Excavation analysis of underground expressway construction

Abstract

            Construction of an underground expressway in Singapore was carried out by cut-and-cover method in soft clay and residual soils. The supporting system consists of heavy steel sheet pile braced with a system of ground anchors and internal strut to form a cofferdam crossing a major river. The movement of the combined bracing system during the excavation period was monitored by five inclinometers at different location around the cofferdam. The time-dependent deformation of each instrumented sections behaved differently due mainly to different excavation sequence and support installation and preload, in addition to differences in structural geometry and slight variation in soil condition. The results from the proposed analyses compare favorably with the field records. The influence of uneven excavation on the deformation of the excavation support system is also studied