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王 波,马世纪,田志银,等. 不同加载条件下含瓦斯煤岩强度极限邻域范围研究[J]. 煤炭科学技术,2024,52(7):114−125. doi: 10.12438/cst.2023-1034
引用本文: 王 波,马世纪,田志银,等. 不同加载条件下含瓦斯煤岩强度极限邻域范围研究[J]. 煤炭科学技术,2024,52(7):114−125. doi: 10.12438/cst.2023-1034
WANG Bo,MA Shiji,TIAN Zhiyin,et al. Study on strength limit neighborhood range of gas-bearing coal rock under different loading conditions[J]. Coal Science and Technology,2024,52(7):114−125. doi: 10.12438/cst.2023-1034
Citation: WANG Bo,MA Shiji,TIAN Zhiyin,et al. Study on strength limit neighborhood range of gas-bearing coal rock under different loading conditions[J]. Coal Science and Technology,2024,52(7):114−125. doi: 10.12438/cst.2023-1034

不同加载条件下含瓦斯煤岩强度极限邻域范围研究

Study on strength limit neighborhood range of gas-bearing coal rock under different loading conditions

  • 摘要: 煤与瓦斯突出灾害的发生机理尚不清楚,据流变假说,含瓦斯煤岩在长期载荷下可能进入“强度极限邻域”,此时受外部冲击扰动更易破坏。为研究不同加载条件下含瓦斯煤岩的“强度极限邻域”,以找到进入该状态的影响规律,并建立相应的微观判别标准,利用自主研发的岩石流变扰动效应三轴试验系统和煤岩流变扰动效应渗流实验装置,开展不同围压、不同瓦斯压力、轴压下的含瓦斯煤岩流变扰动实验,通过核磁共振手段对流变扰动前后煤岩进行分析对比,得到不同加载条件下的孔隙率、孔径分布、T2谱曲线。试验结果表明:①不同加载条件下的煤岩流变过程中,存在一个应力阈值,可以使得煤岩在受到外部冲击扰动后阈值左右邻域有不同力学性质的表现;当施加力小于此阈值时,冲击扰动后,煤岩的孔隙度减小,煤样随之被压缩紧密,T2谱曲线中代表大孔径的谱峰降低,谱峰曲线左移;当施加力大于此阈值时,冲击扰动后,煤岩大孔径孔隙增多,T2谱曲线出现右移,所有谱峰高度增大,说明该应力阈值是用来判断煤岩是否进入“强度极限邻域”关键。②围压和瓦斯压力对煤岩的影响具有相反的力学作用性质,在抗压能力、损伤程度、长期强度、“强度极限邻域”中有所表现,其中,围压越大,煤岩越晚进入“强度极限邻域”,瓦斯压力越大,煤岩则越早进入该邻域。③煤岩的孔径分布、T2谱曲线能直观反映了煤岩“强度极限邻域”内、外微观变化特征。④通过煤岩孔隙率所确定的进入“强度极限邻域”时的轴压与围压、瓦斯压力构建函数方程可判断不同加载条件煤岩进入“强度极限邻域”的时机,作为进入“强度极限邻域”范围时的判别标准,其中围压越大,此时进入“强度极限邻域”范围时的应力阈值越大;瓦斯压力越大,进入“强度极限邻域”时的应力阈值越小。

     

    Abstract: The occurrence mechanism of coal and gas outburst disasters is still unclear. According to the rheological hypothesis, gas-bearing coal and rock may enter the “strength limit neighborhood” under long-term load, and it is more likely to be destroyed by external impact disturbance. The “strength limit neighborhood” of gas-bearing coal rock under different loading conditions is studied to find the influence law of entering this state, and the corresponding micro-discrimination criteria are established,” using the self-developed triaxial test system of rock rheological disturbance effect and the seepage experimental device of coal rock rheological disturbance effect, the rheological disturbance experiment of gas-bearing coal rock under different confining pressures, different gas pressures and axial pressures was carried out. The coal rock before and after rheological disturbance was analyzed and compared by means of nuclear magnetic resonance, and the T2 spectrum curve, porosity and pore size distribution under different loading conditions were obtained. The test results show that: ① In the rheological process of coal rock under different loading conditions, there is a critical value for the sensitivity of external disturbance. When the applied force is less than this critical value, after the impact disturbance, the porosity of coal rock decreases and the specimen is compressed closely. When the force is greater than this critical value, after the impact disturbance, the large pore size of coal rock increases obviously, the T2 spectrum curve shifts to the right, and the peak height increases, It shows that the stress threshold is the key to determine whether the coal rock enters the “strength limit neighborhood”. ② Confining pressure and gas pressure have opposite mechanical properties to coal rock. It is shown in the compressive capacity, damage degree, long-term strength and “strength limit neighborhood”. Among them, the greater the confining pressure, the earlier the coal rock enters the “strength limit neighborhood;” The greater the gas pressure, The greater the gas pressure, the earlier the coal rock enters the neighborhood. ③ the pore size distribution and T2 spectrum curve of coal rock can directly reflect the internal and external micro-variation characteristics of rock’s “strength limit neighborhood.” ④The constitutive equation of axial pressure, confining pressure and gas pressure determined by the porosity of coal rock can be used to judge the timing of coal rock entering the “strength limit neighborhood” under different loading conditions. As a criterion for entering the “strength limit neighborhood,” the greater the confining pressure, the greater the stress threshold when entering the “strength limit neighborhood,” the greater the gas pressure, and the smaller the stress threshold when entering the “strength limit neighborhood.”

     

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