The development characteristics of micro-fractures in the soft coal seam, which are often neglected in water-injection and exploitation of coalbed methane, are more complex compared to the hard coal seam. To investigate the influences of micro fractures on the water-injection effects in soft coal seams, our research took the dust control through water injection in a soft coal seam with soft roof and floor as the object. By using an optical microscope, a scanning electron microscope (SEM), and an X-ray diffractometer (XRD), the development characteristics of micro fractures in the soft coal seam were obtained. The relationship between the development characteristics of micro fractures and the wetting effect of the coal was analyzed by studying the change of water content in coal samples after water injection in the coal seam. The research results showed that micro fractures were well developed, the fractures had poor directivity and connectivity, and some fractures were filled with minerals. In addition, the fractures were mainly 0~10 im wide, and the linear density was more than 6 fractures per millimeter. Fracture width and linear density positively correlated with the water content of coal after water injection, while clay minerals in coal mass exhibited a negative correlation with the water content.

中文翻译：

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基于注水效应的软煤层微裂缝发育特征研究

与硬煤层相比，在注水和煤层气开采中经常被忽视的软煤层微裂缝发育特征更为复杂。为研究微裂缝对软煤层注水效果的影响，以软顶底板软煤层注水抑尘为研究对象。利用光学显微镜、扫描电镜（SEM）和X射线衍射仪（XRD），获得了软煤层微裂缝的发育特征。通过研究煤层注水后煤样含水量的变化，分析微裂缝发育特征与煤的润湿作用之间的关系。研究结果表明，微裂缝发育良好，裂缝方向性和连通性较差，部分裂缝被矿物充填。此外，裂缝主要为0~10im宽，线密度大于每毫米6条裂缝。裂缝宽度和线密度与注水后煤的含水量呈正相关，而煤体中的粘土矿物与含水量呈负相关。