Interference of square footings on geocell reinforced clay bed: Experimental and numerical studies

Abstract

When the building foundations are to be constructed close to each other, either due to less availability of space for the construction or due to plot boundaries force the designer to place the footings nearby each other. When footings are placed close to each other with similar soil conditions, the ultimate or allowable bearing capacity of footings may change due to the interference effect of the failure surface in the soil. The Interference of the two closely spaced footings is a phenomenon that is observed when two footings are closely spaced. Current study illustrates the effect of interference on closely spaced square footings in geocell-reinforced clay beds using model tank experiment and 3-Dimensional numerical modeling simulations. Experimental results suggest that with increase in the clear spacing interference decreases and after 2B spacing between the footings the interference effects are almost zero (B=Width of the footing). The interference effect is quantified as Interference Factor, IF and is defined as ratio of ultimate bearing pressure of an interfering footing to that of an isolated footing. Maximum Interference Factor of about 1.5 is observed when spacing between footings/width of footing ratio was 0.5. whereas in case of un-reinforced clay, and in the case of geo-cell reinforced clay, ultimate bearing pressure was found to be about 4 times than un-reinforced isolated footing. Due to applied stress, there is increase in confinement pressure below the interfering footings at shallow depths, which in turn is due to the interaction between the failure zones of interfering footings that which increases bearing capacity. To this end, FLAC 3D (Fast Lagrangian Analysis of Continua in 3 Dimensions) models were developed and numerical simulations have been carried out with detailed parametric analysis- after validating results with the model experiments.