Research On The Construction Mechanics Of Qichongcun No.two Shallow And Unsymmetrical Big-span Tunnel In Guiyang

In recent years,the highway tunnel from four lanes and two-way six lanes developed into eight lanes in our country.The area and span of tunnel section become more and more big.The tunnel excavation span increases,if keeping the tunnel flat rate,sectional area will be too large,the cost will be greatly increased.In order to ensure that the cost of large span tunnel remains the same height,resulting in flat rate decrease and the tunnel surrounding rock and supporting structure of the force has become more complex,improve the risk of tunnel construction.In recent years,there have been a lot of span highway tunnel collapse and other disasters,so the process of surrounding rock and support structure of large span tunnel excavation must be strengthened,understand its characteristics.In this paper,the numerical simulation method is used to analyze the surrounding rock pressure characteristics of three different spans of the tunnel with two lanes,three lanes and four lanes,and get the basic characteristics of surrounding rock pressure of shallow buried large span tunnel.According to the research on the key technology of the construction of shallow buried large span karst tunnel,the paper relies on the project of Guiyang Qianchun Qichongcun tunnel,monitoring the whole process of construction,the main contents include:the surrounding rock stress,steel arch strain,the contact stress between primary lining and secondary lining,the concrete stress and strain in secondary lining.Based on the analysis of monitoring data,grasp the stress change law of tunnel surrounding rock and support structure.At the same time,using the GTS NX finite element software to simulate the three-dimensional numerical simulation of Qichongcun tunnel,and comparing with the field monitoring data,to deepen the understanding of the construction mechanics of the shallow buried large span tunnel.The research on the law of surrounding rock stress and supporting structure under construction can continuously improve the theoretical system of the surrounding rock stress of shallow buried large span tunnel,and provide guidance for the construction of the site.This paper summarizes some methods of calculating the surrounding rock stress of shallow and unsymmetrical big-span tunnel and obtains a new formula.