Abstract:
Shotcrete on Ivy: Princeton’ s Largest “ Ground-Up Undertaking”
by Jeffrey B. Ayres, P.E.; Keller North America and John R. Morris, P.E.; Morris-Flood Associates, Inc.
A 2000 ft long wall extending up to 40 ft through overburden and into rock. That was the plan to get Princeton University their new environmental studies and School of Engineering and Applied Science buildings constructed along Ivy Lane. Keller North America and Morris-Flood Associates set out to design and install an efficient support of excavation system that extended along multiple buildings and a utility tunnel, while supporting active housing at the top of the slope/hill. The solution ended up being a combination of temporary and permanent soil nail wall installation using online soldier piles and lagging, as well as a robust system of shotcrete and soil nail walls. Constructed over multiple phases Keller installed over 51, 500 SF of earth retention making it the largest “ Ground-Up Undertaking” by Princeton University.
Phase I included the ES & Commons buildings with a basement where Keller installed 33, 500 SF total of temporary soldier piles and lagging, temporary shotcrete, soil nail walls, and permanent shotcrete and soil nails. Keller encountered challenging rock drilling which required changes to construction methods when installing the earth retention systems.
Phase II included the BioE and CBE buildings, pavillion and deep utility tunnel where Keller installed 13, 000 SF permanent and 5, 000 SF of temporary shotcrete and soil nails. Rock was encountered shallower than expected, which led to construction difficulties but more effective rock drilling with open hole drilling. Further, groundwater was encountered at the bottom few tiers of permanent soil nails which led to some additional construction challenges.
Keller utilized value engineering to effectively reduce the amount of shotcrete required on the job by nearly 60% using a rough shotcrete finish, covering plates and accessories with shotcrete to provide the required corrosion protection.