摘要：
基于声发射和数码摄像机录像系统,对不同高比的5组顶板砂岩-煤柱结构体进行单轴压缩试验,研究其力学特性及渐进破坏机制.顶板砂岩-煤柱结构体整体强度是远离交界面和交界面处砂岩、煤样强度的综合,摩擦效应加强了交界面处煤样强度,而削弱了交界面处砂岩强度;顶板-煤柱结构体宏观破坏起裂应力、单轴抗压强度和弹性模量均随岩煤高比递减而呈递减趋势;在同等条件下煤样原生裂纹越发育,顶板-煤柱结构体宏观破坏起裂应力、弹性模量和单轴抗压强度越小.顶板-煤柱结构体宏观破坏起裂导致应力-应变曲线出现阶梯状波动,AE信号出现峰值,大部分起裂位置位于煤样上,但当岩煤高比为9∶1时,交界面处砂岩首先破坏起裂.煤样内裂纹扩展和贯通使其变得较破碎且形成局部破坏,同时局部破坏的贯通导致煤样最终破坏;砂岩破坏是煤样内裂纹扩展贯通至其内部造成的,且由于裂纹扩展能力、速度及角度的不同,砂岩破坏形态呈劈裂破坏、剪切破坏或不发生破坏,随岩煤高比增大,煤样和砂岩破坏程度增大,煤样更加破碎.%In order to study the mechanical characteristics and progressive failure mechanism of the roof-coal pillar structure,uniaxial compression tests were carried out to five groups of sandstone roof-coal pillar structure bodies with different height ratios.The acoustic emission(AE) monitoring technique and the digital video camera system were used to investigate the failure process of the structure.The structural strength of the structure is the combined strength of sandstone,coal and interface.The contact frictional effects enhance the strength of coal in the interface,but weaken the strength of sandstone in the interface.With the decrease of the height ratio of sandstone to coal,the macroscopic failure initiation strength,the uniaxial compressive strength and the elastic modulus of the structure body reduce gradually.Under the same conditions,the more developed the primary cracks in the coal is,the lower the macroscopic failure initiation strength,the uniaxial compressive strength and the elastic modulus of the structure body are.The macroscopic failure initiation of the structure body causes the occurrence of the turning points on the stress-strain curves while the AE energy index reaches a peak value.After the macroscopic failure initiation,the AE energy index drops to the original level.Generally,the macroscopic failure initiations are located in the coal.When the height ratio of sandstone to coal is 9 ∶ 1,however,the macroscopic failure initiation occurs firstly at the interface.The propagation and coalescence of cracks in coal make the coal more broken and the local damage occurs in the coal.The coalescence of the local damages leads to the coal failure finally.The sandstone failure is caused by the crack propagation in coal cross to the sandstone interior.Due to the difference of the propagation ability,velocity and angle of cracks in the coal,the sandstones display the split failure,shear failure or no damage.With the increase of the height ratio of sandstone to coal,the degree of damage of the coal body and sandstone increases,and the coal body is broken more.
