减沉桩基变形控制机理的案例分析

桩数沉降关系是按变形控制设计桩基础(减少沉降桩基础设计)的重要依据,受荷载大小、桩位布置和场地类别等多个因素共同影响。结合某工程现场实测数据,运用近似数值方法和平面应变有限元方法对2幢采用不同桩数的多层住宅桩筏基础进行计算分析,研究不同桩间距对地基压缩变形、基础内力和土体应力应变分布的影响,对桩数减少一半时基础沉降几乎没有变化这一问题给出合理解释。结果表明,作用于基础顶面的荷载水平越低,桩侧与桩端土层可压缩性差异越小,基础沉降量对桩数变化越不敏感。对于深厚软土地基中的低承台群桩基础,按变形控制进行桩基设计,能最大程度地节约基础用桩量,可获得十分显著的经济效益。

Case analysis of settlement control mechanism for settlement reducing pile

The relationship between pile numbers and settlement is the most important reference for pile foundation design, based on the deformation control (or design of reducing settlement pile foundation), which is affected by several factors, such as the loading magnitude,the pile arrangement and the soil type. Combined with the measured data from case history, the approximate numerical method and plane strain finite element method are put forward to analyze two piled raft foundations with different pile numbers for multi-storey residential buildings. The effects of different pile spacings on compressive deformation, internal force of foundation and stress-strain distribution of soils are studied, and a reasonable explanation is given for the problem that foundation settlement is almost unchanged after the pile number is reduced by half. The results show that, the lower the loading magnitude or the smaller the compressibility difference between pile side and pile tip soil layer, the foundation settlement is less sensitive to the change of pile numbers. For low-cap pile group foundation in deep soft soil, pile foundation design based on deformation control can reduce pile numbers considerably, with significant economic benefits.