Research On The Surrounding Rock Stability And Bolt Support Optimazation Of Schist Tunnel

Due to the complicated geological process,there are a lot of different scale and properties of the jointed surfaces in the natural rock mass,which not only destroy the integrity of the rock mass,but also plot a important role in damage mechanism of rock and.Therefore,it is indispensable to analysis of the influence of the distribution of joints on the excavation of underground engineering in jointed rock mass.In this paper,based on the Yangjiazhuang tunnel of Baoji to Lanzhou Passenger Dedicated Line.Firstly,the two-dimensional discrete element software UDEC was used to analyze the influence of jointed rock mass on tunnel stability.Finally,3DEC was used to optimize the bolt support in jointed rock with an angle of 60°.The main works are as follows:(1)The influence of the distribution of joints on the stability of surrounding rock was studied,including different inclination,cross-joint,different connection rate and random joints:(1)The deformation of the surrounding rock varies with the inclination.When the joint inclination is small,the rock tends to bend perpendicular.As the dip angle increases,the rock mass tends to slip;(2)According to the distribution of joints of Yangjiazhuang tunnel,the tunnel excavation in the rock mass of two groups was simulated.The results showed that When the angle difference between the two groups is greater than 30°,the stability of the surrounding rock is poor;(3)The stability of the surrounding rock of the connected joint was worse than that of the non-connected joint model;(4)The random joints are more closer to the distribution of the real joints,and the three sets of joints with random parameters ware simulated.The results showed that,due to the existence of joints,the deformation of the tunnel is bent along the slope direction,forming asymmetrical bias phenomenon.(2)If the design of bolt support is not proper,it will not only result in the waste of funds,but also affect the stability of surrounding rock.Took the model with the joints angle of 60 degrees as an example.The optimization scheme of bolt support forthin-layer surrounding rock was put forward:(1)In order to give full play to the role of the suspension of the anchor bolt,when the bolt supporting in the layered rock tunnel,the direction of the anchor bolt should be perpendicular to the joint surface.(2)When arranging lock bolt in inclined layered rock mass,if you want to give full play to the role of lock foot anchor,can not use the symmetrical arrangement of the left and right sides in homogeneous rock,and need to use left-right asymmetric arrangement.