Study On Deformation Characteristics And Control Of Surrounding Rock In Loess Tunnel

In the process of sustainable economic development in the western region,transportation is an important part.To some extent,many loess mountains hinder the smooth of the road.Therefore,the construction of loess tunnel is more and more concerned by researchers.In the process of loess tunnel construction,many "diseases" seriously threaten the safety of people’s life and property,so it is necessary to fully understand the deformation characteristics of loess surrounding rock to strengthen its support structure.Based on the background of Bingcaoling loess tunnel in Lanzhou City,Gansu Province,this paper establishes two-dimensional and three-dimensional models of the tunnel in the ANSYS finite element software,puts forward a kind of strengthening support structure and compares it with the traditional support,analyzes the deformation characteristics of the surrounding rock in the process of strengthening support during the construction of the tunnel in sections,and also carries out field monitoring and measurement of the tunnel.The main work of this paper is as follows:This paper summarizes the research status of deformation of surrounding rock and supporting structure of loess tunnel at home and abroad.According to the supporting principle of surrounding rock of tunnel,a kind of strengthening supporting structure suitable for loess tunnel is proposed,that is,on the basis of traditional supporting mode,trapezoid support is applied at the arch line and anchor pipe is inserted at the arch foot for grouting.The basic principle of elastic-plastic mechanics of loess is summarized,and the realization of tunnel excavation and support in ANSYS software is explained.The two-dimensional model of the tunnel is established,and the surface settlement,displacement around the tunnel,surrounding rock stress and internal force of the support structure are compared and analyzed after the traditional support and the strengthened support.The results show that the strengthened support structure is more suitable for the loess tunnel and better than the traditional support.The three-dimensional finite element model of the tunnel is established to simulate the excavation and support process in sections,and the influence of the tunnel on the surrounding rock and lining of the excavated section in the process of continuous construction is studied.The results show that the settlement of the rock mass above the tunnel is cumulative in the process of excavation and support,and the settlement of the rock mass at the central axis is the largest,and the settlement of the rock mass on both sides decreases with the increase of the distance from the central axis;the surrounding rock at the arch support is the stress concentration area,which reduces the "stress burden" at the upper arch crown and the arch waist,and the tunnel has been excavated to the next support section The stress increases first and then decreases.Three sections of Bingcaoling tunnel during construction are monitored and measured.The measurement items include vault subsidence,peripheral convergence,surrounding rock stress and initial lining concrete stress.The monitoring data are summarized and the displacement and stress curve with time is drawn.According to the monitoring and measurement results,this paper puts forward suggestions for the construction of Bingcaoling tunnel,which provides theoretical basis for the construction personnel to adjust the construction plan in time..The research results of this paper provide some reference for the construction of similar projects in engineering practice.