Analysis And Control Of Surrounding Rock Stability Of The Tunnel Of Guangzhou Metro Line 18

In this paper,the study area is the coarse sand-rich layer in the water passing through the Xiahengli Waterway of Guangzhou Metro Line 18.The finite difference method FLAC3 D numerical simulation software was used to simulate the changes of surrounding rock stability and supporting structure deformation caused by tunnel excavation when there is stable recharge of groundwater.Combined with the seasonal and tidal changes in the water level of the Lower Hengli waterway,the fluid-solid coupling method is used for numerical simulation analysis.When the double-track shield tunnel is excavated in sequence with the left and right lines,the surrounding water level caused by the seepage action at different river water depths The deformation of rock and support is controlled.With the increase of shield tunneling distance,the following rules are summarized:(1)In the stress field of surrounding rock,the maximum value of the vertical effective stress appears at the position of the arch toe on both sides of the tunnel,and the maximum value of the horizontal effective stress appears at the position of the arch waist on both sides of the tunnel.(2)In the surrounding rock seepage field,super pore water pressure will be formed at the front end of the tunnel face,and the pore water pressure in the disturbance zone at the back end will be distributed in a "funnel shape".The water head difference between the two arch waists of the tunnel is the largest,and the size is affected by the length of the excavation and the depth of the water level Larger.(3)Deformation of the supporting segment.As the degree of deformation of the surrounding rock on the supporting segment increases,the support segment is squeezed toward the center of the tunnel in the vertical and horizontal directions.The vertical deformation of the segment is affected by the cutter head.The impact of the driving distance is more significant than that of the horizontal direction.(4)Under different water level depths,the vertical and horizontal deformations of surrounding rocks are significantly affected by water level changes.Basically,the degree of dome subsidence and arch bottom uplift increase significantly with the increase of water level depth.The maximum principal stress of the tube segment increases with the increase of the water level,and the surrounding water head difference also increases,especially on the left and right sides of the tube segment,and the uneven convergence and deformation of the tube segment to the center increases.(5)Four kinds of supporting segments with different strengths are selected to analyze the deformation of the surrounding rock and optimize the segment parameters.