Research On The Safe Distance Between The Cave And The Guiyang Rail Transit Tunne

When constructing tunnels in karst areas,disasters such as sudden water and mud,landslides and cracks often occur.Karst is widely distributed in Guiyang,and karst is found in all soluble rocks along the Guiyang railway line,with a high proportion of karst and various types of karst.The development of karst has a great impact on the construction of tunnels,and there are many construction difficulties caused by karst,and caverns have a greater impact on the stability of tunnels.Therefore,it is important to study the influence of different cavity diameters,different water pressure and different locations of karst on the stability of tunnels and the safety distance between karst and tunnels to provide reference for tunnel design and construction and ensure construction safety.This paper relies on the Natural Science Foundation of Guizhou Province(Qiankehe Foundation [2019] No.1057),"Research on Safety Analysis and Drainage Prevention of Karst Mountain Urban Rail Transit Tunnel through Water-rich Karst Surrounding Rock",to study the effects of different water pressures,locations and diameters of caves on tunnel stability and safety distance through theoretical derivation,numerical simulation and model tests.The main conclusions of the study are as follows:(1)Based on the mutation theory,the rock layer between the cavern and the tunnel,which is located directly in front of and diagonally below the tunnel,is simplified into a circular plate and a semi-circular plate to derive the formula for the safe distance between the cavern and the tunnel.The theoretical formulae are used to determine the safe distance between the cavern and the tunnel,which is influenced by the tunnel radius,Poisson’s ratio,modulus of elasticity and the pressure difference between the tunnel sections.(2)Establish a numerical and physical model for a single track tunnel based on the Guiyang rail transit section tunnel as a prototype.Through numerical simulation and model test results analysis of single line tunnels,it can be concluded that the diameter,water pressure,and location of karst caves have an impact on the stability of single line tunnels and the safe distance between karst caves and tunnels.As the water pressure in the karst cave increases,the safety distance between the tunnel and the karst cave gradually increases.The impact of different locations of karst caves on the safety distance and tunnel stability between single line tunnels and karst caves varies greatly,while the impact of karst cave diameter on the stability and safety distance of single line tunnels is relatively small.(3)Through numerical simulation analysis of the double track tunnel,it can be concluded that the water pressure in the karst cave directly in front of the left line and the karst caves at different positions have a significant impact on the stability and safety distance of the double track tunnel.