Dynamic Response Characteristics And Seismic Stability Of Rock Slope With Small Spacing Tunnel

Earthquake-induced slope instability is one of the major types of earthquake disasters,the dynamic response law and stability analysis of slope under seismic action have become an important research content in geotechnical engineering.More and more highways were constructed in the strong earthquake areas,and the rock slopes with underlying small spacing tunnels appeared in these areas,which were affected by topography,route,tunnel type and other factors.Because of weak free surface of slope rock,the small spacing tunnel has deteriorated the mechanical environment of the slope and has increased the uncertainty of seismic waves in the slope rock mass,so the slope is easy to collapse under seismic loading.Because of its special structure,it has not caused much attention in geotechnical and seismic engineering.Its response characteristics and the method of calculation and identification of stability under earthquake action needs systematic and in-depth study.This study is based on the National Natural Science Foundation " Seismic Catastrophe Behavior and Anti-seismic Performance Evaluation of Rock Slope Containing Underground Caverns"(ID:51204215),a large-scale shaking table model test was carried out on the rock slope with small spacing tunnel to study the dynamic response law of the slope under earthquake action.The numerical simulation and limit analysis of dynamic response characteristics and stability of the slope were carried out.The research results in this paper have a certain guiding significance for further understanding the dynamic response characteristics and variation rules,evaluating the seismic stability and optimizing the aseismic design of the rock slope with small spacing tunnel.The main research contents and achievements obtained in this study are as follows:(1)Design of model test scheme for large skaking tableOn the basis of the similarity theory,the similarity relation design of the model was completed.According to the purpose of the experiment and the research content,the type of model box,the processing method of the model boundary,the test content and the layout of the monitoring point were determined.In the light of the seismic intensity of strong earthquake area studied in the experiment,the types of earthquake,the intensities of ground motion and the the test loading scheme were selected.(2)Seismic dynamic response analysis of the slope with small spacing tunnelA large-scale shaking table model test was used to study the basic law of acceleration response,frequency spectrum characteristics and dynamic displacement response law of the rock slope with small spacing tunnel.The laws of acceleration and dynamic displacement responses of the slope under different excitation intensity,different exciting directions and different types of seismic waves are comparatively analyzed.The results show that the acceleration amplification coefficient and the peak value of dynamic displacement against the height of slope present obvious nonlinearity,which are influenced by the coupling effect of small spacing tunnel and input seismic wave,the level of surrounding rock,the combination of structure surface and the direction of excitation.(3)Numerical simulation for seismic dynamic response characteristics of the slope with small spacing tunnelThe acceleration response of rock slope with small spacing tunnel was analyzed by MIDAS GTS/NX finite element software,which was compared with the result of shaking table model test.On this basis,the displacement field of model slope,stress field and the influence of the tunnel on the dynamic response of the slope were analyzed.The law of the acceleration response of the slope under the action of different seismic waves was studied by changing the ground motion parameters of the input seismic wave.The results show that the arch foot and arch shoulder of the surrounding rock mass,the middle pinch rock and the slope toe are more prone to tensile failure and shear failure under the earthquake action.(4)Limit analysis of horizontal yield acceleration and seismic safety factor of the slope with small spacing tunnelAccording to the upper bound theorem of plastic limit analysis and pseudo static method,the upper bound solution of the horizontal yield acceleration and safety factor of the rock slope with tunnel was rigorously derived under earthquake loading.This upper solution takes into account the tunnel position,the depth of the tunnel,the resistance of the support structure,the coefficient of the earthquake inertia force,the cohesive force of the rock mass and the strength reduction factor.The sensitivity analysis and influence degree analysis of the factors affecting the earthquake stability coefficient and the horizontal yield acceleration were carried out.It provides a new idea for the limit analysis of the slope with small spacing tunnel.The results show that the sensitivity and influence degree of various factors should be taken into account in seismic design.