煤岩的显微构造特征及其与瓦斯突出的关系——以南桐鱼田堡煤矿为例

MICROSTRUCTURES OF COAL AND THEIR RELATION WITH GAS OUTBURSTS —— A CASE STUDY OF THE YUTIANBAO COAL MINE, NANTONG

煤瓦斯突出与煤岩显微结构构造密切相关。除部分显微结构构造与成煤阶段的环境等有关外,大部分都是构造变形的结果。因此,我们从构造变形类型和特点来划分煤岩显徽构造类型,既简便又利于应用。根据四川南桐鱼田堡煤矿4号及6号煤层的扫描电子显微镜研究,可将煤岩划分成5类:非构造煤、微裂隙煤、微劈理煤、碎裂构造煤和糜棱构造煤。文中详述了各类煤的特点,指出它们所代表的构造意义,并讨论了它们与瓦斯突出的关系。还特别提出糜棱构造煤的一系列塑性变形特征。得出结论:若其他条件均具备,有糜棱构造煤产出的地段,就可能是瓦斯突出最危险的部位。此外,根据观察煤瓦斯突出后的煤岩显微构造变化,提出有关瓦斯突出的过程,并探讨了煤瓦斯突出机理。在瓦斯突出过程中,已经历过塑性变形的煤岩又叠加了脆性变形,因而发生大量煤“粉尘”随突出而抛出。

Outbursts of coal and gas are closely related to coal microstructures. Part of microstruccures of coal are associated with the coal-forming environments, but most of them are produced by tectonic deformation. In this paper the types of microstructures of coal are distinguished according to the types and features of tectonic deformations, which is convenient and easily employed by geologists. Based on the SEM study on coal petrography of No.4 and No.6 coal seams of the Yutianbao coal mine, Nantong coal field, five types of coal are distinguished: nontectonic coal, microfissure coal, microcleavage coal, cataclastic coal and mylonitic coal. The microstructural features of various types are described in detail and their geological implications and relationships with coal and gas outbursts are also discussed. Special attention is paid to a series of the features of plastic defornaation of mylonitic coal and new discoveries related to it. It is concluded that if all other factors influencing outbursts of coal are met, the place with mylonitic coal is the most likely risk site for outbursts.The process and mechanism of coal and gas out bursts are suggested based on a series of changes in microstrucmres of the coal after bursting. In the process of gas outbursts, the plastic deformation is superimposed by brittle deformation, thus ejecting large quantities of coal dust.