Effective Micropile Installation with Innovative Casing Advancement System-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes the installation of 251 rock-socketed micropiles for a 13-story affordable housing development in the Bronx, New York. Construction took place from spring 2019 to spring 2021. The site, comprising three properties acquired by NYC Housing Preservation & Development, required environmental remediation and was directly adjacent to New York City Transit subway tracks and existing MTA pile foundations. The building had no basement or underground parking.<br /><br />The geotechnical investigation included 10 borings to bedrock, two borings extending 10 feet into rock, three monitoring wells, and three test pits. Subsurface conditions and fractured or voided bedrock presented installation challenges. An innovative casing advancement system was used to advance casing and form rock sockets, helping control the work near the subway infrastructure.<br /><br />Key difficulties included grout loss into bedrock fractures and voids, large pieces of wood that obstructed drilling, and stiff clay that could clog pneumatic drilling equipment. Seating casing below fractured rock and re-grouting where needed helped address grout loss. Filling pneumatic air lines with water upon entering clay kept the drill head clear, though it required repeated stops. The presentation emphasizes that thorough geotechnical investigation—and accurate understanding of the depth to intact bedrock—is essential. Casing splices also required substantially more time and effort.<br /><br />The team distinguished between air communication through sound bedrock, which was not considered a cause for concern, and communication through large fractures between ungrouted piles. Overall, the project demonstrates how careful investigation, casing advancement, and adaptation to ground conditions can support effective micropile installation in a constrained urban setting.

Keywords

micropiles

rock-socketed

geotechnical investigation

bedrock fractures

grout loss

casing advancement system

subway-adjacent construction

affordable housing

Bronx New York

environmental remediation