不同偏置裂纹充填体断裂特性试验
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摘要
为了研究含缺陷胶结充填体的断裂特性,分别设置了裂纹偏置比为0、0.25、0.50、0.75,缝高比为0.10、0.25、0.50的胶结充填体试件进行三点弯曲试验,利用高速摄像机进行裂纹扩展模式全程捕捉,借助二维颗粒流软件PFC~(2D)对充填体裂纹扩展全程、破断方式及断裂机制进行分析。试验结果表明:相同缝高比下,随着裂纹偏置比的增加,断裂峰值荷载越大;当偏置比一定时,随着缝高比的增加,断裂峰值荷载越小;裂纹偏置比在0、0.25和0.50时,裂纹从偏置处扩展,且随着偏置比的增加,偏折角增大;裂纹偏置比在0.75时,裂纹从中心处扩展;断裂裂纹可分为3个阶段,且呈锯齿状扩展并在发育的过程中不断有碎裂状颗粒产生和脱落。利用二维颗粒流模拟充填体试件的力链网络、速度场及破断方式,结合其宏观力学的试验结果进行对比分析,探讨了细观断裂机制,其断裂时的峰值荷载与试验值相差不超过3.8%。
To study the fracture characteristic behaviour of the defective cemented backfill, three-point bending tests were carried out on the cemented backfill specimens with the offset ratios of 0, 0.25, 0.50, 0.75 and with the seam height ratios of 0.10, 0.25, 0.50, respectively. A high-speed camera was employed to capture the full-range crack propagation, and two-dimensional particle flow software PFC~(2D) was used to analyse the crack propagation process, the fracture mode and the fracture mechanism of the cemented backfill. The results showed that the fracture peak load increased with the increase of the crack offset ratio at the same seam height ratio. When the offset ratio was constant, the peak load was smaller with the increase of the seam height ratio. When the crack offset ratio was at 0, 0.25 and 0.50, the crack propagated from the offset, and the deflection angle increased with the increase of the offset ratio. When the crack offset ratio was at 0.75, the crack propagated from the centre. The crack propagation process was divided into three stages, and it was serrated-shaped. The fragmented particles were generated and shed during the crack propagation process. Two-dimensional particle flow model was employed to simulate the force chain network, velocity field and fracture mode of specimens. The obtained results were compared with experimental results of macro mechanics to explore the mesoscopic fracture mechanism. The peak loading of the fracture was not more than 3.8% compared with the experimental value.
To study the fracture characteristic behaviour of the defective cemented backfill, three-point bending tests were carried out on the cemented backfill specimens with the offset ratios of 0, 0.25, 0.50, 0.75 and with the seam height ratios of 0.10, 0.25, 0.50, respectively. A high-speed camera was employed to capture the full-range crack propagation, and two-dimensional particle flow software PFC~(2D) was used to analyse the crack propagation process, the fracture mode and the fracture mechanism of the cemented backfill. The results showed that the fracture peak load increased with the increase of the crack offset ratio at the same seam height ratio. When the offset ratio was constant, the peak load was smaller with the increase of the seam height ratio. When the crack offset ratio was at 0, 0.25 and 0.50, the crack propagated from the offset, and the deflection angle increased with the increase of the offset ratio. When the crack offset ratio was at 0.75, the crack propagated from the centre. The crack propagation process was divided into three stages, and it was serrated-shaped. The fragmented particles were generated and shed during the crack propagation process. Two-dimensional particle flow model was employed to simulate the force chain network, velocity field and fracture mode of specimens. The obtained results were compared with experimental results of macro mechanics to explore the mesoscopic fracture mechanism. The peak loading of the fracture was not more than 3.8% compared with the experimental value.
引文
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[17]切列帕诺夫ГП.脆性断裂力学[M].黄克智译.北京:科学出版社,1990:93-141.CHEREPANOVГП.Brittle fracture mechanics[M].Translated by HUANG Ke-zhi.Beijing:Science Press,1990:93-141.
[18]邓清海,巩林贤,薛永强,等.基于颗粒流的带中心孔巴西圆盘试样裂纹扩展分析[J].河南理工大学学报(自然科学版),2016,35(6):869-875.DENG Qing-hai,GONG Lin-xian,XUE Yong-qiang,et al.Analysis of crack propagation of holed-flattened Brazilian disc with particle flow code[J].Journal of Henan Polytechnic University(Natural Science),2016,35(6):869-875.
[19]孔亮,陈凡秀,李杰.基于数字图像相关法的砂土细观直剪试验及其颗粒流数值模拟[J].岩土力学,2013,34(10):2971-2978.KONG Liang,CHEN Fan-xiu,LI Jie.Meso-direct-shear test of sand based on digital image correlation method and its PFC numerical simulation[J].Rock and Soil Mechanics,2013,34(10):2971-2978.
[2]左建平,黄亚民,刘连峰.含偏置缺口玄武岩原位三点弯曲细观断裂研究[J].岩石力学与工程学报,2013,32(4):740-746.ZUO Jian-ping,HUANG Ya-min,LIU Lian-feng.Investigation on meso-fracture mechanism of basalt with offset notch based on in-situ three-point bending tests[J].Chinese Journal of Rock Mechanics and Engineering,2013,32(4):740-746.
[3]MANHANTY D K,SAVENT G Y.Experimental investigations on stable crack growth in three-point bend specimens under mode I and mixed mode(I and II)loading[J].Engineering Fracture Mechanics,1992,43(1):41-53.
