Interpretation of variability of rock mass rating by geostatistical analysis: a case study in Western Turkey
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ORIGINAL PAPER
Interpretation of variability of rock mass rating by geostatistical analysis: a case study in Western Turkey H. Ozturk 1 & M. Erkayaoglu 1 Received: 17 November 2017 / Accepted: 18 June 2018 # Saudi Society for Geosciences 2018
Abstract Geotechnical interpretation of drillholes for rock mass characterization is commonly based on the engineering judgment. This might result in misrepresentation of the rock mass at unsampled locations. This paper investigates the reproducibility of the spatial variability of rock mass quality (rock mass rating, RMR) using geostatistics. Geotechnical data from an exploratory phase mining project in Western Turkey that covers 2.7 km depth with a total of 14 drillholes composed of 700 samples was used to perform a geostatistical analysis. RMR values of positions, where geotechnical logging was missing, were estimated by applying inverse distance weighting (IDW) and the ordinary kriging (OK) methods. The validation process showed that the OK method is consistently estimating the RMR values better than IDW. The spatial variability of RMR values by geostatistical analysis could provide valuable information in the design and development of underground or surface structures. Keywords Geostatistics . Inverse distance weighting . IDW . Ordinary kriging . OK . Mining . RMR
Introduction Feasibility and preliminary design stages of mining and civil engineering projects commonly benefit from following rock mass classifications, especially when the geomechanical properties of the rock mass and its stress characteristics are limited. There are various rock mass classifications that are commonly used to represent a rock mass according to composition and other characteristics, to conduct preliminary evaluations about support requirements, and to estimate the strength and deformation characteristics of the rock mass for either surface- or underground-related projects such as, slopes, tunnels, mines, caverns, and foundations. The rock mass rating (RMR) (Bieniawski 1989) is commonly used in projects during their design and implementation by assessing geomechanical attributes and stability conditions. A detailed literature review of classification systems can be found at Gokceoglu and Aksoy (2000). RMR has been used to compile the stable spans of unsupported excavations (Lang
* H. Ozturk [email protected] 1
Department of Mining Engineering, Middle East Technical University, Ankara, Turkey
1994; Brady et al. 2005), stand-up times of unsupported excavations, ground support conditions of various spans (Bieniawski 1989), mine pillar design (Esterhuizen 2006), cavability of a rock mass (Laubscher 1990), stable pit slope angles (Duran and Douglas 2000), and the determination of the deformation modulus for various design applications (Aydan et al. 2014). A complete list of direct relations between RMR and geomechanical properties (deformation modulus, cohesion, internal friction angle, uniaxial compressive strength, and Poisson’s ratio) of rock mass can be found in Aydan et al. 2014. Rock m
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