A service provided by GeoStabilization International®, a soil nail wall contractor, is karst sinkhole repair around mined coal seams and workings located below existing infrastructure. Often the ground below has current voids with the potential to collapse, causing sinkholes and subsidence. A project completed in Southwestern Virginia remediated the collapse of historic mine workings that had forced the propagation of voids to the surface and the partial collapse of the main access roadway to the local hospital.
A sinkhole is a depression or hole in the ground caused by some form of collapse on the surface layer and is found across the United States. The formation of sinkholes involves natural erosion processes or gradual removal of slightly soluble bedrock (such as limestone) by percolating water, the collapse of a cave roof, or lowering the water table. Sinkholes can also form when groundwater dissolves the carbonate cement holding sandstone particles together and then carry away the loose particles, gradually creating a void. More commonly, when old pipes give way, collapses occur in urban areas due to water main breaks or sewer collapses. They can similarly arise from the over-pumping and extraction of groundwater and subsurface fluids. For more information, visit the USGS Sinkhole page.
Compaction grouting was utilized on a designed pattern to fill the un-collapsed voids directly underneath the roadway and reduce the potential for future collapse events. Some battered and angled holes were then utilized to directly target the collapsed void portions to improve the density of those sections. Because of the overlying bedrock, all holes were predrilled using hammer-drilling techniques; the pre-drill string was then removed before the casing was installed into the predrilled hole. Low-mobility cementitious grout was pumped into the workings to mitigate the areas directly under the roadway.
The presence of extensive voided areas encountered during the drilling gave a good indication of whether actual mine workings were encountered in each hole. The photos show work in progress and evidence of the roadway’s collapse and subsidence in the adjacent slope.
Contact GeoStabilization International® at 855-579-0536 to learn how to utilize our geohazard mitigation services for your geotechnical application. For over twenty years, our teams have been providing sinkhole repair, slope protection, and landslide prevention services.
If you are interested in a no-obligation site visit to determine if our services fit your geohazard mitigation needs, call us at 855-579-0536 or fill out our contact form.
