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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。
Based on acoustic emission and digital video camera recording system, five sets of roof sandstone-coal pillar structures with different height ratios were subjected to uniaxial compression test to study their mechanical characteristics and progressive failure mechanism. The overall strength of the roof sandstone-coal pillar structure is a combination of the strength of sandstone and coal samples away from the interface and the interface. The friction effect strengthens the strength of the coal sample at the interface and weakens the sandstone strength at the interface. The roof- The macroscopic rupture initiation stress, uniaxial compressive strength and elastic modulus all decrease with the decrease of rock coal ratio. Under the same conditions, the more primary cracks occur in the coal sample, and the macroscopic rupture stress , The smaller the elastic modulus and uniaxial compressive strength. The macroscopic rupture of the roof-coal pillar structure led to the step-like fluctuation of the stress-strain curve. The AE signal peaked and most of the initiation sites were located on the coal sample. However, when the rock coal height ratio was 9: 1, Sandstone first rupture. In the coal sample, the crack propagation and penetration make it become more fragmented and local damage, meanwhile, the partial destruction leads to the ultimate destruction of the coal sample. The sandstone failure is caused by the crack propagation extending into the coal sample, and due to the crack propagation ability, Different from the velocity and angle, the failure mode of sandstone is splitting failure, shear failure or no damage. With the increase of rock coal ratio, the destruction degree of coal sample and sandstone increases, and the coal sample is more broken.