Challenge

An abandoned gas station built in the 1950s was being remodeled into a bakery. The general contractor found the original building construction did not include a lintel over the station’s garage door openings. The project designers therefore proposed to install a steel lintel, spanning roughly 20 feet between two new columns, to support a large wall opening that would replace the existing garage doors. New column spread footings would remove large sections of the floor slab and would be difficult to place adjacent to the existing walls. A deep foundation element was therefore proposed to support each new column. Access to the proposed column locations was limited and required smaller pile installation equipment.

Neither a geotechnical investigation nor an environmental study were performed; however, the owner wanted to avoid bringing any potentially contaminated soils to the surface during construction.

Solution

Helical piles were chosen as the ideal deep foundation solution. Helical piles can be installed quickly, with relatively small installation equipment, and do not generate spoils during installation. A square cut was made in the existing floor slab at each proposed column location. Two (2) Model 287 (2.875-inch OD by 0.203-inch wall) hollow round-shaft helical piles with a 10”-12” double-helix plate configuration were installed to support a design working load of 8.5 kips per pile. Standard extensions advanced the piles to an approximate depth of 15 feet to achieve a torque-correlated ultimate capacity of at least twice the design working load (FOS ≥ 2). New construction brackets were fitted to the tops of the installed piles and cast within poured concrete pile caps. Product and equipment were mobilized only one week after the initial site inspection, and the helical pile installation was completed within one day to keep the project on schedule.

Project Summary

Architect: Framework Design, Inc.

Structural Engineer: Apex Engineers, Inc.

General Contractor: Integrated Construction Solutions, Inc.

Certified Pier Installer: Foundation Recovery Systems

Products Installed: (2) Foundation Supportworks® HP287 Helical Piles, 10"-12" Lead Section, Installed Depth of 15 feet, Design Working Load of 8.5 kips