ABSTRACT
Excavations are often required in congested urban areas for the construction of basements, subway stations, or sewer systems, to create underground space bounded by a system of retaining walls. This chapter introduces the types and major components of typical braced excavation systems. It describes the characteristics of lateral earth pressure involved in the design and construction of a braced excavation and examines the basic design and construction procedure of a braced excavation. A number of empirical pressure distributions have been proposed for braced excavations. The braced excavation wall and many other elements of the lateral support system are continuous beams from the structural analysis point of view. Basal heave occurs when the soils at the base of the excavation are relatively weak compared to the overburden stresses induced by the retained side of the excavation. Excavation inevitably induces ground displacements. The displacement is caused primarily by the unbalance of forces as a result of excavation and poor workmanship.
