随着城市化进程中地下空间开发及抗浮问题的凸显,抗拔桩在东南沿海等高水位黏性土地区的应用日益广泛,然而常规钻孔施工工艺面临诸多挑战,如泥皮效应导致桩侧阻力难以达标、扩底成孔困难等。为此,提出考虑扰动效应的束浆挤扩桩抗拔承载...随着城市化进程中地下空间开发及抗浮问题的凸显,抗拔桩在东南沿海等高水位黏性土地区的应用日益广泛,然而常规钻孔施工工艺面临诸多挑战,如泥皮效应导致桩侧阻力难以达标、扩底成孔困难等。为此,提出考虑扰动效应的束浆挤扩桩抗拔承载力计算方法。以上海第(5)1层灰色黏土为对象,建立黏土和砂的弹塑性扰动状态(clay and sand elastic-plastic-disturbed state concept,简称CASM-DSC)模型,精确模拟桩周地基土力学特性。通过用户自定义材料本构(user-defined material mechanical behavior,简称UMAT)子程序,开展数值模拟,分析桩周地基土及挤扩尺寸的扰动效应。修正前期研究的束浆挤扩钢管桩抗拔简化计算方法。结果表明,钻孔开挖显著削弱黏性土的侧阻力,影响桩-土界面的力学性能,扰动系数和范围对地基土应力状态呈二次曲线和线性折减关系。在不同的挤扩长度下,模型桩的极限抗拔承载力随长度增加呈“V”字型特点,且挤扩工艺可改变桩侧受力面积与轴力分布。通过上海徐汇滨江地块的现场试验,验证了简化计算方法的有效性与适用性,其计算误差控制在15%以内,为桩基础工程设计提供了可靠的理论支持与实用计算方法。展开更多
Based on the characteristic that the potential sliding surfaces of rock slope are commonly in the shape of either line or fold line,analysis thought of conventional pile foundation in the flat ground under complex loa...Based on the characteristic that the potential sliding surfaces of rock slope are commonly in the shape of either line or fold line,analysis thought of conventional pile foundation in the flat ground under complex load condition was applied and the upper-bound theorem of limit analysis was used to compute thrust of rock layers with all possible distribution shapes. The interaction of slope and pile was considered design load in terms of slope thrust,and the finite difference method was derived to calculate inner-force and displacement of bridge pile foundation in rock slope under complex load condition. The result of example shows that the distribution model of slope thrust has certain impact on displacement and inner-force of bridge pile foundation. The maximum displacement growth rate reaches 54% and the maximum moment and shear growth rates reach only 15% and 20%,respectively,but the trends of inner-force and displacement of bridge pile foundation are basically the same as those of the conventional pile foundation in the flat ground. When the piles bear the same level lateral thrust,the distribution shapes of slope thrust have different influence on inner-force of pile foundation,especially the rectangle distribution,and the triangle thrust has the smallest displacement and inner-force of pile foundation.展开更多
文摘随着城市化进程中地下空间开发及抗浮问题的凸显,抗拔桩在东南沿海等高水位黏性土地区的应用日益广泛,然而常规钻孔施工工艺面临诸多挑战,如泥皮效应导致桩侧阻力难以达标、扩底成孔困难等。为此,提出考虑扰动效应的束浆挤扩桩抗拔承载力计算方法。以上海第(5)1层灰色黏土为对象,建立黏土和砂的弹塑性扰动状态(clay and sand elastic-plastic-disturbed state concept,简称CASM-DSC)模型,精确模拟桩周地基土力学特性。通过用户自定义材料本构(user-defined material mechanical behavior,简称UMAT)子程序,开展数值模拟,分析桩周地基土及挤扩尺寸的扰动效应。修正前期研究的束浆挤扩钢管桩抗拔简化计算方法。结果表明,钻孔开挖显著削弱黏性土的侧阻力,影响桩-土界面的力学性能,扰动系数和范围对地基土应力状态呈二次曲线和线性折减关系。在不同的挤扩长度下,模型桩的极限抗拔承载力随长度增加呈“V”字型特点,且挤扩工艺可改变桩侧受力面积与轴力分布。通过上海徐汇滨江地块的现场试验,验证了简化计算方法的有效性与适用性,其计算误差控制在15%以内,为桩基础工程设计提供了可靠的理论支持与实用计算方法。
基金Project(50578060) supported by the National Natural Science Foundation of China
文摘Based on the characteristic that the potential sliding surfaces of rock slope are commonly in the shape of either line or fold line,analysis thought of conventional pile foundation in the flat ground under complex load condition was applied and the upper-bound theorem of limit analysis was used to compute thrust of rock layers with all possible distribution shapes. The interaction of slope and pile was considered design load in terms of slope thrust,and the finite difference method was derived to calculate inner-force and displacement of bridge pile foundation in rock slope under complex load condition. The result of example shows that the distribution model of slope thrust has certain impact on displacement and inner-force of bridge pile foundation. The maximum displacement growth rate reaches 54% and the maximum moment and shear growth rates reach only 15% and 20%,respectively,but the trends of inner-force and displacement of bridge pile foundation are basically the same as those of the conventional pile foundation in the flat ground. When the piles bear the same level lateral thrust,the distribution shapes of slope thrust have different influence on inner-force of pile foundation,especially the rectangle distribution,and the triangle thrust has the smallest displacement and inner-force of pile foundation.
