液氮冷浸作用下煤岩细观损伤特性研究

Study on microscopic damage characteristics of coal under liquid nitrogen soaking

为了研究液氮冷浸作用下煤岩内部孔裂隙结构的变化规律,开展液氮冷浸前后煤岩的CT扫描试验,对比分析液氮冷浸作用对煤岩内部微观结构的影响,结果表明:液氮冷浸作用对煤岩内部结构造成了损伤,损伤程度和形式受含水量影响;液氮冷浸后,干燥和水饱和煤样的最大原生裂隙体积增幅分别为340.8%,326.3%;对于水饱和煤样,表现出收缩-冻胀的应力作用,除裂隙体积增加外,同时产生6.78 mm;的新裂隙,利用MATLAB计算,其分形维数增加了0.54%,新增裂隙覆盖范围广,横向裂隙与纵向裂隙相互贯穿,更有利于瓦斯流动。研究结果可为煤岩液氮增渗提供指导。

In order to study the variation laws of internal crack structures of coal rock under liquid nitrogen soaking,the CT scanning experiments were carried out to compare and analyze the effects of liquid nitrogen soaking on the microstructure of coal rock cracks.The results showed that:The internal structure of coal rock was damaged by the cold action of liquid nitrogen soaking,and the degree and form of damage were affected by water content.After soaking in liquid nitrogen,the volume of maximum primary crack increased by 340.8%and326.3%of dry and saturated coal rock samples,respectively.The contraction-frost-expansion stress was exhibited in saturated coal rock samples,and a new crack of 6.78 mm;was generated.The fractal dimension of the saturated coal rock samples was increased by 0.54%,which could be calculated by MATLAB.These new cracks covered a wide range,and the transverse and longitudinal cracks interconnected with each other,which resulted in the increase of gas flow path.The study in this paper could provide guidance for studying the permeability increasing mechanism of the coal rock by liquid nitrogen cold socking.