Addressing the challenges in the deep mining of China's extra-thick coal seams—where mining disturbances readily induce dy-namic hazards,and gas control is hindered by issues such as blind spots in borehole coverage and the insufficient reliability of effective-ness verification—this study was conducted with the single extra-thick,outburst-prone coal seam at the Jinhe Coal Mine in the Yaojie Mining Area as its engineering context.It systematically investigated the dynamic evolution of the stress field throughout the entire min-ing process,the optimization of key technologies for regional outburst prevention at the working face,and techniques for high-efficiency pressure relief and permeability enhancement in local stress zones at the driving face.FLAC3D numerical simulations revealed the devel-opmental characteristics of the arc-shaped pressure relief zone in a fully-mechanized top-coal caving face with a large mining-to-caving ra-tio:the zone's width was 5～7 m during the initial mining period,3～5 m in tectonic zones,and 10～15 m in normal zones.Concurrently,it was discovered that under the superposition of multiple mining-induced stresses,an ultra-high stress concentration phenomenon occurs at the driving face,with the stress concentration factor(λ)reaching as high as 2.4～3.0.Accordingly,a graded risk management and con-trol method based on dominant stress factors was proposed:the longwall face was zoned into a Grade I risk area(λ>2.0)and a Grade II risk area(1.5≤λ≤2.0),while a Grade III risk area(1.0≤λ<1.5)was established for the driving face,for which differentiated prevention and control countermeasures were developed.To address the challenges associated with traditional regional prevention techniques at the work-ing faces,four key technologies were developed and applied to enhance the reliability of outburst prevention:A 3D inversion system for regional measure boreholes,which achieves 3D visualization of borehole trajectories and identification of risk areas,thereby eliminating"3D weak zones"in regional borehole coverage;A stratified and three-dimensional prediction model for gas drainage compliance,which uses the minimum drainage radius of the top slice as the standard for borehole layout to ensure the middle and upper parts of the coal body are fully drained;An inner-liner,wall-clinging gas content sampling device that reduces gas desorption loss,increasing the measured de-sorbable gas content by 6.25%to 20.59%compared to traditional borehole collar sampling;A"by-zone,by-band,by-layer"full-coverage verification method,which intensifies testing in high-risk areas like tectonic zones and soft coal bands and validates key horizons layer by layer,reducing verification blind spots.For high-stress zones at the driving face(such as the 16219-1 driving face,affected by sevenfold mining influence),an improved ultra-high-pressure hydraulic slotting technology and its associated equipment(including high-rigidity lightweight drill rods,an anti-slip device,and a water quality filter)were applied.The results showed that in the high-stress zone of the 16219-1 driving face,the stress concentration factor decreased from 3.0 to 1.6,the coal seam's permeability coefficient increased 10-fold,the time required to meet drainage standards was shortened by one-third,and the residual gas content was reduced to 4.73 m3/t.During driving,CH4 and CO2 gushing remained stable(with a maximum CO2 concentration of 0.48%),and high-energy microseismic events de-creased,achieving the"dual"objectives of outburst elimination and stress reduction.

Protective coal seam mining is an important technical method used to strengthen the effect of gas extraction and prevent accidents caused by gases. However, it is necessary to thoroughly study the selection of the first coal seam to be mined and its effects related to pressure relief and permeability enhancement under the complex conditions of a coal seam group. This includes studying the relationships that govern pressure relief and permeability enhancement and the mechanism of the extraction of gas. In this study, a certain mine was used as engineering background. A damage-permeability model of a coal rock body undergoing mining disturbance was constructed based on experimental results and related theories. COMSOL Multiphysics software was used to perform numerical calculations with the model. The distribution of gas pressure in a coal seam was simulated under different mining conditions for the first mining seam. The first mining layer for protective coal seam mining of a coal seam group was identified. On this basis, the changes in parameters such as coal seam gas content, vertical stress and seepage velocity were studied during the advancement of the working face of the first mining seam. Furthermore, the numerical simulation was used to analyze the arrangement of boreholes for gas extraction from the bottom extraction roadway and the effect of extraction on pressure relief and permeability enhancement during protective coal seam mining. The results of the study showed the following: (1) Selecting 6# coal seam as the first mining seam had the best pressure relief effect on the adjacent seam, followed by 4# coal seam, and 8# coal seam had the worst pressure relief effect. (2) With the advancement of the 6# coal seam working face, the range of the pressure relief of the protected seam gradually expanded, the maximum stress relief degree of 4# coal seam was 25%, and the maximum decrease in gas content was 28.1%. The maximum stress relief degree of 8# coal seam was 60%, and the maximum decrease in gas content was 45.9%. (3) The gas content of coal seams decreased rapidly after extraction using boreholes; the gas contents of 4# coal seam and 8# coal seam decreased 81.25% and 99%, respectively, compared with the original values after 50 days of extraction. The efficiency of extraction by drill holes was related to the degree of decompression in the coal seam.

