瓦斯压力对卸荷原煤力学特性及能量特征的影响
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摘要
运用自主研制的含瓦斯煤热流固耦合三轴伺服渗流试验装置,以原煤煤样作为研究对象,进行了含瓦斯煤固定轴向压力、卸围压的渗流试验,研究了卸围压过程中瓦斯压力对煤样力学特性和能量特征的影响。结果表明:在轴压加载阶段,煤样的变形模量基本不变,泊松比逐渐减小;在定轴压卸围压阶段,煤样的变形模量先小幅度增加,然后逐渐减小,泊松比则逐渐增大。瓦斯压力越高,煤样的承载能力越低,煤样发生破坏时相应的轴向应变和围压卸荷量百分比越小,而煤样破坏时的径向变形和扩容量越大。各应变围压柔量Δεi与瓦斯压力呈线性关系且线性相关性良好。随瓦斯压力升高,轴向应变的围压敏感性降低,径向应变和体积应变的围压敏感性显著升高。随瓦斯压力升高,煤样发生破坏时存储的弹性应变能Ue减小,而总能量U、耗散能Ud和耗散能比例Ud/U都增大。
This paper is aimed to investigate the impact of the gas pressure on the mechanical properties and energy special features of the coal samples under the unloading confining pressure.For the investigation,we have conducted the seepage test of the gas with coal under the conditions of the fixed axial pressure and the unloading confined pressure based on the self-developed triaxial servo-controlled seepage equipment for the thermal-hydrological mechanical coupling of the coal with methane gas. The results of our seepage test show that the deviatoric stress of the coal samples tends to act in an approximately linear manner with the axial strain. Nevertheless,the deformation modulus of the coal samples would remain unchanged,whereas the Poisson's ratio can be made decreased gradually in the axial pressure and confining pressure loading stage. For example,during the stage of the fixed axial pressure with unloading confining pressure,the deformation modulus of the coal samples would be likely to increase slightly and then decrease bit by bit as the Poisson's ratio increases. However,with the unloading of the confining pressure,the coal samples may fail gradually to gain a residual bearing capacity. What is more,the higher the gas pressure,the lower the strength of the coal samples,and the smaller the axial strain and the confining pressure unloading would remain to be until the coal samples would totally fail. However,the radial deformation and the expansion capacity of the coal samples may tend to increase with the increase of the gas pressure. In such a case,there may appear a new description variable,which may be equal to the ratio of the strain to the variation of the confining pressure and then can be presented as a strain-confining pressure compliance. Besides,there ought to exist a linear relationship between the strain-pressure compliance and the gas pressure,which helps to make the linear correlation satisfactory enough.That is to say. the higher the gas pressure,the lower the confining pressure sensitivity of the axial strain would be,and the higher the confining pressure sensitivity of the radial strain and volumetric strain would become. All this suggests that,the energy evolution may proceed or go along with the process of the destruction of the coal samples. Thus,in turn,with the increase in the gas pressure,the elastic strain energy Uemay tend to get reduced,whereas the total energy U,the dissipated energy Udand the dissipation energy ratio Ud/U may all tend to increase until the coal samples would get to fail eventually.
This paper is aimed to investigate the impact of the gas pressure on the mechanical properties and energy special features of the coal samples under the unloading confining pressure.For the investigation,we have conducted the seepage test of the gas with coal under the conditions of the fixed axial pressure and the unloading confined pressure based on the self-developed triaxial servo-controlled seepage equipment for the thermal-hydrological mechanical coupling of the coal with methane gas. The results of our seepage test show that the deviatoric stress of the coal samples tends to act in an approximately linear manner with the axial strain. Nevertheless,the deformation modulus of the coal samples would remain unchanged,whereas the Poisson's ratio can be made decreased gradually in the axial pressure and confining pressure loading stage. For example,during the stage of the fixed axial pressure with unloading confining pressure,the deformation modulus of the coal samples would be likely to increase slightly and then decrease bit by bit as the Poisson's ratio increases. However,with the unloading of the confining pressure,the coal samples may fail gradually to gain a residual bearing capacity. What is more,the higher the gas pressure,the lower the strength of the coal samples,and the smaller the axial strain and the confining pressure unloading would remain to be until the coal samples would totally fail. However,the radial deformation and the expansion capacity of the coal samples may tend to increase with the increase of the gas pressure. In such a case,there may appear a new description variable,which may be equal to the ratio of the strain to the variation of the confining pressure and then can be presented as a strain-confining pressure compliance. Besides,there ought to exist a linear relationship between the strain-pressure compliance and the gas pressure,which helps to make the linear correlation satisfactory enough.That is to say. the higher the gas pressure,the lower the confining pressure sensitivity of the axial strain would be,and the higher the confining pressure sensitivity of the radial strain and volumetric strain would become. All this suggests that,the energy evolution may proceed or go along with the process of the destruction of the coal samples. Thus,in turn,with the increase in the gas pressure,the elastic strain energy Uemay tend to get reduced,whereas the total energy U,the dissipated energy Udand the dissipation energy ratio Ud/U may all tend to increase until the coal samples would get to fail eventually.
