In order to solve the global problem of prevention and control of coal and gas outburst disaster dominated by ground stress in deep coal seam. It is found that hydraulic slotting and gas extraction have double pressure relief for coal seam horizontal stress and gas. The double pressure relief coefficient is proposed. Mechanical seepage experiments of coal samples with different double pressure relief coefficients (β = 0.5, 1.0, 1.5) were designed. The evolution mechanism and mathematical model of macro - fine - micro structure of coal seam fracture under the action of stress and gas relief are obtained. The results show that: with the increase of double pressure relief coefficient β, the fracture of vertical slot coal has a tendency to gradually weaken, and the fracture changes from tension failure to split failure, and from covering the whole coal body to the upper part of the coal. The macro-fracture plays a more dominant role than the micro fracture. When β = 1.0 (△σ = △P), the macro fracture is the most developed. When β = 0.5 (△σ = 0.5△P), the meso-fracture is the most developed. Before and after the test, the proportion of micropores and small pores is the largest, the proportion of large pores is the second, and the proportion of middle pores is the smallest. The proportion of cumulative fracture volume increased gradually and the growth rate was similar. It is found that there is a quadratic or cubic functional relationship between the fracture parameters of vertical slot coal under the double pressure relief coefficient β. It is found that there is a logarithmic function relationship between pore size and cumulative volume ratio. The research results provide a scientific basis for double pressure relief and permeability improvement of coal seam stress and gas, efficient extraction and effective outburst prevention.

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This study investigated the effects of borehole diameter and borehole interval on the stress relief performance of coal seams during mining. A discrete element numerical model was established based on the Voronoi and block models, and the stress relief performance was investigated in terms of axial stress, vertical displacement, and plastic zone development using the control variates method. The results showed that a decrease in the distance from the workface was accompanied by an increase in the effects of mining, the stress concentration, and the vertical displacement of the roof. Coal mining had positive effects on fracture propagation in front of the workface. As the borehole interval increased, the density of boreholes in the coal seams decreased, reducing the stress concentration and fracture propagation in front of the workface. The stress relief performance of the boreholes in the coal seams was improved at a borehole interval of 8 m. However, as the borehole diameter increased, the stress concentration near the boreholes decreased, reducing the effects of the workface mining on stress relief through the boreholes. Meanwhile, increasing the borehole diameter decreased the vertical displacement of the roof but exacerbated fracture propagation in front of the workface, which improved the stress relief performance of the boreholes in the coal seams. This study provides a reference for arranging boreholes in coal seams during mining.

针对松软煤层顺煤层定向瓦斯治理钻孔打不深、打不准、成孔率低的难题,详细分析了现有顺层定向钻进的技术瓶颈,创新尝试使用了底板定向梳状条带消突钻孔,突破了主孔快速开分支、分支孔水力下筛管护孔等技术难题,并选取杨柳煤矿1077中段机巷进行现场试验,在煤层坚固性系数为0.46的松软层中,共完成总进尺8 494 m,实验效果达到设计要求.现场试验表明,底板定向梳状条带消突钻孔有效缓解了采掘接替紧张局面,提高了矿井钻孔施工及瓦斯治理技术水平,为松软煤层定向瓦斯治理钻孔施工提供了新的技术思路.

The shock wave of a coal and gas outburst is a high-pressure and high-speed impact airflow formed rapidly after the outburst. The propagation destroys the ventilation facilities and causes the destruction of the ventilation system. The theoretical research on the outburst shock wave is of great significance. In order to deeply understand the formation mechanism of the outburst shock wave, this paper draws on the shock wave theory to theoretically analyze the microscopic formation process of the outburst shock wave. The main difference between the formation process of a coal and gas outburst shock wave and the formation process of a general shock wave is that the outburst shock wave has a solid–gas flow zone in the high-pressure zone. The calculation formulas of pressure, density, temperature and other parameters before and after the outburst shock wave are derived. After the outburst shock wave passes through, the pressure, temperature and density of the roadway air will change suddenly. The relationship expression between outburst gas pressure and outburst shock wave intensity is derived, which can reflect the role of pulverized coal in the formation process of a shock wave. In order to facilitate the understanding and calculation, the concept of equivalent sound velocity of coal-gas flow is proposed, and the direct calculation of the impact strength of a coal and gas outburst is attempted. This paper is helpful to improve the understanding of the essence of a coal and gas outburst shock wave. It is also of great significance to outburst disaster relief.

