搅拌桩和钻孔桩先后施工对邻近地铁隧道的影响分析

Analysis of the Effect on Existing Subway Tunnel Due to Consecutive Pile Driving of Tri-Axial Cement-Mixing Pile and Bored Pile

摘要: 采用三轴水泥土搅拌桩对钻孔桩位置的土体预先进行地基加固是防止灌注桩成孔时发生塌孔的常用方法。众所周知，由于三轴水泥土搅拌桩在施工过程中的高压注浆和对周边土体的巨大扰动，其施工会导致邻近土体的位移。钻孔灌注桩成孔施工也会导致土体位移。因此，当邻近地铁隧道时，上述的土体位移必须控制在允许范围内，以免对地铁隧道产生不利影响。作为案例，针对三轴水泥土搅拌桩和钻孔灌注桩接续施工对邻近土体及已有盾构隧道的影响，本文就三维有限元数值模拟计算结果和现场试验实测结果进行了比较分析。在上述比较基础上，本文介绍了三轴水泥土搅拌桩沉桩施工导致周边土体位移的相关认识；为确保隧道的安全，就桩基的施工提出了指导性建议。

Abstract: Tri-axial cement-mixing pile (TCMP) is usually used for soil improvement at the place of bored pile (BP) driving in order to avoid caving. But it is known to all that TCMP shall lead to rather large movement of surrounding soil because of the high grouting pressure and profound disturbance when TCMP driving; the BP driving shall lead to soil movement as well. As such, all these movements must be controlled under allowable level lest it should exert adverse effect on adjacent subway tunnel, if any. As a case history, this paper presents a comparison analysis between three dimensional finite element (3D-FEM) simulation and in-situ test, which is focused on the effect of consecutive driving of TCMP and BP on adjacent soil and existing shield tunnel. This paper also presents some knowledge drawn from above comparison about the behavior of surrounding soil due to TCMP driving, and gives some constructive suggestions from the view of tunnel safety.