Study of a Surface Raft Foundation in Dry Cohesionless Soil Subjected to Dynamic Loading

In this study, behaviour of a raft foundation in dry cohesionless soil when subjected to dynamic loadings is presented. The numerical model is validated by model tests on shaking table and numerically by a plane strain finite difference program, FLAC 2D. In both shaking table tests and numerical analyses, the raft located in dry Kasai River sand in Kharagpur has been subjected to 10 cycles of equivalent sinusoidal loadings with an amplitude of 0.2412 g at a frequency of 2 Hz, which represents an irregular time history of the Loma Prieta Earthquake (1989). The results of the above study in terms of response time histories, bending moment and lateral displacement of the raft have been validated with numerical simulations, and the results are in reasonable agreement with the corresponding experimental findings. A methodology to study the behaviour of a raft foundation subjected to harmonic excitations has been proposed in terms of vertical deformations of the raft foundation in dry sand for a given value of dynamic (or degraded) factor of safety.