干燥-饱和循环作用下砂质泥岩抗剪性能劣化试验研究
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摘要
西部生态脆弱矿区煤炭开采过程中的地下水资源保护与利用是实现该区域煤炭绿色开采的前提和必要条件。其中,保水开采与地下水库技术的广泛应用为解决煤水共采问题提供可能。本文以煤矿地下水库煤岩边界在水反复浸入条件下稳定性变化为研究背景,以神东矿区乌兰木伦矿3-1号煤层顶板砂质泥岩为研究对象,通过无损浸水试验获得试样的自然吸水性规律,获得试样含水率到达饱和状态的浸水时间。根据浸水时间,对试样进行干燥-饱和反复浸水,得到不同循环浸水试样含水率随浸水次数呈指数增加关系,而试样抗剪强度和浸水次数呈指数降低关系。黏聚力随浸水次数的增加呈下降趋势,而内摩擦角先增加后减小,表明材料的均一性以及破裂面的形态及裂隙发育的形态、尺寸、方向变化造成了内摩擦角增加,而后期循环浸水占主导因素,表现为内摩擦角减小。根据黏聚力、内摩擦角与干燥-饱和循环次数的关系,建立了基于干燥-饱和循环次数的Mohr-Coulomb准则。声发射计数曲线与剪应力曲线有较强的对应性,在试样破坏时刻声发射事件明显增加,对应声发射累计计数曲线的明显上升阶段。试样在破坏过程中以低RA值为主,破坏时刻对应高RA值,即试样破坏过程中的基础裂隙类型是张拉裂隙,破坏时刻对应明显的剪切裂隙。研究结果表明,地下水库边界煤岩柱在地下水库蓄水-抽水过程中,在浸水-失水作用下其强度发生显著变化,建议在构建地下水库时应考虑水作用引起的边界煤岩柱强度弱化作用。
The protection and utilization of groundwater resources in coal mining process is the prerequisite and necessary condition for realizing green mining at the ecological fragile mining area in western China.Among them,the extensive application of water-preserved mining and underground reservoir technology provides the possibility for solving the problem of coal-water co-production.In this paper,with the background that the stability of the coal and rock boundary of underground reservoir changed under the conditions of repeated immersion in water,the sandy mudstone of the No.3-1 coal seam roof of Wulanmulun Mine was investigated.The natural water absorption law of the sample was obtained by non-destructive water immersion test,and the water immersion time of the sample water content reaching saturation state was obtained.According to the immersion time,the sample was dried-saturated and repeatedly immersed in water.It was found that the water content increased exponentially with the number of immersion,whereas the shear strength and the number of water immersion in the sample decreased exponentially.The cohesive force decreased with the increase of the number of immersion times,while the internal friction angle increased first and then decreased,indicating that the uniformity of the material,and the shape of the fracture surface and the shape,size and direction of the fracture caused the internal friction angle to increase.The cycle immersion later was the dominant factor to make the internal friction angle decrease.Based on the relationship between cohesion,internal friction angle and number of dry-saturated cycles,the Mohr-Coulomb criterion was established based on the number of dry-saturated cycles.The acoustic emission counting curve had a strong correspondence with the shear stress curve.The acoustic emission event increased significantly at the moment of sample failure,corresponding to the obvious rising phase of the cumulative acoustic emission counting curve.The sample mainly had a low RA value during the failure process,and the failure time corresponded to a high RA value,i.e.,the common type of crack in the failure process of the specimen was tensile crack,and the moment of failure corresponded to the obvious shear crack.These results show that the strength of coal and rock pillars in the groundwater reservoir boundary changed significantly under the action of water immersion-water loss during the impoundment-pumping process in the groundwater reservoir.It is suggested that the weakening effect of water on the strength of boundary coal and rock pillars should be considered when constructing the underground reservoir.
