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合肥地铁1号线盾构隧道下穿南淝河,施工中存在安全风险。运用FLAC3D进行了隧道盾构开挖过程的模拟,基于破坏接近度(FAI)对盾构隧道开挖过程中的岩土体稳定性进行分析。通过破坏接近度指标能够全面直观地评价隧道周围各区域岩土体的稳定性程度,定量给出损伤区和扰动区的范围。数值模拟结果表明:盾构开挖使隧道周边土体孔隙、水压力较初始值显著降低,导致了隧洞周边水力坡降增大,进而使地下水向隧洞拱顶及两侧流动,这些部位有发生涌水的可能;盾构开挖过程中,岩土体渗流场产生的渗流作用力对应力场分布产生较大的影响,在流固耦合条件下,隧洞周边岩土体FAI显著增大,部分区域已进入损伤区;在掌子面推进的过程中,当掌子面在分析断面前后2个开挖步数范围内时,断面的破坏接近度的分布变化明显,表明该范围内土体稳定状态受开挖扰动影响显著。研究盾构开挖过程中的破坏接近度分布及演化规律对施工中采取相应施工措施具有重要的指导意义。
Hefei Metro Line 1 shield tunnel under the Nanxun River, there is a security risk in construction. FLAC3D was used to simulate the tunnel shield excavation process and the rock mass stability during excavation of shield tunnel was analyzed based on the failure proximity (FAI). By destroying the proximity index, the stability of rock and soil mass around the tunnel can be comprehensively and intuitively evaluated, and the range of damage area and disturbance area can be given quantitatively. Numerical simulation results show that the excavation of the shield tunnel reduces the pore and water pressure around the tunnel significantly lower than the initial value, which leads to the increase of hydraulic gradient around the tunnel and the groundwater flow to the vault and the sides of the tunnel. In the process of shield excavation, the seepage force produced by the seepage field of rock and soil greatly influences the distribution of stress field. Under fluid-solid coupling conditions, the FAI of rock and soil mass around the tunnel is significantly increased. In some areas Has entered the damaged area; in the process of propelling the fossil surface, when the fossil plane is in the range of 2 excavation steps before and after analyzing the section, the distributive proximity of the section changes obviously, indicating the stable state of the soil Impacted by excavation disturbance significantly. Studying the distribution and evolution of damage proximity in the process of shield excavation has important guiding significance to the corresponding construction measures in construction.