型煤孔裂隙结构及其分形特征实验研究

Experimental investigation on the pore and fracture structure of the reconstructed coal and its fractal characteristics

为了研究煤体内部孔裂隙结构,以不同粒径煤粉压制而成的型煤为对象,基于煤样孔裂隙结构的实验室测试结果,采用分形理论的分析方法,探讨了型煤中孔隙和裂隙的尺度特征.结果表明:由压汞实验数据获得的型煤分形曲线均被分成了符合分形规律的低压段和不符合分形规律的高压段两部分;根据压汞实验数据的分形特性可将型煤内部空间分为裂隙和孔隙.其中,裂隙结构参数可由压汞实验(低压段)获得,而孔隙结构参数可由物理吸附实验(以N2和CO2作为吸附质)获得.同时,亦可进一步结合煤的视密度测试结果计算获得煤样的裂隙率和基质孔隙率.对比发现,型煤的孔裂隙结构和原煤之间的差别较小,说明可以利用型煤代替原煤来研究煤中瓦斯吸附、解吸和渗流的一般性规律.

To study the pore and fracture structure in coals, the coal samples reconstructed by the coal powder with different particle sizes were taken as the study subject. The analytical methods based on the fractal theory were introduced and the scale characteristics of coal pore and fracture were analyzed. The results indicate that the fractal curves of the coal pore and fracture from the mercury intrusion porosimetry(MIP) are all divided into the low-pressure part that meets the fractal law and the high-pressure part that violates the fractal law. According to the fractal properties shown by the MIP, the interspace in coals can be divided into the pores and the fractures. The structure parameters of coal fractures can be obtained by the MIP(Low-pressure part) and that of coal pores can be obtained by a physisorption method(N2 and CO2 as the adsorbate). On this basis, the fracture porosity and matrix porosity in coals will be calculated by combining the apparent density of coals. In comparison, the difference between the pore and fracture structure parameters of the reconstructed coal samples and those of the raw coal samples is small, which indicates that the reconstructed coal samples can be used to replace the raw coal samples to study the general law of gas adsorption, desorption and seepage in coals.