Abstract:
Michels Construction served as the deep foundation contractor, installing piles for preconstruction testing and production for a project in Williston, North Dakota. Braun Intertec served as the geotechnical designer of record and Michels' geotechnical testing consultant for the project. Based on Braun's geotechnical investigations, the site consisted of glacial deposits overlaying weathered bedrock. Driven h-piles were selected by the design team to allow for construction during winter months, thus increasing the overall construction schedule by about 6 months.
A comprehensive testing program was specified, including a 40-pile indicator program that consisted of high-strain dynamic pile testing at EOID and 3-day restrike on all piles, as well as tension, compression, and lateral load tests on 8 piles, with restrike testing on 10 percent of production piles. Part of the reason for the extensive indicator program was to evaluate the needs of predrilling piles. During the indicator pile program, minimal issues with early pile refusal occurred, and production was pushed forward without predrilling.
However, during production, some piles began refusing as high as 8 feet below the surface. Michels and Braun collaborated to evaluate different predrilling methods and conducted additional testing to determine predrill depth, minimum pile penetration depth, backfill material, and other parameters.Â
The major takeaway from this project is that no matter how extensive the preconstruction testing program is on the front end, production installation may vary. The deep foundation contractor, design team, and testing consultant should collaborate to develop the best path forward.