Large-Scale Plate Load Tests to Determine the Collapse Potential at Santorini 150 kV GIS Substation Site

Abstract

Two large-scale plate load tests were carried out at the foundation level of the Santorini 150 kV GIS Substation, where the subsoil was identified as collapsible. The purpose of these load tests was to establish in-situ, the magnitude of the expected settlements due to the collapse of the subsoil structure after inundation, while applying a bearing pressure equal to the maximum expected according to the structural design. After completion of the tests, which are described in detail, the resulting settlements were found to be acceptable, so no soil improvement measures were required and it was concluded that with the design and execution of these innovative load tests, it was possible to measure under actual field conditions the magnitude of settlement due to collapse of the soil structure. This led to a more economical foundation solution, compared to the one that would have been adopted were only laboratory tests taken into account in the calculation of settlements.