Effect of Interface Friction Angle between Soil and Reinforcement on Bearing Capacity of Strip Footing Placed on Reinforced Slope

Abstract

In the last few decades, many experimental and a few numerical investigations were performed to investigate the behavior of strip footing placed on the soil slope. However, most of the previous studies were case specific. Thus, due to the nonavailability of the design charts for the computation of the bearing capacity of strip footing placed on the edge of the slope reinforced with more than one layer of reinforcement, the authors were impelled to conduct the present study. The effect of the interface friction angle between soil and reinforcement, which seems to have a significant effect on the bearing capacity of strip footing, also is not considered in the previous studies. By using the lower bound finite-element limit analysis technique, a set of design charts are prepared to compute the bearing capacity of a strip footing placed on the top of a cohesionless soil slope reinforced with two layers of reinforcement. The effect of (1) slope angle (β), (2) soil friction angle (ϕ), (3) depth of the first layer of reinforcement from the footing base (d1/B), (4) depth of the second layer of reinforcement (d2/B) from the first layer of reinforcement, and (5) interface friction angle between cohesionless soil and reinforcement layer (δ) are considered during the analysis. As expected, with the addition of a reinforcement layer, the bearing capacity increases. The efficacy of the reinforcement layer is quantified in terms of ηγ, which is the ratio between the Nγ values obtained for the reinforced and unreinforced slopes. The value of efficiency factor increases up to a certain value of d1/B for a single layer of reinforcement and d1/B and d2/B for a double layer of reinforcement; after that it reduces. Because of the reduction in the magnitude of δ for single and double reinforced slopes, the effectiveness of the reinforcement decreases. The axial tension (T) generated due to the friction between the moving soil particles and reinforcement is also plotted throughout the reinforcement layer. One can easily compute the optimum length (Lopt) of the reinforcement required to avert tensile failure from these graphs. The effect of soil dilatancy on the bearing capacity of strip footing placed on the double reinforced slope is investigated for a number of cases. Failure patterns are also plotted for a better understanding of the failure mechanisms of strip footing placed on the edge of the reinforced cohesionless soil slope.