原生裂纹对煤岩剪切破坏宏细观演化规律的影响研究

EFFECTS OF ORIGINAL CRACKS ON MACRO-MESO EVOLUTION LAW OF COAL SHEAR FAILURE

利用自主研发的煤岩细观剪切加载试验装置,开展不同加载速率剪切载荷作用下,含水平和垂直表面原生裂纹煤岩的裂纹开裂扩展时空演化模式、宏观裂纹形态及细观裂纹贯通机制的研究。研究结果表明:水平表面原生裂纹影响煤岩宏观裂纹发育数目,破坏后宏观形态呈H型或H+L型,而垂直表面原生裂纹对宏观裂纹发育数目无影响,破坏后宏观形态呈L型;原生裂纹对新裂纹发展演化的影响限于预定剪切面附近局部区域内,位于预定剪切面远处的原生裂纹,以及煤岩岩样制作中在预定剪切面远处产生的岩样缺损,其形态均未发生明显变化,未对剪切面附近宏观裂纹发育产生明显影响;在预定剪切面附近,后期产生的宏观主裂纹会引起前期右侧产生的裂纹受压而闭合,预定剪切面左侧的非贯通垂直原生裂纹,对宏观主裂纹的起裂、扩展无影响;细观分析表明,水平表面原生裂纹使煤岩局部破坏模式复杂多样化,包括压破坏、拉破坏、剪破坏及组合破坏模式,导致裂纹开裂位置可能出现在煤岩中部原生裂纹处,而垂直表面原生裂纹对煤岩破坏模式影响不明显。

Using self-made meso-shear test equipment for gas-containing coal and rock,the researchs on the evolution process of cracking and development,macroscopic crack morphology,and meso-crack coalescence mode of raw coal containing horizontal and vertical surface cracks,are carried out under different loading speed conditions.Results show that horizontal surface crack influenced the numbers of macrocrack development,made macroscopic shear crack morphology of raw coal containing horizontal crack manifested H or H＋L type;while,vertical surface crack had no effect on the number of macroscopic crack development;raw coal containing vertical crack showed L type.Effects of original cracks on the development and evolution of the new crack were limited to the local area near predetermined shear plane,cracks far from predetermined shear plane and rock samples defects far from predetermined shear plane induced by making of raw coal samples,whose shape were not changed significantly,had no significant effect on the macroscopic crack development near shear plane.Nearby predetermined shear plane,later macro main crack will cause pre-generated right side crack closed.Vertical original crack on the left side of the shear plane had no effect on crack initiation and expansion of macro main crack.Meso-analysis show that,horizontal surface original crack made coal rock failure mode complex and diversification,including compressed failure,shear failure,tension failure,and combination mode,lead crack initiation location to appear at the original crack nearby predetermined shear plane,while vertical surface original cracks less affected the coal rock failure mode.