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
1 The foundation is rigid relative to the supporting soil and the compressible soil layer is relatively shallow
2 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.