Phoenix Project #1901
This project called for the installation of 50 drilled micropiles (“DMPs”) to support new column footings as part of the Chelsea Viaduct rehabilitation.
Prior to the start of production work, two sacrificial pile load tests were required to validate the project’s original design assumptions. Proof testing was subsequently performed on a number of production piles as prescribed by the project’s specification.
All of the DMPs were installed in limited headroom due to the presence of the existing viaduct structure. Phoenix modified its drill rig to incorporate an adjustable, segmental mast in order to optimize its work in the different headroom constraints.
The site’s geology also posed a number of installation challenges. The top of rock varied substantially across the project site, resulting in individual pile depths ranging from less than 30 feet to more than 100 feet. Rock hardness was also highly variable from one column location to the next. While all piles contained a six foot deep uncased rock socket, installation times varied from less than 30 minutes to over three hours per pile. Finally, numerous subsurface obstructions greatly impacted Phoenix’ production.
In the end, all piles were installed, cut off, and incorporated into the finished structure.