Numerical Simulation Study On Safety Of Tunnel Lining Structure In Karst Depression

The influence of karst depression landform on tunnel engineering is mainly manifested in the increase of the load of the supporting structure of the lower tunnel caused by the catchment and diversion of water in the depression in rainy season,which poses a great threat to the safety of the tunnel.The mode of action of external water load on lining structure of karst tunnel under extreme rainfall and its influence on the safety of lining structure cannot be determined often leads to unreasonable design parameters and inaccurate cause analysis of tunnel lining structure.Therefore,it is necessary to carry out special research to provide basic data and basis for karst tunnel lining structure design and safety evaluation.In this paper,based on the actual project,the research is carried out on the background of tunnel lining cracking and leakage in karst depression area.The influence of rainfall on karst is analyzed,and the seepage model is established by using finite element software.The influence of karst on the external water pressure of tunnel lining is semi quantitatively analyzed.The results show that the distance between karst and tunnel has the greatest influence on the external water pressure of tunnel lining.According to the influence degree,the order is the distance between karst and tunnel > the scope of dissolution fracture > the permeability of dissolution fracture > the size of karst.Based on the practical engineering,the model of lining water pressure analysis of tunnel lining under Karst depression is established by the coupling of seepage field and stress field,and the safety of lining structure of tunnel under extreme rainfall is studied.The results show that the safety factor of tunnel lining relying on the project is low at the side wall and corner,and the lowest is1.7.Based on the original model,the specific parameters of tunnel lining and grouting circle are changed.According to the research results,the tunnel lining is optimized by increasing the permeability of the lining,and the specific optimization scheme is given.After calculation,all parts of the optimized tunnel lining structure can meet the requirements of the specification,which is reasonable and feasible.The results can be used for reference to the supporting projects and similar projects in the future.