2.3 Analysis of annular raft foundation
The foundation is analysed using conventional method as per IS: 11089 – 1984. This is based on the assumption of linear distribution of contact pressure. The basic assumptions of this method are
The foundation is rigid relative to the supporting soil and the compressible soil layer is relatively shallow
The contact pressure distribution is assumed to vary linearly throughout the foundation
The ring annular raft is analysed from approximately non-uniform pressure distribution to uniform pressure distribution.
The modified pressure intensity p is given by p1+0.5p2, where p1 is uniform pressure due to dead loads (W) and p2 is pressure due to bending (M) effects.