Abstract

Rock abrasiveness immediately affects the wear of cutting indenters of the drilling bits. Rock abrasiveness is ability of rock to wear down the cutting tool during the interaction between the indenter and the rock in the mechanical rock cutting process. There are several methods for estimating the abrasiveness of rocks and minerals. One of the methods of rock abrasiveness testing is the method according to the Slovak technical norm ON 44 1121. The concept of the test resides in the determination of weight loss of normalized metal pins during its circular motion on a surface of a tested rock sample under constant thrust force. The abrasiveness according the norm ON 44 1121 will be termed as „pin rock abrasiveness" FV. The experimental results of the determination of FV abrasiveness were compared to the values of the CERCHAR Abrasivity Index (CAI).

1 The Effect of Anisotropy on Rock Strength Assessment
1.1 Defining "anisotropic behaviour"

Mechanical cutting of rocks is affected by rock properties, which are represented by several mechanical and technological parameters. Rock abrasiveness belongs to such parameters. Rock abrasiveness is ability of rock to wear down the working tool during the interaction between the working indenter and the rock in the mechanical rock cutting process. The cutting indenter is worn down during the interaction, which changes its geometric dimensions, causing the enlargement of a contact area between the tool and the rock surface. Change of these dimensions leads to the change of the advance rate of the tool and the specific cutting energy. Rock abrasiveness immediately affects the wear of cutting indenters of the tool. The wear of indenter exhibits in the decrease of the instantaneous drilling rate and in the increase of the specific cutting energy, which both directly affect the economic issues of mechanical cutting. The applied regime of rock cutting affects the wear of indenter substantially. The smallest intensity of wear occurs in the cutting regime, which is the argument of minimum of specific cutting energy. In such regime, the indenter should reach the greatest lifetime, if considering only the effect of wear (Krúpa & Lazarová 2008).

Intensity and wear rate depend on several simultaneously acting factors in the interaction of the indenter and the rock. The most important factors are:

This content is only available via PDF.
You can access this article if you purchase or spend a download.