Pore structure is the key factor that affects the adsorption/desorption of coal. In order to study the change characteristics of pore structure in structural anisotropic coal under different impact loads, the low- temperature liquid nitrogen adsorption tests were carried out after the split Hopkinson bar (SHPB) impact, then the pore structure variation and fractal dimension were calculated and analyzed. The results show that before and after impact, the adsorption isotherms change from type II (raw coal) to type III (impacted coal). With impact loads increasing, adsorption and desorption isotherms change from hysteresis loops to overlap which are determined by open pore structure and dead end pore structure. Meanwhile, mesoporous and micropores in coal samples are much more obviously damaged by larger impact load, and the adsorption capacity becomes smaller, especially for coal samples in parallel to the bedding. Pore volume mainly distribute in mesoporous and macropores, and SSA mainly distribute in mesoporous and micropores. On the whole, the pore volume and SSA decrease with the increase of impact load. Not only pore volume but also SSA in perpendicular to the bedding are larger than that in parallel to the bedding under same impact load. Fractal dimension D2 decreases with impact load increasing, which causes the adsorption capacity linearly reduces.
This is a preview of subscription content, log in to check access.
Buy single article
Instant access to the full article PDF.
Price includes VAT for USA
Subscribe to journal
Immediate online access to all issues from 2019. Subscription will auto renew annually.
This is the net price. Taxes to be calculated in checkout.
Ai DH, Zhao YC, Wang QF, Li CW (2019) Experimental and numerical investigation of crack propagation and dynamic properties of rock in SHPB indirect tension test. Int J Impact Eng 126:135–146
Everett DH, Stone FS (1958) The structure and properties of porous materials. In: Proceedings of the tenth symposium of the Colston Research Society held in the University of Bristol. Butterworths Scientific Publications, London
Frew DJ, Forrestal MJ, Chen W (2001) A split hopkinson pressure bar technique to determine compressive stress-strain data for rock materials. Exp Mech 41:40–46
Fu YK, Xie BJ, Wang QF (2013) Dynamic mechanical constitutive model of the coal. J China Coal Soc 38(10):1769–1774
Gong M, Zhang FW, Wen B (2012) Numerical simulation and application on blasting to improve gas drainage rate in floor rock of coal roadway. J China Coal Soc 37(6):972–977
Gray GT (ed) (2012) High-strain-rate testing of materials: the Split–Hopkinson pressure bar. In: Characterization of materials. Wiley, New Jersey, pp 1–15
Gregg SJ (1982) Adsorption of gases-tool for the study of the texture of solids. Stud Surf Sci Catal 10:153–164
Guo HJ, Yuan L, Cheng YP, Wang K, Xu C (2019) Experimental investigation on coal pore and fracture characteristics based on fractal theory. Powder Technol 346:341–349
Ibrahim E, Han Z (2019) Impact perforation of aluminium Cymat foam. Int J Mech Sci 150:79–89
Li H, Shi SL, Lin BQ, Lu JX, Ye Q, Lu Y, Wang Z, Hong YD, Zhu XN (2019) Effects of microwave-assisted pyrolysis on the microstructure of bituminous coals. Energy. https://doi.org/10.1016/j.energy.2019.115986
Liu XH, Dai F, Zhang R, Liu JF (2015) Static and dynamic uniaxial compression tests on coal rock considering the bedding directivity. Environ Earth Sci 73:5933–5949
Liu SH, Li FM, Lan H, Pan JF, Du TT (2013) Experimental study of failure characteristics and mechanism of coal under coupled static and dynamic loads. Chin J Rock Mech Eng 32(S2):3749–3759
Liu XH, Zhang R, Liu JF (2012) Dynamic test study of coal rock under different strain rates. J China Coal Soc 33(9):1528–1534
Lu GW, Wang JL, Wei CT, Song Y, Yan GY, Zhang JJ, Chen GH (2018) Pore fractal model applicability and fractal characteristics of seepage and adsorption pores in middle rank tectonic deformed coals from the Huaibei coal field. J Petrol Sci Eng 171:808–817
Mendhe VA, Bannerjee M, Varma AK, Kamble AD, Mishra S, Singh BD (2017) Fractal and pore dispositions of coal seams with significance to coalbed methane plays of East Bokaro, Jharkhand, India. J Nat Gas Sci Eng 38:412–433
Mu CM, Wang HL, Huang WY, Kuang CJ (2013) Increasing permeability mechanism using directional cumulative blasting in coal seams with high concentration of gas and low permeability. Rock and Soil Mech 34(9):2496–2500
Niu QH, Pan JN, Jin Y, Jin Y, Wang HC, Li M, Ji ZM, Wang K, Wang ZZ (2019) Fractal study of adsorption-pores in pulverized coals with various metamorphism degrees using N2 adsorption, X-ray scattering and image analysis methods. J Petrol Sci Eng 176:584–593
