含孔试样渐进性破坏的表面变形特征
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摘要
瓦斯抽采钻孔孔周裂隙漏气是抽采失效的主要原因之一,孔周裂隙扩展在煤体破坏的过程中表现孕育、稳定扩展及迅速扩展3个阶段。为探究孔周裂纹在松软煤体不同破坏阶段的发展特征,开展含孔试样渐进性破坏过程中的孔周裂纹扩展规律研究。将石膏与水以质量比7∶3混合制成类软煤含孔方形试样,进行单轴压缩试验并采用数字散斑相关测量方法(DSCM)获取试样表面全场变形。基于此,提出了利用DSCM系统确定应力门槛值的方法,并将其用于含孔试样渐进性破坏过程的孔周变形精细化分析,利用该方法所确定的应力门槛值可将试样的破坏过程划分为5个阶段,通过提取与计算分析试样表面全场变形数据,得到在不同阶段内试样表面相对位移、以及孔周位移。结果表明:试样表面相对位移发展历经缓慢降低,加速降低以及迅速降低3个阶段,其中加速降低和迅速降低阶段与应力-应变曲线的裂纹稳定扩展和裂纹加速扩展对应;在压缩过程中,由于孔周对称移动造成孔周表面拉伸和压缩错动,最终在表面形成主拉伸裂纹和法向剪切裂纹。
The leak around the gas drilling borehole is one of the major reasons causing the drainage failure,and three stages( crack initiation stage,stable growth stage and unstable cracking stage) of the crack propagation around the gas drilling borehole are performed under the failure of coal. In order to find out the characteristics of crack propagation at different stages,a study on the crack propagation around the gas drilling borehole during the progressive failure was carried out. Plaster and water are blended in a mass ratio of 7 ∶ 3 to make soft coal like blocks,and uniaxial compression tests were performed with digital speckle correlation method( DSCM) getting the surface deformation of specimens. Based on this,a method determining the stress threshold by DSCM was proposed,and the deformation around the hole in the specimens' progressive failure was analyzed though this method. The sample failure process was divided into five stages by the stress threshold determined by this method,then the full-field deformation data were calculated to obtain the surface relative displacement,displacement around the hole and crack mouth opening displacement. The results show that the development of the surface relative displacement can be divided into the gradually decrease stage,the aggravated decrease stage and the rapidly decrease stage,among that the aggravated decrease stage and the rapidly decrease stage are corresponded with the stable growth stage and unstable cracking stage which are found in stressstain curve. As the symmetrical movement around the hole,tensile and compression state are formed which finally results in the tensile crack and the normal shear crack formed on the surface.
The leak around the gas drilling borehole is one of the major reasons causing the drainage failure,and three stages( crack initiation stage,stable growth stage and unstable cracking stage) of the crack propagation around the gas drilling borehole are performed under the failure of coal. In order to find out the characteristics of crack propagation at different stages,a study on the crack propagation around the gas drilling borehole during the progressive failure was carried out. Plaster and water are blended in a mass ratio of 7 ∶ 3 to make soft coal like blocks,and uniaxial compression tests were performed with digital speckle correlation method( DSCM) getting the surface deformation of specimens. Based on this,a method determining the stress threshold by DSCM was proposed,and the deformation around the hole in the specimens' progressive failure was analyzed though this method. The sample failure process was divided into five stages by the stress threshold determined by this method,then the full-field deformation data were calculated to obtain the surface relative displacement,displacement around the hole and crack mouth opening displacement. The results show that the development of the surface relative displacement can be divided into the gradually decrease stage,the aggravated decrease stage and the rapidly decrease stage,among that the aggravated decrease stage and the rapidly decrease stage are corresponded with the stable growth stage and unstable cracking stage which are found in stressstain curve. As the symmetrical movement around the hole,tensile and compression state are formed which finally results in the tensile crack and the normal shear crack formed on the surface.
引文
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[14]张晓平,王思敬,韩庚友,等.岩石单轴压缩条件下裂纹扩展试验研究——以片状岩石为例[J].岩石力学与工程学报,2011,30(9):1772-1781.ZHANG Xiaoping,WANG Sijing,HAN Gengyou,et al.Crack propagation study of rock based on uniaxial compressive test—a case study of schistose rock[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(9):1772-1781.
