Case Study- Effects of Undisclosed Large Diameter Sinkhole on Construction, Clearwater, Florida-Video

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Video Summary

A Florida apartment project encountered an ancient, infilled cover-collapse sinkhole that was not identified during the initial subsurface investigation. Construction of an 18-foot retaining wall and site grading triggered severe settlement—up to five feet—along one section of the wall. Additional borings revealed deep, weak organic soils, while inclinometers later showed ongoing movement extending about 60 feet below ground. A first reconstruction using lightweight aggregate reduced the wall’s load but did not stop the settlement. Further analysis identified a large circular failure mechanism. The successful repair installed long sheet piles in front of the wall, secured with deadman anchors. Settlement also affected a nearby building, which was stabilized and lifted using perimeter helical anchors. Survey and monitoring confirmed that the repaired wall and building were stable, illustrating the importance of recognizing deep lateral failure risks in sinkhole-prone terrain.

Keywords

Florida sinkhole

retaining wall failure

settlement

organic soils

sheet pile repair

helical anchors