考虑土体小应变刚度特征时隔断结构保护效果的三维数值分析

3D numerical analysis of mitigation effect of separation pile and diaphragm wall considering small strain stiffness of soils

我国城市地下交通隧道建设日益频繁,而隧道施工会对周边地面建筑物的安全造成威胁,必要时需要采取措施对重要建筑物进行保护。近年来隔断桩/墙被越来越多地用于工程中,对其保护效果的分析评估就显得很有必要,而土体小应变刚度特征对于合理分析这类变形问题具有重要意义。为此,首先用FISH语言编程在FLAC3D中实现一种能反映土体小应变刚度特征的本构模型,并分别通过模拟小应变三轴试验和土工离心机试验在土单元和边值问题两个层面上验证了该模型的正确性和有效性。在此基础上,对隔断桩/墙减少隧道开挖引起的地面沉降的效果进行了三维数值模拟和参数分析。研究表明,隔断结构的深度对隔断效果影响最为显著,隔断结构应至少深入到隧道底部以下1倍隧道半径的深度;桩径(墙厚)、桩中心间距等因素在合理范围内变化对隔断效果影响不大;隔断桩与地下连续墙的隔断效果差别较小。

Tunneling in urban areas might cause damage to the adjacent buildings,and mitigation methods are required to protect those buildings.The effect of separation pile and diaphragm wall is studied using 3D numerical simulation.A constitutive model for small strain of soils is implemented in FLAC3D and then verified by simulating a small strain triaxial test and a centrifuge test.The main factors are analyzed,and it is revealed that the length of the pile and the wall has the most significant influence on the mitigation effect.To achieve satisfactory mitigation effect,the toe of the pile/wall should be located at least half of the tunnel diameter deeper than the bottom of the tunnel.The pile diameter,pile distance and wall thickness are found to have much less influence on the mitigation effect.Furthermore,the pile and diaphragm wall are found to have similar mitigation effect.