GEOPHYSICAL INVESTIGATION OF ABANDONED MINE TUNNELS

Abandoned mine tunnels are located throughout Pennsylvania and much of Appalachia and many of the mining companies who operated in the area have long ago ceased operations and often little to no historical documentation is available. These abandoned mine tunnels are a concern because they have the potential to collapse over time giving rise to possible impact on surface structures. To help prevent or remediate this impact it is important to develop a non-intrusive method to identify the location of these subsurface voids.

An integrated geophysical investigation utilizing the multichannel analysis of surface waves (MASW) and electromagnetic methods was undertaken in an attempt to locate abandoned mine tunnels. The location of the tunnels within the study area are approximately known based upon historical documents. To help aid in data acquisition for the surface wave survey a seismic streamer was developed. The seismic streamer has an advantage in that it can be pulled behind a vehicle, increasing the speed at which seismic data may be acquired. Analysis of the seismic data reveals geophysical anomalies that are in agreement with the expected depths and location of the mine tunnels. An electromagnetic survey was also conducted using a multiple coil electromagnetic conductivity meter which allows for simultaneous, multi-depth data acquisition. The results of the electromagnetic survey were compared to the seismic results in an attempt to correlate the existence of the tunnels. While a direct correlation is difficult the results of the electromagnetic survey indicate higher conductivity anomalies at the expected depth and location of the tunnels when compared to data acquired over undisturbed land.