Analyzing fissuring in boreholes and comparison of different methods

Vásárhelyi, Balázs and Kovács, László and Váró, Ágnes (2007) Analyzing fissuring in boreholes and comparison of different methods. Central European Geology, 50 (4). pp. 343-351. ISSN 1788-2281

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Abstract

Abstract Fissuring of rocks is frequently of greater importance in practical rock engineering operations than the strength of the intact rock. In practice boreholes are usually analyzed by the RQD method. The limitation of this method has been discussed by several authors: for example, for RQD = 0 % [that is, where the joint intercept (distance between joints in the cores) is 10 cm or less], or RQD = 100%, the RQD provides no information on the core pieces themselves. It does not matter whether the discarded pieces are soil or fresh rock pieces up to 10 cm in length. In early 2003, more than 3,000 meter-long boreholes were analyzed in parallel with two different methods: traditional RQD, and Hansági's C (or Kiruna) Method. According to the results, in the case of a very good or very poor core, the C method shows the jointing patterns better than the widely-used RQD method. The goal of this paper is to present the C method and its advandages/disadvandages. Linear regression was found for the values between 10% < RQD < 90%, but the C value is much more sensitive than the RQD. The classification of the boreholes according to C method is also presented.

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