基于Griffith强度理论的岩石裂纹起裂经验预测方法研究

发布时间：2018-05-04 17:31

本文选题：岩石力学 + 裂纹起裂　；参考：《岩石力学与工程学报》2017年07期

【摘要】：裂纹起裂强度是岩石破坏过程中的重要应力阈值,研究岩石起裂准则对于揭示其破坏机制及预测围岩工程性质有着重要意义。首先进行青砂岩试样的单轴及三轴压缩起裂试验,并基于多种应变响应分析其中的起裂机制及细观破坏特征,指出局部张拉应力集中是起裂破坏的主因,总结提出低围压条件下的张开型起裂模型及高围压条件下的滑动型起裂模型。然后基于Griffith强度理论分析压应力场中岩石缺陷端部的局部最大张拉应力,其大小随差应力σ_1-σ_3的升高而增大,同时在围压条件下受表面摩擦作用的影响较大。针对岩石细观起裂机制提出起裂预测经验准则,准则中引入起裂参数m_(ci)作为围压影响系数以表征摩擦作用,从而适用于不同围压条件下的起裂破坏预测。利用3组起裂试验结果对经验准则进行验证,其准确性及实用性明显优于传统线性起裂准则。最后通过分析不同围压下岩石起裂强度与峰值强度之比σ_(ci)/σ_F,发现试样在围压60 MPa以下时其起裂破坏属于细观张拉破坏机制。
[Abstract]:The crack initiation strength is an important stress threshold in the process of rock failure. The study of rock cracking criteria is of great significance to reveal its failure mechanism and predict the engineering properties of surrounding rock. First, the uniaxial and three axial compression cracking tests of the green sandstone specimens are carried out, and the cracking mechanism and the mesoscopic damage based on a variety of strain response should be analyzed. It is pointed out that the local tensile stress concentration is the main cause of the fracture failure. The open crack model under the low confining pressure and the sliding model under the high confining pressure condition are put forward. Then, based on the Griffith strength theory, the local maximum tensile stress at the end of the rock defect in the stress field is analyzed with the increase of the difference stress Sigma _1- Sigma _3 At the same time, the influence of the surface friction is larger under the confining pressure. In view of the rock meso cracking mechanism, a crack prediction experience criterion is put forward. The initiation parameter m_ (CI) is introduced as the influence coefficient of the confining pressure to represent the friction effect, which is suitable for the prediction of the cracking failure under different confining pressure conditions. The results of 3 sets of cracking tests are used. The empirical criterion is proved to be more accurate and practical than the traditional linear cracking criterion. Finally, by analyzing the ratio of the crack strength to the peak strength of the rock under different confining pressure (CI) / Sigma _F, it is found that the cracking failure of the specimen under the confining pressure of 60 MPa belongs to the meso tensile breaking mechanism.

【作者单位】：中国科学院武汉岩土力学研究所岩石力学与工程国家重点实验室;武汉大学岩土与结构工程安全湖北省重点实验室;中国科学院大学;
【基金】：国家重点基础研究发展计划(973)项目(2014CB046904,2015CB058102) 国家自然科学基金青年基金项目(41602324)~~
【分类号】：TU45

【相似文献】