非均质地基承载力及破坏模式的FLAC数值分析

FLAC-based numerical analyses of bearing capacity and failure mechanism of strip and circular footings on nonhomogeneous foundations

利用基于Lagrangian显式差分的FLAC算法,通过数值计算,对黏结力随深度线性增长的非均质地基上条形基础和圆形基础的极限承载力及地基破坏模式进行了对比计算与系统分析。研究表明:(1)随着地基黏结力沿深度非均匀变化系数的增大,地基的破坏范围逐渐集中在地基表层和基础两侧;(2)即使地基的非均质程度较小,当将非均质地基近似地按均质地基考虑时,由此所估算的承载力可能过于保守;(3)地基承载力系数随黏结力沿深度非均匀变化系数的增大而非线性地增大。与数值解相比,Skempton与Peck等近似公式均可能高估了非均质地基承载力。

Using the FLAC algorithm based on Lagrangian explicit finite difference method, numerical analyses are made on ultimate bearing capacity and failure behavior of strip footings and circular footings founded on nonhomogeneous clays foundations in which soil cohesion increases linearly with depth. Numerical results show that： （1） foundation failure area much more centralizes in surface layer and around footing sides as nonhomogeneous factor kB/c0 increases; （2） bearing capacity are estimated very conservatively if foundation nonhomogeneity is ignored even if kB/c0 is low; （3） bearing capacity factor of footing nonlinearly increases with kB/c0 and interface characteristic of footing and soil has less influence on the bearing capacity shape factor of circular footings except for the homogeneous foundation. Compared with numerical results, it is found that the approximate equations of Skempton and Peck et al. obviously overestimate bearing capacity factor Nc0 for nonhomogeneous soils.