Void and Karst Detection

Void investigations are typically able to be separated into two types: beneath the slab or pavement or near surface (within the top 10 feet (below ground surface (bls)) of soils.

Beneath the Slab or pavement. These studies are typically conducted with a high frequency Ground Penetrating Radar (GPR) antenna and Slab Impulse Response (SIR) equipment (when the budget allows).

In other cases, GPR is more than capable to identify below slab voids or loose soil areas. If these areas are large, a 2D scan in a grid pattern across the survey area will provide good coverage and quality results for these studies. If the area is small (4 feet by 2 feet or smaller) a 3D survey can be completed. This provides a 3D image of the survey area that can be observed in depth slices.

Near Surface Investigations. These studies are typically conducted using a mid-range GPR antenna (200 to 500 MHz) to allow for the necessary soil penetration. During these studies, the Geophysicist looks for areas of soil anomaly and attempts to identify the cause of that anomaly. Causes can vary from a leaking storm water pipe, broken water pipe or a karst feature.