[15]刘宁,张春生,褚卫江.锦屏深埋大理岩破裂特征与损伤演化规律[J].岩石力学与工程学报,2012,31(8):1606-1613.LIU Ning,ZHANG Chunsheng,CHU Weijiang.Fracture characteristics and damage evolution law of Jinping deep marble[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(8):1606-1613.
[16]周辉,孟凡震,张传庆,等.硬岩应力-应变门槛值特点及产生机制[J].岩石力学与工程学报,2015,34(8):1513-1521.ZHOU Hui,MENG Fanzhen,ZHANG Chuanqing,et al.Characteristics and mechanism of occurrence of stress thresholds and corresponding strain for hard rock[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(8):1513-1521.
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[18]MARTIN C D,CHANDLER N A.The progressive fracture of Lac du Bonnet granite[J].International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts,1994,31(6):643-659.
[19]SCHMIDTKE R H,LAJTAI E Z.The long-term strength of Lac du Bonnet granite[J].Int.J.Rock Mech.Min.Sci.&Geomech.Abstr.,1985,22(6):461-465.
[20]李胜利,靳钟铭,魏锦平.软煤大煤样的压裂特性研究[J].太原理工大学学报,1999,30(6):567-570.LI Shengli,JIN Zhongming,WEI Jinping.Study of crack characteristic of big soft coal samples[J].Journal of Taiyuan University of Technology,1999,30(6):567-570.
[21]伍永平,高喜才.不同加载模式软硬煤岩侧向变形特征的对比实验研究[J].煤炭学报,2010,35(S1):44-48.WU Yongping,GAO Xicai.Experimental comparative study on lateral deformation characteristics of coal sample in different loading path[J].Journal of China Coal Society,2010,35(S1):44-48.
[22]彭俊,蔡明,荣冠,等.裂纹闭合应力及其岩石微裂纹损伤评价[J].岩石力学与工程学报,2015,34(6):1091-1100.PENG Jun,CAI Ming,RONG Guan,et al.Stresses for crack closure and its application to assessing stress-induced microcrack damage[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(6):1091-1100.
[2]倪冠华,林柏泉,翟成,等.钻孔密封材料的微观特性及其对密封性能的影响[J].北京科技大学学报,2013,35(5):572-579.NI Guanhua,LIN Baiquan,ZHAI Cheng,et al.Microscopic properties of drilling sealing materials and their influence on the sealing performance of boreholes[J].Journal of University of Science and Technology Beijing,2013,35(5):572-579.
[3]张天军,包若羽,李树刚,等.瓦斯抽采钻孔CF固化膨胀封孔材料性能研究[J].煤矿安全,2016,47(2):5-8.ZHANG Tianjun,BAO Ruoyu,LI Shugang,et al.Research on performance of solidification expansion sealing material for gas extraction drilling[J].Safety in Coal Mines,2016,47(2):5-8.
[4]张超,林柏泉,周延,等.本煤层近水平瓦斯抽采钻孔“强弱强”带压封孔技术研究[J].采矿与安全工程学报,2013,30(6):935-939.ZHANG Chao,LIN Baiquan,ZHOU Yan,et al.Strong-weak-strong borehole pressurized sealing technology for horizontal gas drainage borehole in mining seam[J].Journal of Mining&Safety Engineering,2013,30(6):935-939.
[5]郭德勇,杨雄,单智勇,等.煤层深孔聚能爆破封孔技术[J].北京科技大学学报,2011,33(7):785-789.GUO Deyong,YANG Xiong,SHAN Zhiyong,et al.Sealing technonly of coal bed deep-hole cumulative blasting[J].Journal of University of Science and Technology Beijing,2011,33(7):785-789.
[6]张超,李树刚,曾强,等.浆液在煤岩体裂隙中渗透规律的数值模拟[J].煤矿安全,2015,46(12):19-22.ZHANG Chao,LI Shugang,ZENG Qiang,et al.Numerical simulation on permeation laws of grouting in coal and rock fracture[J].Safety in Coal Mines,2015,46(12):19-22.
[7]LAJTAI E Z,LAJTAI V N.The collapse of cavities[J].International Journal of Rock Mechanics&Mining Sciences&Geomechanics Abstracts,1975,12(4):81-86.
[8]MARTIN C D.Seventeenth canadian geotechnical colloquium:the effect of cohesion loss and stress path on brittle rock strength[J].Can.Geotech.J.,1997,34(5):159-168.