为满足煤矿自动化、智能化生产的快速发展及区域防突的迫切需求,推动煤矿大区域瓦斯灾害治理技术体系发展,针对传统煤层钻孔瓦斯抽采技术"钻不深、抽不出、检不了"等技术难题,系统分析近年来定向钻进、地面井、分段水力压裂、深孔取样、随钻探测等技术与装备在各大矿区不同地质条件下的应用效果.结果表明:目前已形成了基于大区域超前随钻地质勘探及预测、大区域地面及井下瓦斯抽采、非接触式连续在线动态预测等关键技术组成的煤矿瓦斯大区域治理技术体系,为推动煤层瓦斯治理技术的升级变革,实现不用或少用专用瓦斯治理巷道综合治理煤矿大区域瓦斯的目的奠定了基础.最后指出未来将发展核磁探测、伽马、雷达、深孔光纤等探测技术,以实现煤岩及地质异常体识别、瓦斯参数精确测定;发展地面水平井体积压裂高效开发及井上下联合增渗等技术,以提升井上下联合预抽效果;发展区域化超大流量压裂泵组或压裂工厂、连续油管压裂等技术与装备,以提升煤矿井下区域化增渗效果;发展风险信息融合感知、突出前兆特征智能识别、瓦斯超限预警等技术,以实现区域连续精准预测及智能预报警.

针对高应力巷道围岩锚注中注浆锚杆锚固力低和水泥基注浆材料自收缩造成控制效果不佳的问题,提出基于预应力锚和自应力注的破碎围岩锚注加固方法.以平煤十矿变电所巷道为工程背景,基于原支护方式失稳机理分析,探究裂隙岩体自应力浆液加固原理,研发新型高强预应力注浆锚杆系统,形成基于预应力锚和自应力注的破碎围岩锚注支护方案.通过浆岩界面SEM扫描、围岩钻孔窥视、锚杆索受力和围岩变形监测等方法综合评价该新型预应力锚注的工程应用效果.结果表明:通过高强预应力注浆锚杆的轴向约束应力与自应力浆液的膨胀应力使加固围岩处于准三维受力状态,实现了破碎围岩的强化与损伤修复;新型高强预应力注浆锚杆具有预应力大、预应力施加标准、锚固力高、杆体强度高等优点,能够对围岩提供高轴向约束;新型锚注加固后,注浆浆脉充填围岩裂隙,浆液结石体与岩体结合致密;注浆锚杆索受力稳定,巷道表面围岩最大位移为83 mm,说明通过新型预应力锚注加固方案实现了变电所巷道围岩稳定性控制.

普通水泥基浆液加固煤体由于其自收缩常造成浆煤界面松弛及充填空隙,以综放厚煤层异型开切眼松软煤体加固为工程背景,提出基于预应力锚和自应力注的松软煤体锚注加固方法.基于该新型预应力锚注加固煤体原理分析,对比研究普通硅酸盐水泥和超细硅酸盐水泥的基本性能,为自应力浆液原材料的选取提供依据;通过浆液纵向自由膨胀率试验获得自应力浆液的最佳膨胀剂掺量;进行预制裂隙煤体普通硅质浆液和硅质自应力浆液加固试验,对比分析自应力浆液加固煤体的力学性能优势和破坏特征;通过数值模拟和现场监测分析新型预应力锚注加固异型开切眼的有效性.结果表明:通过浆液结石体的膨胀应力和注浆锚杆的轴向约束应力,能够使松软破碎煤体处于准三维的受力状态,实现了其强化与损伤修复;超细硅酸盐水泥浆液由于流动性更大、结石体强度更高而更能满足自应力浆液的加固要求;随着膨胀剂掺量增大,水泥浆液最大纵向膨胀率呈先增大后减小的趋势,自应力浆液的最佳膨胀剂掺量为10％;约束条件下自应力浆液加固煤体的峰值强度比普通浆液加固煤体提高4.6％,说明自应力浆液加固裂隙煤体的效果优于普通浆液;普通浆液和自应力浆液加固煤样初始宏观裂纹均出现在浆煤界面处,最终破坏形态均为以预制裂隙为基础的整体劈裂弹射破坏,但其裂纹发展过程有所不同,自应力浆液加固煤样的裂隙数量少于普通浆液加固煤样;在数值模型中,仅锚杆索支护时煤体悬臂梁结构下沉量较大,新型预应力锚注后其下沉量明显减小;现场监测中锚杆索受力相对稳定,加固煤体下沉量较小,说明新型预应力锚注加固松软破碎煤体的效果较好.

