初始释放瓦斯膨胀能与煤层瓦斯压力的关系

根据突出模拟实验中出现突出时初始释放瓦斯膨胀能的临界值，可以确定煤层发生突出需要达到的瓦斯压力临界值．本文通过现场钻取煤样，并在试验室进行了不同瓦斯压力下的初始释放瓦斯膨胀能测定，发现煤样的初始释放瓦斯膨胀能与煤中的瓦斯压力呈线性关系．根据这一发现，石门揭煤之前的预排瓦斯过程中，只要用少量的实验就可以确定局部煤层瓦斯压力应该降到多少就可以安全揭开煤层，为石门揭煤进行突出预测和预排瓦斯过程中定量检测其防突效果提供了一种方便可靠的方法.     

煤与瓦斯突出的土力学分析

为了探索煤与瓦斯突出机理,根据岩体结构分类方法,把破坏类型为Ⅲ,Ⅳ,Ⅴ类的煤视为散体结构岩体.借鉴土力学流土失稳理论分析煤与瓦斯突出机制,把临界失稳梯度作为煤体的抗突强度指标.通过对煤体瓦斯压力梯度变化过程的分析,指出低透气性煤比高透气性煤更容易发生高强度突出的原因是由于低透气性煤的"失稳分层"的单位体积煤体具有更高的气体膨胀能.提出隔渗帷幕法和反滤层法2种控突思路.     

国投新登煤业31采区北翼瓦斯赋存规律研究

国投新登煤业前期采掘过程中矿井瓦斯涌出量较低,但随着开采深度的增加,瓦斯含量及压力具有明显上升的趋势,矿井迫切需要搞清深部区域的瓦斯赋存规律.结合矿井实际情况针对这一问题进行了研究,分析了影响深部区域瓦斯涌出的各种因素;研究了煤层瓦斯含量与埋藏深度的关系,绘制了31采区北翼的瓦斯含量等值线图;结合《防治煤与瓦斯突出规定》对该区的瓦斯突出危险程度进行了评价,划分出了突出危险区,并给出了防治煤与瓦斯突出的技术措施.现场生产表明,研究结果符合矿井实际情况,对矿井安全生产具有一定的指导意义.     

煤与瓦斯突出的压力容器物理爆炸假说

根据掘进工作面前方支承压力分布特征,建立了掘进工作面前方煤体的压力容器模型．通过分析认为,该模型满足压力容器爆炸的2个条件：气体迅速膨胀和容器壁脆性断裂．进而,基于压力容器发生物理爆炸前的孕育、爆炸后的能量及破坏能力,解释了煤与瓦斯突出的预兆、基本特点和一般规律,并分析了石门自行突出等问题的原因．最后,基于压力容器物理爆炸条件,给出了煤与瓦斯突出的预测指标和防突施工的努力方向,并对已有防突措施进行分析和评价．煤与瓦斯突出的压力容器物理爆炸假说的提出,对揭示煤与瓦斯突出机理具有重要意义．     

Micro shape of coal particle and crushing energy

A large amount of energy is consumed in a coal and gas outburst since a mass of coal is pulverized and ejected, accompanying a great quantity of gas emitted, resulting in a major mining hazard in underground coal mining around the world. Understanding how potential energy stored in gassy coal seams dissipates in the process of outbursting may possibly be a key to clarify the mechanisms responsible for coal and gas outburst. The present study was aimed to evaluate energy for crushing coal to various size fractions in coal and gas outbursts through theoretical and experimental investigation into the shape of fine coal particles and their equivalent diameter. Theoretical analysis indicates that the shape of a particle has a significant impact both on its equivalent diameter and hence on its outer surface area.Microscopic observations demonstrate the particle fraction with diameters less than 0.075 mm, produced from crushing coal samples, mostly takes on a spherical or ellipsoidal shape, and experimental data also show this part of particles consists of 30%–50% surface area newly generated from crushing operation,though these fine coal accounts for only less than ten percentages by weight. Further, analysis of experimental data indicates that the total surface area of this particle size fraction varies exponentially with input crushing energy, and the specific area energy is not a constant but probably in association with physical properties and textures of material.     

Failure modes of coal containing gas and mechanism of gas outbursts

In order to explain the mechanism for gas outburst, the process of evolving fractures in coal seams is described using system dynamics with variable boundaries. We discuss the failure modes of coal containing gas and then established the flow rules after failure. The condition under which states of deformation convert is presented and the manner in which these convert is proposed. In the end, the process of gas outbursts is explained in detail. It shows that a gas outburst is a process in which the boundaries of coal seams are variable because of coal failure. If the fractures are not connected or even closed owing to coal/rock stress, fractured zones will retain a certain level of carrying capacity because of the self-sealing gas pressure. When the accumulation of gas energy reaches its limit, coal seams will become unstable and gas outbursts take place.     

