Study On Mechanical Characteristics And Optimizing Construction Method Of Super-closely-spaced Loess Railway Tunnel

With the rapid development of China’s transportation and the implementation of western development strategy,more and more railway tunnels crossing the loess region have been built.The unique physical and mechanical properties of loess have a potential unfavorable influence on tunnel structure,which brings about a great challenge to tunnel construction,especially for super-closely-spaced loess railway tunnel.In tunnel construction,the reasonable selection of construction methods is the key premise to ensure rapid and safe construction.Therefore,it has great significance for studying the construction method of super-closely-spaced loess tunnel.In view of this,this paper puts forward the optimization method of construction method based on analytic hierarchy process,and studies the construction method optimization of super-closely-spaced loess tunnel,which provides support to select the construction method of super-closely-spaced loess tunnel.On this basis,the construction method suitable for Anjiazhuang Tunnel is determined and applied according to the actual situation of the project,which verifies the rationality of the method.The main work and achievements are listed as follows(1)Through physical mechanics test of surrounding rock in the Anjiazhuang tunnel,basic physical mechanics index was given.The influence of vibration loads on the mechanical properties of surrounding rocks of the newly built tunnel is also studied,which provides a basis for subsequent numerical calculation.(2)Based on the section size of the expanding section of the switch machine in Anjiazhuang Tunnel,considering the factors of tunnel depth,spacing and the distance between invert and tunnel face,a simulation is presented on the excavation process in loess tunnel by means of full face method,ring cut method,seven-step three-stage method,center diagram(CD)method,cross diagram(CRD)method and both diagram method.The mechanical characteristics of different construction methods under different conditions are obtained,which provides solid basic data for the study of optimizing construction methods for super-closely-spaced loess tunnel.(3)Based on the calculation results of the mechanical characteristics of different construction methods under different conditions and considering the construction progress and cost of each construction method,an optimization method of construction method based on analytic hierarchy process(AHP)is proposed.The optimization study of construction method of loess tunnel is carried out to determine the most suitable construction method under different conditions.(4)Based on the analysis results of optimizing construction method of loess tunnel and the actual situation of Anjiazhuang tunnel,the construction method suitable for Anjiazhuang tunnel is determined,and the numerical simulation is carried out.The calculation results are consistent with the monitoring data for the deformation of tunnel surrounding rock,which verifies the reliability of the optimization method of construction method proposed in this paper.Figure[52]table[23]reference[83]...