The effect of combined loading on the bearing capacity of strip footings located on two-layered clayey soils adjacent to geogrid-reinforced slopes

The present paper aims to determine the undrained bearing capacity of strip footings located on two-layered clayey soil in the vicinity of a geogrid-reinforced slope under the effect of combined loading by applying horizontal (H), vertical (V), and bending moment (M) loads. To this aim, by finite element modeling in ABAQUS based on the controlled load-displacement method, the failure envelopes and the failure mechanism of the subsoil of strip footings under the effect of combined loadings were determined in V-H, V-M, and V-H-M loading spaces. The results obtained in two cases of unreinforced and reinforced slopes with geogrids were compared by performing parametric studies regarding the effect of changes in undrained shear strength ratios of clayey layers (Cu1/Cu2) and the ratio of the thickness of the first clay layer to the width of the strip foundation (H1/B). The results showed that by increasing Cu1/Cu2 in V-H loading spaces, the vertical bearing capacity increased, which is caused by the increase in the undrained cohesion of the first layer. Furthermore, in scenarios involving both vertical-horizontal (V-H) and vertical-moment (V-M) load combinations, when subjected solely to vertical loading, a greater volume of soil experienced failure. The results showed that reinforcing the slope with geogrid increases the vertical and the moment bearing capacity by 31 and 35%, respectively. In general, the findings of this study provide new insight into the failure mechanism of strip foundations based on two-layered clayey soils in the vicinity of geogrid-reinforced slopes under the effect of combined loads.