| In recent years,with the rapid development of urban subway construction in China,the scale of subway construction has entered a period of unprecedented development.In the construction process of subway tunnels,they are often affected by the complex and changeable environment around them,and it is inevitable that underground tunnels and house construction will be required to penetrate underground facilities.This requires the construction of subway tunnels to ensure not only tunnel construction.Its own safety standards,but also to ensure the safety and use of other environmental facilities under wear.In this paper,according to the construction characteristics of the subway tunnel project,combined with a subway shield tunnel under construction project examples,in-depth study of the construction impact mechanism,and the use of numerical simulation,on-site monitoring methods,the construction of the surface settlement caused by the tunnel,surrounding rock and building The deformation law of the material is analyzed,and the risk in the construction process is evaluated using the cloud evidence theory,so as to reduce the influence of the shield construction on the surface,the tunnel surrounding rock and the underpass structure.The main research content includes the following aspects:(1)According to the characteristics of the underground metro tunnel tunneling through the section of the Dalian metro tunnel,the construction parameters such as earthwork pressure and excavation rate are set,and the post-grouting,shield attitude and building are also used in the construction process.The mechanism of the failure mode was analyzed,and the construction influencing law of the shield tunnel underneath the structure was summarized,which laid the theoretical foundation for the later research.(2)Through the simulation analysis of the shield tunnel underpassing the building project,the deformation of the surrounding rock,the surface and the building of the tunnel was studied.The rationality of the construction parameters in the mechanism analysis was verified,and the surrounding rock of the surface and the tunnel was obtained.The stability of the building and the construction are closely related to the selection of the construction parameters of the shield tunnel.It is necessary to strengthen the control optimization and actual monitoring of the construction parameters.(3)Through on-site actual monitoring,the impact of shield under-laying on the deformation of buildings and the ground surface is analyzed,and the influence laws of different stages of shield construction are summarized.The actual monitoring results are compared with the numerical simulation results,and the error of fitting results is insufficient.10%,indicating that the method of numerical simulation can accurately estimate the deformation law of the surface and buildings when the tunnel is under the shield tunnel,which can provide the necessary reference for risk evaluation in the construction phase.(4)Based on the analysis of the construction impact mechanism,numerical simulation and actual monitoring results,a risk assessment method based on cloud model and DS evidence theory is proposed,and a risk assessment model is constructed to separately penetrate the buildings and tunnel surrounding rock.The stability is evaluated by risk.The evaluation results show that:building inclination and cracks and unreasonable construction parameters are high-level risk factors that affect the stability of the surrounding rock of buildings and tunnels.Through analysis of the impact laws,control measures are proposed to ensure Shield tunnels provide technical support for the safety of buildings under tunnel sections and the surrounding rock of tunnels. |
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