Advertisement

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

Introduction

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...

Keywords

Coal Cleats Brazilian test Failure load 

List of symbols

P

Loading pressure

D

Sample diameter

L

Sample thickness

σT

Tensile strength

σx

Tensile stress at fracture in the horizontal direction

α

Angle between face cleats and the horizontal

β

Angle between butt cleats and the horizontal

Cα

Internal cohesion of face cleats

φα

Angle of internal friction of face cleats

a

Butt cleat length

b

Spacing between butt cleats

φβ

Angle of internal friction of butt cleats

Cβ

Internal cohesion of butt cleats

λ

Butt cleat continuity factor

C0

Internal cohesion of coal matrix

φ0

Angle of internal friction of coal matrix

σTα

Shear failure strength along face cleat

σTβ

Shear failure strength along butt cleat

Notes

Acknowledgments

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).

References

  1. Banks SL, Schwartz J (2002) Fracture testing of Brazilian disk sandwich specimens. Int J Frac 118:191–209CrossRefGoogle Scholar
  2. Dinh QD, Heinz K (2014) Numerical simulations and interpretations of Brazilian tensile tests on transversely isotropic rocks. Int J Rock Mech Min Sci 71:53–63Google Scholar
  3. Esterhuizen GS, Bajpayee TS, Ellenberger JL (2013) Practical estimation of rock properties for modeling bedded coal mine strata using the Coal Mine Roof Rating. ARMA 13–154Google Scholar
  4. Fu JH, Huang BX, Liu CY, Yang W, Wang LF (2011) Study on acoustic emission features of coal sample Brazilian splitting. Chin J Coal Sci Tech 39:25–28Google Scholar
  5. Gao FQ, Stead D, Kang HP (2014) Numerical investigation of the scale effect and anisotropy in the strength and deformability of coal. Int J Coal Geo 136:25–37CrossRefGoogle Scholar
  6. Jennings JE (1970) A mathematical theory for the calculation of the stability of open cut mines. In: Johannesburg (ed) Proceedings of the symposium on the theoretical background to the planning of open pit mines, pp 87–102Google Scholar
  7. Laubach SE, Marrett RA, Olson JE (1998) Characteristics and origins of coal cleat: A review. Int J Coal Geo 35:175–207CrossRefGoogle Scholar
  8. Li YW (2014) Study on mechanical behavior and fracture cracking mechanism in hydraulic fracturing of coalbed with cleats. PhD dissertation, Northeast Petroleum University, ChinaGoogle Scholar
  9. Li N, Sun ZY, Song DZ (2013) Experimental study on acoustic emission characteristic of raw coal failure under splitting test and uniaxial compression. Chin J Coal Mine Saf 10:45–51Google Scholar
  10. Liu YW, Ou-yang WP (2014) Numerical well test for well with finite conductivity vertical fracture in coalbed. Chin J App Math Mech 35:729–740CrossRefGoogle Scholar
  11. Liu KD, Liu QS, Zhu YG (2013a) Experimental study of coal considering directivity effect of bedding plane under Brazilian splitting and uniaxial compression. Chin J Rock Mech Eng 32:308–315Google Scholar
  12. Liu YS, Fu HL, Wu YM (2013b) Study on Brazilian splitting test for slate based on single weak plane theory. Chin J Coal Society 38:1775–1780Google Scholar
  13. Mankour A, Bouiadjra BB, Belhouari M (2008) Brazilian disk test simulation intended for the study of interfacial cracks in bi-materials. Comput Mater Sci 43:696–699CrossRefGoogle Scholar
  14. Mikl-Resch MJ, Antretter T, Gimpel M (2015) Numerical calibration of a yield limit function for rock materials by means of the Brazilian test and the uniaxial compression test. Int J Rock Mech Min Sci 74:24–29Google Scholar
