LIMIT EQUILIBRIUM ANALYSIS ON STABILITY AGAINST BASAL HEAVE OF EXCAVATION IN ANISOTROPY SOFT CLAY

As the strength of natural clay shows significant anisotropic properties, it is necessary to consider the effects of the anisotropy of soft clay when analyzing stability against basal heave of excavation. Assuming that the soil slip failure mode is a circular arc sliding mode and its center is at the intersection point of the retaining wall and the lowest support, a formula of the anisotropic clay strength based on the results of Hangzhou intact soft clay tests using hollow cylinder apparatus (HCA). Limit equilibrium method is adopted in the derivation of the equation of stability against basal heave of excavation. Furthermore, the influence on stability against basal heave of excavation caused by factors such as the anisotropy ratio of soil, the embedded depth of the retaining wall and the distance between the foundation base and the lowest support is discussed. The method proposed in this paper is verified by a case study on Hangzhou soft clay. It is also shown that the safety against basal heave would be overestimated if the anisotropy of strength is ignored or the Casagrande anisotropic strength formula is adopted.