| The construction of Guiyang urban rail transit in karst mountainous areas is facing various challenges to tunnel construction safety caused by karst caves.During the construction of Guiyang rail transit tunnel,the collapse of karst cave,water inrush and mud inrush will pose a great threat to tunnel construction and even later operation.Therefore,it is necessary to study the influence of karst caves on the safety of urban rail transit tunnels.Based on the research background of Guiyang Rail Transit Project Line 1,combined with the distribution characteristics of karst caves in the project,this paper studies the impact of karst caves on the tunnel safety of Guiyang Rail Transit Project.The main work is as follows:1.Based on the study and analysis of the causes and hydraulic types of karst water and mud inrush,aiming at the characteristics of karst caves in Guiyang Rail Transit Tunnel,a numerical simulation model is established.The effects of different caves with different diameters and spacing on the distribution of displacement field,stress field and plastic zone,as well as the internal force and safety of lining under the conditions of top,side and bottom caves are analyzed,and the influence rules are summarized.2.By comparing the numerical simulation results of surrounding rock displacement,stress,plastic zone range and lining safety factor,the influence of tunnel excavation method on surrounding rock stability and lining safety of karst tunnel is studied.The results show that the stability of surrounding rock and the safety factor of lining are optimum when the karst tunnel is excavated by the the double drift method.3.Based on the theory of instability of rock pillars between tunnels and karst caves,orthogonal experiments are carried out with numerical simulation software to calculate the safe distances between top,side and bottom caves and tunnels.The influence of surrounding rock level,lateral pressure coefficient,tunnel depth and tunnel diameter on the safe distances is analyzed through the calculation results.Finally,using statistical software for multiple regression,a formula for predicting the safe distance of karst caves at the top,side and bottom of Guiyang Rail Transit is established.And the reasonableness of safety distance prediction formula is verified by practical engineering application analysis.4.The influence of water pressure in different karst caves on the stability of surrounding rock,the safety of lining and the safe distance between tunnel and karst cave is studied,and the influence rules of water pressure change in karst caves on the safety and stability of tunnel is summarized and analyzed. |
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