三轴应力下胶结破碎煤岩体渗流稳定性
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摘要
岩块间胶结结构的破坏是陷落柱诱发煤矿突水事故的重要因素之一。为研究胶结破碎煤岩体在三轴承压下的渗流稳定性,分别制作10组含有不同级配结构的煤样,利用自主设计的三轴渗流试验系统对胶结破碎煤岩体的渗透率k、非Darcy流β因子和失稳临界值进行试验测定。结果表明:1)不同Talbot指数n所对应的胶结破碎煤岩体孔隙结构不同,承压变形时其渗透率与有效应力满足函数关系:k=ae~(bσ_c),说明快速压密阶段主要影响的是初始孔隙率,后续结构重调整阶段骨架颗粒发生了剥落、破碎;2)当渗透率k下降到10~(-10)m~2以下、或非Darcy流β增加到10~6 m~(-1)时,都会引起渗流系统失稳,说明两者数量级的改变可诱发β因子突变到负值,其符号的变化可作为煤岩体渗流失稳的临界条件;3)高应力水平状态下,60%的级配结构在渗流过程中均出现失稳阶段,说明渗流参数是否满足βk~2<3.90×10~(-12)m~3,可作为预测煤矿突水事故的重要依据。
The cementation-structure failure between rock blocks is one of the significant factors in coalmine water inrush incident caused by collapse column. In order to investigate the seepage stability of cemented and fractured coal rock mass under tri-axial bearing pressures, 10 sets of coal samples with different grading structures were made. The permeability of cemented and broken coal rock mass, the non-Darcy flow β factor and the instability threshold were tested using self-designed tri-axial seepage testing system. Results show that: 1) When the pore structures of cemented fractured coal rock body being different, the Talbot index n varies. The permeability and effective stress follow functional relak =ae~(bσ_c) when the coal rock deforms under bearing pressure. It indicates that the initial porosity is mainly affected in initial compaction stage. In the subsequent structural re-adjustment stage,the skeleton particles are peeled off and broken. 2) While the permeability k drops below 10~(-10) m~2, or the non-Darcy flow β increases to 10~6 m~(-1), the seepage system instability occurs, indicating that the magnitude change could induce the β factor to a negative value. Therefore, its sign change could be used as a critical condition for the instability of coal and rock seepage. 3) Under the high stress condition, 60%gradation structure experiences instability stage in the seepage process, which means that βk~2<3.90 ×10~(-12) m~3 could be an important basis for predicting coalmine water inrush incidents.
The cementation-structure failure between rock blocks is one of the significant factors in coalmine water inrush incident caused by collapse column. In order to investigate the seepage stability of cemented and fractured coal rock mass under tri-axial bearing pressures, 10 sets of coal samples with different grading structures were made. The permeability of cemented and broken coal rock mass, the non-Darcy flow β factor and the instability threshold were tested using self-designed tri-axial seepage testing system. Results show that: 1) When the pore structures of cemented fractured coal rock body being different, the Talbot index n varies. The permeability and effective stress follow functional relak =ae~(bσ_c) when the coal rock deforms under bearing pressure. It indicates that the initial porosity is mainly affected in initial compaction stage. In the subsequent structural re-adjustment stage,the skeleton particles are peeled off and broken. 2) While the permeability k drops below 10~(-10) m~2, or the non-Darcy flow β increases to 10~6 m~(-1), the seepage system instability occurs, indicating that the magnitude change could induce the β factor to a negative value. Therefore, its sign change could be used as a critical condition for the instability of coal and rock seepage. 3) Under the high stress condition, 60%gradation structure experiences instability stage in the seepage process, which means that βk~2<3.90 ×10~(-12) m~3 could be an important basis for predicting coalmine water inrush incidents.
引文
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[15]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 Tianjun,SHANG Hongbo,LI Shugang,et al.Permeability test and stability analysis of fractured sandstone under staged loading[J].Journal of China Coal Society,2016,41(5):1129-1136.
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[17]张天军,陈佳伟,包若羽,等.不同浸水时间级配破碎煤样的粒度分布分形特征[J].采矿与安全工程学报,2018,35(3):598-604.ZHANG Tianjun,CHEN Jiawei,BAO Ruoyu,et al.Fractal characteristics of particle size distribution of crushed coal samples with different immersion time gradings[J].Journal of Mining&Safety Engineering,2018,35(3):598-604.
[18]MA D,MIAO X X,JIANG G H,et al.An experimental investigation of permeability measurement of water flow in crushed rocks[J].Transport in Porous Media,2014,105(3):571-595.
[19]HE C,LUO L,HAO Q M,et al.Velocity-weakening behavior of plagioclase and pyroxene gouges and stabilizing effect of small amounts of quartz under hydrothermal conditions[J].Journal of Geophysical Research Solid Earth,2013,118(7):3408-3430.
[20]LEGRAND J.Revisited analysis of pressure drop in flow through crushed rocks[J].Journal of Hydraulic Engineering,2002,128(11):1027-1031.
[21]YAO Banghua,CHEN Zhanqing,CAI Wei,et al.Stress distribution characteristics of Paleokarst collapse breccia pipe and water inrush prediction study[J].Electronic Journal of Geotechnical Engineering,2012,17(F):769-784.
[2]郁邦永,陈占清,吴疆宇,等.变质量胶结破碎岩石非Darcy流渗透特性试验研究[J].中国矿业大学学报,2017,46(2):321-327.YU Bangyong,CHEN Zhanqing,WU Jiangyu,et al.Experimental study on non-Darcy flow permeability characteristics of fractured rock with variable mass[J].Journal of China University of Mining&Technology,2017,46(2):321-327.
