ABSTRACT
A Smart Cell is a closed-type grout distribution system that is attached to the bottom of a reinforcement cage for drilled shaft foundations and acts in a similar manner to a hydraulic jack in bi-directional static load testing. Control of the grout is maintained within the device during grouting and a uniform stress is imparted across entire base area simultaneously. The goals of tip post-grouting are to improve the stiffness of the in-situ soil, improve the shaft’s nominal axial resistance, and better align the load transfer curves to the project requirements. This paper will present an overview, basic principles, and the design methodology of tip post-grouting using this technique. The construction, tip post-grouting, select results, and general observations from the grouting performed on more than 40 total drilled shafts for the Urubó vehicular bridge structure crossing the Piraí River in Bolivia will also be presented and discussed below. The general subsurface conditions for the sedimentary deposits at the two bridge sites consist of highly variable soil deposits, bedding, composition, and engineering characteristics. The diameter of the temporarily cased drilled shafts was either 1200 mm and the length ranged from nearly 22 m to nearly 28 m Most of the drilled shaft foundations for these bridge structures were installed with a Smart Cell at the bottom of its reinforcement cage to enhance performance and to reduce uncertainty. Using the measurements of the grouting operation, the premobilization of axial resistance and induced load imparted into the drilled shaft and to the soil beneath the base will be discussed.
