Study On Load Characteristics And Calculation Method Of Squeezing Ground Rock Railway Tunnel

With the development of railway tunnels in China,the theoretical system of tunnel construction has been greatly improved,but the difficulty of tunnel construction is also increasing.Railway tunnels have been developing in the direction of "long,large,deep and difficult",especially in the southwest of China,where the terrain is steep,the surrounding rock is of high grade,and the lithology is poor.The surrounding rock is mainly expansive and weak compressive.After excavation,the surrounding rock is extremely unstable,which makes the construction of tunnels more difficult.In order to better understand the surrounding rock condition,load characteristics,the changing law of surrounding rock,the calculation method of surrounding rock load and the optimization of section,it is particularly important.This paper focuses on the following aspects and discusses them closely:(1)Through investigation and consulting a large number of domestic and foreign research literature on soft and fractured and extruded surrounding rocks,we can understand the related content of extruded surrounding rocks.Through a large number of research and research at home and abroad related research status and deficiencies,on this basis,the paper gives the main research content,technical routes and methods.(2)Research on the adaptability of load calculation method for tunnel structure.By consulting relevant papers and Monographs on extruded surrounding rock,the advantages and disadvantages of structural load calculation methods,influencing factors,and the differences between extruded surrounding rock and general surrounding rock are analyzed.(3)The load characteristics of extruded surrounding rock tunnel are studied by numerical simulation.The relationship between load distribution characteristics of extruded surrounding rock tunnel and Strength-Stress ratio,height-span ratio,lateral pressure coefficient and support stiffness of surrounding rock is studied.(4)Analysis of calculation method of structural load of extruded surrounding rock tunnel.By investigating a large number of literatures about extruded surrounding rock tunnels at home and abroad,monitoring data based on engineering examples are extracted,and the limitations of domestic geological survey are analyzed.Based on the research idea of combining statistical analysis of field measured data with numerical simulation analysis,the load calculation method of extruded surrounding rock tunnel is synthetically obtained.The relationship between structural load and Strength-Stress ratio,height-span ratio and lateral pressure coefficient of surrounding rock is determined,and the empirical formula for calculating the load of extruded surrounding rock tunnel is put forward.(5)Application of load calculation method and section optimization.The load calculation method obtained from the analysis in this paper is checked,and some suggestions on the form and curvature of tunnel section are put forward,and the safety evaluation of the pre-designed tunnel structure is carried out.