Research On Failure Mechanisms And Stability Analysis Of No.1 Slag Accumulation Slope At Qiaoqi Reservoir

No.1 slag accumulation slope at Qiaoqi reservoir was first formed in 2004.The size of it is about 21×10~4m~3.As there was no retaining measures in the front edge of the slope,the rear part of it deformed in the later period under the influence of the Wenchuan earthquake in 2008and Lushan earthquake in 2013 in a decade,as well as persistent rainfall.And the deformation seriously threatens the safety of residents at the toe of the slope.Geological field work and in-situ double loops infiltration test,etc.are presented to analyze the failure mechanisms and stability in different conditions of the slope.The main results of this paper are as follows:(1)The engineering geological environment conditions of the slag accumulation slope are analyzed in detail through the field geological survey.According to different stacking locations,combined with the existing deformation and failure characteristics,it is divided into three parts:Area ?,?? and ?.(2)According to the characteristics of the deformation and the distribution of the cracks in Area I,the deformation and failure mechanism of the slope is analyzed.The slope in this area belongs to the type of progressive landslide,and it is still in a slow-creep stage.It has produced a four-stage platform,and the surface of the slag pile at each stage has a local traction(backward)slip feature.The influencing factors of slope deformation are summed up,and the steep topography and sustained rainfall and earthquake are the key factors in inducing slope instability.(3)The result of in-situ double-loop permeability test showed that the coefficient of permeability difference between the slag accumulation body and the old accumulation body is nearly 100 times.Under the continuous rainfall,a hysteretic saturated zone is formed between the two body,and the bottom slag accumulation body in this area is saturated with water,leading to the shear strength rapidly decreases.At the same time,the pore water pressure and hydrodynamic pressure increase,which causes the slope deforming significantly.(4)The main factors affecting the stability of the slag accumulation slope are the internal friction angle ? and the cohesion force c,and the influence of the internal friction angle is greater.At the same time,the calculation results show that the slope is more sensitive to rainfall,and it is further verified that rainfall may be the main cause of slope instability.