Comparative assessment of 1g and centrifuge uplift tests on steel grillage foundations

Steel grillages, as an alternative to concrete foundations for overhead lines, offer construction advantages in remote and challenging terrains, such as those present in Scotland. Their non-concrete nature allows for transportation to the site and pre-fabrication using low-ground pressure vehicles or helicopters, eliminating the need for haul roads and removing concrete curing times, thereby accelerating construction. This paper compares the response of 1g and centrifuge uplift tests on steel grillage foundations, demonstrating ultimate uplift capacity comparable to a solid plate. However, they are subject to reduced stiffness with increasing grille-to-grille spacing, which is critical when assessing against displacement design criteria. The paper also explores the scaling of uplift displacement and the influence of particle size on stiffness by comparing two different particle sizes in both 1g and centrifuge testing. In 1g testing, two particle sizes were used: D 50 of 0.13 mm (sand) and 4 mm (gravel). Centrifuge testing at 28g employed D 50 sizes of 0.13 mm and 0.19 mm (sands/gravel substitute).