瓦斯抽采技术是矿井治理瓦斯的重要手段，在实际煤层瓦斯抽采过程中，由于巷道施工及采动的影响，煤层应力特征会发生变化，极易造成钻孔封孔区域裂隙贯通漏气，导致钻孔抽采效果下降。因此，保证钻孔封孔质量是提高瓦斯抽采效果的关键，为了提高煤层瓦斯抽采效果，钻孔动态密封技术被逐渐应用于各类高瓦斯及煤与瓦斯突出矿井。然而，由于抽采钻孔孔周裂隙扩展及漏气演化特征尚未完全探明，动态封孔注浆对孔周新生裂隙的封堵规律仍未明确，导致井下瓦斯抽采钻孔动态密封施工过程主要依赖经验，缺乏有效的理论指导及装备支撑，造成钻孔动态封孔对抽采效果提升不明显，制约着矿井瓦斯安全高效开采。为此，本文采用理论分析、物理实验、数值模拟和现场工业性试验等方法，分析了钻孔动态封孔区破坏失稳及漏气时变演化规律，研制了新型半流体动态密封材料，探讨了抽采钻孔动态密封补浆控制机理，提出了瓦斯抽采钻孔动态密封补浆调控技术，并开展了煤层瓦斯抽采钻孔动态密封及补浆调控工业性实验，为矿井瓦斯高效抽采提供技术支持。论文主要研究工作如下：

（1）基于巷道围岩破坏理论，探究了掘进巷道围岩裂隙分布特征，确定了钻孔动态封孔过程中的固态密封及动态密封区域位置，进一步分析了钻孔孔周围岩变形力学特征，理论推导了钻孔封孔区破坏失稳时变模型。在此基础上开展钻孔孔周裂隙演化数值模拟，研究了巷道及钻孔双重施工下的孔周破坏分布规律，并利用物理实验探究了含钻孔煤岩破坏裂隙发育规律，结合声发射系统及三维光学散斑系统获得了钻孔孔周失稳应力-应变特征及裂隙扩展演化特征。

（2）对含瓦斯煤变形特征进行分析，构建含瓦斯煤体损伤影响的渗透率演化模型，并开展了煤体破坏渗流实验，系统的研究了煤体在不同破坏条件下渗透率变化特征，得到了平均应力、围压、瓦斯压力以及变形等关键参数对煤体渗透率的影响规律。在此基础上，结合瓦斯流动特征分析了孔周失稳时变特征，构建了考虑抽采影响的的钻孔瓦斯涌出时变模型及钻孔漏气量动态演化模型，并以刘庄煤矿151108工作面瓦斯赋存条件，建立了钻孔漏气数值模型，研究了钻孔抽采时漏气量动态变化规律，结果表明钻孔接抽后漏气量会在40天内升高60倍以上，需要对钻孔开展持续堵漏保证抽采效果。

（3）分析了瓦斯抽采钻孔动态密封对相关材料的性能要求，开展了动态密封材料基料选型，配以触变剂、增稠剂、高膨胀固体、表面活性剂自主研制了一种新型动态密封材料，结合正交试验分析确定了材料的配比。进一步实验探究了新型动态密封材料的粘度时变特性、保水性及亲煤性，在此基础上，自主研发了煤体分级加载多场耦合实验系统，开展了材料补浆裂隙填充特性试验研究，对煤体破坏全应力应变过程中动态密封材料的补浆量变化规律进行分析，并结合电镜扫描结果分析了新型动态密封材料对煤体破坏裂隙的封堵特征，确定了研发的新型半流体动态密封材料黏结于微裂隙表面形成有效的覆盖层，在补浆时可以有效渗入煤体破坏裂隙内部进行封堵。

（4）分别研究了牛顿流体及宾汉流体渗透注浆扩散机理，分析了钻孔动态密封补浆堵漏机理，构建了瓦斯抽采漏气钻孔动态密封补浆控制模型，揭示了瓦斯抽采钻孔动态密封补浆影响的漏气量演化机制。进一步研究了钻孔动态密封补浆调控技术，提出了瓦斯抽采钻孔抽采状态判别方法以及瓦斯抽采钻孔动态密封效果评价及控制方法，搭建了钻孔动态密封补浆调控系统，研发了钻孔动态密封补浆调控装备，完成了瓦斯抽采钻孔动态密封调控平台开发部署，实现了对瓦斯抽采钻孔动态密封状态实时监测、效果分析评价、连续动态补浆控制及可视化展示。

