Settlement Trough Associated With Diaphragm Wall Construction in Greater Cairo

Abstract

Deep excavation with the use of concrete diaphragm walls, as side supports, has been increasingly applied in Greater Cairo for several purposes such as basements, underground garages, cut-and-cover tunnels, and subway stations. The wide use of concrete diaphragm walls is attributed to the development of powerful trenching equipment, the utilization of bentonite slurry as a support to the sides of trenches, the incorporation of walls into permanent structures, and the relative simplicity of their construction compared with other traditional methods for vertical cut-off purposes. The most challenging task for geotechnical engineers is to estimate the settlement associated with the trenching process, especially if the diaphragm wall is constructed near existing structures. Computational complexities to obtain an acceptable estimate for the settlement field associated with trenching, comprise the sequence of panel construction of the wall, the wall alignment, the panel dimensions, the local soil formation of the site, the presence of groundwater, the rate of construction, the presence of neighboring buildings, and the workmanship quality. The objective of this paper is to present observed settlements of buildings founded on different types of foundations while constructing nearby continuous diaphragm wall panels. The field data were utilized to empirically estimate a generic settlement trough to be used for future projects. Also, the data were back analyzed using a widely practiced two-dimensional plane-strain finite element model to verify its reliability.