Explain about the Raft Foundations

The raft foundations are generally used for large loaded area on soils of low bearing capacity. They are of particular use when soils are of varying compressibility with possible voids on which large differential settlements are likely to occur if individual footings are provided. If the columns are closely spaced, it may become difficult to accommodate large number of small pits and the economy, likely to be achieved by the foundation, will be lost in controlling excavation Rafts can be of plain slab, stiffened edge rafts,