真三轴路径下含瓦斯复合煤岩体渗流及力学破坏特性

Seepage and mechanical failure characteristics of gas⁃bearing composite coal⁃rock under true triaxial path

  • 摘要: 深部开采扰动下“ 煤体-岩体” 复合系统发生整体破坏失稳是导致煤岩瓦斯复合动力灾害 发生的主要原因之一。 为了研究煤岩瓦斯复合动力灾害发生机理,采用真三轴气固耦合煤岩渗流 试验系统,以人工压制具有过渡界面的复合煤岩体试件为研究对象,进行了 5 种不同真三轴应力路 径下含瓦斯复合煤岩体渗流特性及力学破坏特征试验研究。 结果表明,真三轴路径下含瓦斯复合 煤岩体强度符合 Mogi-Coulomb 准则,相比于其他试验路径,真三轴加载路径下试件强度最大,复合 加卸载路径下试件强度次之,σ2 、σ3 发生转换时,试件强度显著降低;试件破坏时,真三轴复合加卸 载路径下试件渗透率增长倍数最多,真三轴卸载路径次之,真三轴加载路径下试件渗透率增加倍数 最少,σ2 、σ3 发生转换时试件渗透率显著增大;此外,复合煤岩体试件破坏特征具有规律性,真三轴 加载路径下,σ1 -σ2 平面煤体中出现剪切裂纹,并在煤岩交界面处交汇,真三轴卸载和复合加卸载 路径下,σ1 -σ2 平面上裂纹从煤体到岩体出现了跨界面扩展的现象,煤体中依然出现剪切裂纹,但 是裂纹在煤岩交界面处交汇之后转变为拉伸裂纹延伸至岩体中,岩体出现劈裂破坏;当 σ2 、σ3 发生 交汇、转换,σ2 小于 σ3 时,试件的 2 个侧面( σ1 -σ2 平面和 σ1 -σ3 平面) 均发生破坏,试件损伤状态相 对复杂。

     

    Abstract: The failure of “coal⁃rock” system under the disturbance of deep mining is one of the main causes of dynamic disaster. In order to study the mechanism of the disaster,five group experiments were designed to study the mechan⁃ ics and seepage characteristics of specimens. The results show that the strength of specimens under the true triaxial path conforms to the Mogi⁃Coulomb criterion. Compared with other experimental paths,the strength of specimens under the true triaxial loading path is the largest,followed by the road is the composite loading and unloading,and the strength decreases under the transformation of σ2 and σ3. When the specimen is damaged,the permeability increases significantly under the true triaxial loading path,followed by the true triaxial unloading path. The permeability increa⁃ ses least under the true triaxial loading path,and the permeability of the specimen increases significantly when σ2 and σ3 are transformed. In addition,the composite specimen damage of coal or rock is regular. In the true triaxial loading tests,shear cracks appear in the σ1 -σ2 plane of coal. Under the other two paths,the shear cracks in the coal intersect at the interface and transform into tensile cracks,which extend to the rock mass,and the rock mass is frac⁃ tured. When σ2 and σ3 are transformed,the σ1 -σ3 plane is also damaged,and the damage degree of the specimen is intense. The cracks of σ1 -σ2 plane from coal to the rock appear across the interface extension,shear cracks still ap⁃ pear in coal,and the cracks intersect at the coal⁃rock interface and then turn into tensile cracks,which extend across the interface into the rock,and the rock appears splitting failure. When σ2 and σ3 are transformed and σ2 is less than σ3,both sides of the specimen (σ1-σ2 plane and σ1-σ3 plane) are damaged,and the damage state of the specimen is relatively complex.

     

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