Study of the application of fine high-pressure liquid jets for cutting slits in rocks

Abstract

1. Fine high-pressure liquid jets at a pressure of 200 MPa or more provide slit cutting in all rocks with different compositions, mechanical properties, structure, and they may be used in creating slits in the rock mass, i.e., initiators for directed hydraulic breaking. 2. Over the outer surface of the slit and in the same plane as the high-pressure jet action on the rock mass a set of cracks forms which will probably facilitate more successful directed hydraulic breaking as a result of a reduction in pressure for the start of the process. 3. The energy content of hydraulic jet cutting of incipient slits does not exceed the energy content of the mechanical cutting method. 4. The data base for cutting rocks with high-pressure liquid jets is sufficient in order to create simple model specimens of slit formers providing performance of laboratory and full-scale experiments for directed rock breaking. 5. Use of high-pressure jets in mining technology also gives rise to some difficulties connected with assimilating high-pressure equipment (boosters), and it necessitates considerable attention to questions of safety techniques. 6. Testing of a model slit former ShchS-42 showed: the set of equipment for jet cutting of slits consists of a collection of simple and light structures convenient to operate; during testing, all of the jet slit former mechanisms, apart from PD-70, operated with out failure; the reliability of PD-70 appeared to be insufficiently high and it required marked changes in its construction.