Cast Blast Modeling
Document type: Case Study

Cast Blast Modelling

2. A 45° plane with a toe position offset 5m from the original toe
 Project Summary of coal at the face prior to blasting (CAST).
 3. The original position of the free face.
USING MODELLING TO EVALUATE BLASTING
OPTIONS
A customer requested assistance in relation to the modelling of
cast blasts at one of their coal mines with a view to identifying
opportunities to improve the operation. The main objectives
were to model several different blasting scenarios and obtain
results for predicted muckpile movement and shape.

The process involved entering all the available site information
(blast design, pattern dimensions and rock mass properties) into
the Hybrid Stress Blasting Model (HSBM) to form the base to be
used for each model. This ensured the actual site conditions
and practices were accurately represented within the models. This information was used to run models established on a typical
base design (design 1) as well as two different designs (designs
2 and 3) that incorporated variable burdens. Each of the three main design options was modelled in order to
ascertain any likely differences in cast values etc. As an
extension to this, the same scenarios were modelled with two
initiation points (top and bottom) within the columns rather than
one. With the results obtained for the three design scenarios
with standardised timing, the last step was to use the general
parameters of one of the models specifically (design 2) and
model some different timing options as well. The modelling results indicated improvements in “gain” of
around 5% through changes to geometry and initiation Project Goals
sequence. The results of the multiple modelling runs were also
used to provide some final general blast design advice for the
 EVALUATING OPTIONS TO IMPROVE CAST
mine.

try and initiation Project Goals
sequence. The results of the multiple modelling runs were also
used to provide some final general blast design advice for the
 EVALUATING OPTIONS TO IMPROVE CAST
mine. The main objectives were to model several different blasting
 scenarios and obtain results for predicted muckpile movement
 Background and shape. These results were then compared with site
 measurements in terms of cast percentage and gain
A COAL MINE CASTING SHORT BENCHES percentage. The main outcome of the modelling was to allow
This mine operates on relatively short benches (under 30m) with a judgment to be formed in relation to the optimum base
large diameter drills drilling vertical blastholes on patterns of pattern parameters and timing regimes for site. These base
relatively large dimensions. At the mine, three measures of cast parameters would then be able to be verified in the field and
are recorded being material past: further refined as results were made available.

1. A 16° plane with a toe position offset 5m from the original toe
 of coal at the face prior to blasting (GAIN).

Cast Blast Modelling

Technology Applied
STATE-OF-THE-ART BLAST MODEL EMPLOYED
The Hybrid Stress Blasting Model (HSBM) was used to perform
the modelling. The HSBM is a state-of-the-art blasting model
that has been developed over many years with an aim to model
the complete blasting process and predict results based on
known detonation and rock breakage physics (i.e. from first
principles). This includes taking into account explosives and
rock mass characteristics, blast layout and confinement and the A design change to compressed burdens at the front of the blast
resulting shock, dynamic stresses and gases generated by the will likely achieve a higher level of cast and gain. The modelling
explosives. The blast outputs are micro and macro damage indicates an increase in gain in the order of 2-2.5%. (near field), vibrations, fragmentation size distribution,  A move towards dual initiation of blast holes (initiated at the
movement and displacement. same time for the lower and upper primer) will likely achieve
 a higher level of cast and gain. The modelling indicates an
 Value Added increase in gain of 1-1.5%.  The move to flatter timing contours (faster inter hole timing)
 will likely achieve a higher level of cast and gain.

ast and gain. The modelling indicates an
 Value Added increase in gain of 1-1.5%.  The move to flatter timing contours (faster inter hole timing)
 will likely achieve a higher level of cast and gain. The
OPPORTUNITIES TO IMPROVE CAST AND GAIN modelling indicates an increase in gain of 2-3%, though this
IDENTIFIED gain may be more variable than the gains achieved by
 burden or priming changes. Modelling of the blasting process is complex. Changes in
geology, for example, can have a significant impact on results. Whilst the “gain” or level of material cast past the theoretical 16
In order to minimise this, current site results were used to degree low wall was a key driver, the importance of the
calibrate some of the model parameters in order to achieve changes in the models with the other two measures of 45
results that are more equivalent to site actual results. As a degree wall and past the face was also considered. The
consequence, the results obtained are much more relative change in these numbers is representative of the
representative of real world outcomes and can be viewed as displacement of the centroid of the material. Whilst only the
providing acceptable “trends” that may be used to guide any “gain” numbers refer to material that does not need to be dug
planned blast design changes going forward.

d of the material. Whilst only the
providing acceptable “trends” that may be used to guide any “gain” numbers refer to material that does not need to be dug
planned blast design changes going forward. The following or pushed, any additional forward movement in the centroid
general conclusions were drawn from the modelling that was location represents a benefit for dozer push applications in that
performed. the material to be pushed does not need to be pushed as far.

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