A rigorous and practical solution aimed at accounting for the effect of groundwater in the assessment of bearing capacity of shallow strip footings in plane strain conditions has been developed using the method of characteristics.

A steady water table in the foundation soil is considered and a bearing capacity factor N_γw to be used in the classical trinomial bearing capacity equation is introduced. The proposed bearing capacity factor depends on the angle of shear strength, on the footing roughness and on the water table depth and is also influenced by the soil unit weight.

Normalizing N_γw with respect to the bearing capacity factor N_γ computed for the case of dry foundation soil, a corrective coefficient has been introduced for which best-fit empirical relationships have been proposed for both smooth and rough foundations. The size of the plastic mechanism under the footing has also been investigated and equations allowing to evaluate its relevant dimensions have been provided.

The proposed solutions have been checked against results obtained via finite element analyses, finding a perfect agreement in terms of both corrective coefficients and shape and size of the soil plastic volume. Finally, the actual bearing capacity problem was solved showing that the trinomial formula, even in presence of a steady water table, still yields conservative values of the bearing capacity.

已经使用特征方法开发了一种严格而实用的解决方案，旨在考虑地下水对平面应变条件下浅条形基础承载力评估的影响。

考虑了地基土壤中的稳定地下水位，并引入了在经典三项式承载力方程中使用的承载力因子N _γw。建议的承载力系数取决于抗剪强度角度、基础粗糙度和地下水位深度，还受土壤单位重量的影响。

相对于为干地基土壤计算的承载力因子N _γ对N _γw进行归一化，引入了修正系数，针对光滑和粗糙地基都提出了最佳拟合经验关系。还研究了基础下塑性机构的尺寸，并提供了可以评估其相关尺寸的方程。

所提出的解决方案已经通过有限元分析获得的结果进行了检查，在修正系数以及土壤塑性体积的形状和大小方面找到了完美的一致性。最后，解决了实际承载力问题，表明即使存在稳定的地下水位，三项式公式仍然产生保守的承载力值。