Underground Blasting Drilling

Underground Blasting Drilling

July 9, 2019

Due to only one free surface underground. Underground Blasting is the main method to cave the tunnel, inclined well and vertical well or for underground mining etc. The underground drill rig is most suitable for this application.

Flowing topics are discussed in details:

  • Introduction
  • Cut design
    • Parallel cut blasting
    • Inclined cut blasting
  • Blasting geometry
  • Drill hole quality and blasting results

Underground blasting in drifts

  • When blasting in a drift there is no free face available to which the explosives charges can act. The free face has to be created by a cut Inclined cut blasting
  • Blasting Cut with inclined boreholes
  • Blasting Cut in Parallel Boreholes
    • Free face in cut blasting with parallel holes = empty borehole of small or large diameter


  • Enlargement of a large diameter center holes
  •  


  • Cormorant Cut

 

  • Distance between Cormorant and enlargement boreholes

Underground blasting hole geometry

  • Underground Blasting with a parallel cut holes
  • Underground Blasting Geometry with Inclined Holes

Underground Drift Blast Drilling

  • Blast Hole Sequence
  • Blast Hole Specific Drilling
  • Blasting Hole Benches
  • Blasting Hole Profile analysis
  • Blasting Hole Drilling Deviation from Contour
  • Underground borehole Drilling along the contour
    • Original section face is 3.75m2
    • Bottom hole downlook 10 – 20 degree
    • Roof hole uplook 15degree
    • Bottom section area 2.1X3.1 = 6.51m2
  • Blasting hole length variation
    • Depth of cut determines the whole advance
    • Boot-holes because cut drilled too long or too short or enlargement holes vary too much in terms of drilled length
    • Length of holes have to be drilled relative to a reference line (cannot be controlled by driller without clear marking
  • Increase efficiency in blasting drift
    • Control of hole length: cut drilled too short
    • Control of hole deviation: too large distance between holes in the bottom (hole distance at face 0,7 m                             in bottom 1 m)
    • Avoid too large outlook of contour holes
    • Change from half-second delay to ms delay (80-100 ms) for all holes (not only for the cut)
    • Control of delay pattern (sequence of holes)
    • Check hole diameter versus cartridge diameter (use the largest cartridge diameter possible in the cut)
    • Check if cartridges burst when charged into hole
    • Change to dynamite type of explosives
  • Blast Borehole Position Deviation
  • Borehole position deviation will influence blasting result very much

Above is some knowledge for underground drilling, it can be as reference for people working in blasting hole drilling indudstry even it does not cover all the points. We also have further reading in below to show more knowledge like rock property and drilling tools selection etc.

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