blasting radius of influence 1

[pelelo]

I plan to build a station for monitoring the slopes on an open pit mine.

Since blasting is going to be a very common activity I am afraid of placing this permanent monitoring container in the radius of influence when blasting activities take place.

Anyone knows if there is a formula or any approach on how to compute the minimun distance at which i should build my station so It won't fall into the blasting influence?

I undestand at some point it depends on the blasting method, equipment, type of rock, blasting depth, etc.

Please let me know.

 

[cvg]

if its in the pit, that it is in the radius. if the slope is subject to sliding, than it is probably at risk. however, you are not really defining what your criteria are. you will be subject to potential fly rock and to seismic waves. the only solution to both is to move a long way away. you need to determine what your criteria is and then talk to the blaster to get data on the explosives type and quantity used.

 

[dhengr]

Are you doing laser measurements to monitor slope stability and movement, to measure volume changes, etc.? Talk with the mine blasting people about the radius of influence of their blasting as relates to ground movement at distance from blast zones. Talk with a local surveyor about setting up monitoring of your intended location, including control monuments a further distance away which you can shoot back on to verify any movement of your location. Talk with your equipment supplier, as relates to their equipment and software. I’ll bet their software allows you to set different equipment coordinates and tie them all together, with work done from a previous location, or because your location has moved slightly.

 

[ebenozen]

I doubt you need monitoring data so close to the blast that you could potentially damage your equipment. No need to monitor in this situation, the answer is obvious.

You need to set up your equipment (seismograph, accelerometers) in the areas that you are concerned about damaging if evaluating blast damage is your objective. Then record blasting information including geology (rock type), powder factor, number of holes, delay times between holes and between rows, explosive type, survey of the pattern and your monitoring data which includes location of monitoring station, the full seismic waveform, frequency, peak particle velocity. Also observe the blasts and look for excessive flyrock or anything else that seems to have gone wrong. With data from several blasts, you can evaluate performance which is not rudimentary.

 

[cvg]

I believe the OP monitoring equipment is for slope stability - extensometers, slope stability radar, Lidar, or possibly prisms. all for monitoring pit wall slide stability and all presumably within the distance where fly rock could cause damage. this is a risk that cannot be easily mitigated in an open pit mine. I question how you can "observe blasts and look for flyrock". MSHA will definitely not allow this type of observation and neither will the pit supervisor. Perhaps a high speed video camera could be used.

 

[miningman]

I know exactly how to safely "observe blasts and look for flyrock" but I am not going to post it here... it requires a practical understanding of explosives and their power. However even if I did provide that information, it would be useless to anyone because you could observe 99 blasts, all loaded by the same individual, all in the same area of a pit, and be happy with your observations and the 100th blast might take out three of your monitors. Build an allowance into your budgets for replacement of some monitors.

 

[cvg]

agree that in addition to placing as far away as is practical that an allowance is necessary. berms and blasting mats can also be used to protect against flyrock

 

[ebenozen]

For slope monitoring, you shouldn't have problems with the blasts affecting your equipment. With blasting in the pit bottom and extensometers near the pit crest and prisms scattered around the slope, the equipment should be well out of harms way. It would be a stretch for flyrock to damage your equipment. The blast would have to go terribly wrong.

I assume that you planned to use prisms and extensometers for monitoring. Did you plan to use any other monitoring devices?

For extensometers, I recommend these

http://www.slideminder.com/.

They work very well and have a telemetry system to transmit the monitoring data and alerts so that you get real-time data (immediate notification of slope movement).

Best of luck.

 

[miningman]

Theres starting to be a serious lack of recognition of the practicalities of blasting here. I am intimately familiar with one occurence many years ago when a substantial piece of flyrock was ejected from the #16 bench of a pit using 40 foot benches, ie 640 vertical feet deep, plus an additional 100 vertical feet or so, to come crashing thru the roof of the office complex about 600 yards away from the pit edge.


Absolutely no one was disciplined, nor were blasting procedures changed. S**t happens when using explosives.

 

[cvg]

fly rock is not the only killer, ground vibrations can just as easily knock rock loose to roll down the nearby slope.

Two classic examples of fly rock / rolling rock are linked

http://banthequarry.org/3-Education/Impacts/Flyrock.htm

 

[ebenozen]

I appreciate your comment miningman and have also heard similar anecdotes of flyrock traveling for great distances. However, to not add further confusion to pelelo's dilema, slope monitoring devices are typically positioned a sufficient distance away from blasts in normal mining scenarios and he shouldn't be overly concerned with damage to his monitoring equipment due to flyrock unless, there are very unique circumstances in this situation.

I hope we've been able to help provide some guidance pelelo. If you have any other questions, I'd be happy to comment. I have lots of experience doing slope monitoring in open pits. Cheers!