Abstract:
The Quaternary stratigraphy of the western coastal belt provide soft sub-surface
conditions for raft foundations. Within the City of Colombo such raft foundations have been
successfully constructed at or below the ground water table, and typically were placed on
dense sand beds and on soft sandstones.A well-balanced loading of a raft helps to prevent
any tilt during long-term settlements in loose sands and cohesive clays. When the Profiles
below the raft are unconsolidated sands, settlements will be mainly instantaneous, during
construction loading of the raft. During excavations for a raft below the ground water
table, shoring sheet piling and dewatering mechanisms will be necessary.
