Comparison And Selection Of Reconstruction And Expansion Schemes For In-service Tunnels In The Loess Area

With the rapid development of China’s national economy and the continuous increase in traffic demand,some tunnels that have been built for a long time have a low design capacity and lack of capacity,which has constrained the rapid development of the economy.In addition,due to the long service life of the tunnel,many tunnels have insufficient clearance,lining cracking and water leakage,which cannot guarantee and meet the safety and service requirements of the tunnel.In order to eliminate potential safety hazards and improve tunnel capacity,we have rebuilt,expanded or reinforced some tunnels that cannot meet the normal use requirements.In this context,this paper relies on the reconstruction project of the Shijiazhuang Tunnel under the three major lines of Shanxi Provincial Road,and compares and analyzes the original site expansion plan,the new tunnel plan and the current tunnel reinforcement plan,and finally selects the original site expansion plan,and combines the field monitoring measurement with numerical simulation.By means of other means,the characteristics of the original site expansion plan are studied and analyzed,and the rationality is analyzed.The main research contents are as follows:1.Through on-site statistical investigation and analysis,the assessment of tunnel diseases and structural conditions,analysis of the disease characteristics of the tunnel and the causes of the disease,and constructive suggestions for related diseases.2.Through the analysis and prediction of the traffic volume of the project,the current traffic volume is investigated,and the trend coefficient of the project is predicted by the elastic coefficient method,which clarifies the necessity of tunnel reconstruction and expansion.3.On the basis of the necessity of reconstruction and expansion,from the project construction conditions,routes,reconstruction and expansion plans,qualitative and quantitative comparison analysis,comparative analysis of the original site expansion,new tunnels and current tunnel reinforcement three options,and finally choose the original site expansion plan.4.For the original site expansion plan,use the finite element analysis software MIDAS/GTS to carry out dynamic three-dimensional analysis of the expansion plan,analyze the vertical,horizontal deformation and surface settlement of the tunnel after the excavation support is completed,and the tunnel deformation tends to be safe and stable.Verification of the feasibility of the original site expansion plan.5.At the construction site,for the original site expansion plan,the monitoring and measurement work will be carried out from the aspects of geological and support state observation,surfacesettlement of shallow buried section,peripheral displacement,and subsidence of the vault.The characteristics of surrounding deformation of surrounding rock and supporting structure are summarized,and the treatment effect is evaluated.Compare the numerical simulation values with the field measured values to judge the accuracy of the numerical simulation.