In case of soils having low bearing capacity, heavy structural loads are often supported by offering raft foundations. Additionally if the structure is susceptible to subsidence on being situated in mining area or because of unsure behavior of its sub-soil water condition, raft foundations needs to be preferred. Raft Foundations offers a cost-effective answer to troublesome site situations, where pile foundation is not advantageous and isolated column footing becomes impracticable.
Raft or mat foundations constitutes of thick reinforced concrete slab overlaying the complete construction space . The slab is strengthened with bars running at proper angles to one another each close to backside and top face of the slab. Generally it’s mandatory to hold the extreme column load by an arrangement of inverted primary beams and secondary beam. These beams are cast monolithically with the raft slab.
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Technique of Construction:
The raft slab typically projects for a thickness of 30 cm to 45cm on all the edges of the outer partitions of the construction, as such the area of excavation is barely greater than the area of the construction itself.
The excavation is made to the required depth and the complete excavated space is properly consolidated. This surface, when dry, offers the base upon which the raft or mat slab is laid. All of the precautions which are essential should be taken care off throughout the reinforced concrete construction. Furthermore additional construction should take place only after curing of raft is completed.