Diaphragm Wall Trench Stability in Recently Reclaimed Land: A Case Study Review

This paper focuses on the design and review of diaphragm wall trench stability using bentonite as the stabilizing fluid on a reclaimed site in Hong Kong SAR, Hong Kong Boundary Crossing Facilities. The site geological conditions were challenging for construction of long diaphragm wall panels due to the presence of considerable thickness of soft Marine Deposit and Alluvium Clays. In addition, a special type of diaphragm wall panel (Y-panel) was required for a multi circular cell cofferdam. The applicability of three-dimensional finite element methods software, Plaxis 3D, to model the trench stability is discussed through a comparison with other analytical trench design methods. Two site trials were undertaken, one for a triple-bite panel, 6.8m long and 1.5m thick, and another for the 5-bite panel (Y-panel), 3.6m x 6.5m. The latter required ground improvement, Cutter Soil Mixing, works to ensure both a satisfactory factor of safety against failure and acceptable lateral movements of the trench.