Construction of barrettes for high-rise foundations

Barrettes are huge concrete piers, basically rectangular. The cross-sectional areas of barrettes have often been more than 75 sq ft (7 m2) and they have been used for depths exceeding 260 ft (80 m) facilitating heavy vertical loads of the order of 3,000 tons/barrette to be transmitted to the bearing layer. Barrettes are used also as Moscovite wall for deep basements of high-rise buildings to resist both vertical and lateral loads. The fact that a single barrette can replace a group of conventional piles results in a more compact, economical, and reliable foundation system. The installation technique of barrettes follows closely the method of constructing diaphragm wall using bentonite slurry, reinforcing cage, and tremie concreting with careful quality control. Although there are certain reservations for using barrettes instead of conventional piles and diaphragm walls, the inherent advantages and the confidence gained by experience have been responsible for their increased usage, especially as heavy load-bearing elements for high-rise foundations and basements.