煤体中瓦斯水合固化的力学作用研究进展

Progress in the mechanical effects of gas solidification by hydrate in coal

为更好地完善我国煤与瓦斯突出预测与防治方法,基于煤与瓦斯突出综合作用假说,提出了瓦斯水合固化防治煤与瓦斯突出的方法。该方法核心是将煤层中瓦斯固化生成瓦斯水合物,不仅能降低瓦斯压力,而且能够提高煤体强度,以达到减弱或消除煤与瓦斯突出危险性的目的。实现了煤体中瓦斯水合物的生成以及含瓦斯水合物煤体力学性质-渗透率原位测试,提出了煤体中瓦斯水合物生成及力学性质-渗透率测试技术及含瓦斯水合物煤体三轴压缩数值建模技术。瓦斯水合固化热力学和动力学条件是防突的理论基础,煤层瓦斯水合物稳定储存是技术前提,瓦斯压力降低及煤体力学性质改善是防突关键,重点围绕水合固化煤体交叉力学问题进行总结。分析认为:(1)瓦斯水合固化防突技术理论框架已经初步形成,并利用数值模拟手段初步探究了瓦斯水合固化对煤体力学特征改善的细观机理;(2)现阶段已证实煤体中水合物生成不仅能降低瓦斯压力,而且能改善其力学性质,高饱和度对提高煤体峰值强度明显;(3)瓦斯水合物生成经历快速、缓慢和稳定3个阶段,且水合物的生成会造成煤体中瓦斯渗流通道阻塞,导致其渗透率降低;(4)高瓦斯压力、高CH4体积分数不仅有助于提高水合物饱和度而且会延缓水合物分解,有助于水合物的稳定存在。需要注意的是,瓦斯水合固化技术防突的可靠度仍需大量重复试验验证,以建立普适化的数据库。综合现有研究结果,对水合固化防突研究目前仍存在的局限性与挑战进行了讨论,并且给出了进一步的研究方向。

Aiming at the real problems such as the occurrence of coal and gas outburst and based on the hypothesis of comprehensive action of coal and gas outburst,a method of gas hydration and solidification to prevent coal and gas outburst is proposed.The core of this method is to solidify the gas in coal seam to form gas hydrate,which can not only reduce the gas pressure,but also improve the coal strength,so as to reduce or eliminate the risk of coal and gas outburst.Based on the idea of“coal and gas outburst prevention using hydrate”,the test of gas hydrate formation in coal and the insitu test of the mechanical property-permeability of gas hydrate bearing coal have been performed,with the numerical modeling technique of the triaxial compression of the gas hydrate bearing coal proposed.The techniques are implemented by comprehensively applying the methods of theoretical analysis,development of testing equipment,indoor test and numerical analysis.In terms of coal and gas outburst prevention,the thermodynamic and kinetic conditions of gas hydrate formation are its theoretical basis,the stable storage of gas hydrate is its technical precondition,and the reduction of gas pressure and the improvement of mechanical properties are its key measures.This paper focuses on the cross mechanics related to the gas hydrate bearing coal.The results show that:①the theoretical framework of gas solidification techno-logy by the hydrate method for outburst prevention has been initially formed,and the meso-mechanism of improving the mechanical characteristics of coal before and after gas hydration has been preliminarily explored by means of the numeric-al simulation.②At present,it has been confirmed that the hydrate formation in coal can not only reduce the gas pressure,but also improve its mechanical properties.High saturation can obviously improve the peak strength of coal.③Gas hy-drate formation experiences three stages:rapid,slow and stable stage.Additionally,the formation of hydrate will cause the gas seepage channel in the coal to be blocked,resulting in a decrease in its permeability.④High gas pressure and high CH4 concentration not only help to increase the saturation but also delay hydrate decomposition,which is conducive to the stable existence of the hydrate.However,a large number of repetitive experiments are still needed to verify the reliability of the method to build up a generalized database.By analyzing current research findings,the limitations and challenges that still exist are discussed,with further research interests pointed out.