Due to the insufficient understanding of the outburst mechanism, the coal and gas outburst disasters in China are more serious. Gas expansion energy is the main source of energy that causes outburst. In order to explore the distribution law of gas expansion energy in outburst coal seams, a gas-solid coupling equation of outburst coal seams was established. The distribution law of coal stress field, deformation field, gas flow field, and gas expansion energy were simulated and analyzed by using COMSOL Multiphysics. The results showed that from the excavation face to the deep part of coal seam, the stress presented unloading zone, stress concentration zone, and original stress zone. The volumetric strain and permeability reached the minimum, while the gas pressure reached the maximum at the peak value of vertical stress. As time goes on, the gas pressure in the fracture near the working face gradually decreased and was less than the pressure in coal matrix. The total gas expansion energy consists of free gas and desorption gas expansion energy. Affected by the excavation, free gas expansion energy maintained a constant value in the original coal seam and gradually decreased in the area close to the working face. The expansion energy provided by desorption gas was zero in the original coal seam. And it first increased and then decreased rapidly near the working face. Compared with stress and coal seam thickness, gas pressure and initial diffusion coefficient had significant influence on gas expansion energy of coal seam. When the diffusion coefficient was greater than 1e-9 m2/s, the gas expansion energy of the coal seam near the working face was significantly higher than that of the original coal seam, which had the risk of inducing outburst.

为研究瓦斯压力对煤与瓦斯突出冲击波传播的影响,自主研制了一套突出煤—瓦斯两相流模拟实验系统,开展了不同瓦斯压力条件下的煤—瓦斯两相流运移规律模拟实验,实现了对突出过程巷道内突出煤—瓦斯两相流运移的可视化监测.实验结果表明:煤与瓦斯突出是一个从突出口开始迅速向煤体内部发展的动力过程,期间瓦斯压力存在多次上下波动;突出过程中巷道内的冲击波超压呈现正压相与负压相交替变化的局面,同时冲击波超压特征值随初始瓦斯压力的增大而呈对数函数递增趋势;冲击波超压在巷道中传播是一个不断衰减的过程,前期衰减较慢,后期衰减加快.

In view of the problems of poor reliability and low accuracy in the monitoring and measurement of gas drainage in surface wells, a set of separate measurement and monitoring system for gas drainage in surface wells has been formed through the research on extraction detection, field self-powered supply, distributed measurement point data acquisition, measurement and monitoring device. The system provides a complete set of technology and equipment for real-time on-line monitoring of surface wells, and improves the accuracy of surface well measurement. At the same time, the surface well gas extraction data is combined with the downhole monitoring system data in real time, which realizes the safety and effective monitoring of mine drainage.

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.

为研究煤粉粒径对煤与瓦斯突出冲击波传播特征的影响,自主研制了一套突出粉煤—瓦斯两相流模拟实验系统,开展不同煤粉粒径条件下的突出模拟实验,突出过程中实时监测模拟巷道不同位置冲击波超压随时间的变化规律.实验结果表明:在各监测点冲击波超压呈现正相与负相交替变化的格局,冲击波超压峰值与突出腔体内煤粉粒径呈正相关关系;突出冲击波在巷道内的传播速度也受煤粉粒径的影响,即煤粉粒径越小,冲击波传播速度越小,且冲击波传播速度沿着巷道呈衰减趋势.

