Performance of Shallow Foundation Overlaying Cavernous Limestone

Abstract

New Minia City, Egypt is one of the most successful and highly growing new urban communities. Construction projects in the city were faced by a foundation soil that can be described as soft, highly fractured and jointed limestone which when exposed to dissolution by acidic rainfall or pipes leakage creates shrink holes and caves. The present numerical analysis study aims at investigating the effect of limestone cavity with varying dimensions and occurrence depth on the performance of shallow foundations. It was concluded that there is no clear information relating positions, shape, dimensions and level of caves. It is recommended and furtherly intended to conduct a detailed field study in order to supply complete information about existing and predicted caves. Mode of failure of limestone soil underneath a strip footing is different from the traditional modes of shear failure. There exists a critical cave width beyond which caves existence underneath shallow strip footing results in reducing bearing capacity of the foundation. Caves with roof level deeper than or equal to 9 times footing width with a cave to footing width ratio less or equal to 3.5 do not result in reducing the bearing capacity of strip footing compared to no-cave case. For practical design purpose charts for reduction factors of ultimate bearing capacity and bearing capacity factors were presented.