Bearing capacity of ring foundations under vertical load

Ring foundations have been used world wide. However, their bearing behaviour has not been well understood. Currently, in the design of ring foundations, simplifications have to be made. This paper presents a centrifuge test program which investigated constant area ring footings on a dense sand. The effects of footing size, ring radii ratio and load eccentricity on bearing capacity have been investigated. The bearing capacity of circular footings increases linearly with prototype footing size in a double-log scale diagram. The bearing capacity of a ring footing can be related to the bearing capacity of a circular footing, using a bearing capacity ratio which is related only to the ring radii ratio. For eccentrically loaded ring footings, the reduction factor of bearing capacity decreases with load eccentricity, independent of ring radii ratio. The paper finally presents a procedure for estimating the bearing capacity of ring footings under axial and eccentric loads.