A case of a braced excavation in Bangkok clay

This paper describes a case of an engineering project where a shoring system called Island Method for a deep and large scale excavation was carried out in Bangkok soft clay ground. The displacement of the retaining wall at the first excavation stage was larger than the computed value by using a design method based on the assumption of a beam on elastic foundation. This induced the authors to analyze the problem by employing a soil-water coupling finite element program based on Critical State Soil Mechanics concepts in order to estimate the deformation and slope stability at the final excavation stage. Since the displacement of the retaining wall must be kept small to secure the capacity for the underground car park, we made some modification of the shoring system and the excavation method. The displacement of the supporting wall were kept smaller than expected.