Job Description: A builder wished to construct a new single story office building for multiple tenants in Canton, Ohio. Soil investigation revealed fill soils over compressible peat and organic clay and finally competent layers of sand and gravel. Other methods of site stabilization, such as excavation to remove the unsuitable soil and replace it premium, compacted fill, were deemed unfeasible due to shallow water table and proximity to other structures.
Commercial Case History
Analysis and Design: The foundation of the new building was designed for support by helical screw piles. Spacing of the piles was determined by the foundation loads and the anticipated achievable load capacity of the piles. Since the building was to be slab-on-grade with no basement, the perimeter frost footing was converted to a reinforced grade beam capable of spanning between piling. The slab was also designed as a structural slab to be supported by perimeter walls and interior grade beams. Since the peat and organic clay layers were found to be extremely weak, the "pulldown" pile or HPM was chosen to increase the lateral stiffness of the helical screw pile in the zone of extremely weak soils.
Click on the image to the left to see a enlarged image of the typical cross section of the building foundation.
Installation: Forty-eight HPM's (helical pulldown micropile) were installed to an average depth of 30 feet below the bottom of the foundation. Martindale Foundation Systems, Inc. also excavated, placed the reinforcing bars, and poured the concrete for the grade beams of the structural foundation. Total time to complete the foundation was a little over one week.