Examples of typical errors detected in geotechnical core logging

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SRK News | Issue 57Exploration Geology: Keys to success

Andrea Russo, Geological, structural and geotechnical mapping


In the first stages of a mining project, it is a cost saving advantage to collect the geotechnical basic parameters required for the geotechnical rock mass assessment during exploration. The most used geotechnical classification systems are: Q system (Grimstad & Barton, 1993), RMR (Bieniawski, 1989), RMR (Laubscher, 1990), IRMR (Laubscher & Jakubec, 2001), and GSI (Hoek et al., 2013).

The empirical classification systems still represent valid tools, especially during exploration as a first approach for mining and geotechnical design, to define ground support, fragmentation, cavability, stope and pillar stability.

For many projects in which SRK has been involved, one of the first tasks is to review the geotechnical database proceeding from exploration-stage geotechnical core logging, and check for errors in data collection. Typical errors in core logging relate to the rock quality designation estimation for example. This includes core pieces less than 10 cm, non-intact rock, or the length of core piece from a mechanical break to a natural joint. In calculating fracture frequency, typical errors are unexplained mechanical breaks and natural joints, and discovering that the angular correction is not applied to calculate the real spacing between discontinuities. Also, we often recognise an incorrect description of the joint condition, especially affecting the roughness condition, as loggers are not considering the scale of core logging.

These errors may be due to using the wrong core logging procedure or an inexperienced worker new to exploration core logging.The described errors can lead to an erroneous geotechnical rock mass assessment that could impact all aspects of a mining project, from the mine design to the economic evaluation.

Andrea Russo: arusso@srk.cl

 

SRK Latin America