钻孔抽采瓦斯是防治瓦斯灾害的重要手段，由于井下煤层倾斜、瓦斯含量等影响，需要采用不同的钻孔参数满足实际工程需求。不同钻孔参数导致密封段漏气通道的分布情况存在差异性，阻碍钻孔密封技术的高效发展。当前广泛采用的全段压入式注浆密封方法，在实际操作中存在注浆压力沿钻孔深度梯度式衰减难题，影响钻孔密封效果，给矿井安全生产留下隐患。因此，为研究本煤层抽采钻孔漏气通道演化规律及高效密封技术，提高瓦斯抽采效果。本文采用理论分析、物理试验、数值模拟及现场试验相结合的方式，建立了钻孔参数与孔周煤体应力应变力学模型，分析了漏气通道受载发育演化规律，探究了钻孔应力区漏气通道分布特征，开发了瓦斯抽采钻孔分段异压动态密封技术，揭示了钻孔应力区注浆密封机制。论文主要研究工作如下：

（1）研究了瓦斯抽采钻孔密封段煤体应力分布特征。基于经典弹塑性理论从钻孔径向及轴向分析了孔周应力分布及漏气通道发育特征，总结分析了导致钻孔密封失效漏气通道发育扩展的主要原因。从不同钻孔参数（倾角、孔径、间距）含孔煤样着手，开展单轴压缩试验，得到各试件单轴抗压强度、弹性模量、峰值应变的数理对应关系，构建了钻孔参数与应力应变的规律方程。

（2）探究了漏气通道受载发育演化规律。借助数字散斑系统研究了不同钻孔参数含孔试件的孔周表观裂隙演化规律，通过声发射监测系统分析了声发射参数变化特征与试件失效的关系，探究了不同钻孔参数漏气通道三维空间分布特征。结果表明，随着钻孔倾角、孔径的增加、间距的减小，试件的单轴抗压强度、弹性模量在减小，峰值应变在增加，声发射计数与能量在减小，试件整体承载力下降。在受载情况下试件以钻孔为中心开始进行破坏，最终形成以钻孔为中心的贯通裂隙。

（3）揭示了钻孔密封段注浆失效机理。搭建了瓦斯抽采钻孔三维物理相似模拟试验平台，开展了钻孔磁性注浆密封检测试验，获得钻孔不同应力分区漏气通道三维空间分布特征，深入分析钻孔漏气通道与密封浆液在不同应力区的对应关系，揭示了传统密封技术失效机理。结果表明，采用同一注浆压力对于钻孔不同应力区浆液的扩散效果不同，其中破碎区、塑性区裂隙填充度在95%以上，密封效果较好；弹性区裂隙填充度仅在66.25%左右，孔周煤体有近1/3的裂隙处于漏气状态。亟需一种兼顾破碎区、塑性区与弹性区的注浆方法，以此提高钻孔密封效果。

（4）研制了新型粘液密封材料。以材料粘度为因变量通过单因素与多因素试验确定了粘液材料的最优配比：羧甲基纤维素钠（CMC）掺量为78%，脂肪酸甲酯磺酸钠（MES）掺量为6%，氧化钙-硫酸钙复合膨胀剂（HCSA）掺量为15%，聚丙烯酰胺（PAM）1%，水料比为60：1。对粘液材料的膨胀性能、保水性能与粘结性能进行研究。结果表明，粘液材料20min膨胀率达到10.5%，自然条件下放置30d保水率保持在82%，粘液材料在放大3500倍其自身孔隙少，且与煤体结合程度较好。

（5）开发了瓦斯抽采钻孔分段异压动态密封技术。阐述了瓦斯抽采钻孔分段异压动态注浆密封原理，基于搭建的三维物理模拟试验平台，开展了粘液段占比试验。此外通过数值模拟研究了水泥基封孔材料与粘液材料的合理注浆压力。研究认为，粘液注浆段最优占比为60%，可实现钻孔的有效支护。水泥封孔段注浆压力为0.5~0.6MPa、粘液封孔段注浆压力大于1.5MPa。最后在常村煤矿、漳村煤矿及余吾煤矿开展现场试验，验证了新型密封技术的密封效果。

论文分析了瓦斯抽采钻孔孔周漏气通道演化规律，揭示了钻孔密封技术失效机理，提出了钻孔分段异压动态注浆密封技术并研制了配套密封材料，在现场得到较好的验证和应用。研究工作对于实现本煤层抽采钻孔的精准密封、提高煤层瓦斯的抽采效率具有指导意义，同时可为煤层瓦斯高效开采及矿井瓦斯灾害防治提供理论和技术支撑。

