Base Stability of Circular Excavations in Soft Clay

The base stability of circular excavations in soft clay is expected to be larger than rectangular excavations due to the shape effect. Up to the present, however, the base stability of circular excavations is usually evaluated with two-dimensional methods although some modification has been made to consider the shape effect. In this analysis, the finite-element method with reduced shear strength is used to evaluate the base stability of circular excavations. The base stability of circular excavations significantly increases with the presence of the hard stratum close to the base of the excavation, and with the depth of the wall inserted into the soft clay layer below the base of the excavation. A design chart for the base stability of circular excavations is provided.