The protection and utilization of groundwater resources in coal mining process is the prerequisite and necessary condition for realizing green mining at the ecological fragile mining area in western China.Among them,the extensive application of water-preserved mining and underground reservoir technology provides the possibility for solving the problem of coal-water co-production.In this paper,with the background that the stability of the coal and rock boundary of underground reservoir changed under the conditions of repeated immersion in water,the sandy mudstone of the No.3-1 coal seam roof of Wulanmulun Mine was investigated.The natural water absorption law of the sample was obtained by non-destructive water immersion test,and the water immersion time of the sample water content reaching saturation state was obtained.According to the immersion time,the sample was dried-saturated and repeatedly immersed in water.It was found that the water content increased exponentially with the number of immersion,whereas the shear strength and the number of water immersion in the sample decreased exponentially.The cohesive force decreased with the increase of the number of immersion times,while the internal friction angle increased first and then decreased,indicating that the uniformity of the material,and the shape of the fracture surface and the shape,size and direction of the fracture caused the internal friction angle to increase.The cycle immersion later was the dominant factor to make the internal friction angle decrease.Based on the relationship between cohesion,internal friction angle and number of dry-saturated cycles,the Mohr-Coulomb criterion was established based on the number of dry-saturated cycles.The acoustic emission counting curve had a strong correspondence with the shear stress curve.The acoustic emission event increased significantly at the moment of sample failure,corresponding to the obvious rising phase of the cumulative acoustic emission counting curve.The sample mainly had a low RA value during the failure process,and the failure time corresponded to a high RA value,i.e.,the common type of crack in the failure process of the specimen was tensile crack,and the moment of failure corresponded to the obvious shear crack.These results show that the strength of coal and rock pillars in the groundwater reservoir boundary changed significantly under the action of water immersion-water loss during the impoundment-pumping process in the groundwater reservoir.It is suggested that the weakening effect of water on the strength of boundary coal and rock pillars should be considered when constructing the underground reservoir.
引文
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[8]李克钢,侯克鹏,张成良.饱和状态下岩体抗剪切特性试验研究[J].中南大学学报(自然科学版),2009,40(2):538-542.LI Kegang,HOU Kepeng,ZHANG Chengliang.Experiment study on shear characteristics of saturated rock mass[J].Journal of Central South University(Science and Technology),2009,40(2):538-542.
[9]HAO R,LI J,CAO P,et al.Test of subcritical crack growth and fracture toughness under water-rock interaction in three types of rocks[J].Journal of Central South University,2015,22(2):662-668.
[10]CHEN T,YAO Q,WEI F,et al.Effects of water intrusion and loading rate on mechanical properties of and crack propagation in coalrock combinations[J].Journal of Central South University,2017,24(2):423-431.
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[12]ZHOU Z,CAO P,YE Z.Crack propagation mechanism of compression-shear rock under static-dynamic loading and seepage water pressure[J].Journal of Central South University,2014,21(4):1565-1570.
[13]许江,陆丽丰,杨红伟,等.剪切荷载作用下砂岩细观开裂扩展演化特征研究[J].岩石力学与工程学报,2011,30(5):944-950.XU Jiang,LU Lifeng,YANG Hongwei,et al.Study of evolution law of microfracturing progress of sandstone under shear loading[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(5):944-950.
[14]衡帅,杨春和,曾义金,等.基于直剪试验的页岩强度各向异性研究[J].岩石力学与工程学报,2014,33(5):874-883.HENG Shuai,YANG Chunhe,ZENG Yijin,et al.Anisotropy of shear strength of shale based on direct shear test[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(5):874-883.
[15]艾婷,张茹,刘建锋,等.三轴压缩煤岩破裂过程中声发射时空演化规律[J].煤炭学报,2011,36(12):2048-2057.AI Ting,ZHANG Ru,LIU Jianfeng,et al.Space-time evolution rules of acoustic emission locations under triaxial compression[J].Journal of China Coal Society,2011,36(12):2048-2057.
[16]WANG M M,TAN C X,MENG J,et al.Crack classification and evolution in anisotropic shale during cyclic loading tests by acoustic emission[J].Journal of Geophysics and Engineering,2017,14(4):930-938.
[17]XU J,LIU Y,PENG S.Acoustic emission parameters of three gorges sandstone during shear failure[J].Acta Geophysica,2016,64(6):2410-2429.
[18]许江,李树春,唐晓军,等.单轴压缩下岩石声发射定位实验的影响因素分析[J].岩石力学与工程学报,2008,27(4):765-772.XU Jiang,LI Shuchun,TANG Xiaojun,et al.Influential factors of acoustic emission location experiment of rock under uniaxial compression[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(4):765-772.
[19]MURALHA J,GRASSELLI G,TATONE B,et al.ISRM suggested method for laboratory determination of the shear strength of rock joints:Revised version[J].Rock Mechanics and Rock Engineering,2014,47(1):291-302.
[20]CAI Y,YU J,FU G,et al.Experimental investigation on the relevance of mechanical properties and porosity of sandstone after hydrochemical erosion[J].Journal of Mountain Science,2016,13(11):2053-2068.
[2]FAN Limin,MA Xiongde.A review on investigation of water-preserved coal mining in western China[J].International Journal of Coal Science&Technology,2018,5(4):411-416.
[3]黄庆享.浅埋煤层覆岩隔水性与保水开采分类[J].岩石力学与工程学报,2010,29(S2):3622-3627.HUANG Qingxiang.Impermeability of overburden rock in shallow buried coal seam and classification of water conservation mining[J].Chinese Journal of Rock Mechanics and Engineering,2010,29(S2):3622-3627.