To address the issues of low gas extraction efficiency and the difficulty of outburst prevention in deep, low-permeability coal seams, hydraulic measures such as hydraulic fracturing, hydraulic slotting, and hydraulic perforation have become important methods to improve coal seam permeability and reduce outburst risks. However, single hydraulic techniques have certain limitations. To further enhance pressure relief and permeability improvement in deep low-permeability coal seams, an ultra-high-pressure water jet “cutting-fracturing combination” pressure relief and permeability enhancement technology was proposed. By synergistically combining the precise pressure relief of hydraulic slotting with the large-scale permeability enhancement of hydraulic fracturing, and based on theoretical analysis, numerical simulation, and field tests, the synergistic mechanism of the “cutting-fracturing combination” was revealed: slots formed by hydraulic slotting induce stress redistribution in the coal mass, creating a plastic weakening zone; fracturing fluid preferentially extends along the plastic weak planes, constructing a connected three-dimensional fracture network, effectively avoiding the pressure relief blind zones and localized stress concentration issues present in single hydraulic fracturing. The key factors influencing the effectiveness of the cutting-fracturing combination were analyzed, and based on the specific conditions of the No. 1 coal seam in Xinji No. 2 Mine, numerical simulations optimized key process parameters: a slot spacing of 10 m ensures effective overlap of plastic zones, avoiding fracturing blank zones; a borehole spacing of 70 m facilitates efficient connectivity of the fracture network, forming a uniform permeability enhancement area. Two types of cutting-fracturing combination pressure relief technologies were proposed: the “controlled” type and the “enhanced” type. The core of the controlled cutting-fracturing technology lies in pre-intervention—control boreholes are pre-drilled at the boundaries of the controlled area to form guiding boundaries, directing the fractures generated by the cutting-fracturing combination to expand uniformly within the controlled area. The enhanced cutting-fracturing technology focuses on local post-treatment—after applying the cutting-fracturing combination, localized high-stress or weak permeability zones may exist, and supplementary hydraulic slotting measures are applied to further enhance pressure relief and permeability. Field applications at the 220106 working face of Xinji No. 2 Mine demonstrated that gas extraction efficiency improved by 2.3 to 2.9 times, borehole engineering workload was reduced by 33% to 38%, and the time to reach extraction standards decreased by 41% to 53%. The cutting-fracturing combination technology successfully achieved large-scale, uniform, and efficient pressure relief and permeability enhancement in low-permeability coal seams, providing theoretical and technical support for safe and efficient coal mining.

Combined with specific engineering examples, the spatial disturbance influence characteristics and laws of the surrounding rock stress in the staggered roadways are analyzed by numerical simulation. This paper concludes that (1) compared with the surrounding rock pressure behavior of the general roadway, the surrounding rock stability of the staggered roadway is relatively poor, showing the characteristics of the local serious roadway rock pressure behavior, such as the intensified destruction of the roadway side, the failure and fracture penetration of the surrounding rock between the roadways, and the relatively serious deformation of the surrounding rock. The reason is that the stress of the surrounding rock at the staggered roadway position is obviously superimposed and disturbed by each other; (2) the influencing factors of the failure and instability of the surrounding rock between interlaced roadways are as follows: the greater the buried depth and the smaller the distance between roadways, the more intense the superposition disturbance of the surrounding rock stress between roadways; the smaller the horizontal azimuth, the greater the influence range of superposition disturbance of surrounding rock stress between roadways; the more unbalanced the original rock stress field, the worse the stability of the surrounding rock between roadways, resulting in the more serious failure and instability of the surrounding rock between roadways; (3) for the staggered roadway layout, increasing the distance between roadways, the closer to the orthogonal layout and selecting the arch section of the lower roadway is conducive to the bearing stability of the surrounding rock between roadways; (4) constrained by the space conditions of staggered roadway, the role of bolt and cable support is limited. Passive support is the key to realize the safety and stability of surrounding rock of staggered roadway, so the control technical scheme of active and passive combined support in staggered roadway position is put forward, the combined support of the upper roadway “bolt + cable + shotcrete + concrete cushion of floor” and lower roadway “bolt + cable + U-shaped steel support passive reinforcement + shotcrete” within the spatial disturbance influence the range of surrounding rock stress in the staggered roadways, and the technical scheme can achieve satisfactory supporting effect.

