砂性土层大直径浅埋隧道掘进试验及离散元模拟

Experimental and Discrete Element Analysis on the Shield Tunneling of a Large Diameter Shallow Tunnel in Sand

隧道断面的增大致使盾构施工的风险增大,尤其是高水压砂性土层,大直径浅埋隧道盾构对周边岩土体的扰动以及土层变形的影响是目前需要研究的新课题。本文以武汉地铁7号线大直径越江隧道段为工程背景,建立了大直径浅埋隧道盾构掘进室内缩尺试验模型,采用螺旋出土盾构设备(包含螺旋杆、螺旋出土器及套筒),以恒定的推进速率进行了隧道掘进,并且对地表沉降进行了监控。同时,本文建立了同尺寸的浅埋隧道盾构掘进离散元模型,对盾构掘进过程中地表沉降、开挖面前方土层中颗粒配位数以及黏结破裂区域进行了分析研究,并与室内试验结果进行了对比分析。结果表明:地表竖向位移与室内试验结果吻合度较高,盾构掘进地表各点处的沉降均随着掘进距离的增大而增大;盾构掘进影响区域主要分布在隧道顶部至地表、一定范围内的周边土体以及开挖面前方一定范围内的盾构区域;颗粒接触点处的黏结破裂区域主要分布在盾构区域和隧道顶部区域。

As the increase of the tunnel cross section,the risk of shield construction increases,especially in the sand strata under high water pressure. It is currently a new topic that the influence of shield construction of the large diameter shallow tunnels on the surroundings and strata deformation should be studied. In this paper,based on the engineering background of Wuhan Metro Line 7 large diameter cross-river tunnel section,the indoor scale test model of shield tunneling for a large diameter shallow tunnel of cross-river metro was established. A spiral excavated shield equipment(including a screw rod,spiral excavator and a sleeve) was used for tunnel tunneling with a constant excavation speed,and the surface subsidence is monitored. Meanwhile,the discrete element model of shield tunneling for shallow tunnel across the river with the same size was proposed. The surface settlement,the coordination number of particles in the soil layer above the excavation face and the area of bond rupture during the shield tunneling were analyzed and compared with the laboratory test results. The results show that the vertical displacement of the ground surface is in good agreement with the laboratory test results,and the settlement at all points of the ground surface during shield tunneling increases with the increase of the tunneling distance. The influence area of shield tunneling is mainly distributed from the top of the tunnel to the surface,the surrounding soil within a certain range and the shield area in front of the excavation face,and the bond fracture area at the particle contact point is mainly distributed in the shield area and the tunnel top area.