Bearing capacity of shallow footing on an unsaturated embankment upon infiltration

Department of Civil Engineering, Indian Institute of Science, Bengaluru 560012, India

^* Corresponding author: rakshandas@iisc.ac.in

Abstract

Due to rapid urbanization and population growth, construction activities have been increased on slopes of unsaturated hilly regions. Thus, constructing shallow footings on these slopes is a common method for supporting infrastructure construction. The main factor causing instability of these unsaturated slopes is the loss of suction upon infiltration resulting in footing failures. Thus, in this study, a shallow footing restingon an unsaturated embankment modelled using Barcelona basic model (BBM) has been numerically analysed to investigate the influence of various factors affecting the bearing capacity upon infiltration. The influence of various critical design parameters, like the distance from the crest of the slope and water table positions, slope angle, and infiltration rate, has been studied comprehensively. As the footing distance increases from the crest (setback distance), soil provides higher bearing capacity upon infiltration due to the confinement. Moreover, it is noticed that the bearing capacity reduces monotonically as the water table rises above the toe, thus depicting the Prandtl-type of failure. Further, as the slope angle increases, bearing capacity decreases at various footing distances upon infiltration. The effect of infiltration rate on bearing capacity of footings depends on the air entry value of the soil. As the air-entry value increases, bearing capacity reduces drastically upon infiltration. This approach helps the design engineers consider these factors while constructing footings on unsaturated slopes.