页岩起裂应力和裂纹损伤应力的试验及理论

发布时间：2018-03-28 12:27

本文选题：页岩　切入点：起裂应力　出处：《煤炭学报》2017年04期

【摘要】：为研究页岩在破坏过程中的起裂机制,对具有不同层理倾角的页岩岩样进行了不同围压下的常规三轴压缩实验,基于裂纹体积应变拐点和岩样体积应变拐点分别确定了页岩的起裂应力和裂纹损伤应力。试验结果表明,在相同围压下,层理倾角对页岩岩样的起裂应力大小影响很小,但对裂纹损伤应力的影响较大,这最终导致了页岩破坏模式和破坏强度对层理倾角的依赖性;当层理倾角相同时,随着围压增大,页岩起裂应力与峰值应力的比值变化逐渐增大,而裂纹损伤应力与峰值应力的比值变化很小,说明在层理倾角相同的条件下围压对页岩中裂纹的起裂有显著的影响,而对裂纹的非稳定扩展影响较小;基于断裂力学的压剪裂纹模型解释了页岩的起裂机制,并利用试验数据验证了该模型的合理性;利用该模型预测页岩中含有裂纹的平均长度约为0.985 mm,与现有文献中的结果较吻合;同时该模型的计算结果表明当页岩中的压剪裂纹长度超过3 mm时,裂纹长度对页岩起裂应力的影响不显著。
[Abstract]:In order to study the fracture initiation mechanism of shale in the process of failure, conventional triaxial compression experiments were carried out for shale samples with different bedding dip angles under different confining pressures. The crack initiation stress and crack damage stress are determined based on the crack volume strain inflection point and the rock sample volume strain inflection point, respectively. The experimental results show that under the same confining pressure, the bedding dip angle has little effect on the initial crack stress of shale rock samples. However, the effect on crack damage stress is great, which leads to the dependence of shale failure mode and failure strength on bedding dip angle, and when the bedding dip angle is the same, with the increase of confining pressure, The ratio of crack initiation stress to peak stress increases gradually, while the ratio of crack damage stress to peak stress changes little, indicating that confining pressure has a significant effect on crack initiation in shale under the same bedding dip angle. The compressive shear crack model based on fracture mechanics explains the fracture initiation mechanism of shale, and the rationality of the model is verified by experimental data. The model is used to predict the average length of crack in shale is about 0.985 mm, which is in good agreement with the results in existing literatures, and the calculated results show that when the length of compression shear crack in shale exceeds 3 mm, The effect of crack length on shale initiation stress is not significant.
【作者单位】：四川大学能源安全与灾害力学教育部重点实验室;四川大学建筑与环境学院;四川大学新能源与低碳技术研究院;
【基金】：四川省应用基础研究计划资助项目(2015JY0280) 四川省科技支撑计划资助项目(2012FZ0124) 国家自然科学基金资助项目(41472271)
【分类号】：TU45

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