Electrical imaging can be an effective geophysical method for locating subsurface voids, specifically for deep-mine void detection.
In the late 1800s, shallow subsurface mining of a local coal bed beneath a 25-foot thick sandstone resulted in mine voids in the Akron. Ohio area. Recently, localized subsidence in the subdivision overlying the deep mine has prompted officials to determine if the homes are at risk. Electrical imaging was selected for determining the extent of the subsurface voids.
Shallow-focused electrical imaging profiles were collected near approximately 70 homes.
Elevated measured apparent resistivity values indicate areas of subsurface voids or zones of fracturing related to adjacent voids.
An analysis of five parameters within a decision matrix indicates that roughly 25 homes have subsurface anomalies that warrant further investigation. Forty-four homes were not interpreted to have subsurface anomalies that warrant further investigation. Of the 25 homes considered at risk, 9 are considered low risk and 6 are considered high risk.
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