Coal Geology

Stratascope / Borescope (Borehole Video Camera) and Mine Roof conditions

Stratascope (or Borescope – Borehole Video Camera) is somewhat new technology to evaluate roof conditions in deep underground mines. Periscope like “stratascope” comes with a camera, video unit and and extension chords (or sticks marked by depths). In new models of the stratascopes you can record every test hole, you can also add audio if you like. The whole stratascope units comes in a small box that you can easily carry underground. Stratascope gives you ability to view the test holes within the mine. Using stratascope you can:

Define contacts between major/minor rock strata (Shale/Sandstone, or Coal Seam, Rider Seam etc)

• Conglomerate
  
• Sandstone
• Siltstone
• Shale
• Coal
• Underclay
  

Define any Fractures and fracture angles (hi angle vs. low angle fractures)

• Vertical fractures in the roof strata
• Horizontal fractures in the roof strata
• Bedding plane fractures within various roof rocks
• Slickensides
• Fracture intensity (no. of fractures)
• Channel bottom irregularities
  

Describe rock strata (Shale, Sandstone, their grain size, color etc)

• Ironsone Inclusions?
• Coal streaks/coal spars?
• Cross bed?
• Load Structures?
• Any Partings?

Major roof falls is related to multiple factors such as fractures, fracture trend orientation with respect to entry, rock types, bedding plane fractures, vertical fractures, faults, folds, stray coal streaks, slickensides and more.

Stratascope is commonly used when there is a known problem in the immediate roof strata of the underground coal mine. Test holes are usually drilled before contacting personnel for Stratascope analysis. The test holes are usually 1 inch in diameter.

There are many different types of Strascope available from different manufacturers. Some examples are (Click on the link to visit their webpage):

• FS-4200 Mining Stratascope
• Stratascope from F.M. Locotos Co. Inc

Stratascope from F.M Locotos Co. Inc has a nice reference page describing their product. Click HERE to check out their product in detail. Stratascope usually has the following components:

• Miniature Video Camera (Fits 1 to 1-1/3 inch holes)
• TV Screen.
• Rechargeable battery
• Microphone
• Insertion Rods
• Cable
  

Recommended Consultant for Stratascope Evaluation: Marshall Miller and Associate

Problems using the Stratoscope:

1. Dust cover within the test holes: Sometimes the test holes are completely or partially covered with dust from another layer. Such as, you may see sandstone particles as a thin layer on shale unit. That may misguide you to interpret the strata having some sandstone streaks in it. Sometimes the dust effect is so bad that you can hardly tell any difference between any rocks.
2. Moisture content: Wetness of the test holes is another problem in some cases. If the hole is very wet, shale and sandstone or other rock units will reflect more light than they should. So, you may not observe a darker color for shale!

Solution?
I am not sure about how to best use strascope in such problem situation I just mentioned above. Use of a brush to clear the dust might be useful. If you have any better solution, please reply and let us know! Some geologists also suggest that use of pressure pump to clean the test holes may increase quality of bore hole video quality.

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