基于应力分阶作用机制的煤岩瓦斯动力灾害特征分析

    Analysis on characteristics of coal-rock gas dynamic disasters based on stress grading action mechanism

    • 摘要: 随着浅部煤炭资源日益枯竭,我国煤炭开采逐步向深部延伸。随着埋深增加,应力状态发生转换,应力场类型也会发生转变,使得煤岩内部应力分布呈现出有层次性的分阶趋势,这种应力分阶作用造成了煤岩体的物理力学特征以及瓦斯赋存、运移环境的差异,从而影响煤岩瓦斯动力灾害的发生特征。为深入分析应力分阶作用对煤岩瓦斯动力灾害发生的影响,对应力分阶作用的影响机制进行了综述。结果表明:在应力分阶作用影响下,应力状态发生转换,导致构造煤发育程度、破坏状态的不同,且破坏程度较高的构造煤层有向静水应力状态发展的趋势;煤中孔隙在临界深度时小孔和微孔更发育,孔比表面积及孔容更大,裂纹转向也随之由水平向过渡为垂向,从而影响了煤层的渗透性和瓦斯的迁移路径;瓦斯含量随埋深增加呈现先增加后减小的变化趋势;深度加深,侧压系数变化,导致突出孔洞的形状由半椭圆形向蝶形变化,浅部与深部不同的应力状态也使得煤岩瓦斯动力灾害形式发生了改变。基于上述研究,提出浅部以瓦斯抽采为主,深部卸荷消能与瓦斯抽采协同的灾害分区治理理念;未来须思考如何完善并实践卸荷消能介质改性协同技术体系,有效减轻或避免由于应力变化引起的煤岩瓦斯动力灾害,以应对深部煤层开采带来的挑战。

       

      Abstract: With the gradual depletion of shallow coal resources, coal mining in China gradually extends to the deep. With the increase of buried depth, the stress state will change and the type of stress field will also change, which makes the internal stress distribution of coal and rock show a hierarchical grading trend. This stress classification results in the difference of physical and mechanical characteristics of coal and rock as well as the environment of gas occurrence and migration, thus affecting the occurrence characteristics of coal and rock gas dynamic disasters. In order to analyze the effect of stress grading on coal gas dynamic disaster, the mechanism of stress grading is reviewed. The results show that the stress state changes under the effect of stress gradation, which leads to the different development degree and failure state of tectonic coal, and the tectonic coal seam with higher failure degree tends to develop towards the state of hydrostatic stress. When the pores in coal are at the critical depth, the pores and micropores are more developed, the pore specific surface area and pore volume are larger, and the crack direction also changes from horizontal to vertical, which affects the permeability of coal seam and the migration path of gas. The gas content increases first and then decreases with the increase of burial depth. With the deepening of depth and the change of lateral pressure coefficient, the shape of the outburst cavity changes from semi-elliptical to butterfly shape. The different stress states in shallow and deep areas also change the dynamic disaster form of coal, rock and gas. Based on the above research, this paper puts forward the idea of disaster zone management that the shallow part is dominated by gas extraction, and the deep part is coordinated by unloading energy dissipation and gas extraction. In the future, it is necessary to think about how to improve and practice the pressure-relief energy dissipation medium modification collaborative technology system to effectively reduce or avoid coal, rock and gas dynamic disasters caused by stress changes, so as to cope with the challenges brought by deep coal seam mining.

       

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