煤岩组合体峰后应力-应变关系模型及脆性特征
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摘要
煤岩体峰后破坏行为对于研究煤矿采空区覆岩破断及移动规律具有重要意义。本文利用煤岩组合体的单轴和三轴加载试验,研究其峰后软化应力-应变关系及脆性特征。通过强度参数分段线性演化方法,以等效塑性应变为应变软化参数,基于Mohr-Coulomb强度准则建立了煤岩组合体峰后非线性应力-应变关系,获得了峰后应力-应变关系理论变化趋势,与三轴加载试验数据较吻合。进一步对影响峰后应力-应变曲线形态的各参数进行敏感性分析,发现峰值强度和残余强度分别对峰值内摩擦角、残余内摩擦角敏感性较强。依据峰后应力-应变曲线形态,提出采用应力软化系数来评价煤岩组合体峰后脆性强弱,研究表明:对于钱家营煤岩组合体,当围压由0增大到5 MPa时,脆性对围压的敏感性较高;而当围压超过5 MPa后,脆性程度随围压变化不明显;出现这个现象的主要原因可能是煤体的强度较低,受低围压影响较为明显。
The post-peak failure behavior of coal and rock masses is of great significance to study rules of goaf strata fracture and movement in the coal mine. The test data of coal-rock combined body in the uniaxial and tri-axial compression test are used to study its post-peak softening stress-strain relationship and brittle characteristics. Based on the piecewise linear evolution of strength parameters, regarding the equivalent plastic strain as strain softening parameter, the nonlinear post-peak stress-strain relationship of coal-rock combined body is obtained by using Mohr-Coulomb strength criterion. On this basis, the post-peak stress-strain curves under different confining pressures are obtained and they are agreed well with the tri-axial compression test data. Sensitivity analyses of the parameters affecting the shape of the post-peak stress-strain curves are carried out and it is shown that the peak strength and residual strength are more sensitive to the peak internal friction angle and residual internal friction angle, respectively. By using stress softening coefficient to evaluate the extent of post-peak brittleness of coal-rock combined body in the Qianjiaying coal mine, it is found that brittleness is the most sensitive to confining pressure from 0 to 5 MPa and then the extent of brittleness trends to be stable with confining pressure increasing. The main reason may be the low strength of coal causes the more obvious influence of low confining pressure.
The post-peak failure behavior of coal and rock masses is of great significance to study rules of goaf strata fracture and movement in the coal mine. The test data of coal-rock combined body in the uniaxial and tri-axial compression test are used to study its post-peak softening stress-strain relationship and brittle characteristics. Based on the piecewise linear evolution of strength parameters, regarding the equivalent plastic strain as strain softening parameter, the nonlinear post-peak stress-strain relationship of coal-rock combined body is obtained by using Mohr-Coulomb strength criterion. On this basis, the post-peak stress-strain curves under different confining pressures are obtained and they are agreed well with the tri-axial compression test data. Sensitivity analyses of the parameters affecting the shape of the post-peak stress-strain curves are carried out and it is shown that the peak strength and residual strength are more sensitive to the peak internal friction angle and residual internal friction angle, respectively. By using stress softening coefficient to evaluate the extent of post-peak brittleness of coal-rock combined body in the Qianjiaying coal mine, it is found that brittleness is the most sensitive to confining pressure from 0 to 5 MPa and then the extent of brittleness trends to be stable with confining pressure increasing. The main reason may be the low strength of coal causes the more obvious influence of low confining pressure.
引文
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[18]LEE Y K,PIETRUSZCZAK S.A new numerical procedure for elasto-plastic analysis of a circular opening excavated in a strain-softening rock mass[J].Tunnelling and Underground Space Technology,2008,23(5):588-599.
[19]朱维申,何满潮.复杂条件下围岩稳定性与岩体动态施工力学[M].北京:科学出版社,1995:128-130.
[20]李庆辉,陈勉,金衍,等.页岩脆性的室内评价方法及改进[J].岩石力学与工程学报,2012,31(8):1680-1685.LI Qinghui,CHEN Mian,JIN Yan,et al.Indoor evaluation method for shale brittleness and improvement[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(8):1680-1685.
[21]左建平,黄亚明,熊国军,等.脆性岩石破坏的能量跌落系数研究[J].岩土力学,2014(2):321-327.ZUO Jianping,HUANG Yaming,XIONG Guojun,et al.Study of energy-drop coefficient of brittle rock failure[J].Rock and Soil Mechanics,2014(2):321-327.
[2]左建平,裴建良,刘建锋,等.煤岩样破裂过程中声发射行为及时空演化机制[J].岩石力学与工程学报,2011,30(8):1564-1570.ZUO Jianping,PEI Jianliang,LIU Jianfeng,et al.Investigation on acoustic emission behavior and its time-space evolution mechanism in failure process of coal-rock combined body[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(8):1564-1570.
[3]HOEK E,BROWN E T.Practical estimates of rock mass strength[J].International Journal of Rock Mechanics&Mining Sciences,1997,34(8):1165-1186.
[4]FANG Z,HARRISON J P.A mechanical degradation index for rock[J].International Journal of Rock Mechanics&Mining Sciences,2001,38(8):1193-1199.
