rock blasting resources 1

[amurphy]

I am designing a water distribution pipeline in an area where bedrock is very shallow and will require blasting for installation of the pipeline below frostline (approx 4 feet below grade). Hardness of the rock has not been determined yet. Neighboring residents have complained of problems with blasting that has previously taken place. I am looking for any general tips or resources that can help me select a blasting method that will minimize disturbance to residents and perhaps assist in developing a health and safety plan.

 

[phillyfrank]

Your best bet is to educate the residents that low-level blasting vibrations that they may notice will NOT cause damage. Follow USBM guidance and keep vibrations well below 0.5 to 1.0 ips depending on frequency. Use good soil/mat cover to minimize noise and flyrock. Cover all detonating cord with soil or sand. Do your best to have pre-balst surveys conducted by experienced persons. Offer to place seismographs for anyone requesting one. Keep very good and careful records. Be careful when intermixing 17, 25, and 42 millisecond delay elements or you can get inadvertant stacking of delays. Double check that all delays are at least 8 milliseconds or more apart.

Use high-brisance blasting agents, well-tamped, and completely filling the hole diameter,with good pea gravel stemming to maximize coupling and maximize high-frequency vibrations.

If there is clay over the rock, go to

http://www.ime.org

and see their advice about carbon monoxide subsurface migration. Use an oxygen balanced blasting agent.

Good luck, but expect lawsuits anyway as blasting is "an inherently dangerous act" and the blaster must prove himself innocent.

 

[reddog99o]

Great advice from Phillyfrank. Get excessive Videos and Stills with the pre-blast survey. Document the heck out of the situation. Have you tried taking out the rock with a hoe-ram? Some softer rocks will lend themselves to this. Noise can be a problem here though. But then, drilling can be as well. Are you blasting close to other utilities? Make awfully sure that the area has been "Dig-Safed" and any necessary exploratory test pits have been dug and recorded. Don't make friends with the residents but be sensitive to their needs. Blasting is a very High Profile venture and some people treat it like some treat workmen's comp. Err on the side of conservatism, and document, document, document.
Watch location of magazines, or that all explosives are in appropriate transportable magazines. Expect visits from your, or the contractor's insurance agent and potentially OSHA. Be particularly vigilant with inspection of the installation, the residents will get only more miffed if you have to go back in for a bad joint during a hydro-test as they were when you were doing the original blasting. Blast appropriately, enough, but no too much so you minimize need for excessive amounts of imported select backfill. Pay the Contractor to designated (specified)Pay Lines to avoid him from overblasting. Make the select replacement material part of the removal item, if it's not too late,that'll help keep him honest.

Good Luck

R.A. Hassett, P.E.

 

[cvg]

why not just use a trencher instead? (with rock teeth installed, of course) Chuck
cgopperton@stantec.com

http://www.stantec.com/