Using buttress walls to reduce excavation-induced movements

Abstract

The buttress wall is an alternative construction method for protection of adjacent buildings during excavation. It is generally recognised, but not verified, that the method has good effects in reducing wall movement and ground settlement, because buttress walls behave as T-shaped concrete beams, which possess comparatively larger stiffness than two-dimensional diaphragm walls. However, the behaviour of buttress walls in excavations is not fully understood, because of a lack of well-monitored case histories and systematic studies. In this study, the effectiveness of buttress walls in reducing wall deflection and ground settlement is evaluated through observed behaviour of a case history, and through finite element studies. The case study indicates that the use of buttress walls in a deep excavation can significantly reduce the deflection of a diaphragm wall. Effective prediction of the behaviour of the buttress wall can be achieved using the three-dimensional finite element method. Parametric studies reveal that deflection of the diaphragm wall is strongly influenced by the condition of the restraint at the bottom of the buttress walls, and by the number of buttress walls. As long as the buttress wall bottom is well restrained, and reasonable numbers of buttress walls are installed, wall deflection can be considerably reduced.