Through Seam Blasting
Document type: Case Study

Through Seam Blasting

Project Summary
IMPROVING MINING EFFICIENCY
During mid 2012, a coal mine approached Dyno Nobel for
assistance in applying the blasting technique of “Through
Seam Blasting”. Through seam blasting improves mining
efficiency by making it possible to blast through one or
more coal seams during a single blast event. This is
beneficial when coal seams are steeply dipping and
enables blasts to be designed to a workable grade below
the coal seam. With the use of precision timing, the mine was able to
recover coal in a pit that had been dormant for 15 years due Cross section of pit
to the challenge of steeply dipping coal seams. The result was minimal coal loss combined with improved
mining efficiency. Project Goals
Background
 RECOMMENCE MINING IN A CHALLENGING
 DORMANT PIT
GEOLOGY RESTRICTS MINING IN PIT The objectives of using the blasting technique of through
The mine had a pit which had not been mined for many seam blasting were to:
years due to steeply dipping seams caused by a fault
  Increase mining efficiency. running sub parallel to the pit. The surface left behind after
mining the last seam averaged 18%. As a result, this pit has  Improve dig rates above the coal seam. not recently been mined due to concerns over coal loss if
nonelectric initiation systems were utilised. The use of  Maintain acceptable dig rates below the coal seam.

e dig rates above the coal seam. not recently been mined due to concerns over coal loss if
nonelectric initiation systems were utilised. The use of  Maintain acceptable dig rates below the coal seam. electronic detonators provided the initiation flexibility to  Minimise coal disturbance and dilution/loss. mine this area again, with minimal coal loss. Due to the
steep grade, the area had to be terraced so as to create
access for drilling and blasting. Technology Applied
 THROUGH SEAM BLASTING TECHNIQUE
 When blasting to coal it is crucial to know the exact location
 of the coal seam. As through seam blasting has explosive
 decks either side of the coal seam an even higher level of
 confidence in the coal seam model is required. Gamma
 logging was conducted after drilling to precisely determine
 the location of the coal seam. Additional information was
 also obtained from drillers who logged the depth of coal as
Terraces established for drill and blast they intercepted it while drilling.

©2014 Dyno Nobel Asia Pacific Pty Limited

Through Seam Blasting

Whilst knowing the location of the coal seam is critical, the
accurate placement of the explosive decks around coal
seams is equally important. Load sheets that are easily
understood by shot firers, along with careful loading
practices, were applied to achieve the desired blast
outcome.
 ®
DIGISHOT PLUS PROVIDES THE REQUIRED
TIMING FLEXIBILITY
The DigiShot Plus electronic platform provided the timing
flexibility required for this project. It is capable of initiating
blasts up to 9,600 detonators with a blast duration of 20s in
1ms increments. Top of coal after overburden removed
Utilising this flexibility, the through seam blast was initiated
as two distinctly different blasts. The overburden above the
coal seam was initiated first with a flat centre lift chevron.
  Increased mining efficiency as a result of being able to
The overburden below the coal seam was then initiated
 blast to an appropriate design RL below the coal seam.
using a different initiation sequence at a predetermined
interval after the first blast. This initiation design allowed the  Reducing operational costs as a result of improving
blast above the coal seam time to initiate and settle thus mining efficiency.
confining the coal and minimising movement and dilution
while the overburden below the seam was blasted.  Increased dig rates for overburden mining above the
 coal seam.

Value Added
THROUGH SEAM BLASTING MADE IT POSSIBLE TO
RECOVER COAL FROM A PIT THAT HAD NOT BEEN
MINED FOR MANY YEARS
Through seam blasting has resulted in improved mining
efficiency at this mine – which should translate to a real
economic benefit. It has provided a blasting option to allow
mining in a pit that has steeply dipping coal seams due to
faulting.
The value to the mine is:
 Minimal coal loss of a coal seam that was unable to be
 efficiently blasted due to the limitations of ®
 pyrotechnic detonators.

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 ©2014 Dyno Nobel Asia Pacific Pty Limited