Pan JN, Niu QH, Wang K, Shi XH, Li M (2018) The closed pores of tectonically deformed coal studied by small-angle X-ray scattering and liquid nitrogen adsorption. Micropor Mesopor Mater 224:245–252
Peng C, Zou CC, Yang YQ, Zhang GH, Wang WW (2017) Fractal analysis of high rank coal from southeast Qinshui basin by using gas adsorption and mercury porosimetry. J Petrol Sci Eng 156:235–249
Pfeifer P, Avnir D (1983) Chemistry in noninteger dimensions between two and three. I. Fractal theory of heterogeneous surfaces. J Chem Phys 79:3369–3558
Rao MY, Yang LW, Feng SL, Ye JP (2005) Technology selection on industrialization development of coal bed methane in China. Spec Oil Gas Reserv 12(4):1–4
Shan RL, Cheng RQ, Gao WJ (2005) Study on dynamic constitutive model of anthracite of yunjialing coal mine. Chin J Rock Mech Eng 24(S1):4658–4662
Shan CG, Zhang TS, Liang X, Zhang Z, Wang M, Zhang K, Zhu HH (2018) On the fundamental difference of adsorption-pores systems between vitrinite- and inertinite-rich anthracite derived from the southern Sichuan basin, China. J Nat Gas Sci Eng 53:32–44
Tan LH, Ren T, Yang XH, He XQ (2018) A numerical simulation study on mechanical behaviour of coal with bedding planes under coupled static and dynamic load. Int J Min Sci Technol 28(5):791–797
Tang JW, Feng L, Li YJ, Liu J, Liu XC (2016) Fractal and pore structure analysis of Shengli lignite during drying process. Powder Technol 303:251–259
Wang F, Cheng YP, Lu SQ, Jin K, Zhao W (2014) Influence of coalification on the pore characteristics of middle high rank coal. Energy Fuel 28:5729–5736
Wang ZY, Cheng YP, Zhang KZ, Hao CM, Wang L, Li W, Hu B (2018) Characteristics of microscopic pore structure and fractal dimension of bituminous coal by cyclic gas adsorption/desorption: an experimental study. Fuel 232:495–505
Wang YB, Yang RS (2017) Study of the dynamic fracture characteristics of coal with a bedding structure based on the NSCB impact test. Eng Fract Mech 184:319–338
Xiong BB, Cristoforo D, Xiao Y (2019) High-strain rate compressive behavior of CFRP confined concrete: large diameter SHPB tests. Constr Build Mater 201:484–501
Yue GW, Li MM, Wang L, Liang WM (2019b) Optimal layout of blasting holes in structural anisotropic coal seam. PLoS ONE 14(6):e0218105. https://doi.org/10.1371/journal.pone.0218105
Yue GW, Liu H, Yue JW, Li MM, Liang WM (2019a) Influence radius of gas extraction borehole in an anisotropic coal seam: underground in-situ measurement and modeling. Energy Sci Eng 7:694–709
Zhang C, Lin BQ, Zhou Y, Zhai C, Sun X (2014a) Application of multi-seam metal jet directed pre-split blasting technology in gas extraction. J China Coal Soc 39(S1):100–104
Zhang SH, Tang SH, Tang DZ, Huang WH, Pan ZJ (2014b) Determining fractal dimensions of coal pores by FHH model: problems and effects. J Nat Gas Sci Eng 21:929–939
Zhang H, Wang L, Bai LY, Addae M, Neupane A (2019) Research on the impact response and model of hybrid basalt-macro synthetic polypropylene fiber reinforced concrete. Constr Build Mater 204:303–316
Zhao YX, Gong S, Hao XJ, Peng Y, Jiang YD (2017) Effects of loading rate and bedding on the dynamic fracture toughness of coal: Laboratory experiments. Constr Build Mater 178:375–439
Zhao YX, Zhao GF, Jiang YD, Elsworth D, Huang YQ (2014) Effects of bedding on the dynamic indirect tensile strength of coal: laboratory experiments and numerical simulation. Int J Coal Geol 132:81–93
Zhou SD, Liu DM, Cai YD, Yao YB (2016a) Fractal characterization of pore-fracture in low-rank coals using a low-field NMR relaxation method. Fuel 181:218–226
Zhou SD, Liu DM, Cai YD, Yao YB (2016b) Gas sorption and flow capabilities of lignite, subbituminous and high-volatile bituminous coals in the Southern Junggar Basin, NW China. J Nat Gas Sci Eng 34:6–21
We appreciate the support of Zhaogu coal mine, and the help of the workers in coal sample collecting. We are also grateful to Dr. Wang Hui, who provided instrument and equipment to accomplish the tests. We are also indebted to the anonymous reviewers for their comments that have helped to improve the manuscript.
Financial support came from the National Natural Science Foundation of China (no. 41772163).
Conflict of interest
The authors declare no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Minmin, L., Weimin, L. & Gaowei, Y. Fractal and pore structure analysis of structural anisotropic coal under different impact loads. Environ Earth Sci 79, 323 (2020). https://doi.org/10.1007/s12665-020-09071-7
- Impact load
- Pore structure
- Fractal dimension
- High rank