Micropiled Post-Tensioned Raft Foundation System

An existing warehouse spanning 12,000 sq m (130,000 sq ft), located in Jazan City on the southwestern coast of the Red Sea in Saudi Arabia, was supported by a reinforced concrete slab- on-grade, while its steel columns stood on bored piles and pile caps. Completed approximately a decade ago, the structure developed severe cracking and floor deformation reaching up to 170 mm (7 in), as per recent site surveys. The deformation evolved without any progressive instrumentation or moni- toring in place, and thus, neither the onset nor the time- dependent behaviour of the issue could be precisely estab- lished. The warehouse remained operational throughout this period, and the owners, faced with ongoing challenges, decided to announce a public bid inviting contractors and con- sultants to propose a feasible rehabilitation solution, given the unique nature of the site and the ongoing operations. To begin with, the city of Jazan is not an easy geotechnical ground to conquer. The region is defined by complex and problematic ground conditions: collapsible loess soil, Sabkha deposits (salt flats), salt domes (which are highly deformable over time), organic expansive clays, flood-prone zones, extreme temperatures, aggressive environmental effects and moderate seismic activity. Salt domes are large underground formations of salt that have pushed upward through overlying layers of rock due to their lower density. Over time, they can deform and shift, causing ground instability at the surface. These structures are particularly problematic for foundations, as the salt can dissolve with water infiltration or move plastically under stress, leading to uneven settlement or sudden subsidence of built structures. Furthermore, the structure in question had to remain in service, limiting the options for rehabilitation due to spatial, operational and construction-related constraints.