西安地铁盾构下穿古城墙沉降分析及加固效果

为研究双线盾构下穿过程诱发地表沉降的规律及上部古城墙的变形特征,依托地铁4号线区间隧道下穿和平门古城墙工程,通过数值模拟和现场测试手段对沉降及加固效果进行分析。结果表明:在袖阀管注浆加固及门洞钢拱架支护等作用下,城墙地基区域地表沉降值减小4mm,城墙结构沉降减小约2.2mm,避免了地基局部隆起过大和倾斜率超限;城墙地基区域加固工况下地表横向沉降曲线为宽而浅的单峰沉降槽,未加固工况下表现为窄而深的双峰沉降槽;左、右线隧道施工存在相互影响,且变形稳定后右线隧道地表沉降峰值大于左线。现场实测与数值计算的结果吻合良好,分析方法和研究结果可为日后黄土地区类似的盾构穿越工程提供有益的参考。

Settlement analysis and reinforcement effect of ancient city wall due to underneath tunneling of Xi'an metro

To investigate the ground surface subsidence induced by double line shield tunneling and the deformation characteristics of the upper wall ancient buildings, numerical simulation and field monitoring were employed based on the interval of Metro Line 4 tunnel beneath the Hepingmen ancient city wall project. The results indicate that due to the sleeve valve pipe grouting reinforcement and the steel arch supporting role, the settlement of the ground surface of the city wall decreases by 4 mm compared with that of the unreinforced condition. Wall structure is reduced by about 2.2 mm, which avoids too large wall foundation local uplift and the tilt rate. After taking the reinforcement measures, the ground settlement displays wide and shallow single-peak curve. Otherwise it is a narrow and deep double-peak curve. There is mutual influence between the left and right line tunnel construction, and the peak value of the ground surface settlement of the right line tunnel is larger than that of the left line after deformation and stability. The field monitoring data agree with the numerical results, and analysis method and results can provide useful reference for the construction of shield tunnel in loess area.