Ultimate bearing capacity of two interfering strip footings on sand overlying clay

Foundations may be constructed at close spacings. Prior investigations have presented insights into the interference effect of two nearby shallow foundations on homogenous soils. However, soils are often deposited in layers, such as a sand layer overlying clay. Hence, the interference effect of two adjacent foundations on their ultimate bearing capacity for sand overlying clay has been a relevant topic, which is complex because it is tied to a coupling effect of the geometric configurations and the soil properties. In this paper, the ultimate bearing capacity of two interfering strip footings on sand overlying clay is determined using an upper-bound limit state plasticity method known as discontinuity layout optimization (DLO). The solution is illustrated as design charts constructed through the use of dimensionless parameters. Parametric studies are performed to explore the influence of geometric and strength parameters on the bearing capacity and the failure mechanism. A simplified model is developed based on the data obtained from DLO. Validations are carried out to demonstrate the accuracy of the developed model using various statistical criteria, including coefficient of determination (R-2), arithmetic mean and coefficient of variation.