摘要
岩石压缩破坏过程存在几个重要应力阀值,即裂纹闭合应力、启裂应力、损伤应力及峰值应力。主要研究裂纹闭合应力确定方法,并讨论用其评价岩石微裂纹损伤的可行性。首先,对确定裂纹闭合应力的方法进行回顾与总结,并提出一种基于轴向应变响应确定裂纹闭合应力的新方法。该方法易于编程操作,可去除人为因素的影响,使得裂纹闭合应力的确定更加客观。基于多组岩石单轴和三轴压缩试验结果验证发现,该方法在单轴和三轴压缩下与其他方法确定的裂纹闭合应力较接近,验证了该方法的合理正确性。最后,采用裂纹闭合应力评价瑞典Forsmark和Oskarshamn地区3组岩石的取样损伤,通过将裂纹闭合应力与取样深度关联可以发现,取样深度较小时,裂纹闭合应力随取样深度线性增加;而取样深度较大时,裂纹闭合应力基本保持不变。裂纹闭合应力与主地应力差也表现出良好的线性对应关系,表明主应力差可能为影响岩样内部微裂纹发育的主要因素。
Several important stress thresholds,termed as the crack closure stress,the crack initiation stress,the crack damage stress and the peak stress,can be identified from the progressive failure process of brittle rocks. The crack closure stress and its relationship with the stress-induced microcrack damage were studied. Firstly,various methods that have been proposed for identifying the crack closure stress were reviewed,and a new method,called as axial strain response(ASR) method,was proposed. An attractive feature of the proposed method is that it does not require subjective interpretation from the user and can be easily programmed. Secondly, the method was verified using the test data from uniaxial and triaxial compression tests. The crack closure stress determined from the ASR method was comparable with that from other methods in unconfined and confined conditions, which validated the proposed ASR method. Finally, the crack closure stress was used to evaluate the stress-induced microcrack damage of three types of rock from Forsmark and Oskarshamn sites,Sweden. By correlating the crack closure stress with the sampling depth,it was found that the crack closure stresses varied with the sampling depth.At the shallow depth,the crack closure stress increases roughly linearly with depth increasing. However,at greater depth,the crack closure stress is more or less constant. A linear relationship between the crack closure stress and thedifference of in-situ stress was also observed,indicating that the magnitude of the difference of in-situ stress may be a key factor that dictated the amount of stress-induced microcracks in the rock.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2015年第6期1091-1100,共10页
Chinese Journal of Rock Mechanics and Engineering
基金
国家重点基础研究发展计划(973)项目(2011CB013501
2010CB732005)
教育部新世纪优秀人才计划项目(NCET–11–0406)
