MEDICAL CENTER AND MOB
Morris-Shea, a leading deep foundation contractor, installed 190 Continuous Flight Auger (CFA) piles as deep foundation construction for a new Novant Health hospital and 56,000-square-foot medical office building in Ballantyne, NC. The Morris-Shea team reviewed and redesigned the original conventional augercast specifications for the medical center deep foundation construction. 24-inch and 36-inch diameter continuous flight auger piles (CFA) were specified as a Value Engineered Alternate to improve load capacity and reduce production scheduling. The CFA piles were drilled by a Fundex F3500 drill rig to depths between 56-feet and 93-feet from elevations at the excavated ground floor and surface floor levels. Morris-Shea utilized seven different CFA pile types to accommodate varied load capacities throughout the project site.
CFA PILE INSTALLATION METHOD
The medical center deep foundation construction utilized CFA tooling that was advanced with high torque rotation and crowd so deep foundation installation could proceed rapidly and without over-rotation. The hollow stem of the tooling was connected by hose to a high-powered mobile concrete pump. A self-consolidating, coarse aggregate concrete mix was pumped under pressure (5000 psi) through the CFA tool to the base of the borehole. Drilling parameters were observed in real time by the rig operator utilizing Morris-Shea’s Automated Monitoring System. The AME display presented the volume of concrete being injected under pressure in conjunction with the tool extraction rate to ensure the construction of a quality monolithic concrete shaft.
VALUE ENGINEERED REDESIGN
The Morris-Shea engineering team redesigned the project’s deep foundation specifications from augercast piles in diameters of 18-inch, 24-inch, and 36-inch to 24-inch diameter and 36-inch diameter continuous flight auger piles. The CFA pile system improved load capacity and reduced installation production schedules.
SOIL CONDITIONS / TESTINGS
Soil testing at the Novant Health Ballantyne, NC Medical Center jobsite determined that the subsurface conditions included clays, silty clays, and partially weathered rock (PWR) throughout the South Charlotte deep foundation project. Morris-Shea performed compression tests on 24-inch diameter CFA piles.