Evaluating the effectiveness of various nozzle designs for high pressure waterjet scaling of loose rocks from mine openings.
42nd U.S. Rock Mechanics Symposium/2nd U.S.-Canada Rock Mechanics Symposium, June 29 - July 2, 2008, San Francisco, California Alexandria, VA: American Rock Mechanics Association, Paper No. 08-299, 2008 Jun; :1-13
Sponsored by CDC NIOSH, research was performed at the Colorado School of Mines Edgar Experimental Mine to evaluate high-pressure waterjets for the scaling of loose rocks in mine openings. The research is motivated by the desire to develop a remote scaling technique as a method of reducing accidents associated with rock scaling. An additional benefit of the method is to improve the adhesion characteristics of shotcrete applied as a support membrane. Ten experiments were performed by scaling a freshly blasted rock surface. Half of the experiments consisted of perimeter holes fully loaded with ANFO, and smoothwall blasting was employed with the remaining experiments. Five different nozzle designs were evaluated: a single orifice straight nozzle, a duel orifice self-rotating nozzle, a single orifice straight nozzle with two different mechanical oscillating systems, and a single orifice acoustically pulsed nozzle. Two scaling experiments were performed with each nozzle type, one with each type of blasting system. Hand scaling was performed after each experiment as a control. Two experiments were conducted in reverse order with hand scaling performed first. This paper summarizes the results of the experimental program, and provides a comparison of the performance of each nozzle type. A comparison of results with conventional and smoothwall blasting is also presented.
Mining-industry; Underground-mining; Coal-mining; Rock-mechanics; Blasting-agents; Tunneling
42nd U.S. Rock Mechanics Symposium/2nd U.S.-Canada Rock Mechanics Symposium, June 29 - July 2, 2008, San Francisco, California
Colorado School of Mines