卸荷应力路径下含瓦斯水合物煤体力学性质试验研究

To understand the mechanical behaviors of gas hydrate bearing coal in the unloading process is the key for the application of coal and gas outburst prevention technology based on the hydrate method. Accordingly, the complete stress-strain curves are firstly measured using the self-developed integrated instrument for gas hydrate formation and triaxial compression. The effects of the initial confining pressure, the hydrate saturation and the stress paths are addressed concerning to the mechanical parameters such as the peak strength, lateral strain, axial strain, volumetric strain, deformation modulus and the poisson ratio. Subsequently, non-linear Mohr-Coulomb criterion is established based on the relation between the confining pressure and the axial pressure of the gas hydrate bearing coal during the unloading conditions. Furthermore, the variations of the strength parameters, the deformation parameters and the hydrate saturation with the unloading quantity are fitted to determine the reduction rules in the strength and deformation parameters during the unloading process. Finally, the mechanical properties of gas hydrate bearing coal are compared with those of the gas bearing coal to reveal the effect of gas hydration on the coal and gas outburst prevention. These results are hoped to enrich and enhance the coal and gas outburst prevention theories based on hydrate and provide some scientific significances and engineering values for promoting the coal and gas outburst prevention technology.

深入认识不同卸荷应力路径下含瓦斯水合物煤体力学性质对于瓦斯水合固化防突技术应用具有重要影响。首先，利用瓦斯水合固化与力学性质测量一体化试验装置，开展含瓦斯水合物煤体应力-应变全过程曲线测定，分析应力路径、饱和度、初始围压对含瓦斯水合物煤体峰值强度、环向应变、轴向应变、体积应变、变形模量、泊松比等影响；继而，确定卸荷作用下含瓦斯水合物煤体围压-轴压相关关系，建立卸荷应力路径下含瓦斯水合物煤体非线性摩尔-库伦强度准则；进而，研究卸荷量、饱和度、强度参数、变形参数等相互作用规律，阐明卸荷过程含瓦斯水合物煤体强度参数与变形参数劣化规律；最后，通过卸荷应力路径下含瓦斯煤体力学性质对比试验，分析瓦斯水合固化前后含瓦斯煤体与含瓦斯水合物煤体力学性质差异，揭示瓦斯水合固化技术对突出防治作用。项目研究成果可望丰富与完善瓦斯水合固化防突技术理论，对于推动我国煤矿突出灾害防治技术进步具有重要科学意义和工程价值。

随着开采强度和能源需求的增大，煤矿开采深度逐年递增，煤与瓦斯突出等动力灾害发生愈加频繁，强度也越来越大。瓦斯水合固化防突技术通过中高压注水和向水中添加有利于水合物形成的促进剂的方法，使煤层中大部分瓦斯气体转变为固态水合物，从而促使煤层赋存瓦斯气体压力降低，同时水合物的生成提高煤体强度，理论上减弱或消除煤与瓦斯突出危险性。本项目利用含瓦斯水合物煤体原位生成与力学性质测定一体化装置开展常规三轴、恒轴压卸围压和升轴压卸围压应力路径下不同饱和度、围压、粒径和卸荷速率影响因素下含瓦斯水合物煤体及含瓦斯煤体力学特性研究，获得其强度和变形参数及破坏模式。同时初步探讨了常规三轴压缩下水合物生成前后煤体的能量变化规律，揭示不同影响因素对含瓦斯水合物煤体峰值强度、环向应变、轴向应变、体积应变、变形模量、泊松比等影响规律，建立适用于加载和卸荷条件的含瓦斯水合物煤体强度准则及含瓦斯水合物煤体本构模型，从煤体力学性质变化角度揭示瓦斯水合固化技术对突出防治作用。目前共发表学术论文14篇论文，其中SCI5篇、EI2篇以及核心期刊7篇；授权发明专利2项，实用新型专利2项，2项发明专利进入实质审查阶段；出版专著1部；一名博士生的毕业论文和本项目相关，在本项目资助下，已有3位硕士毕业，在读硕士6名。