Bubbles in concrete. Hidden chambers or mine rooms. Washouts. Sinkholes. It’s crucial to identify voids like these as early as possible for both safety reasons and maintaining project timelines. Voids can be hazardous to workers and the general public, and discovering them too late can cause project delays and increased costs. RETTEW uses a variety of non-intrusive techniques to detect and accurately map voids.

RETTEW often combines multiple geophysical techniques to identify voids and, in some cases, even determine their contents (e.g., air, water, petroleum, mud). We are experts in detecting voids, washouts, or utility tunnels beneath building floors, vaults, basins, construction sites, and pools. We can also find voids or bridged zones in poured concrete, and map hidden rooms or compartments (e.g., mines).

Washouts, mine workings, tunnels, and karst-related cavities or sinkholes are excellent targets for microgravity surveys. Since gravity surveys are immune to many common electronic or acoustic noise sources, which can impede many geophysical techniques, they are particularly suited to highly developed or industrial sites.

Smaller shallow voids can often be detected using ground penetrating radar (GPR), and deeper voids are sometimes best detected and measured using seismic reflection. Deep, water-filled cavities (i.e., caves or tunnels below the water table) are particularly good targets for seismic shear-wave mapping (MASW) or electrical resistivity imaging (ERI).

Whether detected using gravity, radar, sonar, seismic, or electrical imaging methods, RETTEW provides accurate void footprint mapping, as well as cross-sectional imaging and void volume estimates where required.