| Along with the quantity and the total length of the tunnel in the territory of China continuously extension,the construction technology also got a large improvement and improve accordingly,but the tunnel portal construction stability control is still a worldwide problem to be resolved.Although experts and scholars at home and abroad have carried out extensive research,they has not found completely effective solutions.Tunnel entrance section on the dynamic stability control has been the construction of one of the most important question,the hole construction usually is the main control engineering section of tunnel engineering.The structure and formation usually has a poor stability,complex stress state,the construction technology of high difficulty and large quantities of support.Tunnel entrance section is so easy to collapse,landslides and other disasters.Disposal of bad tunnel entrance will seriously affect engineering work personnel's life and property safety and construction progress.Control technology of the research on the stability of tunnel portal construction is particularly important,for control of tunnel hole deformation,enhances the stability of tunnel portal as a whole.This paper studied some content as the follow:(1)Confirm the main factors influencing the stability of tunnel portal,respectively analyzes the influencing factors on the stability of the hole.The deformation of tunnel portal criterion is the benchmark for determining tunnel and stability is a reliable indicator,in determining the decision base on the premise of,it needs to study the mechanism of deformation of tunnel portal structure and the formation and structure of the tunnel entrance slope failure mode for research.(2)Analysis the hole stability impact of the tunnel,its stability and construction methods,processes,slope gradient.The hole depth and other factors closely related to construct a three dimensional numerical simulation.Study the different excavation construction method of tunnel portal,different buried depth and the influence of different slope of tunnel deformation and stability analysis.To evaluate the stability of tunnel portal and the stability factor of safety.(3)Summarize the tunnel portal reinforcement technology,effectively control the deformation of tunnel hole and the slope to improve the stability of the tunnel.The deformation of the tunnel entrance slope failure process is divided into several obvious stages.To put forward in the stages in the corresponding disposal is measured to controlthe deformation of tunnel portal.(4)Study the tunnel portal monitoring technology.Put forward the monitoring level,cross section and the principle of setting,further proposed the deformation monitoring warning index system,through the project example to test and verify.Combined with a tunnel monitoring data analysis feedback control and prove effectiveness and reliability of stability control measures.(5)In the mouth of the cave landslides of an expressway as example,through analysis on the stability of the mouth of the cave,finite element calculation model to evaluate the stability of the tunnel entrance slope,the design and selection of the hole stability control measure.Tunnel portal integrated geological conditions,the use of numerical analysis and field monitoring measurement and verification of the excavation method,process,rock pre-reinforcement technology and protective measures to control the deformation of the important role in the stability of tunnel entrance control of several key technical measures,on this basis,guide the tunnel portal design scheme and concrete construction technology and procedure,to do good development area. |
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