Two Case Histories of Sinkhole Repair Using Low Mobility Grouting Methods

The geology of the Mid-Atlantic Region of the United States includes carbonate rock prone to solutioning and sinkhole development. Grouting for sinkhole repair has gained popularity in this area for two primary reasons. First, demand has increased for the benefits realized from successfully implemented grouting projects. Second, supply of Geotechnical professionals and contractors advocating its use has increased. There are different approaches taken by professionals and contractors in the Mid-Atlantic Region regarding the use of grouting for sinkhole repair. The broad term of "Pressure Grouting" is often used in the local vernacular to describe the process. This term can be expected to include many different materials, methods, and opinions. One idea that consistently appears around sinkhole repair programs relates to the difficulty in budgeting such projects due to the inherent, obvious unknowns associated with the geology and the sinkhole mechanism. While it must be admitted that the very nature of sinkhole repair presents difficulties in estimating the actual costs, the authors argue that reasonable estimates can be formulated. This paper presents the perspective of Geotechnical Engineers turned grouting contractors. An approach to grouting for sinkhole repair and two case histories are presented herein.