地铁重叠下穿既有隧道软土地基加固参数研究

Study on Ground Improvement of Existing Tunnel with Overlapping Underpass of Subway

软土地区地铁重叠下穿施工及运营具有较高的风险,常需要对既有隧道地基进行加固处理。利用FLAC3D软件建立三维数值模型,对比分析既有隧道软土地基采取不同的加固方案时,上部隧道结构的轴力、弯矩、剪力及位移变化情况。研究表明:(1)采用水泥土搅拌桩满堂加固3 m的地基加固方式对于减少上覆结构内力及位移的效果最好,裙边及抽条加固(间距3 m)3 m的加固效果次之,而满堂加固2 m的效果最差;(2)采用加固方案后,上部隧道结构的内力显著减小,各方向位移也均有减少,以轴力和竖向位移的改善效果最佳。研究成果可为类似地铁隧道下穿工程施工提供参考。

The construction and operation of overlapping subways in soft soil areas have high risks,and it is often necessary to strengthen the existing tunnel foundations.Use FLAC3D software to establish a three-dimensional numerical model,and compare and analyze the changes of axial force,bending moment,shear force and displacement of the upper tunnel structure when different reinforcement schemes are adopted for the soft soil foundation of the existing tunnel.The research shows:(1)The 3 m foundation reinforcement method with cement-soil mixing piles is the best for reducing the internal force and displacement of the overlying structure,and the reinforcement effect of the skirt and strip reinforcement(spacing 3 m)3 m is the second,And the full house reinforcement of 2 m has the worst effect;(2)After adopting the reinforcement scheme,the internal force of the upper tunnel structure is significantly reduced,and the displacement in all directions is also reduced.The axial force and vertical displacement have the best improvement effect.The research results can provide a reference for the construction of similar subway tunnels.