Bearing capacity evaluation for shallow foundations is conventionally completed according to the equations derived for dry or saturated soils neglecting the effect of matric suction. However, many shallow foundations are mostly constructed upon the soil layer above the groundwater table, where a large portion of soils under shallow foundations is in fact in unsaturated conditions. The failure of shallow foundations is usually related to shear failure which is one of the main engineering properties required in foundation design. The shear strength of unsaturated soils depends on the matric suction which usually changes with depth. Since the discretization technique of limit analysis is particularly suitable for considering the variation of soil parameters, the bearing capacity for shallow foundations considering the shear strength of unsaturated soils is therefore evaluated by this technique. The results obtained by the present technique are compared with the ones obtained from different authors, and good agreement is observed. Then a parametric analysis is performed using the present technique, and the bearing capacity for shallow foundations are given considering different soil types, foundation widths, effective internal friction angle ${\phi }^{\prime }$, air-entry pressure 1/α with various n values, different water table depth with surface flux boundary conditions, different unit weight of soil γ, and surcharge load q₀. Some useful conclusions are given and a useful method is therefore provided for the bearing capacity evaluation of shallow foundations on unsaturated soils.

浅地基承载力评估通常根据干燥或饱和土壤推导的方程完成，忽略基质吸力的影响。然而，许多浅地基大多建在地下水位以上的土层上，浅地基下的大部分土壤实际上处于非饱和状态。浅基础的破坏通常与剪切破坏有关，剪切破坏是地基设计所需的主要工程特性之一。非饱和土的剪切强度取决于通常随深度变化的基质吸力。由于极限分析的离散化技术特别适合考虑土体参数的变化，因此，考虑到非饱和土的剪切强度，浅地基的承载能力是通过这种技术来评估的。将本技术获得的结果与来自不同作者的结果进行比较，观察到良好的一致性。然后利用现有技术进行参数分析，考虑不同土壤类型、地基宽度、有效内摩擦角，给出浅地基承载力${\phi }^{\prime }$, 进气压力 1/ α具有不同的n值，不同的地下水位深度与表面通量边界条件，不同的土壤单位重量γ和附加荷载q ₀。给出了一些有用的结论，为非饱和土浅地基承载力评价提供了一种有用的方法。