龙马溪组深部黑色页岩裂纹起裂与损伤阈值的各向异性特征  

Anisotropic characteristics of crack initiation and damage thresholds of deep black shale in Longmaxi Formation

作　　者：王小良 赵毅鑫 姜耀东[1,2] 刘斌 滕腾[1,2] WANG Xiaoliang;ZHAO Yixin;JIANG Yaodong;LIU Bin;TENG Teng(Beijing Key Laboratory for Precise Mining of Intergrown Energy and Resources,China University of Mining and Technology-Beijing,Beijing 100083,China;School of Energy and Mining Engineering,China University of Mining and Technology-Beijing,Beijing 100083,China)

机构地区：[1]中国矿业大学(北京)共伴生能源精准开采北京市重点实验室,北京100083 [2]中国矿业大学(北京)能源与矿业学院,北京100083

出　　处：《煤炭学报》2021年第S01期231-240,共10页Journal of China Coal Society

基　　金：国家自然科学基金资助项目(51874312,U1910206);中央高校基本科研业务费专项资金资助项目(2021YJSNY23)。

摘　　要：为研究页岩渐进破坏过程中裂纹萌生机理与演化规律的各向异性特征,以丁山—东溪地区丁页1井龙马溪组1974 m深部黑色页岩为研究对象,开展了单轴压缩试验,基于能量耗散演化机制确定了2个应力阈值(裂纹起裂应力σ_(ci)与裂纹损伤应力σ_(cd)),阐释了裂纹起裂应力与损伤应力各向异性原因,探讨了峰值应力与2个应力阈值相互关系的各向异性特征,分析了2个应力阈值与峰值应力处应变能与弹性应变能转化率的各向异性特征。结果表明:层理角度对裂纹起裂应力影响较小,而对裂纹损伤应力与峰值应力有显著影响。随层理角度增加,σ_(ci)/σ_(c)与σ_(cd)/σ_(c)整体上先增大后减小,而σ_(ci)/σ_(cd)随层理角度增加没有明显变化规律;σ_(cd)/σ_(c)可作为岩石破坏预警指标,σ_(cd)/σ_(c)越大,试样失稳破坏前预警时间越短,层理角度为45°和60°时,试样破坏较为迅速,失效模式主要为宏观裂缝沿层理弱面滑移。应变能随层理角度增加呈先减小后增大变化规律,层理角度为60°时破坏所需应变能最小,层理角度为0°或90°时破坏所需应变能最大;裂纹起裂应力处弹性应变能转换率对层理角度敏感性较低,而裂纹损伤应力与峰值应力处弹性应变能转换率对层理角度敏感性较高。To investigate the anisotropic characteristics of crack initiation mechanism and evolution law during the progressive shale failure process,uniaxial compression tests have been conducted on the black shale at the depth of 1974 m in Longmaxi formation of Dingye 1 well in Dingshan Dongxi area.Two stress thresholds(crack initiation stressσ_(ci) and crack damage stressσ_(cd))are identified based on the energy dissipation evolution mechanism.The reasons for the anisotropy of crack initiation stress and crack damage stress are explained in detail.The anisotropic characteristics of mutual relationships among the peak stress and the two stress thresholds are discussed.The anisotropic characteristics of the strain energy and elastic strain energy conversion efficiency corresponding to two stress thresholds and peak stress are analyzed.The results show that the bedding angle has little influence on crack initiation stress,but it has significant influence on crack damage stress.With the bedding angle increasing,the ratiosσ_(ci)/σ_(c) andσ_(cd)/σ_(c) increase first and then decrease,while the ratiosσ_(ci)/σ_(cd) have no obvious change law with the bedding angle increasing.The ratiosσ_(cd)/σ_(c) can be used as an early warning index of rock failure.The larger isσ_(cd)/σ_(c),the shorter the warning time before the sample failure.When the bedding angle is 45°and 60°,the sample failure is destroyed rapidly,and failure pattern generally is macro-crack slipping along the bedding plane.The strain energy decreases first and then increases with the bedding angle.The minimum strain energy is required for failure at 60°and the maximum strain energy is required for failure at 0°or 90°.Elastic strain energy conversion efficiency is less sensitive to the bedding angle at the crack initiation stress,while elastic strain energy conversion efficiency is more sensitive to the bedding angle at the crack damage stress and peak stress.

关 键 词：黑色页岩 各向异性 能量耗散 裂纹起裂阈值 裂纹损伤阈值 

分 类 号：TD313[矿业工程—矿井建设]