Roadside Application Of Seismic Surface Waves Over Abandoned Mines

Roadway collapses have occurred along stretches of the Appalachian Highway in<br>southern Ohio due to ground subsidence associated with abandoned coal mine workings. The<br>authors joined a team led by faculty from Wright State University to investigate efficient<br>methods for detection of potential trouble areas before collapses occur. Seismic surface wave<br>measurements were made in both “sounding” and “profiling” modes. In the sounding mode, the<br>Spectral-Analysis-of Surface-Waves (SASW) method is employed to establish shear wave<br>velocity profiles at discrete locations. This approach is intended to delineate areas of reduced<br>overall stiffness, which might be caused by raveling of earth above mine workings, or, if not,<br>imply susceptibility for future instabilities. In the profiling mode, measurements are made at<br>constant offset and constant spacing in order to observe magnitudes and spectral content of body<br>wave interference. This approach is geared toward detection of discrete cavities or major fracture<br>zones caused by cavity collapse. Data were collected along two stretches of highway, one of<br>which has been drilled to establish ground truth. Results of the applications of sounding and<br>profiling methods for rapid assessment of sites with discrete subsurface anomalies are<br>encouraging. Additional analyses are planned to expand the capabilities of surface wave<br>applications through enhanced understanding of reflection and conversion phenomena caused by<br>subsurface anomalies.