三轴应力下不同粒径破碎砂岩渗透特性试验
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摘要
地下工程中破碎岩体往往处于三向应力状态,此类岩体具有孔隙率大、渗透性高等特点,在地应力与高水头作用下易发生渗流失稳破坏,诱发突水灾害。为研究三轴应力下破碎砂岩的渗透特性,运用自主研发的破碎岩石三轴渗流试验系统,采用稳态渗透法进行5种粒径破碎砂岩的渗流试验,得到了三轴应力下破碎砂岩渗透特性变化规律,推导了有效应力与渗流速度之间的关系。试验结果表明:三轴应力下破碎砂岩的有效应力与渗流速度呈线性关系,且轴向位移越大时,随有效应力的增加渗流速度减小的幅度越小;三轴应力下5种粒径破碎砂岩的孔压梯度与渗流速度服从Forchheimer关系,两者之间的相关系数达0.95以上;轴向位移恒定时,随着围压的增大,破碎砂岩渗透率k减小,非Darcy流β因子增大,各级轴向位移下,破碎砂岩的渗透率与围压之间呈指数函数关系;随着孔隙率的减小,5种粒径的破碎砂岩渗透率呈减小趋势,非Darcy流β因子整体增大,且渗透率量级为10~(-14)~10~(-11) m~2,非Darcy流β因子的量级为10~6~10~(12) m~(-1)。
Fractured rocks in underground engineering are generally in the state of triaxial stress, which are characterised by large porosity and high permeability. Under the action of the ground stress and high-water head, it is most likely to result in the failure of seepage instability and induce the disaster of water inrush. In this study, a self-developed triaxial permeability testing system was employed to study the permeability characteristics of the fractured sandstone under different triaxial stress conditions. The permeability tests were carried out on fractured sandstone with five different sizes of fragments by the steady-state permeability method. Finally, the permeability variations of fractured sandstone under triaxial stress states were obtained, and the relationship between effective stress and seepage velocity was deduced. The result showed that the relationship between the effective stress and seepage velocity of fractured sandstone under triaxial stress was approximately linear. When the axial displacement increased, the decreasing amplitude of seepage velocity became smaller with the increase of the effective stress. The pore pressure gradients and the seepage velocities of fractured sandstone with five different diameters of fragments under triaxial stress conditions were coincidenet with the Forchheimer equation. Moreover, the correlation coefficient between these two was above 0.95. When the axial displacement was constant, the permeability k of fractured sandstone decreased and non-Darcy flow β factor increased with increasing confining pressure. Under various axial displacements, the relationship between the permeability and confining pressure of fractured sandstone presented an exponential function. With the decrease of porosity, the permeability of fractured sandstone with five different diameters of fragments exhibited a downward trend, whereas non-Darcy flow β factor increased as a whole. In addition, the magnitude of the permeability was from 10~(-14) to 10~(-11) m~2 and the magnitude of non-Darcy flow β factor was from 10~6 to 10~(12) m~(-1).
Fractured rocks in underground engineering are generally in the state of triaxial stress, which are characterised by large porosity and high permeability. Under the action of the ground stress and high-water head, it is most likely to result in the failure of seepage instability and induce the disaster of water inrush. In this study, a self-developed triaxial permeability testing system was employed to study the permeability characteristics of the fractured sandstone under different triaxial stress conditions. The permeability tests were carried out on fractured sandstone with five different sizes of fragments by the steady-state permeability method. Finally, the permeability variations of fractured sandstone under triaxial stress states were obtained, and the relationship between effective stress and seepage velocity was deduced. The result showed that the relationship between the effective stress and seepage velocity of fractured sandstone under triaxial stress was approximately linear. When the axial displacement increased, the decreasing amplitude of seepage velocity became smaller with the increase of the effective stress. The pore pressure gradients and the seepage velocities of fractured sandstone with five different diameters of fragments under triaxial stress conditions were coincidenet with the Forchheimer equation. Moreover, the correlation coefficient between these two was above 0.95. When the axial displacement was constant, the permeability k of fractured sandstone decreased and non-Darcy flow β factor increased with increasing confining pressure. Under various axial displacements, the relationship between the permeability and confining pressure of fractured sandstone presented an exponential function. With the decrease of porosity, the permeability of fractured sandstone with five different diameters of fragments exhibited a downward trend, whereas non-Darcy flow β factor increased as a whole. In addition, the magnitude of the permeability was from 10~(-14) to 10~(-11) m~2 and the magnitude of non-Darcy flow β factor was from 10~6 to 10~(12) m~(-1).
