85
RIOTRONIC X+
User Manual
Rock
properties
specific
gravity
(g/cm3)
density
(kg/m3)
Solid
rock
density
(kg/m3)
broken
rock
p-wave
velocity
m/s
Uniaxial
Compressive
Strength
(MPa)
Tensile
strength
(Mpa)
Limestone
2.4 - 2.9
2643
1682
2500-6000
546000
10 - 245
6 - 25
Table 1 Properties of limestone
A rough calculation might be as follows:
Burden =3.8 meters.
To find the optimum inter-row timing in our ground, assuming that the rock needed to
explode is limestone, read the tables above. The optimal delay time with 3.8 meters can be
17/18/19/20/21ms.
The delay time changes should not be big, as it could end up causing significant problems,
including greater air blast and over break. The recommended way is to move towards where
the expected result is in steps. Change the intra-row delay by a few milliseconds and see
what the effect is. The reason for doing the initial calculation is not to obtain the optimal
timing, but to give the direction in which the timing should be moving towards. The
following is an example of the shots fired in a typical hard rock quarry where the optimal
timing was thought to be 18/46 and the site was currently using 17/42 non-electrics.
1st blast with RIOTRONIC X+ product, timing = 17/42
2nd = 17/43 Not much of a difference
3rd = 18/43 More throw. Fragmentation a bit more uniform
4th = 19/44 More throw. Fragmentation about the same but air blast up a bit
5th = 18/43 About the same as the 3rd trial
6th = 19/45 Not much change
7th = 17/46 Possibly a bit more throw
8th = 19/43 Rock pile a bit higher
9th = 17/48 Loss of some power trough. Digging a bit tighter
10th = 17/46 About the same as the 7th trial.
So, after a controlled program of 10 blasts this site could optimize its blast timing at 17/46
without having to expose themselves to any radical changes.