Karst Resistant Deep Foundation System—A Case History

Karst environments provide unique challenges to both design and construction of any type of infrastructure. Technological advancements in geophysical exploration as well as increased experience in construction in karst areas have allowed for larger and more complex projects in this type of geology. The reason behind this being we are better able to define and map the subsurface on a level unattainable with borings alone, resulting in a higher level of confidence in the stability of the chosen foundation design and in the ability to remediate karst features before they become apparent at the surface. The design and construction of a large multi-story luxury hotel in the karst landscape of Bowling Green, KY, lived up to these challenges. Planned to be built in a development with significant prior sinkhole activity, an aggressive deep foundation system that would resist sinkhole dropouts underneath the building was required. Detailed geophysical and geotechnical studies were performed, and a micropile system with a post tensioned slab on grade design was chosen. Adding to the challenge, the chosen location of the building was over a previously repaired sinkhole. This paper presents the details of the investigation, design, and construction and addresses the challenges and lessons learned throughout the project.