NEW TECHNOLOGY FOR AN OLD SEAWALL: MICROPILE INSTALLATION AT ELLIS ISLAND NATIONAL PARK IN NEW YORK HARBOR

摘要

The seawalls that surround Ellis Island were constructed in the early 1900s and now show varying degrees of deterioration. An innovative approach to the structural repair of the seawalls was developed; which consisted of the use of micropiles for stabilization of vertical and horizontal seawall movements. The micropiles were installed through the existing seawalls and penetrated through a thick overburden; consisting of soft alluvial deposits and relatively hard glacial till; and were bonded into Manhattan Schist. Drilling of the micropiles often encountered timber and other obstructions. The selection of micropiles for stabilization of the seawalls offered significant advantages over other foundation systems and over alternative soil improvement techniques. They allowed drilling through a variety of materials without the need for significant retooling or changes to the drilling procedure. This reduced the impact of foundation construction on the sensitive historical landscape and structures; and prevented the need for significant foundation work from the water side of the seawalls. In addition; micropiles offered relatively high installation rates and flexibility to adapt to the varying conditions along the seawalls.