| Underground coal mining will inevitably cause the fissure of the overlying loess layer,which can further cause the disaster of loess landslides in the mining area.However,the mechanism of the impact of loess fissures on the slope stability by underground coal mining is not yet clear.Therefore,in this paper,the geotechnical centrifuge model test is used to explore the mechanism of the instability of the fractured loess slope.The research results can provide a theoretical basis for the evaluation of slope instability caused by underground coal mining and the prevention and mitigation of geological disasters in mining areas.The main achievements are as follows:(1)The analysis of the comparison test results shows that the displacement of natural loess slopes is characterized by vertical displacement as the main factor and small horizontal displacement.During the entire test process,the displacement changes are relatively stable,and there is no sudden change.The cracks on the slope are shallow and fine;the displacement of the cracked loess slope is mainly vertical displacement within the slope body,and the horizontal displacement does not change much.In addition to the vertical displacement caused by the consolidation and settlement of the model near the slope,the main The main feature is the horizontal displacement.During the entire test,the displacement changes are abruptly localized,mainly concentrated near the slope,and the cracks on the slope top and slope are deep and wide.(2)After analyzing the characteristics of the natural slope displacement field,the slope body deformation is divided into two parts: micro-deformation affected area and nondeformation influence area;after analyzing the characteristics of the fractured slope displacement field,the slope body deformation is divided into two parts It is the three parts of micro-deformation affected zone,crack propagation-sliding zone and crack through sliding zone.(3)The slope deformation and failure process is divided into three stages: initial deformation stage,stable deformation stage,and crack through failure stage.First,as the underground coal mining progresses,the overlying loess produces fissures,and the fissured loess changes with the stress in the slope.Under the action of the shearing force,the shear point of the different fissure intersections at the foot of the slope will first produce shear failure.The range and value of the tensile stress on the top of the slope gradually expand.When the tensile stress exceeds the tensile strength of the loess,tensile cracks occur on the top of the slope;secondly,the tensile cracks extend downwards,which leads to a narrowing of the range of the shear equilibrium area within the slope.Shear stress is concentrated,and as underground coal mining progresses,new fissure combinations are derived in the loess slope,and the cracks at the foot of the slope expand upward and converge;finally,as underground coal mining progresses,the degree of fissure in the loess slope body becomes more and more High,a potential slip surface is formed in the slope body.After the shear crack and the tensile crack penetrate,the slope body slides along the penetration surface,and the loess slope develops from local failure to overall failure.(4)The ideal sliding surface can be obtained through the cracked slope deformation and failure development map,and the ideal sliding surface is more consistent with the actual situation.This type of slope deformation and failure is mainly completed under the combined action of shear force and tensile tension.Shear cracks are generated first at the bottom of the slope body,which causes tensile cracks at the top of the slope,indicating that this type of slope instability is mainly traction.Instability mode,not push instability mode. |
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