明挖基坑近距离上跨地铁隧道变形控制研究

Study on Deformation Control of Excavated Foundation Pits Crossing Metro Tunnels at Close Range

摘要:

为研究基坑开挖对下卧地铁隧道变形的影响，提出有效的变形控制措施，以南昌新余街管廊上跨地铁隧道为依托，采用有限元数值模拟，研究明挖基坑对地铁隧道变形的影响规律，进而提出变形控制措施，并结合现场监测数据验证其效果。结果表明：明挖基坑引起的地铁隧道变形以竖向隆起为主，水平位移远小于竖向隆起；影响强烈区域出现在基坑正下方，宽度与基坑宽度接近，对2~3倍基坑深度范围以外区域的影响较小；采用全方位高压喷射注浆（MJS工法）先加固后分区开挖回填、减小单次开挖面积的施工方式能有效减小地铁隧道的竖向隆起变形，符合变形控制标准。

Abstract:

To study the impact of foundation pit excavation on the deformation of underlying metro tunnels, the effective deformation control measures are proposed. Relying on the utility tunnel crossing the metro tunnel in Xinyu Street of Nanchang, the finite element numerical simulation is used to study the influence rule of excavated foundation pit on the deformation of metro tunnels, and then the deformation control measures are proposed. And combined with the on-site monitoring data, the effects are validated. The results indicate that the deformation of metro tunnels caused by excavated foundation pits is mainly vertical uplift, and the horizontal displacement is much smaller than the vertical uplift. The area of strong influence is located directly below the foundation pit, and its width is close to that of the foundation pits. The impact on areas outside the range of 2 to 3 times the depth of the foundation pit is relatively small. The construction method of using all-round high-pressure jet grouting (MJS method), which involves reinforcing first and then excavating and backfilling in sections to reduce the area of a single excavation, can effectively reduce the vertical uplift deformation of metro tunnels, which meet the deformation control standards.