Abstract
Rock brittleness is an important index evaluating geotechnical stability and failure mode, and it is also influenced by pore fluid pressure, especially in deep underground mining. To evaluate the brittleness from stress–strain curves of uniaxial compression, uniaxial compressive tests were carried out on water-pressurized coal samples, and a new energetic brittleness index was proposed. The saturated coal samples were classified into brittle, transitional, and ductile groups according to the stress–strain behavior of uniaxial compression. It is found that the pore water enhanced brittle coal strength, but reduced strength of transitional and ductile coal. Compared to ductile and transitional coal samples, the brittle coal is of a lower elastic modulus, but showing a higher capability of elastic energy storage prior to peak stress. For brittle coal, significant acoustic emission (AE) events occurred at the peak stress, but for ductile and transitional coal substantial acoustic emission occurred in the post-peak-stress stage suggesting significant elastic energy storage and insignificant energy dissipation feature prior to peak stress. Assuming that the total energy consists of the accumulated elastic energy prior to the crack coalescence point, and the dissipated energy after the crack coalescence point, a new brittleness index was proposed based on strain energy integration from stress–strain curves of uniaxial compression. The new brittleness index shows great superiority in avoiding the subjective mechanical parameter determination and can be conveniently calculated from uniaxial compression tests.
Similar content being viewed by others
Abbreviations
- E :
-
Elastic modulus
- E i :
-
Unloaded or loaded elastic modulus
- \(\nu\) :
-
Poisson’s ratio
- M :
-
Post-peak modulus
- W :
-
Total energy absorbed
- W e :
-
Elastic energy
- W d :
-
Dissipated energy due to microcrack development
- W S,R :
-
Total energy of pre-peak and post-peak stages
- σt :
-
Tensile strength
- σc :
-
Uniaxial compressive strength
- K :
-
Modulus of yield platform
- W r :
-
Rupture energy at post-peak stage
- ε E ,m :
-
Residual and peak-stress strain
- W m :
-
Maximum strain energy
- ε 0 ,r :
-
Strain of initial point and ending point
- ε cd :
-
Strain coalescence point
- D 0,1,2 :
-
Brittleness indexes
References
Ai C, Zhang J, Li YW, Jia Z, Yang XL, Wang JG (2016) Estimation criteria for rock brittleness based on energy analysis during the rupturing process. Rock Mech Rock Eng 12(49):4681–4698
Altindag R (2010) Assessment of some brittleness indexes in rock-drilling efficiency. Rock Mech Rock Eng 3(43):361–370
Altindag R, Guney A (2010) Predicting the relationships between brittleness and mechanical properties (UCS, TS and SH) of rocks. Sci Res Essays 16(5):35–39
Brace WF, Paulding BW, Scholz CH (1966) Dilatancy in the fracture of crystalline Rocks. J Geophys Res 16(71):3939–3953
Cai M, Kaiser PK (2014) In-situ rock spalling strength near excavation boundaries. Rock Mech Rock Eng 2(47):659–675
Cai M, Kaiser PK, Tasaka Y, Maejima T, Morioka H, Minami M (2004) Generalized crack initiation and crack damage stress thresholds of brittle rock masses near underground excavations. Int J Rock Mech Min 5(41):833–847
Chen G, Li T, Guo F, Wang Y (2017) Brittle mechanical characteristics of hard rock exposed to moisture. B Eng Geol Environ 1(76):219–230
Chen Z, He C, Ma G, Xu G, Ma C (2019) Energy damage evolution mechanism of rock and its application tobrittleness evaluation. Rock Mech Rock Eng 4(52):1265–1274
Costin LS (1988) Damage mechanics in the post-failure regime. Mech Mater 2(4):149–160
Erguler ZA, Ulusay R (2009) Water-induced variations in mechanical properties of clay-bearing rocks. Int J Rock Mech Min Sci 2(46):355–370
Feng R, Zhang Y, Rezagholilou A, Roshan H, Sarmadivaleh M (2019) Brittleness index: from conventional to hydraulic fracturing energy model. Rock Mech Rock Eng 53:739–752
Hajiabdolmajid V, Kaiser P (2003) Brittleness of rock and stability assessment in hard rock tunneling. Tunn Undergr space Technol 1(18):35–48
Heidari M, Khanlari GR, Torabi-Kaveh M, Kargarian S, Saneie S (2014) Effect of porosity on rock brittleness. Rock Mech Rock Eng 2(47):785–790
Hucka V, Das B (1974) Brittleness determination of rocks by different methods. Int J Rock Mech Min Sci 10(11):389–392
Lawn BR, Marshall DB (2010) Hardness, toughness, and brittleness: an indentation analysis. J Am Ceram Soc 7–8(62):347–350
Li YW, Long M, Z LH, Li Wei, Wanchun Z, (2018) Brittleness evaluation of coal based on statistical damage and energy evolution theory. J Petrol Sci Eng 172:753–763
