FROM 100 ABOVE TO 50 BELOW, IN THE HARDEST ROCK IN AMERICA

摘要

This paper will give a detailed insight into hard rock, large diameter surface blasting including some practical tips to improve blasting practices. These tips will be non-technical, of the nuts and bolts type, intended to help the man in the boots. The paper will begin with the importance of communication between the engineering department and the blasters. What looks good on the mine development map might not blast very well. Tight inside corners, 90 degree outside corners, too few rows; are a few of these problems. We will progress through pattern perimeter, blast pattern layout, drilling, pre-loading pattern survey, proper priming, loading methods, stemming, tie-in, and finally shooting. At each step we will include some tips that hopefully will be helpful to the field blaster. Slides and overheads will help illustrate some of the problems discussed. Getting a Good Start At the beginning of the blasting cycle there is one important step that is sometimes overlooked. The blasters, drillers, and engineers should all be involved in pattern design. The engineers are under certain constraints when designing a pattern such as type and amount of material needed, bench height, final pit limits, and pit geology just to name a few, When the engineer designs a pattern to fit these parameters, he may not consider some of the problems he might leave the driller and blaster. Tight corners, poor relief, having to shoot the wrong way on the dip, too close to the high wall for the drill, and open faces on three sides are some of the problems that may be overcome by working together during the planning stages of the blast. Good blasting can accomplish many things that aid pit production other than just good fragmentation. The muck pile can be held back to create a ramp into the blast if necessary. The muck pile can be laid out shallow to keep the bank height lower when using loaders. To accomplish this requires good communication between engineers, drillers, and blasters. The goal of each blast should be determined early in the planning. To quote Frank Chiapetta; "For many operations, blasting is where it all begins. There is no other single unit operation within the total mining system that can affect economies more than when poor blast results are experienced. Depending on the blasting application and ultimate material use, detrimental blast results may result in oversize, excessive fines, back break, flyrock, irregular muck pile, tough digging conditions, potentially damaging ground vibrations, and airblast."