Bidirectional Static Load Test (BDSLT) on a Versatile Barrette Foundation to 18000 tonnes

Cherian, Anil

Barrettes are common foundations for high-rise buildings, especially because of their high bearing capacity, vertical as well as lateral loads. Recently, barrettes have been demonstrated to be more useful for small plots receiving highly concentrated building loads with limited space between foundations. The idea of a single barrette that can replace a group of conventional piles results in a more stable, economical, and reliable foundation system. Bidirectional static load test (BDSLT), a modern full-scale proofing load test method, carried out using hydraulically driven, purpose-built, calibrated, sacrificial loading jacks installed within the foundation unit. This paper articulates the results of three barrette tests of 2.80 m × 1.20 m size of a 300 m high-rise Residential Tower in Business Bay, Dubai, UAE. The main objective of this load test was to proof-load the test barrettes over 180,000 kN (18000 tonnes). For this purpose, 9 × 900 tonnes of bidirectional capacity hydraulic jacks and eight levels of Geokon vibrating wire concrete embedment type strain gauges comprising four units at each level were utilized. The settlement results of a 47 m deep barrette indicate a total settlement of 6.5 mm at the working load of 54,000 kN that is in good agreement with the 6.20 mm induced from the bidirectional static load tests. The interpretation of the load test results pooled with finite element analyses aided optimization of the barrette capacities maintaining a sufficient factor of safety. The barrette total capacity was evaluated based on the load test results and interpretation of deformation, load distribution, induced unit skin friction, and up to 11% reduction of the current length was proposed.