Development And Application Research Of Water-rich And Efficient Sealing Material For Coal Seam Gas Drainage Borehole

Gas extraction is a fundamental measure to manage mine disaster and prevent coal and gas protrusion,extraction borehole is disturbed by mining stress in the roadway,perturbed by hole formation and shrinkage cracks generated by adsorption and desorption of gas in the coal of the hole wall,forming micro-cracks and crack network leakage channels.Sealing material to seal the leakage channel is a key technology to improve the efficiency of gas extraction,and a water-rich and efficient sealing material is developed for the problems of sealing material.The research results show that:A new cement-based sealing material with high flowability,controlled setting time,micro-expansion and mechanical strength was developed by ordinary cement and other gel materials.The range of material ratios was determined by single-factor method,the microstructure of material was analyzed based on XRD and SEM,the relationship between properties of flowability,setting time and swelling rate and the material ratios was analyzed based on orthogonal tests,and the regression model of each property was established using the response surface method to facilitate selection of the best ratio in optimization region.The preferred sealing materials are applied in the field to verify their sealing effects.The research contents and conclusions are as follows:（1）The hydration products of different components added of the materials,and the structures formed by AFt,C-S-H gel,Ca（OH）₂,etc.were dominant,and generated flocculent gel products filled in pore structure to improve the apparent density of materials.（2）The error between established regression model value and measured value is less than 5%,and the predicted values corresponding to optimized area are:water-cement ratio of 1.1,50%of accelerant,0.1%of expansion agent and 3%of reinforcing agent.（3）The compressive strength of preferred different sealing materials ranges from 2.61MPa to 4.52MPa.（4）The industrial test results showed that the average gas extraction concentration has been significantly improved,and the test borehole is three times larger than the mine’s inspection hole,which was effectively improved the gas extraction efficiency.