Comparative Analysis Of Influence Of Three Steps And Retaining Core Soil On Surrounding Rock Deformation Of Mountain Tunnel

China is a mountainous country,especially in the central and western regions.However,with the development of urban transportation construction,the mutual realization of material resources between cities and cities is realized for the economic development of each city and the response to the national economic development.Traffic development is particularly important.Mountain tunnels have emerged as a bridge between these cities and cities.Mountain tunnels are often accompanied by two characteristics: long and long.In response to these two characteristics,we have developed and applied new principles,new technologies,new equipment,new methods,new processes and new materials in tunnel construction technology.The three steps and the core soil method are two construction methods for constructing the mountain tunnel.This paper focuses on the influence of these two construction methods on the surrounding rock deformation of the mountain tunnel,and compares and analyzes the characteristics of the two methods to guide the tunnel construction in the future.This paper relies on the engineering example---Comparative analysis of the No.3 tunnel project of Longzhou Bay,Banan District,Chongqing City.In order to obtain real and effective monitoring data,the excavation sections under the two methods are selected for on-site monitoring,and the obtained monitoring data are collated and analyzed.Based on the selected actual monitored section,Midas-GTS finite element software is used to simulate the influence of excavation on the surrounding rock deformation of the tunnel.The settlement of the cavern and the surrounding convergence are used to reflect the tunnel surrounding under different methods.The influence of rock deformation is directly reflected in each working condition under the two construction methods.At the same time,combined with the simulation data and actual engineering under various working conditions,the influence of the two methods on the surrounding rock deformation of the mountain tunnel is analyzed.Under the condition of the selected supporting form and the surrounding rockgeological constant,the influence of the two construction methods under different cyclic footage on the deformation of the surrounding rock of the tunnel is analyzed.Here,the circulating footage is 2.0m,2.5m,3.0m,3.5m.In this case,the most reasonable cyclic footage is obtained by numerical calculation and analysis during the actual tunnel construction process.The numerical analysis results and the actual monitoring results are compared and analyzed,which proves the controllability of numerical simulation.The obtained results have certain guiding significance in engineering practice.