非均质和各向异性黏土地基承载力的上限解

UPPER BOUND SOLUTION FOR BEARING CAPACITY OF NONHOMOGENEOUS AND ANISOTROPIC CLAY FOUNDATION

非均质和各向异性是黏土地基比较普遍的现象,而目前地基承载力计算中比较成熟的理论主要是针对均质、各向同性土体。在目前已有的多块体上限法计算粗糙条形基础地基承载力的方法中考虑黏土地基的非均质和各向异性,实现考虑非均质和各向异性时黏土地基承载力的上限解法。所采用的多块体破坏模式在计算粗糙条形基础下均质土体的地基承载力时是最优的。为验证该方法的应用情况,将其计算结果与已有的上限方法、特征线方法进行对比发现,该方法是目前上限方法中最优的。利用该方法详细探讨非均质、各向异性对黏土地基承载力计算的影响。上限方法一个十分突出的优点就是可以反映地基破坏面的信息,通过对非均质及各向异性条件下地基破坏面的分析揭示非均质以及各向异性影响地基承载力的内在原因。由计算结果可知,地基土的非均质和各向异性在影响地基承载力的同时也影响着地基破坏面的位置和形状。

Anisotropy and strength nonhomogeneity are common phenomena for clay foundation. However, the existing theories of bearing capacity calculation are mainly applicable to isotropic and homogeneous soils. Upper bound method is used to calculate the bearing capacity of rough strip foundations on clay with anisotropy and nonhomogeneity. The failure mechanism employed in the upper bound method has already been verified by other scholars to be the best one in multi-block upper bound method to calculate the bearing capacity of rough strip foundations on isotropic and homogeneous soils. To examine the proposed method, various calculations have been carried out. The results are compared with those of the characteristic method and other upper bound methods. It can be found that the proposed method gives the best calculation results among the existing upper bound methods in the literaturs. The effects of the anisotropy and strength nonhomogeneity on the values of the bearing capacity are then discussed. Failure envelopes can be obtained in the upper bound limit analysis and the mechanism for the influence of soil anisotropy and nonhomogeneity on the bearing capacity of foundation can be revealed. From the calculation results, it can also be found that the anisotropy and nonhomogeneity of soil affect not only the bearing capacity of foundation but also the location and shape of the failure envelopes.