Mining Publication: Application of Ground Penetrating Radar to Evaluate the Extent of Polyurethane Grout Infiltration for Mine Roof Control: A Case Study

• Ground penetrating radar
• Roof falls

During 2000-2003, roof falls accounted for 4% to 14% of the fatalities in U.S. underground mining operations. NIOSH is conducting research to reduce the frequency, exposure, and risk of these events through an ongoing program of field and lab studies. One area of research involves the evaluation of polyurethane grouting technology that is commonly used to stabilize fractured mine roof strata. Concurrently, NIOSH is conducting work to evaluate the application of ground penetrating radar (GPR) for advanced delineation of problematic mining areas. In this study, NIOSH partnered with Sub-Technical, Inc., who injected a polyurethane grout (also known as glue) into a roof area of NIOSH's Safety Research Coal Mine. The mine roof area was scanned using GPR technology before and after grout injection in an attempt to determine the extent of grout infiltration. A comparison of the pre- and post-grouting radar records showed a significant change at a mine roof depth of about 4-5 ft. The interpreted radar records were then compared with drill core information, borescope evaluation of roof bolt holes in the study area, and underground observations. At this site, the interpretations of the radar records correlated with data obtained from the coreholes, borescope evaluations, and underground observations. The study showed that GPR technology can be a useful tool for detecting changes in mine roof due to the injection of the grout.