Quick determination of gas pressure before uncovering coal in cross-cuts and shafts

The determination of gas pressure before uncovering coal in cross-cuts and in shafts is one of the important steps in predicting coal and gas outbursts. However, the time spent for testing gas pressure is, at present, very long, seriously affecting the application of outburst prediction techniques in opening coal seams in cross-cuts and shafts. In order to reduce the time needed in gas pressure tests and to improve the accuracy of tests, we analyzed the process of gas pressure tests and examined the effect of the length of boreholes in coal seams in tests. The result shows that 1) the shorter the borehole, the easier the real pressure value of gas can be obtained and 2) the main factors affecting the time spent in gas pressure tests are the length of the borehole in coal seams,the gas emission time after the borehole has been formed and the quality of the borehole-sealing. The longer the length of the borehole, the longer the gas emission time and the larger the pressure-relief circle formed around the borehole, the longer the time needed for pressure tests. By controlling the length of the borehole in a test case in the Huainan mining area, and adopting a quick sealing technique using a sticky liquid method, the sealing quality was clearly improved and the gas emission time as well as the amount of gas discharged greatly decreased. Before the method described, the time required for the gas pressure to increase during the pressure test process, was more than 10 days. With our new method the required time is only 5 hours. In addition, the accuracy of the gas pressure test is greatly improved.     

Response characteristics of gas pressure under simultaneous static and dynamic load: Implication for coal and gas outburst mechanism

Coal and gas outbursts are dynamic disasters in which a large mass of gas and coal suddenly emerges in a mining space within a split second. The interaction between the gas pressure and stress environment is one of the key factors that induce coal and gas outbursts. In this study, first, the coupling relationship between the gas pressure in the coal body ahead of the working face and the dynamic load was investigated using experimental observations, numerical simulations, and mine-site investigations. It was observed that the impact rate of the dynamic load on the gas-bearing coal can significantly change the gas pressure. The faster the impact rate, the speedier the increase in gas pressure. Moreover, the gas pressure rise was faster closer to the impact interface. Subsequently, based on engineering background, we proposed three models of stress and gas pressure distribution in the coal body ahead of the working face: static load, stress disturbance, and dynamic load conditions. Finally, the gas pressure distribution and outburst mechanism were investigated. The high concentration of gas pressure appearing at the coal body ahead of the working face was caused by the dynamic load. The gas pressure first increased gradually to a peak value and then decreased with increasing distance from the working face. The increase in gas pressure plays a major role in outburst initiation by resulting in the ability to more easily reach the critical points needed for outburst initiation. Moreover, the stronger the dynamic load, the greater the outburst initiation risk. The results of this study provide practical guidance for the early warning and prevention of coal and gas outbursts.     

基于固气耦合的煤岩-瓦斯二相介质相似材料及其力学特性

含瓦斯煤是具有多孔特性和气固耦合特性的二相介质复合材料。为了精准模拟含瓦斯煤的物理力学属性,基于相似准则和主控参数相似比尺,进行了80余组材料配比试验和力学参数试验,研制了煤岩-瓦斯二相介质相似材料。对比了相似材料和原煤的相似性,并基于新材料进行了三维煤与瓦斯突出相似模拟试验。主要结论如下：1）煤粉和腐殖酸钠水溶液为骨料和胶结剂配制的煤岩相似材料的弹塑性参数和吸附性参数均与原煤相似;2）适当体积比的CO2和N2二元混合气体的膨胀能和CH4膨胀能一致,CO2和N2二元混合气体可作为CH4相似气体,且安全性高;3）研制的煤岩-瓦斯二相介质相似材料与含瓦斯原煤的物理力学参数具有高度相似性,实现了气固耦合特性模拟;4）三维物理模拟试验再现了石门揭煤引发煤与瓦斯突出现象,得到与现场接近的突出孔洞形态和突出粉煤质量,验证了相似材料的合理性,也为进一步研究煤与瓦斯突出规律,监测突出前兆信息提供了科学手段。     

二道岭矿区地质构造的控气规律研究

针对内蒙古二道岭矿区构造复杂,构造部位及影响带多显示瓦斯异常和煤与瓦斯突(喷)出多发、易发等特点,应用瓦斯地质理论,重点研究构造对煤层瓦斯赋存和突(喷)出的控制作用及规律。研究表明,"封闭型"压性、压扭性构造为煤层瓦斯的保存提供了良好的"封存效应",是控制区内煤层瓦斯含量整体较高和不均衡分布的关键因素;构造类型、性质和组合方式共同控制着煤层瓦斯的分区、分带和煤与瓦斯突(喷)出范围及机率。     

