摘要
传统线弹性断裂理论已不再适用于表征煤岩体韧性断裂特征,为了描述煤岩体Ⅰ/Ⅱ混合型裂纹扩展行为,通过Ⅰ型半圆盘三点弯曲(SCB)实验和贯穿剪切(PTS)实验,构建基于PPR势能函数的泥岩及煤Ⅰ/Ⅱ混合型黏聚裂纹模型。实验结果表明:煤SCB试件峰值载荷后非线性损伤过程中,裂纹尖端张开位移(CTOD)增加量是泥岩试件的3.48倍;同时,通过数字图像相关方法(DIC),测定煤岩试件中断裂过程区(FPZ)长度,其中煤试件的FPZ长度约为6.21mm,是泥岩试件的2.75倍,这直接导致煤试件的韧性断裂破坏特征表现得更为显著。煤岩贯穿剪切(PTS)实验中,煤PTS试件的最大切向位移为0.055 mm,远大于泥岩试件的最大切向位移,表明煤PTS试件Ⅱ型韧性断裂特征明显高于泥岩试件:此外,两类煤岩试件Ⅱ型断裂能高于其Ⅰ型断裂能,这说明发生Ⅱ型剪切断裂需要消耗更多的能量。最后,进行煤岩体Ⅰ/Ⅱ混合型单边缺口梁(SENB)三点弯曲实验及与其相对应的数值模拟研究,数值模拟过程分别基于所建立的PPR黏聚裂纹模型和线弹性断裂理论。通过以上对比可知,相较于线弹性,断裂理论,基于所建立的PPR黏聚裂纹模型的数值模拟结果更加符合实验结果,验证了所建立的PPRⅠ/Ⅱ混合型黏聚裂纹模型适合用于表征煤岩体Ⅰ/Ⅱ混合型韧性断裂行为。
Due to the traditional linear elastic fracture theory is no longer applicable to characterize the ductile fracture characteristics of coal and rock mass,the PPR unified potential-based cohesive crack model for mixed modeⅠ/Ⅱfractures in mudstones and coals by using semi-circular specimen under three-point bending(SCB)tests and punch-through shear(PTS)tests to describe theⅠ/Ⅱmixed crack propagation behavior in coal and rock mass.The experimental results show that the increase of crack tip opening displacement(CTOD)in the nonlinear damage process after load peak of the coal SCB specimen was 3.48 times that of the mudstone specimen.Meanwhile,the digital image correlation method(DIC)was used to measure the length of fracture process zone(FPZ)in the coal and mudstone specimens.The FPZ length of the coal SCB specimen was about 6.21 mm,which was 2.75 times that of the mudstone specimen.And the FPZ length of the coal SCB specimen can significantly cause a ductile fracture failure of the coal body.During the punch-through shear(PTS)experiments,the average maximum tangential displacement of PTS coal specimen is 0.055 mm,which is significantly larger than that of mudstone specimen,and the characteristics of the typeⅡductile fracture of PTS coal specimen are significantly higher than that of mudstone specimen.In addition,the pure modeⅡfracture energy of the two types of samples is higher than that of the pure mode I fracture energy,indicating that the occurrence of modeⅡshear fracture consumes more energy.Finally,the mixed modeⅠ/Ⅱsingle-edge notched beam(SENB)through three-point bending test.And the corresponding numerical simulation were carried out for the coal and mudstone,which the numerical simulation process is based on the PPR cohesive crack model and the linear elastic fracture theory,respectively.Through a comparison with the linear elastic fracture theory,the numerical simulation results based on the PPR cohesive crack model are more in line with the experimental results.Therefore,the cohesive crac
作者
杨健锋
柴敬
张丁丁
马哲
刘永亮
YANG Jianfeng;CHAI Jing;ZHANG Dingding;MA Zhe;LIU Yongliang(College of Energy Engineering,Xi’an University of Science and Technology,Xi’an,Shaanxi 710054,China;Key Laboratory of Western Mine Exploitation and Hazard Prevention,Ministry of Education,Xi'an University of Science and Technology,Xi'an,Shaanxi 710054,China)
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2021年第S02期3014-3023,共10页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金青年科学项目(52004203)。