  15. Muskhelishili HN (1954) Several basic problems of mathematical theory of elasticity. Soviet Academy of Sciences Press, MoscowGoogle Scholar
  16. Poulsen B, Adhikary DP (2013) A numerical study of the scale effect in coal strength. Int J Rock Mech Min Sci 63:62–71Google Scholar
  17. Qu XR, Wu JW, Shen SH (2014) Experimental study on calculation of the tensile strength of coal based on the point load test. Chin J Eng Geo 22:8–11Google Scholar
  18. Scholtès L, Donzé FV, Khanal M (2011) Scale effects on strength of geomaterials, case study: Coal. J Mech Phy Solids 59:1131–1146CrossRefGoogle Scholar
  19. Simpson NDJ, Stroisz A, Bauer A, Vervoort A, Holt RM (2014) Failure mechanics of anisotropic shale during Brazilian tests. ARMA 14–7399Google Scholar
  20. Tan XS, Xian XF (1986) Analysis and determination of multiple groups of jointed mass strength conditions. Chin J Mine Cons Tech 38:38–41Google Scholar
  21. Tan X, Konietzky H, Fruhwirt T (2014) Brazilian tests on transversely isotropic rocks: laboratory testing and numerical simulations. Rock Mech Rock Eng. doi: 10.1007/s00603-014-0629-2 Google Scholar
  22. Tavallali A, Vervoort A (2010a) Effect of layer orientation on the failure of layered sandstone under Brazilian test conditions. Int J Rock Mech Min Sci 47(2):313–322CrossRefGoogle Scholar
  23. Tavallali A, Vervoort A (2010b) Failure of layered sandstone under Brazilian test conditions: effect of micro-scale parameters on macro-scale behaviour. Rock Mech Rock Eng 43:641–653CrossRefGoogle Scholar
  24. Tremain CM, Laubach SE, Whitehead NH (1991) Coal fracture (cleat) patterns in upper cretaceous fruitland formation, San Juan Basin, Colorado and New Mexico: implications for exploration and development. In: Schwochow S, Murray DK, Fahy MF (eds) Coalbed methane of Western North America. Rk. Mt. Assoc. Geol., pp 49–59Google Scholar
  25. Vervoort A, Min KB, Konietzky H, Cho JW, Debecker B, Dinh QD, Frühwirt T, Tavallali A (2014) Fracturing of transversely isotropic rock under Brazilian test conditions. Int J Rock Mech Min Sci 70:343–352Google Scholar
  26. Wang YX, Cao P (2007) Analysis of influence on errors in Brazilian test of hard rock. Chin J Geo Eng 29:1085–1089Google Scholar
  27. Whittles DN, Yasar E, Reddish DJ, Lloyd PW (2002) Anisotropic strength and stiffness properties of some UK coal measure siltstones. J Eng Geo Hydro 35:155–166CrossRefGoogle Scholar
  28. Wu JW, Yan LH (2004) Comparison study on two kinds of indirect measurement methods of tensile strength of coal in lab. Chin J Rock Mech Eng 23:643–1647Google Scholar
  29. Yan ZF (2009) Research of the coal mechanical properties coal reservoir fracturing simulation in Jincheng district, Shanxi Province. PhD dissertation, China University of Geosciences, BeijingGoogle Scholar
  30. Yan LH, Wu JW (2002) Test and analysis of tensile strength of coal in Huaibei Yangzhuang coal mine. Chin J Coal Sci Tech 30:39–41Google Scholar
  31. Yang Q, Chen YR, Liu YR (2008) Theory and method of determining equivalent strength parameters of rock mass. Chin J Rock Mech Eng 27:1993–1999Google Scholar
  32. Yu ZH, Liu TQ (1985) Rock Mass Mechanics. China Coal Industry Press, BeijingGoogle Scholar
  33. Zhang JC (2014) Numerical simulation of hydraulic fracturing coalbed methane reservoir. Fuel 136:57–61CrossRefGoogle Scholar

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

Personalised recommendations