,based on the double wedge calculation method,a quasi-three-dimensional double wedge stability calculation method for the slope dumped on weak layer is proposed.