既有地铁线上跨基坑管幕 MJS 地基加固施工实例分析

Analysis on Subgrade Consolidation by Pipe Curtain and MJS for Existing Metro Line Overcrossing Foundation Pit

摘要:

以徐州新建彭祖大道下方的隧道开挖区间为研究对象，针对徐州的地质条件研究了该地下工程近距离上跨既有运营地铁2号线对2号线的影响，并且采取了管幕加MJS工法联合加固地基的施工方案，对既有地铁2号线进行加固保护和控制地表的沉降。通过有限元分析可以看出，管幕法联合MJS工法可以有效控制既有2号线的变形隆起数值，在一级放坡施工阶段，铺设管幕数值为3.92 mm，未铺设管幕数值则为6.45 mm，并且在铺设管幕的情况下开挖基坑的变形也得到了较好的控制，证实了联合两种方案可以有效地保护既有2号线和基坑的施工安全。最后以10 d为一个周期进行监测，数据呈现出正常的变化规律，监测的结果与施工工况、土质状况基本吻合。

Abstract:

Taking the tunnel excavation section under the newly built Pengzu Avenue in Xuzhou as the research object, aiming at the geological conditions of Xuzhou, the impact of the underground project overcrossing the existing Metro Line 2 in a short distance on Metro Line 2 is studied. And the construction scheme of pipe curtain method plus MJS method is used to jointly consolidate the subgrade. The existing Metro Line 2 is consolidated and protected to control the surface settlement. Through the finite element analysis, it can be seen that the pipe curtain method plus the MJS method can effectively control the deformation and uplift value of the existing Metro Line 2. In the first-level grading construction stage, the value of the laid pipe curtain is 3.92 mm, and the value of the un-laid pipe curtain is 6.45 mm, and the deformation of the excavated foundation pit is also well controlled when the pipe curtain is laid, which proves that the combination of the two schemes can effectively protect the existing Metro Line 2 and the construction safety of foundation pit. Finally, taking 10 d as one cycle for monitoring, the data show a normal variation law, and the monitoring results are basically consistent with the construction conditions and soil conditions.