Infrared measurement of temperature field in coal gas desorption

In order to reveal the temperature change in coal gas desorption process, the temperature variation in coal gas desorption process under different particle sizes is analyzed with infrared thermal imager. The infrared video signals obtained by the experiment are processed with SAT. Then the infrared radiation signals are processed by EMD with Hilbert–Huang and the infrared radiation noise is effectively removed. The research results show that the desorption process, with the change of the temperature, is an endothermic process. The coal absorbs heat when the gas is desorbed and the temperature drops. The coal body temperature drop range is obviously related to coal particle size. The smaller the particle size is, the bigger the temperature drop becomes. The temperature variation curves in the process of coal gas desorption under different particle sizes are fitted, and they comply with the exponential function. The research results lay the theoretical and experimental foundation for non-contact prediction on working face of coal and gas outburst with infrared thermal image technology.     

承压煤岩低气压渗流灾变

为探索含低压瓦斯煤层的瓦斯异常涌出灾变成因与机理,对目前该领域的文献进行了分析与总结,并通过工程案例实证分析,证明了此种灾变的存在;在流固耦合实验系统上,按背景工程约束与加载条件开展含低气压煤样承压物理试验,得到了灾变全程应力-声发射-流量实验数据及试样外表破坏情况;用UDEC,按背景工程边界与加载条件开展气-固耦合离散元数值试验,得到了灾变全程应力-应变--流速-位移速率等实验数据及试样内部破裂情况.研究结果表明:3种研究方法获得了一致性较高的结果,0.4 MPa气体压力下,煤层承压过程应力-煤-气耦合作用,可以导致发生喷出气体的灾变,在煤矿现场多表现为瓦斯异常涌出超限;在单自由度边界条件下施加单向压载,承压煤岩弹性变形前期,气体沿原生裂隙和孔隙呈常速稳态渗流;弹性变形后期,原生裂隙和孔隙被压密,气体呈减速稳态渗流;屈服阶段,扩容新生裂隙产生,气体呈加速非稳态渗流;达到极限荷载或峰后不久,发生气体喷出灾变;采、掘作业面正常通风条件下,气流瓦斯浓度持续降低,是煤层发生瓦斯异常涌出的警示信息,应引起高度重视.     

A mathematical model of gas flow during coal outburst initiation

A proposed concept of outburst initiation examines the release of a large amount of gas from coal seams resulted from disintegrating thermodynamically unstable coal organic matter(COM). A coal microstructure is assumed to getting unstable due to shear component appearance triggered by mining operations and tectonic activities considered as the primary factor while COM disintegration under the impact of weak electric fields can be defined as a secondary one. The energy of elastic deformations stored in the coal microstructure activates chemical reactions to tilt the energy balance in a ‘‘coal–gas" system.Based on this concept a mathematical model of a gas flow in the coal where porosity and permeability are changed due to chemical reactions has been developed. Using this model we calculated gas pressure changes in the pores initiated by gas release near the working face till satisfying force and energy criteria of outburst. The simulation results demonstrated forming overpressure zone in the area of intensive gas release with enhanced porosity and permeability. The calculated outburst parameters are well combined with those evaluated by field measurements.     

新安煤田煤与瓦斯突出特征及控制因素分析

为了掌握煤与瓦斯突出的特征和控制因素,提高煤矿防突工作的针对性,本文通过统计分析了新安煤田内义煤集团的4个煤与瓦斯突出矿井近年来发生的瓦斯动力现象,综合分析得出新安煤田煤与瓦斯突出具有以小型突出为主、突出前有预兆并受作业方式诱导、突出点附近瓦斯质量体积和瓦斯压力高、易发生在掘进工作面和煤层变化带的特征;分析总结了埋藏深度、瓦斯赋存、地质构造、煤层厚度变化、构造软煤、作业工艺是控制新安煤田煤与瓦斯突出的主要因素,为该煤田防治煤与瓦斯突出提供了理论指导.     

利民煤矿煤与瓦斯突出的地质构造条件研究

在对湖南利民煤矿煤与瓦斯弱突出区域、强突出区域和未突出区域的地质构造特征作详细分析后 ,发现煤层顶底板断 褶构造发育不协调、边界条件不一样 ,引起Ⅰ、Ⅱ、Ⅲ、Ⅳ各区的应力分布不均匀 ,构造复杂程度具一定的差异性 ;同时探讨了构造应力场和煤与瓦斯突出的关系 ,认为构造应力决定着突出强度的大小 ,进而控制煤与瓦斯突出的区域、密度、强度的差异性 .所得结论为矿区煤与瓦斯突出预测防治提供了理论依据 .     

