The Application of Water Jets in Coal Mining

Water is one of the natural erosion agents which through time has changed the face of the earth. Application of this principle to remove earth and rock by man is a long established technique. This paper briefly describes the changes in technology which have brought the application of water jets from the slow erosion of soil to the point where in Canada some 3,400 tons per shift are currently mined in a coal mine using high pressure water jet technology. The use of water jets has shown sufficient promise that there are several research programs currently being funded by the U.S. Bureau of Mines and other Federal agencies in the field of excavation technology. Three current areas of water jet mining are described. The first is the use of water at 10,000 psi as a modification of the cutting head of a longwall mining machine. The work which is being carried out at the University of Missouri is briefly described with the rationale for the jet parameters chosen for the experimentation. The second method of mining is a project currently under way in Canada where in a seam 50 ft thick and dipping at an angle of some 40 degrees, a low pressure, high volume flow rate up to 1,500 gallons per minute water jet system produced up to 3,400 tons per manshift. The third method of mining is an experimental program being carried out by Flow Research, Inc. in Washington state. With this method coal is mined from underground seams to boreholes driven from the surface, coal being reamed to the borehole by high pressure water jets and crushed in the bottom of the borehole prior to being pumped out of the borehole for external usage. This method does not, therefore, require access to the underground