Generation of pulsations in high-speed water jets enables to increase the cutting performance of water jets due to the fact that the impact pressure generated by an impact of slug of water on the target material is considerably higher than the stagnation pressure generated by corresponding continuous jet. Highly complex dynamics of the flow of pulsating water jet was studied at the Institute of Geonics in Ostrava both theoretically with aid of CFD methods and experimentally using methods of direct measurement of pressure pulsations and impact forces generated by the jet. Cutting effects of pulsing water jets were tested extensively in laboratory to verify their performance in hard rock cutting. Interaction of the pulsing jet with rock material was studied using image analysis to define processes occurring during the interaction as well as the influence of the pulsing jet on newly created rock surface. In this paper, selected results obtained during laboratory tests of cutting of rocks by pulsing water jets are presented. Tests were performed on basalt, sandstone and granite samples and performance of the pulsing water jet was compared with the performance of continuous one under the same testing conditions.
Ornamental and dimensional stones have always played a significant role in all human activities. The need for stones both for construction and decorative purposes never ceased and became more and more important. The world production of and trade in ornamental and dimension stones is experiencing an expansive trend as the result of a broad change in the building criteria of modern industrialized architecture. The demand for natural stone materials is also growing for diversified uses in urban and interior decoration and in production design. This can be easily Concluded from the steady increase observed in the stone production since 1920s and also from the particularly significant rate of increase since 1986. The total production of ornamental stone in 1986 was 21.7 million tons whereas this figure rose to 62.4 million tons in 2000 - an increase of almost 300% in fourteen years.
Consequently, dimension stone quarrying and processing activity is undergoing a considerable technological progress during the last decades aimed at meeting both the demand of larger supplies and the requirement of better quality stone materials. Traditional methods of quarrying and processing of stones are becoming inadequate, since they are characterized by dust, noise, vibrations and waste creation. In addition to that, they are likely to cause negative effects regarding both the stone recovery and the quality of the material produced. Major damages may be induced to the rock by the destructive action of traditional technologies of stone quarrying, resulting in a higher proportion of waste as well as in a possible weakening of the mechanical properties of quarried blocks and finished products.
Considerable progress has been achieved in the sector of soft materials (like marbles, ophicalcites and travertine) due to implementation of the mechanical stone cutting using diamond tools (wires, chains or belts).