Research On Optimization Of Supporting Structure In Expressway Tunnel Construction

Traffic branch tunnels are widely used in tunnel engineering,and have their own characteristics of short service life,small cavern section,and low durability requirements.The traditional composite lining is often too safe and wasteful for traffic branch tunnels.At the same time,due to the narrow space,large slope,complex environment and other factors in the traffic branch tunnel,it is difficult to apply secondary lining,and it is difficult to guarantee the safety and quality.Therefore,based on the research on the cooperative bearing mechanism of the support structure,it is of great significance to propose a support structure form suitable for the traffic support tunnel.This paper relies on the construction of the branch tunnel of the Wangjiawuji Tunnel of the Yibin-Panzhihua Expressway on the G4216 line,and adopts the methods of investigation and analysis,numerical simulation calculation,and on-site testing to carry out the support structure cooperative bearing mechanism,support structure optimization plan and waterproof and drainage measures.Research.The main work and research results of the paper are as follows:(1)The numerical simulation software FLAC3 D is used to optimize the single-layer lining of the construction support tunnel from the angles of shotcrete thickness,steel frame form and spacing,bolt length and position,etc.The form and parameters of the support structure.Combined with the interaction principle between the supporting structure and the surrounding rock,the bearing mechanism of the single-layer lining is analyzed,and the supporting force and the sharing ratio of the supporting structure are studied.(2)Combined with on-site construction,from the perspectives of shotcrete performance improvement,sprayed layer spraying process and support structure waterproofing and drainage,a specific implementation plan for single-layer lining of construction support tunnels is proposed.(3)Through field tests,monitor the distribution and changes of surrounding rock displacement,surrounding rock pressure,steel frame stress,and shotcrete stress of grade IV and V grades of surrounding rock sections.Verify and analyze the cooperative bearing mechanism of the supporting structure,and analyze and evaluate the supporting effect and safety on site.