[5]JOSEPH T G,BARRON K.The post-failure characteristics of rock[J].Cim Bulletin,2003,96(1070):66-74.
[6]WANG S,YIN X,TANG H,et al.A new approach for analyzing circular tunnel in strain-softening rock masses[J].International Journal of Rock Mechanics&Mining Sciences,2010,47(1):170-178.
[7]陆银龙,王连国,杨峰,等.软弱岩石峰后应变软化力学特性研究[J].岩石力学与工程学报,2010,29(3):640-648.LU Yinlong,WANG Lianguo,YANG Feng,et al.Post-peak strain softening mechanical properties of weak rock[J].Chinese Journal of Rock Mechanics and Engineering,2010,29(3):640-648.
[8]韩建新,李术才,汪雷,等.基于广义Hoek-Brown强度准则的岩体应变软化行为模型[J].中南大学学报(自然科学版),2013,44(11):4702-4706.HAN Jianxin,LI Shucai,WANG Lei,et al.Model for strain-softening behavior of rock mass based on generalized Hoek-Brown strength criterion[J].Journal of Central South University(Science and Technology),2013,44(11):4702-4706.
[9]张春会,赵全胜,黄鹂,等.考虑围压影响的岩石峰后应变软化力学模型[J].岩土力学,2010,31(增刊2):193-197.ZHANG Chunhui,ZHAO Quansheng,HUANG Li,et al.Post-peak strain softening mechanical of rock considering confining pressure effect[J].Rock and Soil Mechanics,2010,31(Sup 2):193-197.
[10]ZUO J P,WANG Z F,ZHOU H W,et al.Failure behavior of a rock-coal-rock combined body with a weak coal interlayer[J].International Journal of Mining Science and Technology,2013,23(6):907-912.
[11]左建平,谢和平,孟冰冰,等.煤岩组合体分级加卸载特性的试验研究[J].岩土力学,2011,32(5):1287-1296.ZUO Jianping,XIE Heping,MENG Bingbing,et al.Experimental research on loading-unloading behavior of coal-rock combination bodies at different stress levels[J].Rock and Soil Mechanics,2011,32(5):1287-1296.
[12]左建平,陈岩,张俊文,等.不同围压作用下煤岩组合体破坏行为及强度特征[J].煤炭学报,2016,41(11):2706-2713.ZUO Jianping,CHEN Yan,ZHANG Junwen,et al.Failure behavior and strength characteristics of coal-rock combined body under different confining pressures[J].Journal of China Coal Society,2016,41(11):2706-2713.
[13]刘少虹,秦子晗,娄金福.一维动静加载下组合煤岩动态破坏特性的试验研究[J].岩石力学与工程学报,2014,33(10):2064-2075.LIU Shaohong,QIN Zihan,LOU Jinfu.Experimental study of dynamic failure characteristics of coal-rock compound under one-dimensional static and dynamic loads[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(10):2064-2075.
[14]牟宗龙,王浩,彭蓬,等.岩-煤-岩组合体破坏特征及冲击倾向性试验研究[J].采矿与安全工程学报,2013,30(6):841-847.MOU Zonglong,WANG Hao,PENG Peng,et al.Experimental research on failure characteristics and bursting liability of rock-coal-rock sample[J].Journal of Mining&Safety Engineering,2013,30(6):841-847.
[15]窦林名,田京城,陆菜平,等.组合煤岩冲击破坏电磁辐射规律研究[J].岩石力学与工程学报,2005,24(19):3541-3544.DOU Linming,TIAN Jingcheng,LU Caiping,et al.Research on electromagnetic radiation rules of composed coal-rock burst failure[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(19):3541-3544.
[16]BROWN E T.Rock characterization,testing and monitoring:ISRM suggested methods[M].Oxford:Pergamon Press,1981:113-116.
[17]韩建新,李术才,李树忱,等.基于强度参数演化行为的岩石峰后应力-应变关系研究[J].岩土力学,2013,34(2):342-346.HAN Jianxin,LI Shucai,LI Shuchen,et al.Study of post-peak stress-strain relationship of rock material based on evolution of strength parameters[J].Rock and Soil Mechanics,2013,34(2):342-346.
[18]LEE Y K,PIETRUSZCZAK S.A new numerical procedure for elasto-plastic analysis of a circular opening excavated in a strain-softening rock mass[J].Tunnelling and Underground Space Technology,2008,23(5):588-599.
[19]朱维申,何满潮.复杂条件下围岩稳定性与岩体动态施工力学[M].北京:科学出版社,1995:128-130.
[20]李庆辉,陈勉,金衍,等.页岩脆性的室内评价方法及改进[J].岩石力学与工程学报,2012,31(8):1680-1685.LI Qinghui,CHEN Mian,JIN Yan,et al.Indoor evaluation method for shale brittleness and improvement[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(8):1680-1685.
[21]左建平,黄亚明,熊国军,等.脆性岩石破坏的能量跌落系数研究[J].岩土力学,2014(2):321-327.ZUO Jianping,HUANG Yaming,XIONG Guojun,et al.Study of energy-drop coefficient of brittle rock failure[J].Rock and Soil Mechanics,2014(2):321-327.