North Carolina State University – Center for Technology & Innovation Parking Garage
Continued growth of the North Carolina State University’s Non-Woven Institute (NWI) drove the development of a new industrial building. The new 3-story, 105,000 sf for Technology & Innovation on North Carolina State University’s Centennial Campus will house both high-bay industrial laboratory and office space. The development also consists of a new 4-level, 26,000 sf parking garage.
Subsurface explorations on the site encountered up to 14 ft of loose to medium dense uncontrolled fill underlain by residual soils consisting of very loose to medium dense silty sand and soft to stiff silt. Partially weathered rock (PWR) was encountered at depths varying from 6 feet to more than 50 ft (maximum explored depth) across the site. In addition, the heavily loaded footing for the new parking garage would be imposing new loading on an existing underwater stormwater storage system.
Geopier® ground improvement was used to control settlement in the loose uncontrolled fill for the heavily-loaded parking garage foundations. However, the presence of an existing underground stormwater storage system located along the perimeter building wall presented design and construction challenges.
Footings bearing at elevations above the stormwater storage system would impart loads on the system and also cause vibrations during ground improvement installation. Alternatively, lowering of footings in this area presented constructability issues related to excavations.
A low vibration, driven Ductile Iron Pile solution was developed to support the parking garage footings adjacent to the storage system. The piles were designed to penetrate the fill and residual soils and terminate after achieving “set” on the weathered rock. Pile working loads up to 40 tons were developed by end bearing on rock. The small diameter piles generated limited vibration during installation and effectively transferred foundation loads to the rock bearing layer to minimize impacts on the existing stormwater system.
GeoConstructors, Inc, installer of both Geopier® ground improvement and DuroTerra’s Ductile Iron Piles, offered up a combined foundation solution to provide overall foundation support. The Ductile Iron Pile solution consisted of Series 118/7.5 (118 mm diameter with 7.5 mm wall thickness) piles installed to terminate on very dense weathered rock. A total of 24 Ductile Iron Piles were installed in 3 days. Pile lengths ranged from 14 to 29 ft before reaching “set” of 1 inch or less of movement in 50 seconds.
North Carolina State University - Raleigh, NC
Danis Construction Company - Raleigh, NC
HagerSmith Design - Raleigh, NC
Fluhrer Reed Structural Engineers - Raleigh, NC
Mosher Engineering - Raleigh, NC