黄土地区地铁盾构施工安全防控技术研究具有较高的理论意义与应用价值，位于黄土地区的西安地铁盾构工程具有地表条件复杂、穿越文物和建（构）筑物多等特点。以西安地铁二号线安远门—北大街区间盾构隧道施工下穿护城河拱桥工程为背景，采用FLAC3D数值模拟方法预测了盾构下穿护城河拱桥施工引起的拱桥变形，计算结果表明，在施工前必须对拱桥及下方地层进行加固，才能确保施工过程拱桥安全稳定。提出在拱桥区域内堆载沙袋、在拱桥基础背后进行袖阀管注浆的加固措施，现场实测表明，拱桥变形在允许范围之内，提出的施工安全防控技术合理有效。

It is of great importance to study the safety control technology for shield boring in loess. The shieldbored tunnels of Xi’an Metro, which are located in loess strata, have to cross underneath complex ground surface conditions, cultural relics, buildings and structures. The shieldbored tunnel from Anyuanmen station to Beidajie station on Line 2 of Xi’an Metro crosses underneath a moat arch bridge. In the paper, the deformation of the moat arch bridge caused by shield boring is analyzed by means of FLAC3D program. The calculation result shows that the ground below the moat arch bridge has to be consolidated before shield boring, so as to ensure the safety and stability of the bridge. It is proposed that sand bags should be piled in the moat arch bridge zone and Soletanche grouting should be conducted behind the foundation of the bridge. The site measurement shows that the deformation of the moat arch bridge is within the allowance scope and the countermeasures taken are rational and effective.