Study On The Construction Of Shallow Buried Bias Section Of Chaoyang Tunnel

With the rapid development of China's economy,the government's strong investment,and the in-depth implementation of poverty alleviation policies,the construction of highways in remote mountainous areas has continued to increase.There are many force majeure factors in the route selection of the tunnel.Sometimes one or more problems will be encountered during the construction of the selected line.The tunnel bias is a typical problem.The tunnel bias is divided into a structural bias and a topographic bias.The tunnel bias is likely to cause stress asymmetry on both sides of the diverticulum and the asymmetry of the diverticulum.The supporting ability of tunnel support is far stronger than that of pulling capacity.Displacement asymmetry on both sides of the tunnel tends to cause torsional deformation of the lining,and some locations are subjected to tensile deformation,which is not conducive to the stability of the chamber.Diluting the tunnel under the influence of bias can effectively protect tunnel excavation and later operation.This paper focuses on the tunnel excavation under topographic bias by relying on the Huitougou tunnel.The paper mainly analyzes the problem of the step height in the excavation of the two-step method.According to the previous literature and specification requirements and other aspects of data,it is determined that the step height in the two-step excavation is 5.0m~7.0m.Using Midas/GTS for numerical simulation,the step gradient is 0.5m,and a total of 5.0m,5.5m,6.0m,6.5m,and 7.0m steps are selected for analysis.The main contents are as follows:1.Analyze the actual monitoring data in the Huitougou tunnel to study the distribution of the displacement of the diverticulum under the topographic bias.It shows that the deep side displacement of the chamber is larger than the shallow side displacement.2.Simulate and analyze the displacement of the chamber and the stress distribution of the surrounding rock under different buried depths,different surface inclination angles,and different surrounding rock levels,and compare the simulations under different working conditions of different steps at different heights to study the displacement of the chamber and the stress distribution of the surrounding rock.The correlation of the excavation parameters leads to a reasonable lower step height in the two-step excavation.3.Analyze the relationship between the convergence of the diverticulum and the stress distribution,and study the specific performance of the new Austrian theory in actual engineering.4.To study the settlement of the vault in each step of the construction of the step method and to find out the law of the stress of the surrounding rock during the excavation of the chamber.