One of the most valuable tools used in mining investigations is the borehole camera. It allows engineers to view and make video recordings of boreholes, wells, mine shafts, sink holes and other accessible subsurface avenues.
Most borehole cameras are portable and operate with a 12 volt DC connection to a rechargeable battery. Images are digitally recorded, and some have sound recording built in. Options including readout displays on the viewer and cable winding mechanisms are also available.
Lithologic or Stratigraphic Logging
While the borehole camera is less than ideal for detailed lithologic logging, it can allow a reasonable level of lithology determination. Sandstones, shales, and coals can usually be differentiated. Separation of shales and siltstones are at times possible Conglomeratic zones, nodules, coal spars, and concretions can be easily viewed within units with contrasting colour. Lithologic determinations work best with a colour camera setup.
The location, orientation, rough width (aperture size), and condition (open, plugged, or stained) of fractures can be viewed and recorded. The frequency of fractures inside lithologic units, with changes in depth, topographic location, and the location of wells concerning geologic structure, mines, and other salient features are all of interest. With the specific equipment, fracture strike and dip can be estimated. Using an integral ruled gauge, the fracture aperture can usually be determined. The degree to which fractures are filled is essential to ground water contributions, the type of fill material or precipitate could indicate the water quality yielded by that fracture, or if bacterial plugging has occurred.
Well Bore and Casing Integrity
The camera can be used to observe the general condition of the well bore in terms of off-sets, zones of sloughing, precipitate build-ups, sediment accumulation at the bottom, or blockages. The cracks or holes in the casing, casing deterioration, leaking joints, and casing buckling can be documented. If the pump is left in place, the condition of the pump, piping and/or wiring can be determined as well.
Ground Water Information
A multitude of information concerning the ground water can be ascertained with the borehole camera.
Impacts from mine subsidence can be observed with borehole inspection camera. This is particularly true if the holes are viewed before and after an event. Mining-related observations include unnaturally widened and newly-created fractures, ruptured, sheared, or pinched casing, and rubblised or caved zones above subsided sections. The mining-induced fractures are frequently at angles oblique to horizontal and vertical. The fracture surface is commonly rougher and more irregular than fractures derived from natural forces.