Borehole gas extraction is an important method for preventing gas disasters. Due to the influence of factors such as the inclination of underground coal seams and gas content, different borehole parameters are required to meet the demands of actual engineering projects. Variations in borehole parameters lead to differences in the distribution of leakage channels in the sealing section, hindering the efficient development of borehole sealing technology. The currently widely adopted full-section press-in grouting sealing method faces the challenge of a gradient attenuation of grouting pressure along the depth of the borehole during actual operations, which affects the sealing effectiveness and poses safety risks for mine production. Therefore, to study the evolution mechanism of gas leakage channels in extraction boreholes and develop efficient sealing technologies, and to improve the effectiveness of gas extraction, this paper combines theoretical analysis, physical experiments, numerical simulations, and field tests. A mechanical model of borehole parameters and stress-strain relationships in the surrounding coal body was established, analyzing the evolution mechanism of leakage channels under stress. The distribution characteristics of leakage channels in the stress zone around boreholes were investigated, and a segmented differential pressure dynamic sealing technology for gas extraction boreholes was developed, revealing the grouting sealing mechanism in the stress zone of boreholes. The main research work of this paper is as follows:

(1) Investigation of the stress distribution characteristics of the coal body in the sealed section of gas extraction boreholes: Based on classical elastoplastic theory, the radial and axial stress distribution and the development characteristics of leakage channels around the borehole were analyzed. The primary causes of borehole sealing failure and leakage channel development and expansion were summarized. Uniaxial compression tests were conducted on coal samples with boreholes under different parameters (inclination angle, diameter, spacing), obtaining the relationships between uniaxial compressive strength, elastic modulus, and peak strain of each specimen. A functional equation relating borehole parameters to stress-strain characteristics was constructed.

(2) Exploration of the evolution mechanism of leakage channels under stress: Using digital speckle systems, the evolution patterns of visible cracks around boreholes in specimens with different parameters were studied, and the changes in acoustic emission parameters were analyzed using acoustic emission monitoring systems to investigate the relationship between acoustic emission parameters and specimen failure. The spatial distribution characteristics of leakage channels under different borehole parameters were explored. The results show that as borehole inclination and diameter increase and spacing decreases, the uniaxial compressive strength and elastic modulus of the specimen decrease, peak strain increases, and the acoustic emission count and energy decrease, leading to a reduction in overall bearing capacity. Under stress, the specimen starts to fail from the center of the borehole, eventually forming through-going fractures centered on the borehole.

(3) Revealing the failure mechanism of borehole grouting in the sealed section: A three-dimensional physical similarity simulation platform for gas extraction boreholes was established, and magnetic grouting sealing detection tests were conducted. The three-dimensional spatial distribution characteristics of leakage channels in different stress zones of boreholes were obtained. The relationship between leakage channels and sealing slurry in different stress zones was deeply analyzed, revealing the failure mechanism of traditional sealing technologies. The results indicate that applying the same grouting pressure produces different slurry diffusion effects in different stress zones of boreholes. In the fractured and plastic zones, the fracture filling rate is over 95%, achieving good sealing effects, whereas in the elastic zone, the filling rate is only about 66.25%, leaving nearly one-third of the fractures around the borehole in a leakage state. A grouting method that takes into account the fractured, plastic, and elastic zones is urgently needed to improve borehole sealing effectiveness.

(4) Development of a novel viscous sealing material: Using material viscosity as the dependent variable, single-factor and multi-factor experiments were conducted to determine the optimal mixture ratio of viscous materials: 78% sodium carboxymethyl cellulose (CMC), 6% sodium methyl ester sulfonate (MES), 15% calcium oxide-calcium sulfate composite expansive agent (HCSA), 1% polyacrylamide (PAM), and a water-to-material ratio of 60:1. The expansion, water retention, and bonding performance of the viscous material were studied. Results showed that the expansion rate of the viscous material reached 10.5% within 20 minutes, with a water retention rate of 82% after 30 days under natural conditions. The material exhibited low porosity when magnified 3500 times and demonstrated good bonding with the coal body.

(5) Development of segmented differential pressure dynamic sealing technology for gas extraction boreholes: The principle of segmented differential pressure dynamic grouting sealing for gas extraction boreholes was described, and proportioning tests of viscous sealing sections were carried out using the established three-dimensional physical simulation platform. Additionally, numerical simulations were conducted to study the optimal grouting pressure for cement-based and viscous sealing materials. The research concluded that the optimal proportion of the viscous grouting section is 60%, achieving effective borehole support. The grouting pressure for the cement sealing section was determined to be 0.5–0.6 MPa, while the pressure for the viscous sealing section was over 1.5 MPa. Field tests were subsequently conducted in Changcun, Zhangcun, and Yuwu coal mines, verifying the sealing effectiveness of the novel sealing technology.

The study analyzed the evolution mechanism of leakage channels around gas extraction boreholes, revealed the failure mechanism of borehole sealing technology, proposed a segmented differential pressure dynamic grouting sealing technology, and developed supporting sealing materials. The research has been validated and applied in field conditions, providing valuable guidance for achieving precise sealing of extraction boreholes and improving gas extraction efficiency in coal seams. The findings also offer theoretical and technical support for efficient gas extraction from coal seams and the prevention of mine gas disasters.