Regression analysis of major parameters affecting the intensity of coal and gas outbursts in laboratory

Estimating the intensity of outbursts of coal and gas is important as the intensity and frequency of outbursts of coal and gas tend to increase in deep mining. Fully understanding the major factors contributing to coal and gas outbursts is significant in the evaluation of the intensity of the outburst. In this paper, we discuss the correlation between these major factors and the intensity of the outburst using Analysis of Variance(ANOVA) and Contingency Table Analysis(CTA). Regression analysis is used to evaluate the impact of these major factors on the intensity of outbursts based on physical experiments. Based on the evaluation, two simple models in terms of multiple linear and nonlinear regression were constructed for the prediction of the intensity of the outburst. The results show that the gas pressure and initial moisture in the coal mass could be the most significant factors compared to the weakest factor-porosity. The P values from Fisher's exact test in CTA are: moisture(0.019), geostress(0.290), porosity(0.650), and gas pressure(0.031). P values from ANOVA are moisture(0.094), geostress(0.077), porosity(0.420), and gas pressure(0.051). Furthermore, the multiple nonlinear regression model(RMSE: 3.870) is more accurate than the linear regression model(RMSE: 4.091).     

井田地质构造对煤与瓦斯突出影响的定量研究

通过对平顶山十二矿进行的煤与瓦斯突出区域预测研究 ,仔细分析了井田地质构造与突出的关系 .在该井田的构造复杂区 ,首次采用数学方法 ,将影响突出的构造因素定量化 ,并对构造复杂程度系数计算公式作了改进和简化 ;提出了确定复杂程度突出临界值的原则 ,并结合井田突出实际 ,划定了构造复杂程度系数的突出临界值 ,将其作为一项判断突出的依据 ,对十二矿进行了瓦斯地质区划 ,取得了良好的预测效果     

A rapid and accurate direct measurement method of underground coal seam gas content based on dynamic diffusion theory

Coal seam gas content is frequently measured in quantity during underground coal mining operation and coalbed methane (CBM) exploration as a significant basic parameter. Due to the calculation error of lost gas and residual gas in the direct method, the efficiency and accuracy of the current methods are not inadequate to the large area multi-point measurement of coal seam gas content. This paper firstly deduces a simplified theoretical dynamic model for calculating lost gas based on gas dynamic diffusion theory. Secondly, the effects of various factors on gas dynamic diffusion from coal particle are experimentally studied. And sampling procedure of representative coal particle is improved. Thirdly, a new estimation method of residual gas content based on excess adsorption and competitive adsorption theory is proposed. The results showed that the maximum error of calculating the losing gas content by using the new simplified model is only 4%. Considering the influence of particle size on gas diffusion law, the particle size of the collected coal sample is below 0.25 mm, which improves the measurement speed and reflects the safety representativeness of the sample. The determination time of gas content reduced from 36 to 3 h/piece. Moreover, the absolute error is 0.15–0.50 m³/t, and the relative error is within 5%. A new engineering method for determining the coal seam gas content is developed according to the above research.     

Coal and gas outburst dynamic system

Coal and gas outburst is an extremely complex dynamic disaster in coal mine production process which will damage casualties and equipment facilities, and disorder the ventilation system by suddenly ejecting a great amount of coal and gas into roadway or working face. This paper analyzed the interaction among the three essential elements of coal and gas outburst dynamic system. A stress-seepage-damage coupling model was established which can be used to simulate the evolution of the dynamical system, and then the size scale of coal and gas outburst dynamical system was investigated. Results show that the dynamical system is consisted of three essential elements, coal-gas medium(material basis), geology dynamic environment(internal motivation) and mining disturbance(external motivation). On the case of C13 coal seam in Panyi Mine, the dynamical system exists in the range of 8–12 m in front of advancing face. The size scale will be larger where there are large geologic structures. This research plays an important guiding role for developing measures of coal and gas outburst prediction and prevention.     

Propagation law of shock waves and gas flow in cross roadway caused by coal and gas outburst

In order to study the propagation law of shock waves and gas flow during coal and gas outburst, we analyzed the formation process of outburst shock waves and gas flow and established the numerical simulation models of the roadways with 45° intersection and 135° intersection to simulate the propagation of outburst gas flow and the process of gas transport. Based on the analysis of the simulation results, we obtained the qualitative and quantitative conclusions on the characteristics and patterns of propagation and attenuation of outburst shock waves and gas flow. With the experimental models, we investigated the outburst shock waves and gas flow in the roadways with the similar structures to the simulated ones. According to the simulation results, when the angle between the driving roadway and the adjacent roadway increased, the sudden pressure variation range in adjacent roadway and the influencing scope of gas flow increased and the sudden pressure variation duration decreased. The intersection between the driving roadway and the adjacent roadway has no effect on airflow reversal induced by the shock waves and gas flow.