Settlement Analysis of Shallow Foundation on Frictional Soil Under Combined Effect of Static and Cyclic Load

Abstract

The settlement of a surface strip footing on dense sand due to long-term repetitive load (1 million cycles) is analyzed with the help of finite element method (FEM). The analysis is performed by applying both static and cyclic load on the center of footing, in the vertical direction and observing the corresponding settlement. The intensity of the static load is determined by dividing the ultimate static load by the factor of safety (FS). The static load is calculated for different values of FS i.e., 2, 2.5, 3, 3.5. The intensity of the dynamic load (qd(max)) is some percentage of the ultimate bearing capacity (qu) of the foundation. Three values of (qd(max)/qu) have been considered in the study, i.e., 5%, 10%, and 13%. Three different frequencies of cyclic load (0.5 Hz, 1 Hz, and 2 Hz) have also been considered. Based on the settlement pattern of the foundation, the critical number of load cycles (ncr) for each case is determined beyond which the increase in settlement becomes insignificant for further load cycles. The study reveals that even a minor change in the frequency of loading can result in major variations in the ncr.