Study On Model Test And Constraint Mechanism Of Rock Slope Foundation For Basement Lateral Constraint

With the rapid development of the construction industry,the urban land is increasingly scarce.The phenomenon that houses are built on the rocky slopes happens all the time in the process of the construction of mountainous cities.Thus,the stability of the rock slope foundation itself should be considered in order to ensure the security of the house when built on the slope.It is also necessary to consider the restraining capacity of surrounding rock soil on the house under the earthquake condition.For a high-rise building with basement,the lateral constraint of surrounding rock mass on basement plays an important role in the selection of embedded end and calculation of structural internal force of high-rise building,since basement and surrounding rock mass form an interaction system under earthquake action.However,there is no clear calculation method to measure the strength of the constraint effect of foundation on the basement,especially in the condition of the rock slope foundation,which is obviously different from the traditional semi-infinite space foundation.In this thesis,the constraint effect of rock slope foundation on basement is studied through theoretical analysis,shaking table model test and numerical simulation.The main research contents and achievements of this paper are as follows:(1)Two modes of lateral restraint of basement of rock slope foundation are proposed,based on the sliding failure of rock slope on the adjacent side and the strength failure of foundation rock mass on the back side respectively.The foundation calculation model of bedding rock slope with basement is established.By analyzing the process of foundation strength failure and slope sliding failure of bedding rock slope,the determination method of the maximum constraint on basement is put forward.Based on the calculation formula of the maximum binding force of the basement damaged by slope sliding,and considering the influencing factors such as the distance of the slope,slope height,slope Angle and structural plane strength,the horizontal resistance coefficient is proposed to measure the restraining ability of the rock slope foundation on the basement.The formulas for calculating the internal forces and displacements of basement structures in rock slope foundation are derived,and the effects of different horizontal resistance coefficients on the internal forces and displacements of structures are analyzed.(2)According to the 1:20 similarity ratio,building shaking table model test is built to studied lateral restraint effect of basement rock slope foundation through testing and analyzing the top construction and after construction cut slope acceleration response to two kinds of working condition of slope,rock slope failure mode and the stress characteristic of the basement side wall foundation under the input of different types and different seismic wave amplitude.The result shows that the top construction and after construction cut slopes of two different working conditions of the slope acceleration response rule.Along with the increase of peak acceleration of input seismic waves,the acceleration response is constantly increase,acceleration amplification factor that increases with the increase of elevation,present a certain altitude effect.The failure process and failure mode of rock slope foundation under two conditions of roof construction and slope cutting after construction under earthquake are analyzed.For slope cutting slope after building and building,both increase with seismic amplitude increases,the rock slope in the basement of the foundation side slope rock mass above the structural surface appear rupture,the gap between the basement and rock is gradually increasing,the rock mass above the structural plane slides downward along the structural plane.then shear extrusion occurs due to the phenomenon of shear stress concentration in a slope toe.The stress distribution pattern of the basement side wall under two different conditions of roof construction and cut slope after construction is obviously different.The pressure of the basement side wall increases with the increase of seismic amplitude,but along the direction of depth,the pressure of the rock at the middle point of the basement side wall in the roof construction condition achieve the largest.In the condition of slope cutting after construction,the lateral rock pressure in the basement increases linearly along the depth direction before the slope cutting,while the lateral rock pressure in the basement wall decreases somewhat after the slope cutting,and is larger at the top and smaller at the bottom along the depth direction.(3)Based on FLAC3 D finite difference software,a numerical analysis model of lateral constraint effect of rock slope foundation on basement is established to analyze the acceleration response law,slope deformation mechanism and stress characteristics of basement side wall under the construction condition of slope roof.It is shown that the numerical simulation results are basically consistent with the results of shaking table model test.The sensitivity analysis of the horizontal resistance coefficient of the rock slope foundation is carried out by using the normalization method through changing the distance of the basement slope,the height of the side slope,the angle of the slope and the strength parameters of the structural plane by the control variable method.The analysis results show that,the strength parameters of the structural plane have little influence on the horizontal resistance coefficient on the premise that the slope does not slide along the structural plane,and the order of the main influencing factors of the horizontal resistance coefficient of the rock slope foundation is shown as follows: slope height > slope distance >slope Angle.(4)According to the results of sensitivity analysis,the constraint effect of different adjacent slope distances and side slope heights on the basement was further studied.By linear regression analysis,The function relation between the horizontal resistance coefficient of rock slope foundation and the slope height and the distance near the slope are obtained.Then,the determination method of the strength of the constraint effect of rock slope foundation on basement is made clear.It provides a theoretical basis for the selection of the embedded end and the calculation of the internal force of the high-rise building located on the foundation of the rock slope under the action of seismic load.