Geotechnical Forensic Investigation of Observed Cracks on a Building in Tallahassee, Florida

In July 2010, two vapor extraction wells were installed about 15 feet from a building at an angle of 50 degrees to the horizontal using rotosonic drilling technique (RDT). In June 2011, a crack approximately 0.5 inch wide on the wall of the building was reported. Several other small cracks were observed on the building following inspection by the authors. The owner of the building expressed concerns that the rotosonic drilling was the cause of the cracks and wanted assurance that subsequent drillings would not exacerbate the problem. Geotechnical forensic investigation was performed to evaluate the potential cause(s) of cracking in the building and whether future drilling would impact the building and the foundation structure system. The investigations involved performing site reconnaissance surveys, site-specific field investigations, real-time vibration monitoring, crack monitoring, and geotechnical laboratory analyses. This paper presents the results from the forensic investigations. Based on these results, potential causes for the development of cracks in the wall of the building and recommended repair measures are discussed