引文
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[13] LYouchang(吕有厂),QIN Hu(秦虎). Investigationinto mechanical responses and energy dissipation proper-ties of coal containing methane to confinement unloading[J]. Journal of China Coal Society(煤炭学报),2012,37(9):1505-1510.
[14] XU Guoan(许国安),NIU Shuangjian(牛双建),JINGHongwen(靖洪文),et al. Experimental study of energyfeatures of sandstone under loading and unloading[J].Rock and Soil Mechanics(岩土力学),2011,32(12):3611-3617.
[15] CONG Yu(丛宇),WANG Zaiquan(王在泉),ZHENGYingren(郑颖人),et al. Energy evolution principle offracture propagation of marble with different unloadingstress paths[J]. Journal of Central South University:Science and Technology(中南大学学报:自然科学版),2016,47(9):3140-3147.
[16] HUANG D,LI Y R. Conversion of strain energy in triax-ial unloading tests on marble[J]. International Journalof Rock Mechanics&Mining Sciences,2014,66(1):160-168.
[17] XU Jiang(许江),PENG Shoujian(彭守建),YINGuangzhi(尹光志),et al. Development and applicationof triaxial servo-controlled seepage equipment for thermo-fluid-solid coupling of coal containing methane[J]. Chi-nese Journal of Rock Mechanics and Engineering(岩石力学与工程学报),2010,29(5):907-914.
[18] LI Xiangchun(李祥春),NIE Baisheng(聂百胜),HEXueqiu(何学秋),et al. Influence of gas adsorption oncoal body[J]. Journal of China Coal Society(煤炭学报),2011,36(12):2035-2038.
[19] HE Xueqiu(何学秋). Rheological dynamics of gas-bearing coal(含瓦斯煤岩流变动力学)[M]. Xuzhou:China University of Mining and Technology Press,1995.
[20] JIANG Yaodong(姜耀东),ZHU Jie(祝捷),ZHAOYixin(赵毅鑫),et al. Constitutive equations of coalcontaining methane based on mixture theory[J]. Journalof China Coal Society(煤炭学报),2007,32(11):1132-1137.
[21] GAO Chunyu(高春玉),XU Jin(徐进),HE Peng(何鹏),et al. Study on mechanical properties of marbleunder loading and unloading conditions[J]. ChineseJournal of Rock Mechanics and Engineering(岩石力学与工程学报),2005,24(3):456-460.
[22] QIU Shili(邱士利),FENG Xiating(冯夏庭),ZHANGChuanqing(张传庆),et al. Experimental research onmechanical properties of deep-buried marble under dif-ferent unloading rates of confining pressures[J]. ChineseJournal of Rock Mechanics and Engineering(岩石力学与工程学报),2010,29(9):1807-1817.
[23] YIN Guangzhi,JIANG Changbao,XU Jiang,et al. Anexperimental study on the effects of water content oncoalbed gas permeability in ground stress fields[J].Transport in Porous Media,2012,94(1):87-99.
[24] LI Tianbin(李天斌),CHEN Ziquan(陈子全),CHENGuoqing(陈国庆),et al. An experimental study of en-ergy mechanism of sandstone with different moisture con-tents[J]. Rock and Soil Mechanics(岩土力学),2015,36(S2):229-236.
[2] WU Yushan(吴玉山). The effects of the process of stres-ses on mechanical properties of tuff rocks[J]. ChineseJournal of Geotechnical Engineering(岩土工程学报),1983,5(1):112-121.
[3] TANG Jupeng(唐巨鹏),YU Ning(于宁),CHEN Shuai(陈帅). Impact of the gas pressure on the jet outburstenergy of coal and gas[J]. Journal of Safety and Envi-ronment(安全与环境学报),2017,17(3):943-948.
[4] WOLD M B,CONNELL L D,CHOI S K. The role ofspatial variability in coal seam parameters on gas outburstbehaviour during coal mining[J]. International Journalof Coal Geology,2008,75(1):1-14.
[5] LI Jianlin(李建林). Unloading rock mass mechanics andits application(卸荷岩体力学理论与应用)[M]. Bei-jing:China Building Industry Press,1999.
[6] WU G,ZHANG L. Studying unloading failure character-istics of a rock mass using the disturbed state concept[J]. International Journal of Rock Mechanics&MiningSciences,2004,41(S1):419-425.
[7] LI Hongzhe(李宏哲),XIA Caichu(夏才初),YAN Zi-jian(闫子舰),et al. Study on marble unloading me-chanical properties of Jinping hydropower station underhigh geostress conditions[J]. Chinese Journal of RockMechanics and Engineering(岩石力学与工程学报),2007,26(10):2104-2109.