To solve the high-stress hazard faced in the process of deep mining process, the pressure relief characteristics of gas bearing coal and the deformation characteristics of surrounding rock in deep roadway are studied by means of laboratory test, similar simulation analysis, and field investigation. The investigation results and engineering application showed that the specimens could more easily reach the failure point due to the axial pressure relief under high confining pressure. In addition, the deformation and failure degree of the surrounding rock was higher due to the disturbance from the deep high-stress roadway. The scope of the height affected by the pressure relief of the overlying strata reached above 10 m. Moreover, the initial gas emission could reach 4.41–14.39 times that of the original coal seam by drilling a hole in the coal seam at 10 m from the roof. Thus, the short-distance floor roadway exerted an obvious pressure relief effect on the overlying coal seam.

瓦斯灾害是煤矿安全生产的"第一杀手",瓦斯抽采是防治瓦斯事故的治本之策,而低透气性煤层是制约瓦斯抽采的关键因素.由于浅部资源逐渐枯竭,我国煤矿开采深度以每年10～30, m速度向深部延深,开采煤层表现出显著的"低煤层渗透性、高围岩地应力、高煤层瓦斯压力"特征.面对深部矿井煤岩复合动力灾害,单一采用地面井或者井下钻孔预抽等措施,在高地应力、低渗透性条件下难以取得较为理想的抽采效果,同时无法消除煤岩内部积聚的弹性应变能、降低采掘区域内地应力威胁,需结合有效的卸压增透措施才能满足复合动力灾害的治理需求.由此,研究一种既能满足煤层瓦斯快速抽采达标,又能达到降低煤层应力的技术手段,是煤矿科研工作者共同努力的方向.

针对采场厚硬顶板强矿压问题,在采场厚硬顶板采动失稳影响特征分析基础上,运用力学理论构建采场厚硬顶板采动承载力学模型,分析采场厚硬顶板采动承载状态及能量积聚演化发布规律,从能量转化角度分析采场厚硬顶板破断致积聚能量释放与强动压显现关系,推导出工作面液压支架动载响应估算方程,揭示厚硬顶板破断失稳强矿压显现影响特征.研究结果表明,1)厚硬顶板在破断失稳前处于覆岩承载状态和自身弹性势能积聚,在破断瞬间显现略高于重力作用的加速运动失稳,加之悬伸跨度较大,导致厚硬顶板条件工作面动压显现尤为强烈;2)悬伸跨度、上覆岩层荷载是厚硬顶板采动承载和能量聚散演化的关键影响因素,上覆岩层荷载、自身厚度和强度是厚硬顶板极限悬伸跨度的关键影响因素;3)在工作面液压支架动态阻力响应的力源构成中,厚硬顶板破断积聚能量释放所形成的动态阻力占比最高,上覆岩层荷载做功转化所形成的动态阻力占比次之;4)在工作面液压支架动态阻力响应的影响因素中,厚硬顶板的悬伸跨度、上覆岩层荷载起直接加剧影响,岩层厚度增加厚硬顶板极限悬伸跨度,进而间接加剧动态阻力响应,直接顶厚度可对动态阻力响应起缓冲降低作用,支架控顶距的加剧影响程度不明显.

为研究保护层开采过程中被保护层动态卸压效果,建立了煤层变形与瓦斯流动的应力-渗流耦合理论模型,数值模拟研究了被保护层的动态卸压效应及瓦斯运移规律,在此基础上,设计了保护层开采条件下的底板穿层钻孔强化抽采方法.研究表明:(1)被保护层卸压范围随保护层工作面推进逐步扩大,被保护层最大垂直应力降低了 30％左右.(2)采动卸压作用下被保护层瓦斯逐渐向采空区流动造成瓦斯压力下降,降幅可达35％.(3)通过保护层开采卸压结合穿层钻孔抽采提高了瓦斯抽采效率,瓦斯抽采浓度由10％左右提升到35％以上,达到了快速消突的目的.

