ORIGINAL PAPER Determination of rock type and moisture content in flysch using TLS intensity in the Elerji quarry (south-west Slovenia) Tina Živec 1 & Andreja Anžur 2 & Timotej Verbovšek 1 Received: 18 July 2017 /Accepted: 5 February 2018 # Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Terrestrial laser scanning (TLS) was performed in tectonically undisturbed flysch in the Elerji quarry (south-west Slovenia), which represents heterogeneous rock mass with alternation of marlstone and sandstone beds. A 9.3-m-thick lithological profile was measured in detail and then compared to TLS values of reflected intensity and mineralogical composition of general marlstones and sandstones. The results showed distinguishable differences between the intensity values of marlstones and sandstones, as these two groups were found to be statistically different. It was also possible to discriminate these units with regard to their moisture content, as different values were observed for combinations of lithology and moisture content. Correlations of intensity and RGB (red, green, blue) values for the mineralogical composition of marlstones and sandstones revealed a good correlation of intensity with combined calcite and quartz content; however, such correlation is valid only for sandstones due to their bigger grain size. Larger quartz grains can scatter the laser beam and lower the correlation. The results showed that acquiring data from heterogeneous rock mass using TLS could be used for the geotechnical engineering classifica- tion of distant, inaccessible outcrops and excavated faces, based on the well-established RMR (Rock Mass Rating) and GSI (Geological Strength Index) rock mass classification systems. Both RMR and GSI classification systems classify rock mass based on rock composition, structure and surface conditions of discontinuities. Lithological segmentation of heterogeneous rocks presents, therefore, an important input parameter for their further classification. Keywords Flysch rock mass . TLS . Signal intensity . Reflectance . South-west Slovenia . Moisture content . Rock mass characterisation Introduction Flysch rock mass is described as a facies with cyclic alterna- tion of coarse- and fine-grained clastic rocks, and is characterised as a heterogeneous rock mass. Individual litho- logical units in heterogeneous rock masses have different geomechanical parameters. This results in a geotechnical be- haviour of flysch which is dependent on the proportion of individual lithological units. In rock engineering, the rock mass characterisation is im- portant, as it describes the conditions encountered along the investigated areas, including the properties of intact rocks and discontinuities, which influence the mechanical behaviour of rock masses. Designers face complex rock masses with spe- cific geomechanical parameters. Consequently, the purpose of developing rock mass classification systems was to regulate the established procedures of field investigations and provide necessary geotechnical project design approaches and guide- lines. Rock mass classification systems are based on rock mechanics, with the prime purpose for support requirements in tunnel design, such as the Rock Mass Rating (RMR) devel- oped by Bieniawski (1989) and the Q-system developed by Barton ( 1974). Both classification systems were soon established as part of the workflow in engineering geology for rock mass characterisation. After using them for many years, limitations and reliability issues have been emphasised by several authors (Fookes 1997; Ranasooriya 2009). Applying the RMR and Q-system was especially limited in * Tina Živec tina.zivec@gmail.com 1 Faculty of Natural Sciences and Engineering, Department of Geology, University of Ljubljana, Privoz 11, 1000 Ljubljana, Slovenia 2 DFG Consulting d.o.o., Pivovarniška ulica 8, 1000 Ljubljana, Slovenia Bulletin of Engineering Geology and the Environment https://doi.org/10.1007/s10064-018-1245-2