（5）以刘庄煤矿11-2#煤层为试验条件，现场检测了瓦斯抽采钻孔破裂特征，研究了试验区域钻孔漏气区分布范围，确定了钻孔封孔总长度20m，固态封孔区长度为8m，动态密封区长度为9m。进一步布置了动态密封效果评判及补浆调控系统，开展了瓦斯抽采钻孔动态密封工业性试验，考察了动态密封补浆调控技术、材料及装备的实际应用效果。结果表明：瓦斯抽采钻孔采用全周期动态密封及调控技术进行封孔后，平均抽采浓度提升2.5倍，可以有效提高钻孔抽采效率。

本文系统的研究了煤层瓦斯抽采钻孔失稳漏气机理以及动态密封补浆调控对钻孔瓦斯抽采的影响机理，研发了动态密封效果评判及补浆调控系统、半流体动态密封材料及相关配套装备，实现了煤层瓦斯抽采钻孔动态密封及补浆自动调控，提高瓦斯抽采能力，为矿井瓦斯高效抽采提供技术支持，保障矿井安全生产。

Gas extraction technology is a pivotal approach for managing and mitigating gas hazards in mining operations. In the practical application of coal seam gas extraction, the stress characteristics of the coal seam are susceptible to alteration due to roadway construction and mining activities, which can readily induce fractures in the borehole sealing area, consequently leading to gas leakage and a significant reduction in extraction efficiency. Therefore, ensuring the integrity of borehole sealing is paramount for enhancing gas extraction efficiency. To optimize coal seam gas extraction, dynamic borehole sealing technology has progressively been implemented across a range of high-gas and outburst-prone coal mines. However, due to the incomplete understanding of fracture propagation around the extraction borehole and the evolving characteristics of gas leakage, the mechanisms underpinning dynamic grouting for sealing newly formed fractures around the borehole remain inadequately elucidated. Consequently, the construction of dynamic borehole sealing for underground gas extraction largely depends on empirical methods, which lack rigorous theoretical guidance and adequate equipment support, thereby resulting in only marginal improvements in extraction efficiency through dynamic sealing grouting. This limitation significantly hinders the safe and efficient extraction of gas in mining operations. To address these challenges, this paper integrates theoretical analysis, physical experiments, numerical simulations, and field industrial tests to examine the time-varying patterns of damage and instability that contribute to gas leakage in dynamic sealing zones surrounding boreholes. A novel semi-fluid dynamic sealing material has been developed, and the control mechanisms governing dynamic sealing grouting in extraction boreholes have been systematically investigated. This study proposes advanced dynamic sealing and grouting control techniques for gas extraction boreholes and undertakes industrial-scale experiments to validate these techniques in the context of coal seam gas extraction, thereby providing robust technical support for enhancing the efficiency of gas extraction in mines. The primary research contributions of this paper are as follows:

(1) Grounded in the theory of surrounding rock failure in roadways, the fracture distribution characteristics within the surrounding rock of roadways were comprehensively investigated. The specific locations for solid sealing and dynamic sealing regions during the borehole sealing process were accurately determined. The mechanical deformation characteristics of the surrounding rock around boreholes were further analyzed, leading to the theoretical derivation of a time-varying model for the failure and instability within the borehole sealing zone. Building on this foundation, a numerical model of fracture evolution around boreholes was established to examine the distribution patterns of damage around boreholes subjected to the dual construction of roadways and boreholes. Physical experiments were conducted to investigate the fracture development patterns in coal and rock containing boreholes. Utilizing acoustic emission systems and three-dimensional optical speckle systems, the stress-strain evolution characteristics, fracture propagation, and spatial distribution around unstable boreholes were meticulously analyzed and documented.

