Analysis of Surface Subsidence Law During the Construction of Pipe Shed at Tunnel Entrance in Strongly Weathered Mudstone Area
The rock mass in the strongly weathered mudstone area is relatively fragmented,with poor self-stabili-zation ability of the surrounding rock.The construction process of the tunnel is complex,and the deformation of the surrounding rock and surface settlement are obvious.Pipe shed grouting construction can pre reinforce the rock mass and is an effective method for constructing tunnels in weak and fractured strata.Taking a high-speed railway tunnel as the research object,the engineering geological conditions of the tunnel and the construction technology of the pipe shed are described in detail.The surface settlement deformation laws on the left and right sides of the tunnel entrance section at different positions are obtained,and the final surface settlement at each point is predicted based on regression analysis method.The results show that pipe shed grouting can effectively control surface settlement above the tunnel,but its reinforcement has a significant impact on surface settlement outside the affected area;The further away from the grouting reinforcement area of the pipe shed,the smaller the surface settlement,and the surface settlement on the left side of the tunnel is higher than that on the right side,with a maximum settlement value of 264.6 mm.The surface subsidence values at each point follow an exponential function variation pattern,experiencing three stages in sequence:rapid subsidence,slow subsidence,and basic sta-bility.Moreover,measuring points with small subsidence deformation tend to stabilize earlier.
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