盾构隧道下穿改建桥梁对桩基的影响分析

Analysis on Influence of Shield Tunnel under Rebuilt Bridge on Pile Foundation

以杭州地铁6号线为工程依托,采用FLAC 3D有限差分软件对地铁隧道下穿改建后公路桥梁工况进行了数值模拟。分析了桩基竖向及水平方向变形,并提出了提高施工稳定性的方案。其主要结论如下:(1)桩基竖向会产生上浮及沉降2种变形,最大值分别为9.72 mm,–2.24 mm,均小于施工限值12 mm;(2)桩基水平位移最大值出现在开挖隧道所在平面及淤泥质粉土与粉质粘土交界一定范围内;(3)有桩台的原址基桩顶几乎不产生水平位移;(4)可采用降低施工速度,增加注浆压力及采用同步注浆方法提高施工稳定性。

Based on Hangzhou Metro Line 6,FLAC 3D finite difference software is used to simulate working condition of subway tunnel underneath the rebuilt highway bridge.The vertical and horizontal deformation of pile foundation was analyzed,and the scheme to improve the construction stability was put forward.The main conclusions are as follows:(1)the maximum uplift is 9.72 mm,and the maximum settlement is–2.24 mm,which are less than the construction limit of 12 mm;(2)the maximum value of horizontal displacement of pile foundation occurs in the plane where the tunnel is excavated and the boundary between muddy silt and silty clay;(3)there is almost no horizontal displacement on the top of the original pile foundation with pile abutment;(4)reducing construction speed,increasing grouting pressure and adopting synchronous grouting method can improve construction stability.