针对大倾角煤岩层巷道围岩局部应力集中导致普通断面形状和支护方案难以控制围岩稳定的问题,本文以新汶矿区某矿6196疏水巷为工程背景,通过理论分析、数值模拟、工程实践等方法研究深部大倾角煤岩层巷道围岩应力分布特征和层间剪切滑移变形机制;综合考虑半圆拱形断面承载能力强、应力集中程度低和斜顶梯形两帮受力合理的优点,设计偏心圆弧拱形断面,提出非对称耦合支护方案,并通过工程实践验证其有效性.研究结果表明:大倾角煤岩层巷道上覆岩层的重力作用使巷道帮角部位发生剪切滑移变形,在巷道2个对角处产生应力集中而在另外2个对角处产生应力释放;大倾角煤岩层巷道左侧顶底板位移整体大于右侧顶底板位移,右帮水平位移整体大于左帮水平位移;基于偏心圆弧拱形断面和非对称耦合支护方案进行围岩控制,顶帮锚杆载荷逐渐趋于稳定,巷道顶底板和两帮的平均变形量分别为134 mm和112 mm,说明围岩变形均在允许范围,深部大倾角煤岩层巷道变形得到了有效控制.

In view of the occurrence conditions of coal seam groups in most mining areas in China, the protective layer mining mode is mainly adopted to carry out gas treatment in regional coal seam. In this paper, based on the pressure relief mining of the protective layer, the principle, type and geological conditions of the co-mining mode of the protective layer coal and gas under the condition of coal seam group are analyzed. In Taoyuan Coal Mine, there are some problems such as frequent handling, low efficiency, difficult to control the drilling track, poor drainage effect, etc. The directional long drilling hole is used instead of bottom drainage roadway to reduce the moving time of drilling rig. According to the coal seam characteristics of Taoyuan Coal Mine, the directional drilling rig and other equipment suitable for Taoyuan Coal Mine are selected, and the directional long drilling technology is studied, A total of 13 directional long boreholes have been constructed in the inner section of II 8223 machine roadway, with a total length of 2336m, a lower screen pipe of 2249m, a cumulative coal slag discharge of 480.17t, and an equivalent diameter of 442mm. By January 14, 2020, 78577m3 has been pumped by directional long boreholes, with an average pumping concentration of 15% ~ 100%, and an average net pumping volume of 0.05m3/min ~ 0.40m3/min. It saves the construction of floor drainage roadway, reduces the amount of drilling work for gas control, saves 6 million yuan of gas control investment in the inner section of II 8223 machine roadway, shortens the time for reaching the standard of drainage for 2 ~ 3 months, effectively alleviates the tension of mine production replacement, and realizes safe, economic and efficient mining.

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.

To solve the problem of grout-rock interface relaxation due to self-shrinkage of cement-based material grouting in deep fractured rock masses, a bolt-grouting reinforcement method for deep fractured rock masses based on prestressed anchor and self-stress grouting was proposed. A self-stressed grouting reinforcement model and a new prestressed bolt-grouting reinforcement model for a single fractured rock mass were established. The mechanical characteristics of fractured sandstone specimens with ordinary and new bolt-grouting reinforcement were studied in physical experiments. The effectiveness of the new prestressed bolt-grouting reinforced rock mass was verified in engineering applications. Results showed that within a certain range, the greater the expansion restraint stress of the slurry stone is, the stronger the reinforcement effect on the fractured rock mass is. The expansion restraint stress of the slurry stone and the axial stress of bolt both contributed to the increase of the maximum principal stress of the fractured rock mass. The peak strength of the new prestressed bolt-grouting reinforced sandstone was 10% higher than that of the ordinary bolt-grouting reinforced sandstone. Its peak strain was slightly lower than that of the ordinary bolt-grouting reinforced sandstone. Moreover, the elastic deformation stage of the new prestressed anchor-grouting reinforced sandstone was shortened, and its reinforcement effect was enhanced. The surrounding rock of the substation roadway, which could not be well controlled by anchor-net support, U36 steel support or ordinary bolt-grouting reinforcement, was effectively controlled by new prestressed bolt-grouting reinforcement, and the maximum displacement of the surrounding rock on the roadway surface was 83 mm.

