Base stability analysis of braced deep excavation in undrained anisotropic clay with upper bound theory

It is imperative to evaluate factor of safety against basal heave failure in the design of braced deep excavation in soft clay. Based on previously published field monitoring data and finite element analyses of ground settlements of deep excavation in soft clay, an assumed plastic deformation mechanism proposed here gives upper bound solutions for base stability of braced deep excavations. The proposed kinematic mechanism is optimized by the mobile depth (profile wavelength). The method takes into account the influence of strength anisotropy under plane strain conditions, the embedment of the retaining wall, and the locations of the struts. The current method is validated by comparison with published numerical study of braced excavations in Boston blue clay and two other cases of excavation failure in Taipei. The results show that the upper bound solutions obtained from this presented method is more accurate as compared with the conventional methods for basal heave failure analyses.