A pressure relief and permeability enhancement method through short-distance floor roadway was proposed to solve the difficult outburst prevention during the gas extraction at the coal roadway strips in deep outburst coal seams with high ground stress and low gas permeability. On the basis of an equivalent model of the surrounding rock in a deep roadway, the analytical solutions of deep roadway excavation to the stress and deformation of pressure relief at overlying short-distance coal roadway strips were obtained using the unified strength theory and nonassociated flow rules. Next, the criteria for determining the reasonable position of floor roadway were established, and a mechanical model of short-distance floor roadway for the pressure relief and permeability enhancement zone at the overlying coal seam was constructed. Finally, the scope of the zonal disintegration at the coal roadway strips in the elastic and elastic–plastic zones of the surrounding rock in the roadway, as well as the expression of gas permeability change, was given. The engineering trial calculation and practice showed that the stress and strain of the surrounding rock in the roadway were evidently influenced by the intermediate principal stress coefficient. Moreover, the vertical stress and vertical displacement of overlying coal seam were gradually reduced with the increase in the intermediate principal stress coefficient and vertical distance of the floor roadway. The minimum reasonable distance arranged for the 213 floor roadway in Qujiang Coal Mine was 6.21 m, and the effective pressure relief should be conducted within 10.6 m from the coal seam floor. When the pressure relief was located at 9.0 m from the coal seam floor, the investigation results were basically consistent with the theoretical analysis results, exerting obvious pressure relief and permeability enhancement effects on the overlying short-distance coal roadway strips.

Aiming at the problem of gas control in the working face and the roadway to be excavated at the same time due to the small construction length of bedding borehole under the condition of the occurrence of soft coal, a technology of "one hole and two elimination" pre-drainage to eliminate gas outburst by using air screw motor drilling was put forward, and the field test was carried out in the 17102(3) working face of Pansu Coal Mine.The results show that this technology can effectively control the borehole trajectory, ensure the uniform and reasonable range of borehole outburst elimination, solve the problems of long gas treatment cycle caused by the construction of gas treatment roadway, improve the effective drainage time of borehole, ensure enough time and space for gas treatment, and be beneficial to the mining and replacement of mine.

松散含水层薄基岩采场易出现压架、出水事故,为保证薄基岩采场安全回采,针对顾北煤矿1512(3)工作面的地质情况,综合采用理论分析、力学实验、工业性试验等研究方法,研究了薄基岩采场风化带地面预注浆加固前后顶板结构、岩芯力学特性、回采矿压显现规律,并分析注浆加固效果.结果表明:风化带地面注浆有效扩散范围可达15m以上,注浆后风化带岩石胶结性、致密性、隔水性、稳定性增强,岩芯平均抗剪强度提高了40.6％,整体承载能力明显提升,配合高工作阻力的液压支架,实现了安全回采.

Conventional hydraulic fracturing has several disadvantages, including a short effective extraction time and low fracture conductivity during long-term extraction. Aiming at overcoming these shortcomings, a similar simulation test of repeated hydraulic fracturing was conducted in this study, and the evolutionary rules regarding the injection water pressure and stress distribution of the coal seam roof during this repeated hydraulic fracturing were revealed. The research results show that after multiple hydraulic fracturing, the number of cracks in the coal seam and the range of fracturing influence have increased significantly. As the number of fracturing increases, the initial pressure required for cracking decreases. The highest water injection pressure of the first fracturing was 2.8 MPa, while the highest water injection pressures of the second and third fracturing were 2.7 MPa and 2.4 MPa, respectively. As the number of fracturing increases, the area of increased stress will continue to expand. After the first fracturing, the impact radius of fracturing is 100 cm. After the second fracturing, the radius of influence of fracturing expanded to 150 cm. When the third fracturing was over, the radius of influence of the fracturing expanded to approximately 250 cm. It can be seen that, compared with conventional hydraulic fracturing, repeated hydraulic fracturing shows better fracturing effect. The research results can be used as a basis for repeated hydraulic fracturing field tests to increase coal seam permeability.

In order to solve the problems of serious hole collapse and poor gas drainage effect of large diameter directional long borehole in roof under complex geological conditions, based on the gas geological conditions of 32 coal seam in Zouzhuang coal mine, the research on hole protection technology of full hole under large diameter directional long borehole of roof under complex geological conditions was carried out. The construction efficiency was improved by 32%, the drilling hole forming effect was good, and the gas drainage effect reached the expectation.

In order to reduce the outburst risk of soft broken high gas coal seam, based on the gas geological conditions of Luling Mine field, the technology of segmented roof fracturing in water level section of U-shaped well in broken soft coal seam was tested. The safe drilling in the roof rock of horizontal section of coal seam was realized by directional drilling, and the trajectory of horizontal section was controlled in the roof rock of target coal seam 10000m 3 / d, the pumping effect is good.

