Construction engineering and management

Most failures of structures are probably caused by their foundations.Underpinning is the introduction of new foundations or supports underexisting structures without disturbing the stability of the existing structures.If done because the foundation is inadequate it is called remedialunderpinning. Deepening or enlarging a foundation because of deeper newconstruction adjacent to the building is called precautionary underpinningt I).Underpinning is also intended to preclude or arrest settlements ofstructures which may render structures unserviceable. Unacceptablesettlements derive from irregular weakness, consolidation or compaction ofground below foundations (2).The most commonly used methods of underpinning that have becomewell established through usage are the pit underpinning, underpinning byconventional piles, root piles (pali radice) and reticulated root piles(reticulated pali radice), micropiles, Pynford stooling and grouting.Underpinning by grouting includes either the chemical grouting or thecompaction grouting that can be extended to controlled jacking offoundations. The versatility and apparent simplicity of application ofgrouting techniques which permit accessibility to and aggregation of varying shapes of treated soil zones, makes them attractive in many underpinning circumstances