顺层抽采钻孔封孔段渗漏机制及协调变形控制方法研究

The improvement of the sealing quality of drainage borehole has attracted a lot of attentions in the research field of gas drainage in China. For traditional sealing techniques such as "blocking of two ends and middle injection" and "secondary sealing", the uncoordinated deformation of the sealing section and coal around borehole will induce the decay of gas concentration. Using on-site monitoring and numerical simulation methods, the present project aims to determine the time-varying rules of the borehole stress environment. Through the self-developed experimental system on borehole dynamic degradation-permeation evolution, the progress of uncoordinated deformation, leakage-creep generation and expansion, and the dynamic evolution of permeability will be studied under dynamic changes of in-situ stress and gas pressure. Considering both the behaviors of uncoordinated deformation of hetero-structures, coal matrix gas desorption-diffusion-deformation and gas-air flow in fracture, the models of uncoordinated deformation of hetero-structures of sealing boreholes, and fluid-solid multi-fields coupled equations will be established to reveal the uncoordinated deformation and leakage mechanism of sealing section of in-seam drainage borehole. Finally, in order to achieve the coordinated deformation of the hetero-structure of sealing section, a co-deformation sealing method is proposed by varying the physical and mechanical properties of the sealing material. The expected results will provide theoretical foundation for the development and application of innovative sealing materials and processes.

如何提高抽采钻孔密封质量一直是我国瓦斯抽采领域学者们的研究热点。针对“两堵一注”和“二次封孔”等封孔工艺中密封介质与孔周煤体不协调变形导致抽采瓦斯浓度衰减的问题，本项目拟采用现场监测和数值模拟相结合的方法，探明顺层抽采钻孔受力环境的时变规律；通过自主研制抽采钻孔封孔段劣化-渗透动态演化实验系统，研究地应力和瓦斯压力动态变化过程中抽采钻孔封孔段不协调变形、渗漏裂隙生成-扩展和渗透率动态演化规律；考虑封孔段异质结构体不协调变形、煤基质瓦斯解吸-扩散-变形、裂隙瓦斯-空气渗流等行为，建立抽采钻孔封孔段异质结构体不协调变形控制方程和流-固多场耦合计算模型，揭示抽采钻孔封孔段不协调变形及渗漏机制；最终，以实现封孔段异质结构体协调变形为目标，从改变封孔材料的物理力学特性入手，提出顺层抽采钻孔封孔段协调变形控制方法。预期研究成果可为新型封孔材料及工艺的研发和推广应用奠定理论基础。

钻孔瓦斯抽采是目前煤矿井下瓦斯灾害防治和煤层气资源开发的主要工程方法，约占井下瓦斯抽采总量的90%以上。钻孔密封是钻孔瓦斯抽采的核心基础，直接决定着抽采瓦斯的浓度、效率、成本及利用率。钻孔密封段是由煤岩体、密封材料及抽采管组成的典型层状异质结构体，由于各材料物理化学性质的差异性，导致在应力作用下极易形成不协调变形损伤裂隙，造成抽采瓦斯浓度快速衰减，严重制约钻孔瓦斯长期有效高质量抽采和高效利用。本项目通过现场测试钻孔孔内结构及钻孔围岩应力动态分布特征，利用TAW-2000高温岩石三轴伺服试验机+Vallen AMSY-6声发射系统实验测试钻孔密封段异质结构体单体试件和组合试件的失稳破坏特征及全过程声发射参数演化特性，厘清了了钻孔密封段应力加载路径及异质结构体破坏规律；通过构建了考虑煤岩体塑性软化、扩容及蠕变特性和中间主应力效应条件下的钻孔围岩及密封段粘弹性-塑性软化-塑性流动力学模型，推导了考虑煤岩力学性质及时间效应等多因素耦合条件下的巷道围岩、钻孔围岩、密封段异质结构的应力分布及径向位移解析解，进一步分析了钻孔密封段异质结构损伤机理；通过建立了基于钻孔密封段异质结构动态损伤、裂隙瓦斯不稳定渗流及空气渗流等时间效应条件下的钻孔密封段流-固耦合模型，得出了顺层钻孔密封段异质结不构协调变形损伤条件下的漏气控制方程；在此基础上，提出以相变凝胶密封材料为物质基础的密封段不协调变形控制方法，并开发出了环保型相变凝胶钻孔密封材料和自适应保压式封孔器配套，且取得了良好的现场应用效果。该研究成果可为钻孔瓦斯高质量抽采提供科学可靠的理论基础及技术支撑，有效助力含瓦斯煤矿区节能减排和“双碳”目标的实现。