Explain in detail about the Large excavations
Large excavations required for construction of rafts may need dewatering, depending on the ground water flow and the choice of a raft instead of pile will be governed by the ground water level. It may also be easier to construct well foundations than to have pile foundations in some situations. Pits for construction of foundations may be damaged If they are carried through weathered soil like shales and concreting should not be delayed too much after the exposure.