Settlements during Underpinning with Different Processes: Case of a Hospital in Rio de Janeiro, Brazil

Abstract

The hospital building of the Federal University of Rio de Janeiro, Brazil, has been only partly occupied since its construction in the 1960s. The failure in 2010 of two columns in the unoccupied part led to the decision to demolish this area. After demolition, settlement of the adjacent block developed, and underpinning was needed. The underpinning consisted of the installation of micropiles (also known as root piles) incorporated into the existing footings by a new cap. Pile installation was achieved by rotary drilling with an auxiliary tube, and the debris was removed by water circulation. Then, rebars were placed, and cement-sand mortar was pumped in as the auxiliary tube was removed. Because significant settlement occurred when pile drilling, circulation water was replaced by compressed air, and piles with smaller diameters were adopted. Continuing settlements led to a change in the underpinning solution: the use of jacked piles. This paper addresses the observed settlement during underpinning and correlates them with the different underpinning processes. The micropiles produced considerable settlement during their installation, and the underpinned columns still underwent additional settlement before stabilization. Jacked piles produced very small settlement during their installation and practically stopped settlement when complete.