Analysis On Seepage Field Evolution Characteristics And Lining Safety Of Railway Tunnel In Karst Area

At present,it is still a difficult problem for engineering circles in the world to build long tunnel in high-pressure and water-rich karst area.In Yesanguan tunnel project,the high drainage branch tunnel is used instead of the low drainage tunnel to solve the hidden danger of tunnel safety caused by cavity development and sudden precipitation,which is rare at home and abroad.Based on Yesanguan tunnel project and the construction plan of Yesanguan tunnel,this paper investigated the karst caves in operation in this section of railway,analyzed the water pressure data of high-pressure water-rich karst tunnels with large filling caverns,and obtained the water pressure distribution law and structural load characteristics under the action of water in the caverns through comprehensive treatment.By RFPA(Realistic Failure Process Analysis)analysis software,the stratigraphic structure model,karst area is studied in operating railway tunnel surrounding large rich water soluble cavity pressure exists through the infiltration characteristics of surrounding rock,and the cavity water infiltration process in the surrounding rock by fine analysis of the multiple factors The specific law of influencing factors on water seepage process is given.The field measurement and numerical simulation data are analyzed,and the corresponding quantitative calculation formula and applicable scope are obtained by combining mathematical analysis method.Specifically,this paper includes the following contents:(1)Investigate and analyze the safety accidents of railway tunnels operating in karst areas,analyze the causes of similar accidents in combination with domestic and foreign literatures,and process and analyze the monitoring data of surrounding rock and tunnel lining before and after the construction of the drainage tunnel based on Yesanguan tunnel "+602" water inrush and mud inrush accident.The cause of the accident,the accident form,the rule of the dissolved cavity and other characteristics are obtained,and the factors affecting the reduction effect of the dissolved cavity water infiltration in karst area are further obtained.(2)Conduct classified simulation analysis on the osmotic influencing factors according to their direct closeness,so as to obtain the specific influencing mechanism and basic influencing law of the influencing factors in the infiltration process of the cavity,providing theoretical basis for subsequent quantitative analysis.(3)in the surrounding rock of rock-salt cavity and water phases in the process of infiltration,and according to the influence factors of each stage involves the integration analysis combined with simulation results,the formula derivation +simulation data fitting,the reaction cavity water infiltration in the surrounding rock pressure reduction effect coefficient of quantitative analysis,and put forward the range of allowable error scope and formula.(4)According to the quantified formula of seepage reduction effect obtained,the safety evaluation method under the influence of large dissolved cavity of railway tunnel operating in karst area is obtained through comprehensive analysis,and the drainage tunnel design idea is deduced based on the evaluation method,which provides certain theoretical calculation basis for the construction and design of similar projects in the future.