Optimum Design Of Initial Supporting Structure And Construction Plan Of Shallow Buried Large-section Tunnel

In recent years,China’s infrastructure has developed rapidly,and the transportation industry as a pillar industry that benefits the country and the people has a pivotal position in infrastructure.However,China’s terrain is complex,especially in the mountains and rivers in the southwest.Tunnel construction has become the biggest problem in opening up the national transportation network.In the process of tunnel construction,the support structure should be regarded as the most important safety guarantee,so it is of great significance to optimize the design of the tunnel support structure and construction plan.Based on the Puding Expressway Lingding Tunnel,this paper combines the field measurement data,design documents,construction documents and relevant specifications,and uses the finite element software ABAQUS to simulate the site tunnel excavation and support process,and compares the design of the tunnel support structure with the construction plan.Choose to provide reference,the main content is as follows:(1)Summarize the development process of the surrounding rock pressure theory and support theory,calculate and analyze the case in this paper through the surrounding rock pressure calculation theory,and calculate the upper surrounding rock pressure of the Lingding tunnel based on the judgment that the case is a shallow buried tunnel And discuss and analyze the applicability of modern supporting structure theory in this case.(2)Combined with the field measurement data and supporting structure parameters,the finite element software ABAQUS was used to conduct three-dimensional modeling and analysis,and the finite element model was compared with the actual monitoring surface settlement and vault settlement.Based on the displacement field of surrounding rock,plastic zone of surrounding rock,stress field of shotcrete,stress field of anchor rod and stress field of steel arch,the application time of initial supporting structure,the thickness of shotcrete and the spacing of steel arch,etc.Support parameters are further optimized and analyzed.The results show that the reasonable construction time of the initial supporting structure can not only give full play to the surrounding rock self-stability,but also enable the initial supporting structure to play a better supporting performance;after optimizing the thickness of the shotcrete,it can improve the construction efficiency and reduce The purpose of the project cost,and give full play to the supporting role of the anchor rod and the steel arch frame;the reasonable spacing of the steel arch frame can reduce the number of disturbances to the surrounding rock during construction,improve the stability of the surrounding rock and improve the efficiency of support.(3)On the basis of optimized supporting parameters and the premise of ensuring the stability of surrounding rock,in order to give full play to the initial supporting structure bearing capacity and improve construction efficiency,from the surrounding rock displacement field,surrounding rock plastic zone,shotcrete stress From the perspectives of the field,the stress field of the anchor rod and the stress field of the steel arch,the two construction schemes of the three-step seven-step excavation method and the upper and lower step method for the Lingding tunnel are compared and analyzed.The results show that fewer steps in the up and down steps method can reduce the stress redistribution in the surrounding rock,improve the stability of the surrounding rock and speed up the construction progress.The conclusion can provide reference and suggestions for similar engineering practices.