Estimate the hourly production and unit cost of rock excavation by drilling and basting. The rock is limestone having a seismic velocity of 6000 ft/s. Trial blasting indicates that 3" holes drilled in 12 ft. rectangular pattern will provide the desired fracturing. A hole depth of 22 ft. yield an effective depth of 20 ft. The average drilling rate is estimated to be 80 ft. /h. A powder factor of 1lb/BCY of ANFO will be used.(20 pts.)
Cost Information:
Labor: Drilling Crew $50.00/hr.; Blasting Crew $52.00/hr.
Equipment: Drilling Equipment = $90.00/hr.
Materials: ANFO $0.50/lb; Primer, caps & stemming = $6.00/hole.