富水砂层浅埋地铁隧道深孔注浆扰动机理研究

Disturbance Mechanism of Deep-Hole Grouting for Shallow Metro Tunnels in Water-Rich Sand Layers

  • 摘要: 针对青岛地铁隧道穿越富水砂层施工过程中存在的涌砂、涌水等不稳定性问题所采取的深孔注浆加固措施,文章结合地铁 3号线某区间富水砂层隧道工程实例,通过 FLAC3D数值计算与现场实测手段进行了富水砂层地区地铁隧道施工中深孔注浆加固扰动机理研究。研究结果表明:(1)注浆深度和注浆压力对地层扰动变形影响显著,应综合考虑、合理选取,青岛富水砂层地区宜采用 1.4~1.5 MPa的注浆压力;(2)地表持续隆起时,双线隧道上方的地表地层呈现 M状隆起,隧道中线部位注浆压力对地层扰动影响明显,隆起最大位于拱顶部位;(3)地表在注浆初期迅速隆起,掌子面开挖至监测断面前-3D范围内时地表开始快速沉降,-2D范围内沉降放缓,开挖通过监测断面后至 1D范围内地表较快沉降,然后逐渐趋于稳定;(4)注浆施工对建筑物的影响程度要小于单纯的地表抬升,上方建筑物随地层的 M状变形出现正曲率变形,损害建筑物结构时,建筑物墙体一般会形成倒八字裂缝;(5)隧道内拱顶沉降和净空收敛均在下穿监测断面时变形较快,当开挖至距监测断面 2D范围后,变形趋势逐渐减小,至 3D范围后逐渐趋于稳定。

     

    Abstract: Regarding the deep-hole grouting reinforcement measures for sand gushing and water inflow during con? struction of a Qingdao metro tunnel passing through a water-rich sand layer, the disturbance mechanism of deephole grouting reinforcement for construction of metro tunnels under these conditions is studied by FLAC3D numerical calculation and site measurement. Grouting depth and pressure should be determined properly since they have a significant effect on ground disturbance and deformation, and a grouting pressure of 1.4~1.5 MPa should be used for the water-rich sand layer in Qingdao. When the ground surface keeps heaving, the surface above the double-tube tunnel heaves in an "M" shape, the grouting pressure at the tunnel′s central line has an obvious effect on ground disturbance, and the maximum heaving occurs at the tunnel crown. The ground surface heaves rapidly at the early stage of grouting and subsides quickly when the working face is within a scope of -3D in front of the monitoring section, then the ground settlement slows down within a scope of -2D and gets faster within the scope of 1D after it passes through the monitoring section, finally it tends to be stable. The effects of grouting construction on a building is less compared to that of surface uplifting, and a building above the tunnel deforms in a positive curvature with the occurrence of ground deformation in an "M" shape; a reversed splayed crack occurs at the building wall when the building structure is damaged. Additionally, crown settlement and clearance convergence are fast when working face passes through the monitoring section and tend to decrease when it is within 2D scope away from the monitoring section,then stabilizes gradually within a scope of 3D.

     

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