During the geotechnical evaluation for a new 13-story building in Rochester, Minnesota, Braun Intertec encountered extremely variable and decomposed bedrock conditions approximately 30 feet below ground surface. The decomposed conditions included layers of dolo-stone between soil-filled cavities and areas of bedrock decomposed to a soillike consistency. Braun Intertec evaluated several foundation methods and worked with the owner and design team to develop foundation options for the site conditions. This case study presents and compares the design options considered and discusses the risk tolerance of the project for the various foundation elements used to support the structures. It also discusses the construction quality-control program to monitor and test the deep foundation systems, construction challenges, adjustments made during construction and lessons learned from the project.
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