Research And Application Of Optimization Of Slope Stability Support Scheme For "Road-Reconstructed Bridge" Of Expressway Expansion

With the rapid development of the economy,the number of cars has been increasing rapidly,especially in the developed areas,the traffic volume has shown a sharp upward trend,which makes the existing highways unable to meet the requirements of the roads and hinders the development of urban economy on both sides of the roads.Communication,it is urgent to transform the existing roadbed into a bridge--"road-to-bridge" while the original expressway is being expanded.Based on the "road-to-bridge" project of the sixth contract section of the Beijing-Shanghai Expressway Reconstruction and Extension Project(Linyi Section),this paper studies the stability of slopes in the project,under the premise of continuous crossover,small deformation and rapid construction.Through the field investigation,numerical simulation and optimization design,the feasibility study of excavation support for subgrade slope is studied,which is of great significance to the actual project.The main research results are as follows:(1)According to the actual situation of the "road-to-bridge" project area,this paper determines the excavation plan of the subgrade slope as "the core soil method",first introduces the implementation plan and construction process of the "road-reconstruction bridge" project;According to the characteristics of the project and the applicable conditions of the anchor cable support structure,the difference between the anchor cable and the ordinary prestressed anchor cable is studied.Finally,the stability of the slope after excavation must be studied without interrupting the traffic.Considering the vehicle load effect,by investigating the vehicle flow and vehicle type around the "road-to-bridge" section,the vehicle calculation model and mathematical model of the five-axle truck are determined,and the five-axle trucks are obtained at different speeds.Load time history curve.(2)Using FLAC3D numerical simulation software to establish the calculation model of the original subgrade,and obtain the physical and mechanical parameters such as elastic modulus,cohesion force and internal friction angle of the subgrade slope according to the geological survey report,and apply it to the later simulation calculation..After the initial stress calculation is carried out on the original subgrade slope under the conditions of no vehicle load and vehicle load applied,the subgrade slope is stepped and excavated until excavation reaches the bottom level of the pit,which is obtained during the excavation process.The horizontal displacement of the slope surface,the displacement of the bottom of the pit,the horizontal displacement of the road surface and the vertical displacement of the road surface,and comparing the displacement variation law under two working conditions,the vehicle load is excavated and supported during the subgrade slope excavation The role of can not be ignored.(3)Based on the orthogonal simulation experiment,four factors and three levels of optimization are applied to the four factors of anchor cable prestress,anchor cable diameter,anchor cable spacing and steel plate thickness in the anchor cable support structure.By simulating nine kinds of test schemes,the three control indexes of the horizontal displacement of the subgrade of the subgrade slope,the displacement of the bottom of the pit and the horizontal displacement of the road surface are obtained,and the four control factors affecting the stability of the slope are analyzed by using the extreme difference analysis method.Sorting,and finally combining the engineering economic factors on the basis of the safety of the subgrade slope,choose a roadbed slope support scheme that is both safe and economical.(4)Apply the optimized support scheme to the "road to bridge" slope engineering support,and verify the feasibility of the support scheme in the actual construction process,but since the project has not yet been put into practical use,The research in this paper is to provide sufficient theoretical preparation for the application of the later stage of the project.