引文
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[19]徐志华,孙大伟,张国栋.堆石料应力-应变特性大型三轴试验研究[J].岩土力学,2017,38(6):1565-1572.XU Zhi-hua,SUN Da-wei,ZHANG Guo-dong.Study on stress-strain behavior of rockfill using large-scale triaxial tests[J].Rock and Soil Mechanics,2017,38(6):1565-1572.
[20]张天军,任金虎,陈占清,等.破碎岩石三轴渗流试验系统及方法:中国,ZL201410032061.6[P].2014-04-30.ZHANG Tian-jun,REN Jin-hu,CHEN Zhan-qing,et al.Triaxial permeability test system and method for broken rocks:China,ZL201410032061.6[P].2014-04-30.
[21]赵阳升.多孔介质多场耦合作用及其工程响应[M].北京:科学出版社,2010.ZHAO Yang-sheng.Multi-field coupling in porous media and its engineering response[M].Beijing:Science Press,2010.
[2]王路珍,陈占清,孔海陵,等.加载历程对配径碎煤渗透特性影响的试验研究[J].岩土力学,2013,34(5):1325-1330.WANG Lu-zhen,CHEN Zhan-qing,KONG Hai-ling,et al.Experimental study of impact of loading history on permeability characteristics of broken coal with different grain size gradations[J].Rock and Soil Mechanics,2013,34(5):1325-1330.
[3]李顺才,陈占清,缪协兴,等.饱和破碎砂岩随时间变形-渗流特性试验研究[J].采矿与安全工程学报,2011,28(4):542-547.LI Shun-cai,CHEN Zhan-qing,MIAO Xie-xing,et al.Experimental study on saturated and fractured sandstone deformation-seepage characteristics with time[J].Journal of Mining&Safety Engineering,2011,28(4):542-547.
[4]LEGRAND J.Revisited analysis of pressure drop in flow through crushed rocks[J].Journal of Hydraulic Engineering,2002,128(11):1027-1031.
[5]PRADIP KUMAR,G N,VENKATARAMAN P.Non-Darcy converging flow through coarse granular media[J].Journal of the Institution of Engineers(India):Civil Engineering Division,1995,76:6-11.
[6]缪协兴,陈占清,刘卫群.采动岩体渗流理论[M].北京:科学出版社,2004.MIAO Xie-xing,CHEN Zhan-qing,LIU Wei-qun.Seepage theory of mining rock[M].Beijing:Science Press,2004.
[7]李顺才,缪协兴,陈占清,等.承压破碎岩石非Darcy渗流的渗透特性试验研究[J].工程力学,2008,25(4):85-92.LI Shun-cai,MIAO Xie-xing,CHEN Zhan-qing,et al.Experimental study on seepage properties of non-Darcy flow in confined broken rocks[J].Engineering Mechanics,2008,25(4):85-92.
[8]李顺才,陈占清,缪协兴,等.破碎岩体流固耦合渗流的分岔[J].煤炭学报,2008,33(7):754-759.LI Shun-cai,CHEN Zhan-qing,MIAO Xie-xing,et al.Bifurcation of fluid-solid coupling flow in broken rock[J].Journal of China Coal Society,2008,33(7):754-759.
[9]陈占清,李顺才,浦海,等.采动岩体蠕变与渗流耦合动力学[M].北京:科学出版社,2010.CHEN Zhan-qing,LI Shun-cai,PU Hai,et al.Mining rock creep and seepage coupling dynamics[M].Beijing:Science Press,2010.
[10]刘卫群,缪协兴,陈占清.破碎岩石渗透性的试验测定方法[J].实验力学,2003,18(1):57-61.LIU Wei-qun,MIAO Xie-xing,CHEN Zhan-qing.Atesting method for determining the permeability of overbroken rock[J].Journal of Experimental Mechanics,2003,18(1):57-61.
