The formation of cavities in the subsurface is generally linked to some kind of underground water movement, and in rarer cases, cavities can remain after the decomposition of buried organic matter.
In any case, whatever the cause, it can be said that the cavity itself is an undesirable phenomenon, especially when it occurs in a built environment, as its presence generally results in structural instability. Therefore, it is important to localize and eliminate cavities as soon as possible, thereby preventing accidents and serious damage. The exact size and position of a potential cavity can be determined by excavating the given area; however, if the position of the cavity is unknown, significant costs can be incurred depending on the size of the area to be excavated.
The costs of such an excavation can be significantly reduced by applying non-destructive measurement methods. Subsurface cavities have different physical properties compared to their surroundings, so they can be effectively investigated with GPR ground radar and electrical measurements. Ground penetrating radar surveys can accurately determine the location and geometry of cracks and and leaks, as water-saturated areas change the electromagnetic properties of the soil. For example, this method can effectively identify pipe breaks.
Thanks to the rapid field deployability of radar measurements, information can be quickly obtained from large areas. After processing the measured data, a map can be created showing the exact position and extent of the detected cavity(ies).