Dynamic Response And Shaking Table Test Of Loess Slope Reinforced By Frame Prestressed Anchors

As a new type of flexible supporting structure,the frame prestressed anchors has emerged in the flexible supporting structure with geotechnical anchorage as the core,but its theoretical research is disconnected from the practical application.In loess area,the application of the frame prestressed anchors in slope engineering is becoming more and more frequent.It is very necessary to carry out the dynamic response analysis of frame prestressed anchors to strengthen loess slopes under earthquake in a timely manner.This paper relies on the National Natural Science Foundation project of China(No.51768040)“Analysis of failure mechanism and stability of loess slopes reinforced by frame prest ressed anchors under earthquake.” According to the deformation characteristics of the slope reinforced by frame prestressed anchors under earthquake,the method of combining qualitative analysis and quantitative analysis is used to study the dynamic response of loess slopes reinforced by frame prestressed anchors with the help of large-scale shaking table test and finite element numerical simulation,and the permanent displacement of slope strengthened by frame prestressed anchors is discussed.The specific work done in this paper is as follows:(1)Based on the equivalent mass spring model and considering the coupling effect between creep soil and prestressed anchors,the dynamic calculation model for loess slopes strengthened by frame prestressed anchors consider ing the slope height effect is established.In this model,the soil behind the retaining wall is expressed in the form of concentrated mass.The effect of the frame structure on the soil is regarded as the parallel coupling of linear springs and linear dam pers,and the free section of the anchor is regarded as a linear spring.Considering the creep characteristics of loess,the soil is regarded as a Generalized Kelvin body,and the anchoring section of the anchor is regarded as an equivalent spring body,which are coupled in parallel.Considering the influence of slope height,the dynamic calculation model is solved.Finally,the dynamic response of the slope was analyzed through an engineering example and verified by the finite element numerical simulation software PLAXIS 3D.(2)Based on the mechanism of energy absorption and energy dissipation of the flexible retaining structure,considering the supporting effect of the frame prestressed anchors on the slope,the seismic displacement model of the loess slo pe reinforced by the frame prestressed anchors is established by the energy method.The controllable allowable displacement of the slope generated by the flexible retaining structure is divided into the seismic displacement and the safety reserve displacem ent.The factors influencing the allowable displacement of the slope are analyzed,the permanent displacement of the loess slope is solved,and the energy loss of the supporting structure is quantified.Finally,the feasibility of the model is verified by a practical engineering case.The model can provide a basis for seis mic optimization design of the slope supported by the frame prestressed anchors.(3)Based on the similarity principle,a large-scale shaking table test is designed and completed for the loess slope reinforced by the frame prestressed anchors with similarity ratio of 1:10.The content includes model similar design,boundary treatment,measurement point arrangement,ground motion input,etc.Through shaking table tests,the acceleration response law,dynamic earth pressure response law,displacement response law and anchor strain law of the slope are qualitatively evaluated respectively,and the dynamic response results are verified and supplemented by PLAXIS 3D.