Banco FIE Oruro

The project

The Banco FIE in Oruro is a 6-floor, 3,100 m² bank building. Because of its function, it needed at least a basement to house the vault. The soil study placed the water table one meter deep and the adjoining lots had adobe houses: we had to excavate below the water without causing the slightest harm to the neighbors. Our work covered the structural design and supervision of the works.

The structural challenge

The allowable soil bearing was barely around 0.8 kg/cm². With a conventional analysis, the foundation slab reached 1.8 kg/cm² at its critical points, more than double what the soil could bear. We therefore carried out a nonlinear analysis of the soil-slab interaction, which accounts for the redistribution of forces, bringing the stress down to 1 kg/cm². To close the remaining gap, an 80 cm thick foundation soil improvement was designed, down to the depth where the pressure bulb equals the allowable bearing.

The Galindo solution

Several methods were evaluated for the excavation. Sheet piling was ruled out because driving it could damage the neighboring houses, the elements were not recoverable after the works and its cost was high; ring-beam construction, because of its complexity. We chose an excavation in alternating bays protected with sprayed cement grout, with set-accelerating and waterproofing admixtures, also advancing the wall reinforcement to minimize the slope's exposure time.

A pilot test on site validated the method and brought good news: the actual water table was almost at the depth of the foundation slab, which made the work easier. During the inspection, a neighboring adobe wall in very poor condition was detected: with the owner's permission, it was demolished and replaced with a new one of brick and reinforced concrete. The building was completed with slender cantilevered stairs only 12 cm thick and reinforced concrete spiral stairs.