Abstract Improving the coal seam permeability is an important measure for increasing the coal bed methane (CBM) production and preventing gas disasters. Hydraulic technologies are effective ways of improving coal seam permeability. However, hydraulic technologies can also cause water to enter the coal seam, allowing the coal seam to soak for a long time. In this study, to obtain the influence of water soaking on the microscopic characteristics of coal, X‐ray diffraction (XRD), scanning electron microscopy (SEM), free swelling ratio tests, and low‐temperature nitrogen adsorption tests (LT‐NATs) were conducted. The mineral compositions of raw coal samples, the variation regularities of micromorphologies, and pore characteristics of the samples with different soaking times were obtained. The results showed that the coal samples contained about 8.5% clay minerals, of which 71% were illite/smectite mixed‐layer. Expansions of different sizes in the areas where the surface of the soaked coal samples contained clay minerals were observed, and the swelling was also observed macroscopically. The swelling not only led to an increase in the coal sample volume but also led to a decrease in pore volume. This change was magnified with the increase in soaking time (within 30 days). The cumulative pore volume of the samples soaked for 30 days was 0.00681 cm3/g. This was a reduction of 29.9% compared to the unsoaked samples. Moreover, the pore volumes show a logarithmic dependence on soaking time. This study provides evidence that the coal containing clay minerals will swell obviously when soaked in water, and the hydration swelling of clay minerals has a great influence on the swelling of coal. This swelling would lead to a decrease in the pore volume and the efficiency of CBM transport, thus affecting the effect of hydraulic measures.

在煤层水力压裂现场实施过程中,存在着对煤层破坏的复杂性及施工盲目性等问题.分析水力压裂流体在煤层中的流动规律,不仅可以优化水力压裂施工参数,而且可以为水力压裂后煤层抽采钻孔的布置提供依据,因此提出了水力压裂过程中流体的径向流流动模型.以该模型为指导,在郭家河煤矿1307工作面进行了水力压裂现场试验.结果表明:在一定的注水压力下,随着压裂时间的延长,压裂煤层的水区半径及透气性系数进一步增大,同时该煤层经过水力压裂后瓦斯抽采浓度和纯量都有较大程度的提高,在水力压裂影响半径区域内,抽采孔距离压裂孔越远,瓦斯抽采纯量和抽采浓度提升的幅度越大.现场试验证明了水驱气理论在煤层水力压裂工程应用中有较好的适用性.

Coal and gas outburst is one of the major serious natural disasters during underground coal, and the shock air flow produced by outburst has a huge threat on the mine safety. In order to study the two-phase flow of a mixture of pulverized coal and gas of a mixture of pulverized coal and gas migration properties and its shock effect during the process of coal and gas outburst, the coal samples of the outburst coal seam in Yuyang Coal Mine, Chongqing, China were selected as the experimental subjects. By using the self-developed coal and gas outburst simulation test device, we simulated the law of two-phase flow of a mixture of pulverized coal and gas in the roadway network where outburst happened. The results showed that the air in the roadway around the outburst port is disturbed by the shock wave, where the pressure and temperature are abruptly changed. For the initial gas pressure of 0.35 MPa, the air pressure in different locations of the roadway fluctuated and eventually remain stable, and the overpressure of the outburst shock wave was about 20~35 kPa. The overpressure in the main roadway and the distance from the outburst port showed a decreasing trend. The highest value of temperature in the roadway increased by 0.25 °C and the highest value of gas concentration reached 38.12% during the experiment. With the action of shock air flow, the pulverized coal transportation in the roadway could be roughly divided into three stages, which are the accelerated movement stage, decelerated movement stage and the particle settling stage respectively. Total of 180.7 kg pulverized coal of outburst in this experiment were erupted, and most of them were accumulated in the main roadway. Through the analysis of the law of outburst shock wave propagation, a shock wave propagation model considering gas desorption efficiency was established. The relationships of shock wave overpressure and outburst intensity, gas desorption rate, initial gas pressure, cross section and distance of the roadway were obtained, which can provide a reference for the protection of coal and gas outburst and control of catastrophic ventilation.