| Because of complex terrain conditions in the mountainous area of Southwest China,the proportion of the tunnel is up to 40%?50%.Restricted by the topography,the bias problems of shallow buried section of tunnels are very common,therefore,it is difficult to control the deformation of the tunnel with bias pressure,the problems have serious impacts on tunnel construction and operation safety.In this paper,unsymmertial loading tunnel Mangbushan Tunnel of Weixin to Zhenxiong Section of Yi-Bi Highway is taken as the research object,on the basis of field monitoring data analysis,3D numerical analysis model is built,this article simulates actual tunnel engineering deformation,the influence of the degree of bias on the deformation of tunnel surrounding rock is analyzed,and the deformation and control method of surrounding rock under different slope angles,depth,bolt support parameters and tunnel excavation sequence with small spacing are studied.The paper mainly focuses on the following aspects.(1)Field monitoring of surrounding rock deformation in Mangbushan Tunnel is carried,and a 3D numerical analysis and calculation model for unsymmetrial loading tunnel is built,the simulation results of 3D models are compared with the actual monitoring data,the parameters of the numerical model are optimized.The study provides a theoretical basis for the follow-up study.Besides,the change rule of surrounding rock displacement in tunnel engineering is also analyzed.(2)The construction conditions of various slope angles and depth are fully considered,9 different unsymmertial loading tunnel models including 15m 25m 35m buried depth and 15° 25° 35° slope angles are established.The influence of buried depth and slope angle on the deformation of the bias tunnel is analyzed.Considering the bolts length 3.0?7.0m,and bolts spacing 0.8?1.2m,4?5 conditions of bolts length,5 conditions of bolts spacing are established,then bolts supporting force and surrounding rock deformation under different supporting parameters are analyzed,it is concluded that the optimal value of bolt length and spacing on construction and economy in different conditions.Based on that,a reasonable length and spacing parameter of bolt support is established,and the achievement will plays a guiding role for tunnels construction which under similar surrounding rock conditions in the future.(3)Through numerical simulation,the reasonable excavation sequence of small spacing tunnel under different construction conditions is studied.The paper establishes a total of 9 different bias and small spacing tunnel models,including 5m 15m 25m buried depth and 15° 25° 35° slope angles of the tunnel outside of the body of the mount.Staggering the two small spacing tunnels excavation for 10m,the deformation rule of arch crown settlement,arch shoulder settlement and surrounding displacement of small spacing tunnels under different construction sequence is studied,then the optimal construction sequence of shallow buried bias small spacing tunnel is determined.The representative tunnel model is selected to optimize bolt support.After comparing the deformation of tunnel surrounding rock under general support and optimized support scheme,the study confirms the control effect of the optimization scheme of bolt support,and verifies the practicability of the previous study at the same time.Furthermore,the study provides a theoretical basis for the selection of bolting support during actual engineering construction. |
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