The Application of Waterjets in a Stressed Rock Environment

The use of high pressure waterjets is becoming increasingly common in industrial operations as a means of improving productivity. Although waterjets were initially developed as a mining tool, they have found only a limited use to the present time. Recent developments in the technology, however, promise the creation of relatively small light-weight equipment for use in mines. It is important in considering the applications of this tool, however, that both its advantages and limitations be understood. This is particularly true when laboratory results are transferred to the predictive behavior of underground machinery. A waterjet cuts with a very narrow slot. When this cut is made in a stressed material such as a pillar on the face of a longwall panel the slot can quite easily be closed by stress relief of the surrounding rock. Strategies to circumvent this problem and tools for the use of waterjets in removing highly stressed ground are discussed with relevance to both drills and excavators which might be used in removing highly stressed ground such as that found in longwall chain pillars.