[3]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 Luzhen,CHEN Zhanqing,KONG Hailing,et al.Experimental study on the influence of loading history on the permeability characteristics of broken coal[J].Rock&Soil Mechanics,2013,34(5):1325-1330.
[4]郁邦永,陈占清,吴宇,等.胶结破碎泥岩渗透性试验研究[J].采矿与安全工程学报,2015,32(5):853-858.YU Bangyong,CHEN Zhanqing,WU Yu,et al.Experimental study on permeability of cemented and fractured mudstone[J].Journal of Mining&Safety Engineering,2015,32(5):853-858.
[5]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,2005,42(9):1385-1388.HUANG Xianwu,TANG Ping,MIAO Xiexing,et al.Experimental study on the relationship between permeability characteristics and porosity of fractured sandstone[J].Rock&Soil Mechanics,2005,42(9):1385-1388.
[6]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),2003,123(2):11-13.SUN Minggui,LI Tianzhen,HUANG Xianwu,et al.Experimental study on permeability characteristics of non-Darcy flow in fractured rock[J].Journal of Anhui University of Science&Technology(Natural Science),2003,123(2):11-13.
[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 Shuncai,MIAO Xiexing,CHEN Zhanqing,et al.Experimental study on permeability characteristics of non-Darcy seepage in confined broken rock[J].Engineering Mechanics,2008,25(4):85-92.
[8]张天军,尚宏波,李树刚,等.三轴应力下不同粒径破碎砂岩渗透特性试验[J].岩土力学,2018,39(7):2361-2370.ZHANG Tianjun,SHANG Hongbo,LI Shugang,et al.Experimental study on permeability characteristics of fractured sandstones with different particle sizes under triaxial stress[J].Rock&Soil Mechanics,2018,39(7):2361-2370.
[9]陈占清,缪协兴,刘卫群.采动围岩中参变渗流系统的稳定性分析[J].中南大学学报(自然科学版),2004,35(1):129-132.CHEN Zhanqing,MIAO Xiexing,LIU Weiqun.Stability analysis of parametric seepage system in mining surrounding rock[J].Journal of Central South University(Science and Technology),2004,35(1):129-132.
[10]缪协兴,陈占清,茅献彪,等.峰后岩石非Darcy渗流的分岔行为研究[J].力学学报,2003,35(6):660-667.MIAO Xiexing,CHEN Zhanqing,MAO Xianbiao,et al.Study on the bifurcation behavior of non-Darcy seepage in post-peak rock[J].Chinese Journal of Theoretical&Applied Mechanics,2003,35(6):660-667.
[11]李连崇,唐春安,左宇军,等.煤层底板下隐伏陷落柱的滞后突水机理[J].煤炭学报,2009,34(9):1212-1216.LI Lianchong,TANG Chun’an,ZUO Yujun,et al.The mechanism of delayed water inrush under concealed collapse column under coal seam floor[J].Journal of China Coal Society,2009,34(9):1212-1216.
[12]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,2010:70-139.
[13]冯梅梅,吴疆宇,陈占清,等.连续级配饱和破碎岩石压实特性试验研究[J].煤炭学报,2016,41(9):2195-2202.FENG Meimei,WU Jiangyu,CHEN Zhanqing,et al.Experimental study on compaction characteristics of continuous graded saturated rock[J].Journal of China Coal Society,2016,41(9):2195-2202.
[14]唐平,孙明贵.岩石渗流系统动力学响应及分析[J].矿山压力与顶板管理,2003,20(2):115-117.TANG Ping,SUN Minggui.Dynamic response and analysis of rock seepage system[J].Mineral Pressure&Roof Management,2003,20(2):115-117.
[15]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 Tianjun,SHANG Hongbo,LI Shugang,et al.Permeability test and stability analysis of fractured sandstone under staged loading[J].Journal of China Coal Society,2016,41(5):1129-1136.
[16]马丹,白海波,陈占清,等.侧限压缩下破碎矸石混合粒径非Darcy流渗透特性[J].采矿与安全工程学报,2016,33(4):747-753.MA Dan,BAI Haibo,CHEN Zhanqing,et al.Non-Darcy flow permeability characteristics of broken vermiculite mixed particle size under confined compression[J].Journal of Mining&Safety Engineering,2016,33(4):747-753.
[17]张天军,陈佳伟,包若羽,等.不同浸水时间级配破碎煤样的粒度分布分形特征[J].采矿与安全工程学报,2018,35(3):598-604.ZHANG Tianjun,CHEN Jiawei,BAO Ruoyu,et al.Fractal characteristics of particle size distribution of crushed coal samples with different immersion time gradings[J].Journal of Mining&Safety Engineering,2018,35(3):598-604.
[18]MA D,MIAO X X,JIANG G H,et al.An experimental investigation of permeability measurement of water flow in crushed rocks[J].Transport in Porous Media,2014,105(3):571-595.
[19]HE C,LUO L,HAO Q M,et al.Velocity-weakening behavior of plagioclase and pyroxene gouges and stabilizing effect of small amounts of quartz under hydrothermal conditions[J].Journal of Geophysical Research Solid Earth,2013,118(7):3408-3430.
[20]LEGRAND J.Revisited analysis of pressure drop in flow through crushed rocks[J].Journal of Hydraulic Engineering,2002,128(11):1027-1031.
[21]YAO Banghua,CHEN Zhanqing,CAI Wei,et al.Stress distribution characteristics of Paleokarst collapse breccia pipe and water inrush prediction study[J].Electronic Journal of Geotechnical Engineering,2012,17(F):769-784.