An investigation into the mechanical cutting of rock materials with particular reference to fracture mechanics

Abstract

A comprehensive series of laboratory rock cutting tests were carried out on both core specimens and large blocks of different rock material. Five types of rock were used, Springwell sandstone, Matlock limestone, Welton chalk, Pennant sandstone and Teesdale Whinstone. As part of the investigations the influence of physical and mechanical properties of rock materials on their cuttability has been assessed during the early part of the research programme. Furthermore, a study was undertaken to investigate the influence of rock discontinuities on cutting parameters employing different degrees of saturation. The Finite Element Method has been used to identify the optimum geometric configuration for rock cutting experiments. Furthermore, it was used to model rock cutting operations and was proven that it is possible to simulate the failure conditions existing in rock cutting experiments by using Finite Element analysis. Rock fracture toughness as a rock property was found to have a good correlation with cutting parameters. ISRM suggested methods, short rod and three point test (Chevron Bend Test) were used in determining rock fracture toughness. In addition, rock fracture toughness was also compared with other characteristics of rock such as uniaxial compressive strength, tensile strength, shore hardness and NCB cone indenter index.