Bearing capacity of ring foundations over a rock mass using numerical analysis

Ring foundations are used for circular industrial structures and often placed over a rock mass. However, the bearing capacity factors for ring foundation are not available in the literature. Hence upper and lower bound finite element limit analysis (FELA) to evaluate the bearing capacity factors for the ring foundation resting over a rock mass. The Hoek-Brown constitutive model was adopted to study variations in the geometry of ring foundation, Geological Strength Index (GSI), intact rock constant (m(i)), and unit weight of rock mass (gamma) on the bearing capacity of the ring foundation. The bearing capacity factors N-sigma are presented for the different values of GSI, m(i), and gamma. The failure patterns under varying ring geometry and the rock mass unit weight are presented and discussed. The results show an increase in the bearing capacity with an increase in Hoek-Brown parameters for a rock mass. The bearing capacity is observed to be decreasing with an increase in the ratio (R-i/R-o) of the inner radius (R-i) to the outer radius (R-o) of the ring foundation. Design tables are provided as a ready reference for practitioners to evaluate the bearing capacity of the ring foundations resting over a rock mass.