Performance of a new coal-dust-based composite sealing material for gas-drainage borehole

Traditional sealing materials for gas-drainage boreholes are characterized by poor stability, low permeability, and low adaptability. This study aimed to solve these shortcomings by developing a new coal-dust-based (CD) composite sealing material, in which coal dust was used as base material and was supplemented by amino resin as the binder, and also added several other additions. Through the research of the properties of the CD sealing material, the results show that this material has a favorable liquidity with the material-water ratio of 1:1.1 similar to 1:1.5, the material shows the best mechanical property when the coal-dust/resin ratio is 1.0, and the expansion rate can reach up to 11.43%, which indicate that the CD sealing material can satisfy the technical requirements on sealing technology. Moreover, the sealing simulation experiments were also performed to evaluate the sealing effect of this developed material and the traditional sealing materials, the results indicate that the CD sealing material can diffuse sufficiently around borehole to form a larger grouting range, with maximum penetration radius of 36 mm. The Scanning Electron Microscope (SEM) results also reveal that the CD sealing material can penetrate into microfractures with 10 mu m aperture and combine closely with coal mass. And the Fourier Transform infrared spectroscopy (FTIR) results also reveal that some physical or chemical reactions were happened between resin molecules and coal-dust to form a firm coating. Compared with the traditional sealing materials, the CD sealing material has a superior sealing performance.