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Deep excavations with vertical sides require lateral supports to prevent cave in of the earth and to protect the adjacent areas against ground subsidence and lateral movement of the subsoil. When excavations are shallow and ample space is available, the sides of the excavation can be sloped at a safe angle to ensure stability. However, in deep excavation, especially in built up areas there may not be adequate space for providing safe slopes. Moreover it becomes uneconomical to provide safe slope because of large quantities of earth involved. |
