【作者】 安丰华；

【导师】 程远平；

【作者基本信息】 中国矿业大学 ， 安全技术及工程， 2014， 博士

【摘要】 煤炭作为我国的主体能源，煤与瓦斯突出事故一直是限制其安全高效开采的因素之一。近年来突出防治技术的发展和煤矿安全需求的增强都对煤与瓦斯突出机理研究提出了更高的要求，以综合假说为基础的定性化认识受限于对针对性、科学化的防突技术指导，对突出机理定量化研究有待加强。本文运用岩石力学、渗流力学、吸附理论等理论方法，基于双重孔隙介质模型建立了煤与瓦斯突出发动之前煤岩—瓦斯演化控制方程，以有效应力、吸附变形及渗透性演化等耦合项来表明瓦斯场—煤岩应力应变场之间相互作用，并通过突出能量条件来表征突出倾向性，分析了瓦斯、地应力、煤体力学性质对突出能量的影响及突出能量分布和演化对突出蕴育、失稳的控制作用。研究获得的结论主要在以下几个方面。（1）煤中微孔是控制煤体吸附性能的主要因素。在煤孔隙孔径较小时（气体分子直径量级）孔壁吸附势会发生重叠，对瓦斯吸附力增强，在很小压力下即可达到吸附饱和，即减小了Langmuir压力。因此，不仅是煤最大吸附能力，Langmuir压力同样受微孔发育影响，特别是孔径较小的微孔。由于变质程度增加煤中微孔发育，Langmuir压力随煤阶提高呈下降趋势。（2）根据屈服煤体峰后渗透性随软化模量增长规律，结合双重孔隙介质渗透性模型建立了采掘过程中扰动煤体的渗透性演化方程。对采掘后前方煤体渗透性进行的研究表明，采掘扰动后煤体渗透性具有分区分布特性，从煤层深部原始地带至煤壁渗透性依次经过降低区、升高区和骤增区，其分区分布特征是与煤体应力分带分布形成机制密切相关的。由于渗透性分区性，煤层瓦斯分布也具有分区特点，煤壁附近高渗低压煤体构成了防止煤体瓦斯突出的安全带。之后分析了不同赋存形式瓦斯对煤体变形破坏的影响，除游离瓦斯对煤体受力有孔隙压力的影响外，煤中吸附态瓦斯的变化也会改变煤体受力状态，影响到煤体的屈服破坏，排放瓦斯后煤体强度的增加能降低突出发生的危险性。（3）大型突出案例表明突出地点往往具有瓦斯局部异常，富存了大量瓦斯。而富集区周边存在环状低渗带是瓦斯得以长期保存的一个条件。在化简为一维流动模型后，进一步分析表明低渗带渗透性大小及宽度是影响高压瓦斯保存的主要因素。低渗带内存在的高瓦斯压力及压力梯度使得进入低渗带后突出可能性大大增强，所保存的高压瓦斯能够为突出灾害提供巨大的能量，形成了大型突出的条件。（4）煤体强度破坏及煤—瓦斯系统积聚能量超过其储存能力是系统失稳发动突出的条件，因此可以通过突出潜能积聚程度来分析煤体突出危险性。基于此，提出了以突出发动潜能与突出发动过程耗能之比作为失稳判据判断突出倾向性。并通过分析煤体突出发动潜能的积聚形式及发动过程耗散途径，建立了相应的计算公式。（5）瓦斯、地应力及煤体力学性质等突出因素是突出能量的主要影响因素。瓦斯条件是突出发动能量积聚的主要影响因素，煤层所受构造应力同样对突出能量积聚有重要影响，增加了煤体突出倾向。煤体力学性质对突出影响主要表现为煤体强度及破碎功的影响。（6）通过突出模拟实验验证了瓦斯及应力荷载是煤体突出潜能的主要来源，对突出能否发动及突出规模具有决定作用。另外，可通过不同突出潜能实验条件，根据其突出发动情况，获得煤体失稳突出所需的能量，从而对煤—瓦斯系统能量保持能力进行研究。（7）井下开采过程中由于煤层条件非均性，采掘面前方破坏区煤体突出潜能及能量储存能力的分布也是随煤层条件而变化的。在遭遇低透气性、高瓦斯、高应力、构造煤等条件时，破坏区煤体积聚能量超出其能量储存能力，系统能量处于不平衡状态，释放能量从而造成突出，因此突出能量分布及其演化对突出的发生具有控制作用。更多还原