[8] SU Chengdong(苏承东),GAO Baobin(高保彬),NANHua(南华),et al. Experimental study on acoustic emis-sion characteristics during deformation and failure proces-ses of coal samples under different stress paths[J]. Chi-nese Journal of Rock Mechanics and Engineering(岩石力学与工程学报),2009,28(4):757-766.
[9] QIU Zhaoyun(邱兆云),PAN Yishan(潘一山),LUOHao(罗浩),et al. Experimental study of the impact ofthe effective stress on the mechanical properties of thecoal[J]. Journal of Safety and Environment(安全与环境学报),2016,16(6):54-58.
[10] LEI Wenjie(雷文杰),LIU Xiangfeng(刘相风). Gasflowing features of hard and soft coal seems under the 3-D compression stress[J]. Journal of Safety and Environ-ment(安全与环境学报),2018,18(1):156-160.
[11] ZHANG Dongming(张东明),ZHENG Binbin(郑彬彬),ZHANG Xianmeng(张先萌),et al. Experimentalstudy on the deformation characteristics and permeabilitylaws of gas infiltrated sandstone under unloading confi-ning pressure condition[J]. Rock and Soil Mechanics(岩土力学),2017,38(12):3475-3483.
[12] ZHANG Dongming(张东明),ZHENG Binbin(郑彬彬),YIN Guangzhi(尹光志),et al. Mechanics andpermeability characteristics of steep seam roof sandstoneunder disturbance stress[J]. Journal of China Coal So-ciety(煤炭学报),2017,42(S1):128-137.
[13] LYouchang(吕有厂),QIN Hu(秦虎). Investigationinto mechanical responses and energy dissipation proper-ties of coal containing methane to confinement unloading[J]. Journal of China Coal Society(煤炭学报),2012,37(9):1505-1510.
[14] XU Guoan(许国安),NIU Shuangjian(牛双建),JINGHongwen(靖洪文),et al. Experimental study of energyfeatures of sandstone under loading and unloading[J].Rock and Soil Mechanics(岩土力学),2011,32(12):3611-3617.
[15] CONG Yu(丛宇),WANG Zaiquan(王在泉),ZHENGYingren(郑颖人),et al. Energy evolution principle offracture propagation of marble with different unloadingstress paths[J]. Journal of Central South University:Science and Technology(中南大学学报:自然科学版),2016,47(9):3140-3147.
[16] HUANG D,LI Y R. Conversion of strain energy in triax-ial unloading tests on marble[J]. International Journalof Rock Mechanics&Mining Sciences,2014,66(1):160-168.
[17] XU Jiang(许江),PENG Shoujian(彭守建),YINGuangzhi(尹光志),et al. Development and applicationof triaxial servo-controlled seepage equipment for thermo-fluid-solid coupling of coal containing methane[J]. Chi-nese Journal of Rock Mechanics and Engineering(岩石力学与工程学报),2010,29(5):907-914.
[18] LI Xiangchun(李祥春),NIE Baisheng(聂百胜),HEXueqiu(何学秋),et al. Influence of gas adsorption oncoal body[J]. Journal of China Coal Society(煤炭学报),2011,36(12):2035-2038.
[19] HE Xueqiu(何学秋). Rheological dynamics of gas-bearing coal(含瓦斯煤岩流变动力学)[M]. Xuzhou:China University of Mining and Technology Press,1995.
[20] JIANG Yaodong(姜耀东),ZHU Jie(祝捷),ZHAOYixin(赵毅鑫),et al. Constitutive equations of coalcontaining methane based on mixture theory[J]. Journalof China Coal Society(煤炭学报),2007,32(11):1132-1137.
[21] GAO Chunyu(高春玉),XU Jin(徐进),HE Peng(何鹏),et al. Study on mechanical properties of marbleunder loading and unloading conditions[J]. ChineseJournal of Rock Mechanics and Engineering(岩石力学与工程学报),2005,24(3):456-460.
[22] QIU Shili(邱士利),FENG Xiating(冯夏庭),ZHANGChuanqing(张传庆),et al. Experimental research onmechanical properties of deep-buried marble under dif-ferent unloading rates of confining pressures[J]. ChineseJournal of Rock Mechanics and Engineering(岩石力学与工程学报),2010,29(9):1807-1817.
[23] YIN Guangzhi,JIANG Changbao,XU Jiang,et al. Anexperimental study on the effects of water content oncoalbed gas permeability in ground stress fields[J].Transport in Porous Media,2012,94(1):87-99.
[24] LI Tianbin(李天斌),CHEN Ziquan(陈子全),CHENGuoqing(陈国庆),et al. An experimental study of en-ergy mechanism of sandstone with different moisture con-tents[J]. Rock and Soil Mechanics(岩土力学),2015,36(S2):229-236.