[9]傅宇方,黄明利,任凤玉,等.不同围压条件下孔壁周边裂纹演化的数值模拟分析[J].岩石力学与工程学报,2000,19(5):577-583.FU Yufang,HUANG Mingli,REN Fengyu,et al.Numerical analysis of crack evolution around borehole in rock sample subject to confining pressures[J].Chinese Journal of Rock Mechanics and Engineering,2000,19(5):577-588.
[10]马少鹏,王来贵,赵永红.岩石圆孔结构破坏过程变形场演化的实验研究[J].岩土力学,2006,27(7):1082-1086.MA Shaopeng,WANG Laigui,ZHAO Yonghong.Experimental study on deformation field evolution during failure procedure of a rock borehole structure[J].Rock and Soil Mechanics,2006,27(7):1082-1086.
[11]朱谭谭,靖洪文,苏海健,等.孔洞-裂隙组合型缺陷砂岩力学特性试验研究[J].煤炭学报,2015,40(7):1518-1525.ZHU Tantan,JING Hongwen,SU Haijian,et al.Experimental investigation on mechanical behavior of sandstone with coupling effects under uniaxial compression[J].Journal of China Coal Society,2015,40(7):1518-1525.
[12]EBERHARDT E,STEAD D,STIMPSON B,et al.Identifying crack initiation and propagation thresholds in brittle rock[J].Canadian Geotechnical Journal,1998,35(2):222-233.
[13]周火明,杨宇,张宜虎,等.多裂纹岩石单轴压缩渐进破坏过程精细测试[J].岩石力学与工程学报,2010,29(3):465-470.ZHOU Huoming,YANG Yu,ZHANG Yihu,et al.Fine test on progressive fracturing process of multi-crack rock samples under uniaxial compression[J].Chinese Journal of Rock Mechanics and Engineering,2010,29(3):465-470.
[14]张晓平,王思敬,韩庚友,等.岩石单轴压缩条件下裂纹扩展试验研究——以片状岩石为例[J].岩石力学与工程学报,2011,30(9):1772-1781.ZHANG Xiaoping,WANG Sijing,HAN Gengyou,et al.Crack propagation study of rock based on uniaxial compressive test—a case study of schistose rock[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(9):1772-1781.
[15]刘宁,张春生,褚卫江.锦屏深埋大理岩破裂特征与损伤演化规律[J].岩石力学与工程学报,2012,31(8):1606-1613.LIU Ning,ZHANG Chunsheng,CHU Weijiang.Fracture characteristics and damage evolution law of Jinping deep marble[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(8):1606-1613.
[16]周辉,孟凡震,张传庆,等.硬岩应力-应变门槛值特点及产生机制[J].岩石力学与工程学报,2015,34(8):1513-1521.ZHOU Hui,MENG Fanzhen,ZHANG Chuanqing,et al.Characteristics and mechanism of occurrence of stress thresholds and corresponding strain for hard rock[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(8):1513-1521.
[17]MICHAEL A Sutton,JEAN-JOSOrteu,HUBERT Schreier.Image correlation for shape,motion and deformation measurements[M].Springer,2009.
[18]MARTIN C D,CHANDLER N A.The progressive fracture of Lac du Bonnet granite[J].International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts,1994,31(6):643-659.
[19]SCHMIDTKE R H,LAJTAI E Z.The long-term strength of Lac du Bonnet granite[J].Int.J.Rock Mech.Min.Sci.&Geomech.Abstr.,1985,22(6):461-465.
[20]李胜利,靳钟铭,魏锦平.软煤大煤样的压裂特性研究[J].太原理工大学学报,1999,30(6):567-570.LI Shengli,JIN Zhongming,WEI Jinping.Study of crack characteristic of big soft coal samples[J].Journal of Taiyuan University of Technology,1999,30(6):567-570.
[21]伍永平,高喜才.不同加载模式软硬煤岩侧向变形特征的对比实验研究[J].煤炭学报,2010,35(S1):44-48.WU Yongping,GAO Xicai.Experimental comparative study on lateral deformation characteristics of coal sample in different loading path[J].Journal of China Coal Society,2010,35(S1):44-48.
[22]彭俊,蔡明,荣冠,等.裂纹闭合应力及其岩石微裂纹损伤评价[J].岩石力学与工程学报,2015,34(6):1091-1100.PENG Jun,CAI Ming,RONG Guan,et al.Stresses for crack closure and its application to assessing stress-induced microcrack damage[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(6):1091-1100.