Subgrade evaluation and repair of a roadway depression caused by a deep seated sinkhole

Sinkholes and roadway depressions are one of the common and reoccurring problems along interstate highways, state roads, county roads, and local roads within the State of Florida. Such incidents cause significant problems that may include lane and/or road closure, interruption to the public normal way of life, construction delays and interruption to construction schedule. This paper presents a case history of identification and repair of a roadway depression in Columbia County, Florida. The noted distress was attributed to sinkhole activity based on the detection of a cavity in SPT borings, zones of low blow counts, disturbed soils in GPR pseudo sections, and a highly variable limestone bedrock surface. Pressure grouting using high slump neat cement was used to remediate the sinkhole. A total of 147.5 cubic yards of grout was required for remediation. The majority of the grout (approximately 70%) was pumped into the detected void. The remainder of the grout was pumped into zones approximately 15 feet above the top of the bedrock surface.