| Southwest China is located in the east of the Qinghai Tibet Plateau.In this field,steep topography,fierce landform incision,complex strata and geological structure,intense neotectonic activity and frequent earthquakes caused a large number of landslides.Because bedding rock slopes are prone to overall bedding slippage,their stability has attracted much attention in many slope engineering projects.Under the action of earthquakes or construction dynamic loads,they are more likely to cause large-scale geological disasters,major lives and property loss.For earthquake-induced bedding rock slopes,existing research focuses mainly on solving dynamic stability coefficient,but it cannot reflect the dynamic response characteristics and deformation failure laws of slope under seismic load.In this paper,the stability of bedding rock slope under seismic loading is taken as the research object.Based on the knowledge of rock mechanics,engineering geology and engineering earthquake,the methods of shaking table model test,theoretical analysis and numerical simulation are used to study the macro and micro cumulative damage characteristics and strength degradation model of rock mass structural planes under seismic cyclic loading,cumulative damage evolution mechanism and cumulative damage model of slope rock mass under earthquake action and slope stability under earthquake.The main research content and results are as follows:(1)The earthquake-induced bedding rock landslides are mainly tensile and shear failure.Through a summary analysis of the failure characteristics and genetic models of a large number of earthquake-induced bedding rock landslides,it is found that the tensile action of the earthquake load causes deep and large crack on the trailing edge of the slope or deformation along the interlayer structural plane;the shearing action of the seismic load causes the structural surface to be constantly worn and dulled,forming a potential sliding surface;finally,the slope slides.According to the structural characteristics of different slopes,the typical genetic models can be divided into tension-shear-slip along the strata strike type,tension-shear-sliding along the rock formation,tension-bulking-sliding along the rock formation,cracking-sliding along the horizontal rock formation and shattered-bedding slope.(2)With the increase of the normal stress and the undulation angle of the structural plane,the stronger the shearing effect of the structural plane,the higher the degree of deterioration.In this paper,the PFC particle flow numerical simulation method is used to study the influence of normal stress,undulation angle and cyclic shear number on the shear strength degradation effect of structural plane.When the normal stress is constant,the greater the undulation angle,the greater the height of the structure surface undulations being worn or sheared,and the greater the shear modulus,the more obvious the brittle failure characteristics of the undulations.When the undulation angle is constant,as the normal stress increases,the smaller the volume of the debris filling and the smaller the height of the accumulation,the higher the degree of structural surface degradation.(3)The shear failure modes of structural planes are mainly slip?slip-shear and slip-compression induced fracturing-shear.Based on the analysis of cyclic shear failure characteristics of structural plane,it is found that with the increase of normal stress and undulation angle,the shear failure mode of structural planes first changed from slip failure to slip-shear failure,and then gradually changed to slip-compression crack-shear failure.(4)The empirical formulas of dilatancy angle varying with the number of cyclic shears and varying with the shear displacement are proposed,respectively.According to the cyclic shear test of the structural surface,the dilatancy angle of the structural surface decreases with the increase of the number of cyclic shears,and shows a trend of gradual convergence,while the post-peak dilatancy angle has a good nonlinear relationship with the shear displacement.According to the change law of the dilatancy angle in the cyclic shear test of the structural plane,an empirical formula for the dilatancy angle considering the changes in normal stress,rock wall strength,and the number of cyclic shears is established.The empirical formula for the change of shear displacement,which reflects the degradation process of the structural surface in the cyclic loading stage.(5)The empirical formula for the peak shear strength of the structural plane and the calculation expression for the shear stress after the peak shear strength are established.According to the cyclic shear test of the structural plane,it is found that the initial failure occurs at the peak strength of the structural plane shear test,the tensile stress failure occurs at the uphill surface of the structural plane undulation.When the normal stress is small,the shear stress has multiple peaks,and when the normal stress is large,the secondary peaks appear insignificant.After the peak,as the shear displacement increases,the shear strength shows a non-linear decreasing trend.Based on the original data of the experiment and verification by fitting,this study puts forward the empirical formula of the peak shear strength considering the normal stress and the initial fluctuation angle change and the calculation expression of the shear stress after the peak shear strength.(6)The dynamic calculation model,critical condition,dynamic balance equation and slope sliding displacement calculation method considering the effect of structural plane deterioration are proposed for the dynamic calculation model of the bedding rock slope under the action of seismic load.Based on the in-depth analysis of the failure mechanism,dynamic response,cumulative damage,and dynamic degradation effects of bedding rock slopes under seismic loads,a dynamic calculation model for bedding rock slopes under seismic loads is proposed.According to the force analysis of the slope,the critical condition and dynamic balance equations after the slope instability are proposed.Combining the dynamic degradation effect of structural planes,a calculation method for permanent displacement of bedding rock slopes considering the degradation effect of structural planes is proposed,and detailed calculation steps are given.(7)The calculation results of the permanent displacement calculation method of bedding rock slopes considering the effect of structural plane degradation are more conservative.In this paper,through the generalized bedding rock slope shaking table physical test and the Huashengdi bedding rock landslide numerical test verification analysis,it is found that the dynamic degradation effect of structural plane under seismic loads directly affects the deformation displacement and stability of the quality slope.Because the traditional displacement calculation method does not consider the effect of the deterioration of the rock mass structural plane parameters under the action of the seismic load,the structural plane parameters are too large in the calculation process,therefore,there is a certain error in determining the stability of the slope. |
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