Abstract:
As part of a deep sewer tunnel repair, Schnabel installed a circular secant pile access shaft. Low overhead power lines dictated that an initial shaft of ribs-and-lagging be constructed, and the secant piles drilled from within the initial shaft. These rare site constraints resulted in unique mobilization and assembly difficulties. Disposing of spoils, setting steel reinforcement and placing concrete were also exacerbated by both vertical and horizontal confinement. The resulting sixty secant piles drilled up to fifty-one feet deep successfully sealed off ground water, loose sands and soft clays from the excavation and allowed the sewer repair to be completed. This paper will discuss the construction challenges affecting many different aspects of assembling the drill rig and installing secant piles from within a thirty-four foot diameter shaft.