Study On Stability Of Surrounding Rock In Tunnel Hanging On Rock Wall

Mountain tunnels are one of the most effective ways to traverse mountains and heavy hills,The number of tunnels is increasing with the deepening of traffic construction in mountainous areas,and the construction conditions are becoming more and more stringent,How to build road tunnels reasonably under the condition of limited construction environment and construction funds has become a major problem.In the early stage of construction,working people opened holes on the airside of the nearly 90°cliff,and excavated them to form a structure that combines half-mountain tunnels with roadbeds and shed tunnels.This is called tunnel.The research on highway tunnel hanging on rock wall at home and abroad has only a few studies.However,the surrounding rock stability of the tunnel hanging on rock wall still needs further analysis and discussion.This academic dissertation is based on the tunnel hanging on rock wall in Shibanhe Village,Hezhang County,Guizhou Province,to research the stability of the surrounding rock of the tunnel hanging on rock wall.Numerical simulation and physical model test method are used to analyze the changes in stress and displacement of tunnel hanging on rock wall under different sidewall opening widths and rock slope inclination conditions,so as to provide references for similar projects in the future.The main research contents and results are as follows:（1）Comparative analysis of the advantages and disadvantages of various schemes along the river and mountains,expounded the advantages of the wall-mounted tunnel structure during construction and operation.Collected and investigated the structural types of typical wall-mounted tunnels in China and the geological conditions of the tunnel site,combined with the literature,analyzed the factors affecting the stability of the surrounding rock of the wall-mounted tunnels and the possible deformation.（2）Through FLAC^3D finite difference software,three-dimensional models of 6different sidewall opening widths w and 4 different rock slope inclination i working conditions were established,and the displacement,stress change and plastic zone of the sidewall around the cave and the empty side during the excavation process were analyzed.The changing law of surrounding rock displacement,stress,and plastic zone with the width of the side wall and the slope of the rock wall,the displacement of the most sensitive position under the influence of the two factors is fitted,and the more sensitive position around the cave should be strengthened.（3）Based on the geometric similarity ratio of 1:20,the relationship between physical parameters and the prototype parameters was deduced through the similarity principle and similarity criteria.After consulting the literature,the similar materials were determined,and the mix ratio test was used to determine the best mix ratio of the original rock.（4）Designed and produced a model test box,carried out physical model tests of 3types of sidewall opening widths and 3 types of rock wall inclination,and measured the displacement and stress data during the excavation process by using an embedded displacement meter and a miniature earth pressure cell.Comparing the results with the numerical simulation results,the change trends of the two in the excavation process are basically consistent,which further confirms the reliability of the two methods.