ORIGINAL PAPER Estimating engineering properties of igneous rocks using semi-automatic petrographic analysis Saeed Aligholi 1,2 & Gholam Reza Lashkaripour 1 & Mohammad Ghafoori 1 Received: 15 December 2017 /Accepted: 7 May 2018 # Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract An experimental study that contributes to the understanding of the relationships between petrographic features and engineering properties of igneous rocks is conducted. To this end, a wide range of igneous rocks were tested for their engineering properties including abrasivity (Cerchar abrasivity index), mechanical (point load strength index Is (50) ), basic physical (dry density and porosity) and dynamic (P-wave velocity) characteristics. Moreover, a semi-automatic method has been developed to analyze petrographic data that relies on digital image acquisition from representative parts of representative thin sections of samples, semi-automatic image segmentation and image analysis. The method quantifies 18 petrographic features including size descrip- tors (area, perimeter, equivalent circular diameter, minimum Feret’ s diameter, maximum Feret’ s diameter), shape descriptors (elongation, orientation, eccentricity, compactness, rectangularity, solidity, convexity), rock fabric coefficients (index of interlocking, index of grain size homogeneity, texture coefficient) and mineralogical indices (saturation index, feldspathic index, colouration index). The Pearson’ s correlation coefficient and multivariate regression analysis are employed to analyze the relationships between extracted petrographic features and engineering properties. In general, fine-grained and basic igneous rocks compared to the acidic and coarse-grained ones possess higher engineering quality and lower abrasiveness potential. The results imply that mineralogical composition tends to be more important than rock fabric characteristics in determining the engineering properties of igneous rocks. Furthermore, among rock fabric characteristics, size descriptors have significant influ- ence on the engineering properties. Overall, it was found that mineralogical composition and rock fabric characteristics provide a suitable complement to reliably predict engineering properties of igneous rocks. Keywords Igneous rock . Index properties . Cerchar abrasivity index . Image processing . Petrographic image analysis . Multivariate regression model Introduction It is believed that engineering properties of intact rocks are some functions of their petrographic features and physical characteristics. Rocks are mostly composed of varying per- centages of minerals with different grain size, grain shape and micro-fabric characteristics (Aligholi et al. 2017a). Many research studies have dealt with the relationship be- tween rock fabric and mechanical properties of different rock types (Olsson 1974; Hugman and Friedman 1979; Howarth and Rowlands 1987; Hatzor and Palchik 1997; Akesson et al. 2003; Jeng et al. 2004;Přikryl 2001, 2006; Ozturk and Nasuf 2013; Tandon and Gupta 2013; Pappalardo et al. 2016). Rock fabric properties affecting the mechanical performance of rocks are grain size, shape and degree of interlocking, porosity (crack and pore), grain orientation and the nature of grain boundaries (Howarth and Rowlands 1987). On the other hand, some research studies were performed to investigate the rela- tionship between mineral constituents and mechanical behav- ior of different rocks (Bell 1978; Fahy and Guccione 1979; Gunsallus and Kulhawy 1984; Ulusay et al. 1994; Tugrul and Zarif 1999 ; Zorlu et al. 2008 ; Yilmaz et al. 2011 ; Hashemnejad et al. 2016; Moradizadeh et al. 2016). As noted by Howarth and Rowlands (1987), as well as Tandon and Gupta (2013), some of these studies reported contradict out- comes, for example about the relationship between quartz * Gholam Reza Lashkaripour lashkaripour@um.ac.ir 1 Department of Geology, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran 2 Department of Civil Engineering, Monash University, Clayton, VIC 3800, Australia Bulletin of Engineering Geology and the Environment https://doi.org/10.1007/s10064-018-1305-7 Downloaded from http://iranpaper.ir http://www.itrans24.com/landing1.html