Correlation of TBM and drilling machine performances with rock brittleness

The correlations between three different methods of measuring brittleness and both drillability and borability were statistically investigated using the raw data obtained from the experimental works of different researchers. Strong exponential relationships between the penetration rates of tunnel boring machine (TBM) and the brittleness of B-1 (the ratio of compressive strength to tensile strength) and B-2 (the ratio of compressive strength minus tensile strength to compressive strength plus tensile strength) were found. There is no correlation between the penetration rates of the diamond drilling tool and the brittleness values. Strong exponential correlations exist between the penetration rates of rotary drills and the brittleness of B, and B2. However, no correlation between the penetration rate of rotary drills and the brittleness of B-3 (the product of percentage of fines in impact strength test and compressive strength) was found. The penetration rate of percussive drills does not exhibit a correlation with the brittleness of B, and B2, but the penetration rate of percussive drills is strongly correlated with the brittleness of B-3. It was concluded that each method of measuring brittleness has its usage in rock excavation depending on practical utility. (C) 2002 Published by Elsevier Science B.V.