Study On Construction Method Of Forked Tunnel With Large And Multi Section

Due to the characteristics of large section size,low flattening rate and complex section form,the force of the surrounding rock and supporting structure of the forked tunnel with large and multi-arch is complicated.This paper presents a construction method of reverse excavation in the large section tunnel with a three-lane tunnel as the pilot tunnel,which relies on the liantang section tunnel of the transit high-speed connecting line project in the east of shenzhen city,guangdong province.Combined with Midas GTS numerical simulation software and field monitoring data,This paper studies the relationship between the deformation of surrounding rock,stress of supporting structure and the construction method of the forked tunnel with large and multi-arch tunnel,and the rationality of it.The research work of this paper is as follows:(1)Summarized the construction and research status of forked tunnel and large section tunnel both at home and abroad,and discussed the feasibility of a new construction method of forked tunnel with large and multi-arch tunnel based on the theoretical and experimental research investigated by scholars and investigation of forked tunnel and large section tunnel has been built.(2)Expounded the general situation and key points of the supporting project,analyzed the mechanical characteristics of the large section tunnel and the mechanical mechanism of subdivision excavation,and put forward the reverse excavation method with a guide tunnel,and explained the construction sequence and details of the construction method.(3)Studied the influence of the reverse excavation method on the stability of surrounding rock in the construction process by numerical simulation method,and the results of surrounding rock deformation,plastic zone distribution and supporting structure stress are extracted to discuss the construction feasibility of the reverse excavation method in the supporting project.(4)Monitored the construction process of the supporting project,and analyzed surrounding rock displacement,development and distribution characteristics of the steel arch stress and contact pressure of surrounding rock,discussed the influence of each step of reverse excavation method on surrounding rock and supporting structure,and verified the feasibility and rationality of this construction method through on-site monitoring results,which provides reference for safe and rapid construction of similar forked tunnels with large and multi-arch.