GeoModel, Inc. conducts sinkhole detection and void detection surveys throughout the United States. GeoModel, Inc. uses ground penetrating radar (GPR) to locate subsurface sinkholes and voids. GeoModel, Inc. only uses licensed Professional Geologists with Master’s degrees in Geology to conduct each sinkhole and void detection survey.
In addition to the GPR survey, the GeoModel, Inc. Professional Geologist will also observe geologic features in the area that may be related to any sinkhole activity or underground voids. Back in the office, the GeoModel, Inc. geologist will conduct research of other sinkholes and the geology in the area and recent hazard events such as a flood or drought.
Basic Principles of Ground Penetrating Radar for Sinkhole and Void Detection
Ground Penetrating Radar (GPR) produces a continuous record of subsurface soil and rock conditions, in the form of a cross-sectional profile. Radar profiles can be used to detect the presence of sinkholes and voids by observing the GPR data on the computer screen in real time.
GPR uses an antenna, or transducer, to transmit brief pulses of energy into the ground. The antenna is housed in a protective box that is pulled along the ground by hand or behind a vehicle or ATV. Direct contact with the ground promotes the transfer of the radar waves into the ground for the detection of sinkholes and voids.
The depth of penetration of the ground penetrating radar signal depends on the radar antenna used and the conductivity of the subsurface materials surrounding the sinkhole or void. Antennas with low frequencies, such as 200 megahertz (MHz), have greater penetration (up to 30 feet) in highly resistive material such as dry quartz sand or clean limestone.
High frequency antennas, such as 400-MHz, have lower (more shallow) penetration but higher resolution. Investigations of shallow sinkholes or smaller voids (10 feet or less deep), or soil horizon subsidence, can be conducted with these higher frequency antennas.
Sinkhole detection or void location surveys are conducted most often in karst limestone areas. However, sinkhole location and void detection investigations may also be recommended in areas with soft soil, in areas where water or sewer pipes have broken, after a flood to check for flood damage, or where mining or other surface or subsurface disturbance activities have occurred.