1. The drill in problem 55 is used to drill blast holes 12-1/4 in diameter and 50 ft in length in...

Question

1. The drill in problem 55 is used to drill blast holes 12-1/4 in diameter and 50 ft in length in one pass. The move time from hole to hole is 5 minutes, leveling requires 45 seconds, and collaring requires 30 seconds. The average penetration rate is 70 ft/hour. Hoist speed is 80 ft/min. If the drill is operated 6 hours per shift, how many holes could be drilled in a shift?

2. If the driller in problem 56 makes $24.00/hour (including fringes), the life of the bit is 6000 feet, and the life of the drill pipe is 50,000 feet, what would be the operating cost per foot of hole? If the hole spacing is 30 ft and the burden is 25 ft, the bench height is 40 ft and the specific gravity of the rock is 2.8, what would be the drilling cost (operating) per ton?

Dr Shweta · Accepted Answer

Solution
Ans 1 
Given: 
Blast holes = 12-1/4′′ in diameter, length = 50 ft, move time from hole to hole = 5 minutes, levelling time = 45 seconds, collaring time = 30 seconds, average penetration rate = 70 ft/hour, hoist speed = 80 ft/min, drill is operated 6 hours/ shift
To find: Number of holes that could be drilled in a shift
Calculation: 
Number of holes that could be drilled in a shift can be calculated as – 
Tc = ld. i/n.

1. The drill in problem 55 is used to drill blast holes 12-1/4 in diameter and 50 ft in length in one pass. The move time from hole to hole is 5 minutes, leveling requires 45 seconds, and collaring...

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