Rock Mechanics and Rock Engineering

, Volume 49, Issue 6, pp 2173–2180 | Cite as

Effects of Loading Direction on Failure Load Test Results for Brazilian Tests on Coal Rock

  • Yu-Wei LiEmail author
  • Jun Zhang
  • Yu Liu
Technical Note


The tensile strength of coal is a critical parameter in the design of hydraulic fracturing for coal beds, the roof supports in coal mines, and the analysis of coal mine tunnel stability (Esterhuizen et al. 2013; Liu and Ou-yang 2014; Zhang 2014). Previous researchers have investigated two methods for determining the tensile strength of coal. These are direct measurement through uniaxial tension tests and indirect measurement using the Brazilian splitting test (BST). The BST method has been adopted mainly because coal has low strength and develops a set of joints, called cleats. These cleats, along with bedding planes, make it difficult to prepare test samples for conducting direct tension tests. The BST now serves as the most common approach for measuring coal tensile strength (Poulsen and Adhikary 2013; Scholtès et al. 2011; Li 2014; Yu and Liu 1985). However, BST results tend to show a high level of discreteness due to the different orientations of the cleats and...


Coal Cleats Brazilian test Failure load 

List of symbols


Loading pressure


Sample diameter


Sample thickness


Tensile strength


Tensile stress at fracture in the horizontal direction


Angle between face cleats and the horizontal


Angle between butt cleats and the horizontal


Internal cohesion of face cleats


Angle of internal friction of face cleats


Butt cleat length


Spacing between butt cleats


Angle of internal friction of butt cleats


Internal cohesion of butt cleats


Butt cleat continuity factor


Internal cohesion of coal matrix


Angle of internal friction of coal matrix


Shear failure strength along face cleat


Shear failure strength along butt cleat



The research was supported by Natural Science Foundation of Heilongjiang Province of China (E2015035), Natural Science for Youth Foundation of China (No. 51504068) and the Youth Science Foundation of Northeast Petroleum University (2013NQ105).


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Copyright information

© Springer-Verlag Wien 2015

Authors and Affiliations

  1. 1.Department of Petroleum EngineeringNortheast Petroleum UniversityDaqingChina
  2. 2.Petroleum Engineering Research Institute of PetroChinaDagang Oilfield CompanyTianjinChina

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