Behavior of Eccentrically Inclined Loaded Ring Footings Resting on Granular Soil

For civil engineers, the determination of ring footing bearing capacity subject to the combination of inclined and eccentric loading is a great topic of interest. In this paper, a novel approach is proposed to predict the behavior of ring footing subject to combinations of inclined and eccentric loading using the failure envelope approach, which can explain shallow footings behavior. Load eccentricity, inclination angle, and diameter ratio for ring footings are the most effective parameters on the failure envelope. In this regard, a series of experiments were conducted to investigate the behavior of ring footing subject to a possible form of eccentrically inclined loading. Three values of diameter ratio were considered, including n = 0.2, 0.4, and 0.6, along with a circular footing (n = 0). According to the test results, the conical 3D failure envelope and its equation were developed for each type of footing model. With constant vertical load the failure envelopes show that when the eccentricity is increased, the possible inclination angle is decreased. Also, by increasing the vertical loading, the possible eccentricity and inclination angle is decreased. Based on the observations, and obtained failure envelopes for different diameter ratios, when a ring footing is subject to combined eccentric inclined loading, n=0.4 is optimum. In the following, by using the failure envelope, the concepts of critical eccentricity and critical inclination angle were defined in a way that is suitable for studying the stability of ring footings in the V-H-M/B space.