[11]马占国,缪协兴,李兴华,等.破碎页岩渗透特性[J].采矿与安全工程学报,2007,24(3):260-264.MA Zhan-guo,MIAO Xie-xing,LI Xing-hua,et al.Permeability of broken shale[J].Journal of Mining&Safety Engineering,2007,24(3):260-264.
[12]马占国,缪协兴,陈占清,等.破碎煤体渗透特性的试验研究[J].岩土力学,2009,30(4):985-988,996.MA Zhan-guo,MIAO Xie-xing,CHEN Zhan-qing,et al.Experimental study on permeability of broken coal[J].Rock and Soil Mechanics,2009,30(4):985-988,996.
[13]孙明贵,李天珍,黄先伍,等.破碎岩石非Darcy流的渗透特性试验研究[J].安徽理工大学学报(自然科学版),2003,23(2):11-13.SUN Ming-gui,LI Tian-zhen,HUANG Xian-wu,et al.Penetrating properties of non-Darcy flow in fragmentized rocks[J].Journal of Anhui University of Science and Technology(Natural Science),2003,23(2):11-13.
[14]黄先伍,唐平,缪协兴,等.破碎砂岩渗透特性与孔隙率关系的试验研究[J].岩土力学,2005,26(9):1385-1388.HUANG Xian-wu,TANG Ping,MIAO Xie-xing,et al.Testing study on seepage properties of broken sandstone[J].Rock and Soil Mechanics,2005,26(9):1385-1388.
[15]张天军,任金虎,陈占清,等.多种矿物成分破碎岩石渗透试验[J].辽宁工程技术大学学报(自然科学版),2014,33(4):465-469.ZHANG Tian-jun,REN Jin-hu,CHEN Zhan-qing,et al.Experimental study on the permeability parameters of broken rock with various mineral composition[J].Journal of Liaoning Technical University(Natural Science),2014,33(4):465-469.
[16]张天军,任金虎,陈占清,等.混合破碎岩样渗透特性试验研究[J].湖南科技大学学报(自然科学版),2014,29(03):1-5.ZHANG Tian-jun,REN Jin-hu,CHEN Zhan-qing,et al.Experimental study on the permeability characteristic of mixed broken rock sample[J].Journal of Hunan University of Science&Technology(Natural Science Edition),2014,29(03):1-5.
[17]张天军,任金虎,陈占清,等.破碎泥岩渗透特性试验研究[J].河南理工大学学报,2014,33(4):426-431.ZHANG Tian-jun,REN Jin-hu,CHEN Zhan-qing,et al.Experimental study on permeability characteristics of broken mudstone[J].Journal of Henan Polytechnic University,2014,33(4):426-431.
[18]张天军,尚宏波,李树刚,等.分级加载下破碎砂岩渗透特性试验及其稳定性分析[J].煤炭学报,2016,41(5):1129-1136.ZHANG Tian-jun,SHANG Hong-bo,LI Shu-gang,et al.Experimental study on permeability characteristics of broken sandstone and its stability analysis under step loading[J].Journal of China Coal Society,2016,41(5):1129-1136.
[19]徐志华,孙大伟,张国栋.堆石料应力-应变特性大型三轴试验研究[J].岩土力学,2017,38(6):1565-1572.XU Zhi-hua,SUN Da-wei,ZHANG Guo-dong.Study on stress-strain behavior of rockfill using large-scale triaxial tests[J].Rock and Soil Mechanics,2017,38(6):1565-1572.
[20]张天军,任金虎,陈占清,等.破碎岩石三轴渗流试验系统及方法:中国,ZL201410032061.6[P].2014-04-30.ZHANG Tian-jun,REN Jin-hu,CHEN Zhan-qing,et al.Triaxial permeability test system and method for broken rocks:China,ZL201410032061.6[P].2014-04-30.
[21]赵阳升.多孔介质多场耦合作用及其工程响应[M].北京:科学出版社,2010.ZHAO Yang-sheng.Multi-field coupling in porous media and its engineering response[M].Beijing:Science Press,2010.