[4]王双明,黄庆享,范立民,等.生态脆弱矿区含(隔)水层特征及保水开采分区研究[J].煤炭学报,2010,35(1):7-14.WANG Shuangming,HUANG Qingxiang,FAN Limin,et al.Study on overburden aquclude and water protection mining regionazation in the ecological fragile mining area[J].Journal of China Coal Society,2010,35(1):7-14.
[5]顾大钊.煤矿地下水库理论框架和技术体系[J].煤炭学报,2015,40(2):239-246.GU Dazhao.Theory framework and technological system of coal mine underground reservoir[J].Journal of China Coal Society,2015,40(2):239-246.
[6]YAO Q,CHEN T,JU M,et al.Effects of water intrusion on mechanical properties of and crack propagation in Coal[J].Rock Mechanics and Rock Engineering,2016,49(12):4699-4709.
[7]姚强岭,王傲,陈田,等.反复浸水对煤样力学性质损伤的声发射实验研究[J].采矿与安全工程学报,2016,33(5):938-944.YAO Qiangling,WANG Ao,CHEN Tian,et al.The effect of repeated water intrusion on mechanical characters of coal samples by acoustic emission testing[J].Journal of Mining&Safety Engineering,2016,33(5):938-944.
[8]李克钢,侯克鹏,张成良.饱和状态下岩体抗剪切特性试验研究[J].中南大学学报(自然科学版),2009,40(2):538-542.LI Kegang,HOU Kepeng,ZHANG Chengliang.Experiment study on shear characteristics of saturated rock mass[J].Journal of Central South University(Science and Technology),2009,40(2):538-542.
[9]HAO R,LI J,CAO P,et al.Test of subcritical crack growth and fracture toughness under water-rock interaction in three types of rocks[J].Journal of Central South University,2015,22(2):662-668.
[10]CHEN T,YAO Q,WEI F,et al.Effects of water intrusion and loading rate on mechanical properties of and crack propagation in coalrock combinations[J].Journal of Central South University,2017,24(2):423-431.
[11]ZHAO Z,WANG W,WANG L,et al.Compression-shear strength criterion of coal-rock combination model considering interface effect[J].Tunnelling and Underground Space Technology,2015,47:193-199.
[12]ZHOU Z,CAO P,YE Z.Crack propagation mechanism of compression-shear rock under static-dynamic loading and seepage water pressure[J].Journal of Central South University,2014,21(4):1565-1570.
[13]许江,陆丽丰,杨红伟,等.剪切荷载作用下砂岩细观开裂扩展演化特征研究[J].岩石力学与工程学报,2011,30(5):944-950.XU Jiang,LU Lifeng,YANG Hongwei,et al.Study of evolution law of microfracturing progress of sandstone under shear loading[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(5):944-950.
[14]衡帅,杨春和,曾义金,等.基于直剪试验的页岩强度各向异性研究[J].岩石力学与工程学报,2014,33(5):874-883.HENG Shuai,YANG Chunhe,ZENG Yijin,et al.Anisotropy of shear strength of shale based on direct shear test[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(5):874-883.
[15]艾婷,张茹,刘建锋,等.三轴压缩煤岩破裂过程中声发射时空演化规律[J].煤炭学报,2011,36(12):2048-2057.AI Ting,ZHANG Ru,LIU Jianfeng,et al.Space-time evolution rules of acoustic emission locations under triaxial compression[J].Journal of China Coal Society,2011,36(12):2048-2057.
[16]WANG M M,TAN C X,MENG J,et al.Crack classification and evolution in anisotropic shale during cyclic loading tests by acoustic emission[J].Journal of Geophysics and Engineering,2017,14(4):930-938.
[17]XU J,LIU Y,PENG S.Acoustic emission parameters of three gorges sandstone during shear failure[J].Acta Geophysica,2016,64(6):2410-2429.
[18]许江,李树春,唐晓军,等.单轴压缩下岩石声发射定位实验的影响因素分析[J].岩石力学与工程学报,2008,27(4):765-772.XU Jiang,LI Shuchun,TANG Xiaojun,et al.Influential factors of acoustic emission location experiment of rock under uniaxial compression[J].Chinese Journal of Rock Mechanics and Engineering,2008,27(4):765-772.
[19]MURALHA J,GRASSELLI G,TATONE B,et al.ISRM suggested method for laboratory determination of the shear strength of rock joints:Revised version[J].Rock Mechanics and Rock Engineering,2014,47(1):291-302.
[20]CAI Y,YU J,FU G,et al.Experimental investigation on the relevance of mechanical properties and porosity of sandstone after hydrochemical erosion[J].Journal of Mountain Science,2016,13(11):2053-2068.