Perimeter blasting in shaft sinking 1

[boomer]

does anyone have experience with perimeter blasting in u/g shaft sinking by tracing re-pump emulsion loaded holes with detonating cord? 25 or 50 gn

 

[Tex]

Boomer,<br>
<br>
Sorry, I haven't had much u/g experience and don't know exactly what you are talking about. However most emulsions that I'm familiar with are adversely affected by detonating cord especially in small diameter holes. Any special reason on why you wish to use det cord?<br>
<br>
Tex<br>

 

[Digger]

Boomer: <br>
Tracing with det cord usually only works with Anfo. The cord shoots so much quicker than the ammonium nitrate that it actually fuses about 50% of the anfo charge and lessens the total charge in the hole. B Line doesn't detonate the anfo. <br>
<br>
If you have to stay with an emulsion you might have better luck controlling overbreak by messing with the hole burden and spacing and then reducing your total charge. Are you benching or going full bottom? What type of ground? <br>
<br>
Regards. <br>
<br>

 

[rodneya]

Does anyone have experience using large coreload det cords in perimeter blasting. I am after some feedback of effectiveness, hole spacing etc

Thanks.

 

[boomer]

Digger
Tracing of repump (bulk) emulsion used in shaft sinking is becoming common practice in N. Canada. The idea isn't side initiation as in anfo loaded holes but destruction of a portion of the sensitizing glass or gas bubbles in the emulsion. Burden and spacing are constantly reviewed as the shaft deepens

 

[exploengineer]

Boomer,

I have done alot of perimeter blasting using emulsion traced with cord and using only 200 grn/ft det cord.

There are two schools of thought on using cord with emulsion:
1. Use the cord to cause lower order detonation of the emulsion, which takes place of the decoupling theory normally associated with perimeter blasting. This is caused by the low energy det cord destroying part of the emulsion as someone stated earlier.
2. Use the cord to detonate the emulsion and spread the patterns out and use a smaller diameter hole.

In hard rock, I've had best results using just 200 grn alone or using a continuous presplit product manufactured by SEC. This product is cartridged watergel with det cord running down the center.

If cost is a major issue, pumping emulsion with a lower core load det cord tracer is the way to go. As someone else stated earlier, there has been excellent results with this technique in North America.

Frank Lucca

http://www.terradinamica.com

 

[tiggertoo]

boomer,

Currently sinking shaft with emulsion & 18 grain cord for wall control. What's your interest?