Centrifugal modeling of bearing capacity of shallow foundations on sands

The study of shallow footings under plane-strain conditions became important when many researchers reported the lack of agreement between theoretical and experimental findings. A better understanding of the behavior of granular material under different stress levels and strain conditions encouraged further research in this field. In order to understand the behavior of footings and study the differences between theoretical and experimental observations, an experimental program was devised taking into account some factors that affect the theoretical assumptions. In this paper, the centrifuge has been utilized to study the effects of load eccentricity, load inclination, and initial burial on the bearing capacity of shallow strip footings on a dense sand. Fine silica sand, F-75 in a dense state with a relative density of 88%, was used. A planestrain condition was obtained by testing three adjacent footings of the same width along one line. Footings were loaded with a stiff mechanism to give uniform displacement and, therefore, the one in the middle was under a plane strain condition. Test results indicate that plane strain conditions were modeled using this design. Experimental values of the bearing capacity factors N_q and N_γ are presented and compared to theoretical values given by different researchers. Results show that the linear pressure distribution at the base of the footing is a good approximation of observed behavior. It was noticed that single-sided failure always occurs regardless of load eccentricity and inclination. In addition, results show that failure occurs in a progressive manner.