(2) The deformation characteristics of gas-bearing coal were thoroughly analyzed, leading to the construction of a permeability evolution model that incorporates the damage effects associated with gas-bearing coal. Permeability experiments on damaged coal were carried out to systematically study the variation characteristics of coal permeability under different failure conditions. The influence of key parameters such as mean stress, confining pressure, gas pressure, and deformation on coal permeability was comprehensively quantified. Building on these findings, the time-varying characteristics of borehole instability were analyzed in conjunction with gas flow dynamics. A time-varying model for gas emission from boreholes, accounting for extraction influences, and a dynamic evolution model for borehole gas leakage were developed. Utilizing the gas occurrence conditions at the 151108 working face of Liuzhuang Coal Mine, a numerical model for borehole gas leakage was established to study the dynamic variation patterns of gas leakage during borehole extraction. The analysis revealed that gas leakage increased by 67 times within the first 40 days of extraction.

(3) The performance requirements for dynamic sealing materials in gas extraction boreholes were systematically analyzed. The selection of base materials for dynamic sealing was meticulously undertaken, leading to the independent development of a novel dynamic sealing material incorporating thixotropic agents, thickeners, high-expansion solids, and surfactants. The optimal material ratios were determined through orthogonal experimental analysis. Further experiments were carried out to investigate the time-varying viscosity, water retention, and coal affinity characteristics of the newly developed dynamic sealing material. Building on this, an independently developed coal body graded loading multi-field coupling experimental system was utilized to investigate the grouting characteristics of the material when filling fractures. The variation patterns of grouting volume throughout the full stress-strain process of coal body failure were analyzed, and the sealing characteristics of the novel dynamic sealing material within coal body fractures were examined using scanning electron microscopy. It was determined that the newly developed semi-fluid dynamic sealing material is capable of effectively penetrating coal body fractures under grouting pressure, adhering to microfracture surfaces to form a robust covering layer.

(4) The diffusion mechanisms of Newtonian and Bingham fluid grouting were individually examined, and the mechanisms underlying dynamic sealing grouting for gas leakage prevention were systematically analyzed. A dynamic sealing grouting control model for gas extraction boreholes was established, elucidating the gas leakage evolution mechanism influenced by dynamic sealing grouting. Further research was conducted on dynamic sealing grouting control technology, leading to the development of a method for determining the extraction status of gas extraction boreholes, alongside evaluating and controlling the effectiveness of dynamic sealing. A comprehensive dynamic sealing grouting control system was established, accompanied by the development of dynamic sealing grouting control equipment. Furthermore, the dynamic sealing control platform for gas extraction boreholes was successfully completed and deployed. This facilitated real-time monitoring of dynamic sealing status, in-depth effectiveness analysis, continuous dynamic grouting control, and visual display capabilities.

(5) Using the 11-2# coal seam of Liuzhuang Coal Mine as the testing condition, on-site detection of fracture characteristics within gas extraction boreholes was conducted, and the distribution range of leakage areas around boreholes in the test region was comprehensively analyzed. The total sealing length for the borehole was determined to be 20m, with the solid sealing area measuring 8m and the dynamic sealing area extending to 9m. The dynamic sealing effectiveness evaluation and grouting control system were subsequently arranged, followed by industrial tests on dynamic sealing for gas extraction boreholes to evaluate the practical application of dynamic sealing grouting control technology, materials, and equipment. Results indicated that the average extraction concentration increased by a factor of 2.5 following borehole sealing with full-cycle dynamic sealing and control technology. Dynamic sealing and grouting control technology has been demonstrated to significantly enhance borehole extraction efficiency.

The results of the thesis systematically investigates the mechanisms of instability and gas leakage in gas extraction boreholes, alongside the influence of dynamic sealing grouting control on borehole gas extraction.  A dynamic sealing effectiveness evaluation and grouting control system, along with a semi-fluid dynamic sealing material and associated supporting equipment, were developed. This innovation facilitated the automatic control of dynamic sealing and grouting for coal seam gas extraction boreholes, thereby enhancing gas extraction capacity and providing critical technical support for efficient gas extraction in mines, ultimately ensuring safe and sustainable mine production.