New deep foundations for a pair of four story student dormitories on the campus of Arizona Northern Arizona University in Flagstaff, Arizona. General contractor hardison/downey construction, inc. was advised that the large settlement concerns indicated a deep foundation system. Highly variable site conditions would make foundation construction unpredictable and time consuming. hardison/downey construction, inc. approached
to value engineer the pile construction prioritizing construction duration.
The Challenge & Solution:
The site is an old drainage course with weathered rock bearing strata overlain by an undocumented fill of sands and boulders varying in thickness from 0 to 40 feet. Excavation and re-compaction, drilled cast in place piers, driven piles and floating mat foundations were all rejected for performance, price or constructability reasons. Time being critical, the helical pier solution minimized required pier by pier design revisions that had to be approved by the engineering, contracting and regulatory stakeholders. Representative full-scale compression testing verified the capacity and stiffness of per plan installations and up to 70 piers requiring shallow pre-drilling and post grouting.
Material distribution of 500
Chance SS175 Helical Piers. Pile engineering was completed by SteelHead Engineering of Freedom, California. Geotechnical engineering was by Speedie & Associates, Inc. of Phoenix, Arizona. Special inspection services were provided by Bingham Engineering Consultants, LLC.