The foundations for most structures are invariably established below the surface of the ground. Thus they can not be constructed until the soil or rock above the base level of the foundations has been excavated. Open excavations are supported in some soils by lateral support called bracings. It is generally the engineer’s duty to decide the construction procedure proposed by the builder and to check the design of bracing. In previous soils, excavation below the water table usually requires drainage of the site either before or during construction. The general aspects of excavating and providing support for the sides of the pits or cuts are discussed in the following sections.
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