【Abstract】 As the main energy resource in China, coal and gas outburst always is a main factorrestricting the safe and high-efficiency production of coal. As the technology development ofoutburst control and the increased demand of coal mines for security, higher requirement forcoal and gas outburst mechanism is presented. The qualitative understanding of outburstbased on comprehensive hypothesis is limited to guide the control technology pointedly andspecifically. The quantitive research of outburst mechanism should be enhanced.Using rock mechanics, mechanics of flow through porous media and adsorption theory,the governing equations of coalmass-gas evolution before outburst initiation were establishedbased on double porosity media model. Coupling terms such as effective stress,adsorption-induced deformation and permeability, showed the interaction between coal gasfield and coal/rock stress-strain field. With the energy for outburst initiation used forrepresenting the outburst tendency, the effect of coal gas, ground stress and mechanicalproperties of coal on energy for outburst initiation and the effect of distribution and evolutionof energy for outburst initiation on coal and gas outburst were analyzed. The main researchwork were listed in the following.(1) Micropore in coal is the dominant factor of adsorption property. When the poreaperture is small, with the magnitude of gas molecular diameter, the adsorption potential ofpore wall would overlap. The adsorption force increases in this case, and the adsorptionreaches saturation at low gas pressure, meaning low Langmuir pressure. Therefore, besidesthe maximum adsorption capacity of coal, the Langmuir pressure is affected by themicropores as well, especially the small ones. Due to the micropores increase as the coal rank,Langmuir pressure shows the declining trend as the coal rank increase.(2) After the study of permeability increase with the softening modulus after stress peakof coal mass, combing the permeability model of double porosity medium the permeabilityevolution equation in the process of excavation was established. The study of permeability infront of working face showed the zonal distribution characteristics that from the original zoneof coal seam to the coal wall the permeability changed though the decrease zone, increasezone and surge increase zone. This characteristics was closely related to the stress zonaldistribution characteristics. As the permeability of coal, the coal gas was zonally distributed aswell. The coal mass near the coal wall had high permeability and low gas content, as a safetybelt preventing the outbursts. And then the effect of different forms of coal gas ondeformation and failure of coal was studied. Besides the effect of pore pressure from the free gas, the change of adsorbed gas affected the stress state and failure of coal mass. The strengthenhancement after coal gas discharging could reduce the outburst risk.(3) From the perspective of permeability distribution, the formation of large-scaleoutburst was studied. Abnormal abundance of coal gas occurs around the location oflarge-scale outburst and an annular low-permeability zone in coal seam was necessary forabundant gas preservation. With a simplified one-dimensional flow model, the results shownthat permeability decrease and length of the low-permeability zone were the key factorsaffecting the high-pressure gas preservation. The high gas pressure and gradient increased theoutburst tendency when the excavation entered into the low-permeability zone. Thehigh-pressure gas preserved by the low-permeability zone could provide enough energy for alarge-scale outburst.(4) To analyze the tendency of coal and gas outburst, the conditions required by theunstability of coal-gas system were studied. Yield failure and energy accumulated in coal-gassystem over the storage capacity were required for an outburst, and the accumulation degreeof energy for outburst could show the outburst danger. Based on the energy condition foroutburst, the ratio between accumulated energy for outburst initiation and the energyconsumed in the process was utilized as outburst criterion. The corresponding calculationequations of accumulated energy and consumed energy were established.(5) Coal gas, ground stress and mechanical properties of coal were the main factors forenergy for outburst initiation. Coal gas was the main factor for energy accumulation. Thetectonic stress loaded on coal seam had an effect for energy accumulation as well, increasingthe outburst tendency. The effect of mechanical properties of coal was mainly due to thestrength and crushing work.(6) Through the outburst simulation experiment, it was verified that coal gas and stressload were the main source for energy for outburst initiation, and the energy for outburstinitiation had decisive effect on outburst. Besides, through different engergy conditions, therequied energy for outburst initiation with certain mechanical property of coal mass could beobtained based on the outburst results. This provides a method for analyzing the energystorage capacity of coal-gas system.(7) Because of the heteropic coal seam conditions in the exploitation process, thedistribution of energy for outburst initiation in the broken coal in front of the working faceevolved. When the excavation met the conditions such as low permeability, high gas, highstress and tectonic coal, the accumulated energy for outburst initiation would beyond thestorage capacity. The system energy became into unbalanced state, and released energy resulting in outburst. Hence, the distribution and evolution of energy for outburst initiationcontrolled the outburst initiation.更多还原