Abstract
In order to study the failure characteristics of coal-rock assemblage under the condition of unloading confining pressure. This study carries out the unloading confining pressure tests of coal-rock combination under three different pressure rates. The stress–strain curves of coal-rock combination in tests were observed, and the failure, deformation, and strength characteristics were analyzed. The result shows the combination has an obvious volume expansion phenomenon dominated by the simple shear failure of the coal part in the process of unloading the confining pressure. The rock part starts to damage with the increment of the confining pressure value and the unloading rate. The fracture angle of the sample is proportional to the initial confining pressure and inversely proportional to the unloading confining pressure rate; the fragmentation and intensity degree of coal-rock combination are significantly different under different test conditions. The fragmentation degree under the unloading confining pressure rate of 0.03 MPa/s, 0.06 MPa/s, 0.09 MPa/s is increased progressively, and the opposite trend appears on intensity degree. Axial deformation is dominant in the axial compression loading stage. The axial and circumferential deformations increase slowly at the stage of constant axial pressure, and the axial deformation is relatively larger. The circumferential deformation increases sharply at the stage of decreasing axial pressure. The internal friction angle is in direct proportion to the unloading rate, the cohesion and residual strength are in inverse proportion to the unloading rate, and the residual strength is in direct proportion to the initial confining pressure.
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The data that support the findings of this study are available from the corresponding author, upon reasonable request.
References
Al-Ajmi AM, Zimmerman RW (2005) Relation between the Mogi and the Coulomb failure criteria. Int J Rock Mech Min Sci 42(3):431–439. https://doi.org/10.1016/j.ijrmms.2004.11.004
Chen Y, Zuo J, Li Z et al (2020) Experimental investigation on the crack propagation behaviors of sandstone under different loading and unloading conditions. Int J Rock Mech Min Sci 130:104310. https://doi.org/10.1016/j.ijrmms.2020.104310
Guo J, Liu P, Fan J et al (2021) Influence of confining pressure unloading rate on the strength characteristics and fracture process of granite using lab tests. Adv Mater Sci Eng. https://doi.org/10.1155/2021/7925608
Guo H, Sun Z, Ji M et al (2022) An investigation on the impact of unloading rate on coal mechanical properties and energy evolution law. Int J Environ Res Public Health 19(8):4546. https://doi.org/10.3390/IJERPH19084546
Kang P, Jing Z, Hao L et al (2023) Mechanical properties of thermally treated granite subjected to different multi-stage unloading paths. Environ Earth Sci. https://doi.org/10.1007/S12665-022-10656-7
Li F, Yin D, Wang F et al (2022) Effects of combination mode on mechanical properties of bi-material samples consisting of rock and coal. J Market Res 19:2156–2170. https://doi.org/10.1016/J.JMRT.2022.05.174
Lü Y, Liu Q, Jiang H (2010) Study of mechanical deformation characteristics of granite in unloading experiments of high stress. Rock Soil Mech 31(2):337–344. https://doi.org/10.16285/j.rsm.2010.02.039
Ma T, Ma D, Yang Y (2020) Fractal characteristics of coal and sandstone failure under different unloading confining pressure tests. Adv Mater Sci Eng. https://doi.org/10.1155/2020/2185492
Ma Q, Tan Y, Liu X et al (2021) Experimental and numerical simulation of loading rate effects on failure and strain energy characteristics of coal-rock composite samples. J Cent South Univ 28(10):3207–3222. https://doi.org/10.1007/S11771-021-4831-6
Si X, Gong F (2020) Strength-weakening effect and shear-tension failure mode transformation mechanism of rock burst for fine-grained granite under triaxial unloading compression. Int J Rock Mech Min Sci 131:104347. https://doi.org/10.1016/j.ijrmms.2020.104347
Song H, Zuo J, Liu H et al (2021) The strength characteristics and progressive failure mechanism of soft rock-coal combination samples with consideration given to interface effects. Int J Rock Mech Min Sci 138:104593. https://doi.org/10.1016/J.IJRMMS.2020.104593
Sun L, Zhang L, Cong Y et al (2021) The meso-fracturing mechanism of marble under unloading confining pressure paths and constant axial stress. Sci Rep 11:17835. https://doi.org/10.1038/S41598-021-97359-4
Wang T, Qi F, Chang J (2022) Analysis of energy transmission and deformation characteristics of coal-rock combined bodies. Geofluids. https://doi.org/10.1155/2022/5304250
Xie H (2019) Research review of the state key research development program of China: deep rock mechanics and mining theory. J China Coal Soc 44(05):1283–1305. https://doi.org/10.13225/j.cnki.jccs.2019.6038
Yin D, Chen S, Xing W et al (2018) Experimental study on mechanical behavior of roof-coal pillar structure body under different loading rates. J China Coal Soc 43(5):1249–1257. https://doi.org/10.13225/j.cnki.jccs.2017.1091
Yu W, Wu G, Liu Z et al (2020) Experimental study on solid uniaxial compression of coal-rock-anchor combination and mechanical mechanism of anchor. Chin J Rock Mech Eng 39(01):57–68. https://doi.org/10.13722/j.cnki.jrme.2019.0500
Zhang L, Wang Z, Shi L (2011) Experimental study of hard rock failure characteristic under unloading condition. Chin J Rock Mech Eng 30(10):2012–2018. https://doi.org/10.1016/j.cnsns.2011.01.018
Zhangk K, Zhou H, Pan P et al (2010) Characteristics of strength of rocks under different unloading rates. Rock Soil Mech 31(7):2072–2078. https://doi.org/10.16285/j.rsm.2010.07.043
Zuo J, Xie H, Meng B (2011) Experimental study on grading loading and unloading characteristics of coal-rock combination. Rock Soil Mech 32(5):1287–1296. https://doi.org/10.16285/j.rsm.2011.05.028
Zuo J, Chen Y, Cui F (2018) Investigation on mechanical properties and rock burst tendency of different coal-rock combined bodies. J China Univ Min Technol 47(1):81–87. https://doi.org/10.13247/j.cnki.jcumt.000795
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The project funded by this thesis is: research on the rheological failure mechanism of surrounding rock of weakly cemented roadway based on energy dissipation; The fund number is: 02030018901.
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Hu, S., Zhou, X., Ru, W. et al. Study on Mechanical Property of Coal-Rock Combination Under Different Unloading Confining Pressure Rate. Geotech Geol Eng 41, 2629–2644 (2023). https://doi.org/10.1007/s10706-023-02417-5
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DOI: https://doi.org/10.1007/s10706-023-02417-5