ORIGINAL PAPER The Effect of Lineation on Anisotropy in Dry and Saturated Himalayan Schistose Rock Under Brazilian Test Conditions Jagadish Kundu 1 • Bankim Mahanta 2,3 • Kripamoy Sarkar 1 • T. N. Singh 2 Received: 24 January 2017 / Accepted: 11 August 2017 Ó Springer-Verlag GmbH Austria 2017 Abstract The paper presents experimental observations of the anisotropic effect of dry and saturated lineated schis- tose rock on deformational behaviour and fracture patterns under indirect tensile loading conditions. Dry mylonitic quartz–mica schist (M-QMS) shows strength minima in between lineation orientation of 20°–30° with loading direction, whereas dry crenulated quartz–mica schist (C- QMS) shows strength minima in between 45° and 60°. Water saturation significantly reduces the failure strength and shifts the strength minima towards a higher angle. In addition, the water saturation effect induces plasticity along the lineation direction. P-wave velocity is found to be maximum along lineation direction, which continuously decreases to a minimum value across the lineation. Three types of fracture patterns, namely layer activation, central and non-central, are observed for both the rock types. For both the rock types, tensional fractures occur when the lineation is inclined at 0° and 90° to the loading direction, whereas shear and mixed-mode fractures occur at all other orientations. Fracture through the layer activation is prominent in saturated specimens compared to the dry specimens for b angle range of 15°–60° and 15°–45° in the case of M-QMS and C-QMS, respectively. Keywords Anisotropy Á Tensile strength Á Lineation Á Saturation Á Fracture pattern 1 Introduction The hilly terrains of Himachal Pradesh in India are con- sidered to have major potential for hydroelectricity due to the presence of five perennial river basins and sufficient headwater in the state. Till date, nine projects have been completed and are successfully harnessing electricity from the Himalayan Rivers. Many underground excavations have been planned and are under construction in the hills of Himachal Pradesh in order to exploit hydroelectricity. Formations in the area contain varied lithology and ani- sotropic rocks, which are always troublesome to geotech- nical engineers in underground as well as open excavations such as cut slopes (Kundu et al. 2016a; Mahanta et al. 2016a). Most metamorphic rocks and laminated sedimen- tary rocks are considered to be anisotropic and heteroge- neous (Gholami and Rasouli 2014; Hoek 1964; Khanlari et al. 2015; Mahanta et al. 2016b; McLamore and Gray 1967; Nasseri et al. 2003; Singh et al. 2015; Tavallali 2010; Tavallali and Vervoort 2013). Though stress distribution in isotropic rock is well understood, a poor understanding of anisotropic rocks affects the performance of the tunnel boring machine (TBM) as well as excavation of cavern using drill blast method (Gong et al. 2005). Boreholes, in the case of petroleum, mining and geothermal applications, are also rigorously affected by the anisotropic effect of rocks (Stjern et al. 2003). In situ stress development and the deformational behaviour of rock and materials are the most important considerations for any design and con- structions in a rock mass. However, the understanding of these aspects in isotropic rock masses has developed to a & Bankim Mahanta bankim42mahanta@gmail.com 1 Department of Applied Geology, Indian Institute of Technology (Indian School of Mines) Dhanbad, Dhanbad, Jharkhand, India 2 Department of Earth Sciences, Indian Institute of Technology Bombay, Mumbai, Maharashtra, India 3 IITB-Monash Research Academy, Indian Institute of Technology Bombay, Mumbai, Maharashtra, India 123 Rock Mech Rock Eng DOI 10.1007/s00603-017-1300-5