Interpretation of the results of mechanical rock properties testing with respect to mining methods

Abstract

The article is concerned with the influence of cutting direction on rock cutting resistance, which is a frequently neglected issue. Investigations into the mechanical properties of the unmined rock are carried out at the stage of works involving deposit identification or mining method selection. The most frequently performed tests include uniaxial compressive strength and, sometimes, mineability of the unmined rock. The results of these tests are strongly correlated with the direction in which they have been carried out. Additionally, depending on the method of mining (cutting, planning, drilling) and the site of sampling (sidewall, face), the direction of cutting is usually inconsistent with the direction of testing. In the article, the author has drawn attention to the commonly applied directions of cutting and presented recommendations on the direction of testing to be followed in underground mining plants in order to properly determine the unmined rock properties. The results of the author's research into a hard coal mine, rock salt and sandstones, shales and dolomites, conducted in three perpendicular directions have also been quoted. Furthermore, the subject literature in this field has been reviewed, and selected investigations presented. The research results confirm that depending on the cutting direction, there may be considerable, even fivefold differences in the value of mechanical properties. Knowing the planned cutting direction and the direction of testing is a necessary condition for interpreting the results in a proper way, choosing a suitable mining technique, the type of tools and process parameters, as well as achieving the projected efficiency and energy consumption.