Large-scale uplift tests to improve design of pad foundations for Overhead Line Equipment

This paper presents the results of large-scale uplift tests on pad foundations conducted at the UKCRIC Soil-Foundation–Structure Interaction (SoFSI) Laboratory at the University of Bristol, simulating conditions relevant to overhead electrical line infrastructure. Pad foundations with a 1 m × 1 m footprint and different geometries were embedded at depths of up to 2 m in manually compacted dry sand. The results complement and validate previous centrifuge tests and numerical modelling studies aimed at improving current foundation design practices. They confirm: (i) the superiority of theoretical uplift-prediction methods that account for both the weight of the soil wedge and the frictional forces mobilised along the failure planes, both governed by soil dilation; (ii) the potential for optimising foundation geometry through chamfering to increase uplift capacity and reduce concrete volumes; and (iii) that simple projection of the uplift failure wedge to the ground surface can lead to an overestimation of the failure wedge size. Direct comparison with centrifuge tests shows close agreement in maximum uplift capacity, although some discrepancies were observed in the displacement at the peak failure state. Nevertheless, this full-scale validation provides confidence in implementing the novel design methods for pad foundations supporting overhead electrical line infrastructure