[4]CHATTOPADHYAY J,DUTTA B K,KUSHWAHA H S.Experimental and analytical study of three-point bend specimen and throughwall circumferentially cracked straight pipe[J].International Journal of Pressure Vessels and Piping,2000,77(8):455-471.
[5]管辉,黄炳香,冯峰.灰岩试样三点弯曲断裂特性试验研究[J].煤炭科学技术,2012,40(7):5-9.GUAN Hui,HUANG Bing-xiang,FENG Feng.Experiment study on three point bending broken features of limestone sample[J].Coal Science and Technology,2012,40(7):5-9.
[6]张廷毅,高丹盈,郑光和,等.三点弯曲下混凝土断裂韧度及影响因素[J].水利学报,2013,44(5):601-607.ZHANG Ting-yi,GAO Dan-ying,ZHENG Guang-he,et al.Fracture toughness of concrete and influencing factors under three-point bending[J].Journal of Hydraulic Engineering,2013,44(5):601-607.
[7]田文岭,杨圣奇,黄彦华.卸围压下砂岩力学特性及细观机制颗粒流分析[J].岩土力学,2016,37(增刊2):775-782.TIAN Wen-ling,YANG Sheng-qi,HUANG Yan-hua.Particle flow analysis of mechanical behavior and meso-mechanism of sandstone under unloading confining pressure[J].Rock and Soil Mechanics,2016,37(Supp.2):775-782.
[8]常庆明,程钊,袁丹丹,等.基于PFC2D的镁碳质耐火材料断裂行为模拟研究[J].武汉科技大学学报,2016,39(4):273-277.CHANG Qing-ming,CHENG Zhao,YUAN Dan-dan,et al.PFC2D-based simulation study of the cracking behavior of Mg O-C refractory[J].Journal of Wuhan University of Science and Technology,2016,39(4):273-277.
[9]JEOUNGSEOK Y.Application of experimental design and optimization to PFC model calibration in uniaxial compression simulation[J].International Journal of Rock Mechanics and Mining Sciences,2007,44(6):871-889.
[10]刘新荣,傅晏,郑颖人,等.颗粒流细观强度参数与岩石断裂韧度之间的关系[J].岩石力学与工程学报,2011,30(10):2084-2089.LIU Xin-rong,FU Yan,ZHENG Ying-ren,et al.Relation between meso-parameters of particle flow code and fracture toughness of rock[J].Chinese Journal of Rock Mechanics and Engineering,2011,30(10):2084-2089.
[11]中国航空研究院.应力强度因子手册[M].北京:科学出版社,1981:188-189.Chinese Institute of Aeronautics.Handbook of stress intensity factors[M].Beijing:Science Press,1981:188-189.
[12]魏炯,朱万成,李如飞,等.岩石抗拉强度和断裂韧度的三点弯曲试验研究[J].水利与建筑工程学报,2016,16(3):128-132.WEI Jiong,ZHU Wan-cheng,LI Ru-fei,et al.Experiment of the tensile strength and fracture toughness of rock using notched three point bending test[J].Journal of Water Resources and Architectural Engineering,2016,16(3):128-132.
[13]丁遂栋.断裂力学[M].北京:机械工业出版社,1997:113-123.DING Sui-dong.Fracture mechanics[M].Beijing:China Machine Press,1997:113-123.
[14]单辉祖.材料力学[M].北京:高等教育出版社,2009:165-179.SHAN Hui-zu.Mechanics of materials[M].Beijing:Higer Education Press,2009:165-179.
[15]范向前,胡少伟,陆俊.非标准混凝土三点弯曲梁双K断裂韧度试验研究[J].建筑结构学报,2012,33(10):152-157.FAN Xiang-qian,HU Shao-wei,LU Jun.Experimental research on double-K fracture toughness of non-standard three point bending concrete beam[J].Journal of Building Structures,2012,33(10):152-157.
[16]吴礼舟,王启智,贾学明.用人字形切槽巴西圆盘(CCNBD)确定岩石断裂韧度及其尺度律[J].岩石力学与工程学报,2004,23(3):383-390.WU Li-zhou,WANG Qi-zhi,JIA Xue-ming.Determination of mode-rock fracture toughness with cracked chevron notched Brazilian disc(CCNBD)and application of size effect law[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(3):383-390.
[17]切列帕诺夫ГП.脆性断裂力学[M].黄克智译.北京:科学出版社,1990:93-141.CHEREPANOVГП.Brittle fracture mechanics[M].Translated by HUANG Ke-zhi.Beijing:Science Press,1990:93-141.
[18]邓清海,巩林贤,薛永强,等.基于颗粒流的带中心孔巴西圆盘试样裂纹扩展分析[J].河南理工大学学报(自然科学版),2016,35(6):869-875.DENG Qing-hai,GONG Lin-xian,XUE Yong-qiang,et al.Analysis of crack propagation of holed-flattened Brazilian disc with particle flow code[J].Journal of Henan Polytechnic University(Natural Science),2016,35(6):869-875.
[19]孔亮,陈凡秀,李杰.基于数字图像相关法的砂土细观直剪试验及其颗粒流数值模拟[J].岩土力学,2013,34(10):2971-2978.KONG Liang,CHEN Fan-xiu,LI Jie.Meso-direct-shear test of sand based on digital image correlation method and its PFC numerical simulation[J].Rock and Soil Mechanics,2013,34(10):2971-2978.