Based on the gas geological conditions of 17102(3) working face in Pansan Coal Mine, using theoretical analysis, engineering practice and other methods, the hydraulic fracturing sand permeability technology and technology are studied. Through the comparative analysis of permeability enhancement and drainage effect between fractured area and non fractured area, it can be seen that after sand fracturing, the permeability coefficient of coal seam is increased by 13.31 times, the average 100 hole purity is increased by 2.3 times, the time of reaching the standard of drainage is reduced by 26 days, and the hydraulic fracturing sand permeability enhancement technology ensures the safe and efficient mining of working face.

In view of the current monitoring and effect investigation of coal seam fire prevention measures and technologies, it has the characteristics of numerous on-site observation points, large data volume, poor effectiveness and low efficiency, which brings great difficulties to the analysis of coal seam fire prevention situation. In this paper, the arrangement of observation points of coal seam fire prevention measures or technical requirements is combined with the result of fire prevention data processing to avoid the isolation of fire prevention data analysis. It can directly show the data, curve and changing trend of coal seam fire prevention and extinguishing in the measuring point layout. It can timely and effectively put forward the corresponding coal seam fire prevention measures to improve the mine fire prevention management measures.

针对软岩保护层开采后上覆被保护煤层卸压瓦斯治理问题,以淮北芦岭煤矿首例软岩保护层开采试验为工程背景,采用综合研究方法研究软岩保护层开采覆岩采动裂隙带演化特征.结果表明:Ⅲ11软岩保护层开采后覆岩冒落带和裂隙带最大发育高度分别为10.1～12.4,52.7～59.95 m,采空区侧及上覆被保护层煤层下部存在竖向裂隙发育区和远程离层裂隙发育区;设计地面采动井和拦截钻孔抽采覆岩8、9煤层卸压瓦斯,优化地面采动井终孔位置垂直方向距顶板法距20 m,倾斜方向距风巷或机巷平距35 m,拦截钻孔终孔位置距9煤底板5 m.考察期卸压瓦斯抽采实践表明,软岩保护层开采后覆岩"两带"发育高度的判断和卸压瓦斯富集区域的辨识是合理正确的.

In order to solve the problems of poor drainage effect and low efficiency caused by poor sealing quality of deep gas drainage boreholes, based on the gas geological conditions in Huainan mining area, comprehensive theoretical analysis and field engineering practice, the distribution law of surrounding rock fracture zone in different lithologic roadways was studied, and the sealing technology combining pressure grouting, screen pipe protection and deep and shallow hole grouting was put forward. Field tests showed that the technology was effective. The average gas extraction concentration and hundred hole extraction purity of boreholes are 3.75 times and 3 times higher than those of common boreholes respectively, and the field application effect is remarkable.

Abstract Aiming at the existing regional prediction methods of outburst danger and shock hazard can not meet the needs of precise control of coal and gas dynamic disasters in deep coal roadway excavation working face, using weight comprehensive index method, 13 factors reflecting the outburst and rock burst are considered, such as gas pressure, content and impact energy index, the buried depth of coal seam and gas pressure are taken as the key indexes, and the integrated regional prediction of dynamic risk in deep coal roadway strip is realized; The dividing index of the dynamic risk state grade in the roadway strip is determined, which is divided into four grades: no dynamic risk, weak dynamic risk, general dynamic risk and serious dynamic risk, and the corresponding countermeasures are worked out. The application results show that the integrated regional prediction method realizes the safe and rapid excavation of in Ding Ji mine 1222(1) coal roadway and Xie Yi mine 5131(5) coal roadway which the grade are general dynamic risk, it has important reference significance for similar conditions of mine.

In view of the phenomenon of spontaneous combustion of coal seam occurring during the period of end caving under complex mining conditions, taking the 1116 (3) stope of Guqiao mine as the object of study, the causes of spontaneous combustion during the period of end caving are analyzed, according to the specific geological conditions of the stope to develop corresponding fire prevention measures, including the reduction of air supply and air leakage in goaf, reduce the amount of coal left, reasonable drainage, nitrogen injection for spontaneous combustion prevention, grouting for spontaneous combustion prevention and permanent closure, fundamentally eliminates the potential for spontaneous combustion during the period of 1116(3) stope end caving. The engineering practice shows that this kind of measure has reference value for the prevention and control of spontaneous combustion during the period of stope end caving.