Liu GF, Feng XT, Feng GL, Chen BR, Chen DF, Duan SQ (2016) A m ethod for dynamic risk assessment and management of rockbursts in drill and blast tunnels. Rock Mech Rock Eng 8(49):3257–3279
Martin CDCNA (1994) The Progressive fracture of Lac du Bonnet Granite. Int J Rock Mech Min Sci 31(6):643–659
Meng F, Zhou H, Zhang C, Xu R, Lu J (2015) Evaluation methodology of brittleness of rock based on post-peak stress–strain curves. Rock Mech Rock Eng 5(48):1787–1805
Munoz H, Taheri A, Chanda EK (2016) Rock drilling performance evaluation by an energy dissipation based rock brittleness index. Rock Mech Rock Eng 8(49):3343–3355
Nicksiar M, Martin CD (2012) Evaluation of methods for determining crack initiation in compression tests on low-porosity rocks. Rock Mech Rock Eng 4(45):607–617
Paterson MS, Wong T (2005) Experimental rock deformation - the brittle field. Springer, Berlin, Heideberg, pp 17–44
Perera MSA, Ranjith PG, Peter M (2011) Effects of saturation medium and pressure on strength parameters of Latrobe Valley brown coal: carbon dioxide, water and nitrogen saturations. Energy 12(36):6941–6947
Poulsen BA, Shen B, Williams DJ, Huddlestone-Holmes C, Erarslan N, Qin J (2014) Strength reduction on saturation of coal and coal measures rocks with implications for coal pillar strength. Int J Rock Mech Min Sci 71:41–52
Sainsbury BL (2019) Consideration of the volumetric changes that accompany rock mass failure. Rock Mech Rock Eng 1(52):277–281
Stacey TR (2016) Addressing the consequences of dynamic rock failure in underground excavations. Rock Mechs Rock Eng 10(49):4091–4101
Tarasov B, Potvin Y (2012) Absolute, relative and intrinsic rock brittleness at compressure. Min Technol 121(4):218–225
Tarasov B, Potvin Y (2013) Universal criteria for rock brittleness estimation under triaxial compression. Int J Rock Mech Sci 4(59):57–69
Tarasov BG, Randolph MF (2011) Superbrittleness of rocks and earthquake activity. Int J Rock Mech Min Sci 6(48):888–898
Wang JA, Park HD (2001) Comprehensive prediction of rockburst based on analysis of strain energy in rocks. Tunn Undergr space Technol 1(16):49–57
Wang Y, Xiao LI, Yanfang WU, Yuxing B, Shouding LI, Jianming HE, Zhang B (2014) Research on relationship between crack initiation stress level and brittleness indexes for brittle rocks. Chin J Rock Mech 33(2):264–275
Wasantha PLP, Ranjith PG (2014) Water-weakening behavior of Hawkesbury sandstone in brittle regime. Eng Geol 178): 91–101.
White GW (1959) Glossary of geology and related sciences by JV Howell. Isis 50(3):269–270
Xie HP, Li LY, Peng RD, Ju Y (2009) Energy analysis and criteria for structural failure of rocks. J Rock Mech Geo Eng 1(1):11–20
Xue L, Qin S, Sun Q, Wang Y, Lee LM, Li W (2014) A Study on crack damage stress thresholds of different rock types based on uniaxial compression tests. Rock Mech Rock Eng 4(47):1183–1195
Yao Q, Li X, Zhou J, Ju M, Chong Z, Zhao B (2015) Experimental study of strength characteristics of coal specimens after water intrusion. Arab J Geosci 9(8):6779–6789
Yao Q, Tian C, Ju M, Liang S, Liu Y, Li X (2016) Effects of water intrusion on mechanical properties of and crack propagation in Coal. Rock Mech Rock Eng 12(49):1–11
Zhang J, Ai C, Li YW, Che MG, Gao R, Zeng J (2018) Energy-based brittleness index and acoustic emission characteristics of anisotropic coal under triaxial stress condition. Rock Mech Rock Eng 51(11):3343–3360
Zhang Z, Xie H, Zhang R, Zhang Z, Gao M, Jia Z, Xie J (2019) Deformation damage and energy evolution characteristics of coal at different depths. Rock Mech Rock Eng 5(52):1491–1503
Zhao XG, Cai M, Wang J, Ma LK (2013) Damage stress and acoustic emission characteristics of the Beishan granite. Int J Rock Mech Min 64:258–269
Zhong C, Zhang Z, Ranjith PG, Lu Y, Choi X (2019) The role of pore water plays in coal under uniaxial cyclic loading. Eng Geol 257:105125
Zhou H, Chen J, Lu J, Jiang Y, Meng F (2018) A new rock brittleness evaluation index based on the internal friction angle and class I stress–strain curve. Rock Mech Rock Eng 7(51):2309–2316
Acknowledgements
This study was financially supported by the National Natural Science Foundation of China (Grant No. 51674047 and 51911530152), the National Science Fund for Distinguished Young Scholars (Grant No. 51625401), and the Program for Changjiang Scholars and Innovative Research Team in University (IRT_17R112).
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Liu, X., Zhang, Z., Ge, Z. et al. Brittleness Evaluation of Saturated Coal Based on Energy Method from Stress–Strain Curves of Uniaxial Compression. Rock Mech Rock Eng 54, 3193–3207 (2021). https://doi.org/10.1007/s00603-021-02462-7
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00603-021-02462-7