Rock Blasting Volume Calculations
Rock Blasting Volume Calculations
(OP)
Rock was encountered on my job site while excavating for a stormwater mamagement pond. The contractor has offered a unit price for the blasting of the rock. I have asked the contractor to explain how they will calculate this volume but it seems they are adding in the volume of the overburden which does not need to be blasted to be made excavatable. How is this volume normally calculated and how is it calculated when trenching for utilities is involved?





RE: Rock Blasting Volume Calculations
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Rock Blasting Volume Calculations
RE: Rock Blasting Volume Calculations
RE: Rock Blasting Volume Calculations
In blasting, you must drill deeper then needed to facilitate breaking the rock to grade. this extra drilling is called subdrill. Many contractors will try and charge for this.
So, accepted practice is (length x width x cut depth)/27.
In regards to overburden. It depends how much is present, and if removed, can the cut depth still be blasted safely. Its hard to blast for 2 feet of rock. We will not load less then a 6 foot hole for safety reasons. If you strip the overburden and then you must drill alot deeper, your costs go way up for blasting and fill.
Normally, if the cut is less then 10 feet, leave the overburden if possible (it helps for control and containment) and pay them for it. But, they might find that its too difficult to keep an open hole and have to strip it anyway.
I hope my rambling helps.
Frank Lucca M.I.Exp.E.
www.terradinamica.com
RE: Rock Blasting Volume Calculations
RE: Rock Blasting Volume Calculations