Methods to enhance the tensile capacity and optimise the design of concrete pad foundations for overhead line equipment were investigated with the aim of reducing environmental impacts and costs. Using finite-element analysis and centrifuge modelling in sand, the effects of chamfering the pad's upper edge and varying the density of the material used to backfill the excavation were explored. A 30–40° chamfered edge on the pad increased the tensile capacity by up to 40% at low embedment ratios, shifting the failure surface origin from the pad top to the bottom. The backfill density above the foundation was shown to influence the failure mechanisms. When the backfill was less dense than the native soil, vertical failure surfaces formed. Conversely, when the relative densities of both the backfill and native soil were 60% or higher, transitional shear planes emerged. When the backfill’s relative density exceeded that of the native soil, an increase in uplift capacity was observed. However, the effectiveness of backfilling appears to be sensitive to disturbance at the vertical excavation interface. Sloping the backfill sides to 25° allowed the failure surface to develop at the soil’s dilation angle, independent of excavation effects. These findings offer practical strategies to improve foundation efficiency and sustainability in overhead line projects.
Brown et al. (Wed,) studied this question.