ORIGINAL PAPER Correlations of in situ modulus of deformation with elastic modulus of intact core specimens and RMR values of andesitic rocks: a case study of the İzmir subway line C. Kıncal 1 & M. Y. Koca 1 Received: 28 May 2018 /Accepted: 1 December 2018 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract The main purpose of this paper is to obtain the rock mass rating (RMR) from different methods considering either the elastic modulus of intact rock specimens (E i ) and the modulus of deformation of andesitic rock mass (E M ) or only the value of the in situ modulus of deformation, and to compare these values. This paper also presents comparisons between the values of deformation modulus obtained from pressuremeter tests in andesitic rock mass and the values of elastic modulus of intact rock core specimens retrieved from the same boreholes and depths at which pressuremeter tests have been carried out. The pressuremeter tests were conducted on weathered and fractured andesites observed along the İzmir subway route. Correlations between in situ moduli of deformation gathered from 32 pressuremeter test points and calculated RMR values for the andesites at the railway elevation of the İzmir subway were obtained as follows: E MPT = 0.0237 × e (0.0975 × RMR) ,R 2 = 0.848 and RMR = 38.043 × E MPT (0.3291) ,R 2 = 0.77. Finally, the results of comparisons between the modulus of deformation obtained from pressuremeter tests and the geomechanical quality of the rock mass, discontinuity effect, and the basic intact rock properties such as uniaxial compressive strength (UCS) and elastic modulus (E i ) have been discussed. In addition, engineering geological conditions of the andesitic rock masses located at the railway elevation of the İzmir subway were determined in detail. Keywords Andesitic rock mass . Weathering grade . Pressuremeter test . Modulus of deformation . RMR Introduction İzmir is the third largest city in Turkey, with a population of over five million and is located in western Turkey. A general transportation project is planned to solve the everyday increas- ing transportation problems of the city. The first phase of the İzmir subway passes through the most heavily populated and historically protected areas between the Fahrettin Altay and Basmane districts of the city (Fig. 1). This work includes engineering geological studies along a 9.3-km length of the İzmir subway route. This 9.3-km part of the subway comprises 2.4 km of cut and cover tunnel, mainly of fill, alluvium, and flysch, a 4.1-km deep tunnel mainly of volcanic rocks with andesitic character and Neogene aged sedimentary rocks, and remaining struc- tures are made up of 2.4 km of viaduct and 400 m of surface rail in alluvium. A geological cross-section of the scheme is depicted in Fig 2. While cut and cover tunneling is planned for the alluvium infill and flysch in the western part, deep tunnel- ing is planned for the Neogene aged sedimentary and volcanic rocks in the middle part and viaduct, and other structures are planned in the alluvium in the eastern part of the subway (Fig. 2). The total length of the subway route is 37 km and it spans a major part of the İzmir shoreline. Seventeen of the 91 boreholes drilled along the İzmir sub- way line were penetrated andesitic rocks just on or near the railway’ s elevation (Fig. 2). Descriptions of the core speci- mens and in situ tests performed during drilling facilitate an understanding of the excavation profile of the İzmir subway before the actual tunneling activity. In situ tests were conduct- ed in each borehole along the zone affected by the tunnel excavation. Afterwards, graphs showing the relationships be- tween the value of limit pressure (P L ) obtained from the Menard pressuremeter test (MPT) and the elastic modulus of * C. Kıncal cem.kincal@deu.edu.tr 1 Geological Engineering Department, Engineering Faculty, Dokuz Eylül University, Tinaztepe Campus, Buca, İzmir, Turkey Bulletin of Engineering Geology and the Environment https://doi.org/10.1007/s10064-018-01443-5