【作者】 张冰；

【导师】 李术才； 仝兴华； 王汉鹏；

【作者基本信息】 山东大学 ， 工程力学， 2020， 博士

【摘要】 煤与瓦斯突出是一种极其复杂的矿井动力事故,常常造成大量的人员伤亡、恶劣的社会影响和重大的经济损失,已成为制约我国煤炭工业健康发展的关键因素。揭示煤与瓦斯突出的致灾机理,对突出进行准确预测、预警,才能有效预防突出事故发生。然而,由于突出过程的复杂性及涉及因素的多样性,现有突出机理研究仍不能准确阐述各因素在突出中的作用机制,无法用数学模型定量地描述各因素的作用效应,无法为突出预警提供科学可靠的理论依据,加之突出前兆信息研究方法发展不均衡,物理模型试验作为在各方法中尚处于弱势地位,突出前兆信息演化规律研究及突出预警理论技术仍不满足安全生产的需求。本文采用室内试验、理论分析、数值模拟、模型试验等多种手段,从煤与瓦斯突出都存在的瓦斯卸压这一关键致灾因素入手,研究分析了简单工况下煤体瓦斯卸压损伤致突机理,重点研究了瓦斯卸压过程中吸附气体解吸扩散规律、气体动力作用诱发的煤体损伤劣化规律、煤体有效应力变化规律,构建了描述该动态过程更准确的含瓦斯煤气固耦合动力学模型,并基于煤体瓦斯卸压损伤致突机理,提出了具有普适性的突出前兆敏感指标,开展了巷道掘进诱发的煤与瓦斯突出模拟试验,监测并揭示了普适性敏感指标的敏感性、演化趋势及突出前兆特征。获取的主要成果如下:(1)自主研发了“煤粒瓦斯放散测定仪”,满足复杂赋存环境中煤样瓦斯吸附、解吸特性测试的需求。采用该仪器开展了不同环境气压、不同损伤状态煤样的瓦斯解吸试验,获取了卸压过程关键变量对瓦斯解吸动态参量的影响规律:1)瓦斯解吸速度、解吸量随着环境气压增大而减小;2)环境气压对扩散系数的影响程度与时间有关,在初始阶段影响甚微,在4000 s后影响程度逐渐增大;3)随着煤体损伤增大,瓦斯扩散渗流路径变化,瓦斯解吸量明显增大,两者呈线性关系。基于测试获取的试验数据,构建形成了适用性更广的煤体瓦斯解吸扩散模型。(2)研发形成的“含瓦斯煤动静组合加载试验系统”,实现了“静态应力+冲击扰动”和“静态应力+瞬时卸气压扰动”组合加载下吸附瓦斯煤变形破坏机制的可视化研究。采用该仪器开展了不同损伤状态/气体卸压速率/气体种类条件下的吸附煤体气体卸压试验,获取了瓦斯卸压动力作用诱发的煤体损伤劣化规律:1)气体卸压动力作用可对煤体造成了明显的不可逆损伤,导致煤体损伤变量骤增,甚至张拉破坏;2)基于气体卸压过程中煤体不可逆损伤产生与否及其增量大小,可将煤体损伤状态分为三个阶段:无影响阶段、稳定影响阶段、不稳定影响阶段;3)解吸气体量越大,气体卸压诱发损伤增量越大;4)煤体损伤增量随气体卸压速率呈线性增大关系。基于损伤变量变化率与各影响因素之间的数学关系,构建形成了考虑气体卸压动力作用的煤体损伤演化数学模型。(3)采用“含瓦斯煤三轴力学渗透试验仪”,开展了不同煤体损伤状态/气体压力/气体吸附含量条件下三轴受力吸附煤样卸压变形试验,基于有效应力与基质变形的对应关系,获取了瓦斯卸压动态过程煤体有效应力变化规律:1)随着游离气体、吸附气体的放散,煤体有效应力骤增;2)由于煤样损伤变量差异,游离气体、吸附气体放散诱发的有效应力瞬时增量呈现明显差异;3)吸附气体、游离气体放散诱发的有效应力增量分别与吸附气体含量、气体压力呈截距为零的线性关系。基于试验结果,探明了游离气体、吸附气体对煤体有效应力的影响机制:游离气体直接分担了部分外荷载,吸附气体产生的吸附膨胀应力抵消了煤体骨架所承担的外荷载;并据此在煤体双孔-单渗透理论模型基础上推导获取了适用于瓦斯卸压动态过程的含瓦斯煤有效应力数学模型。(4)针对瓦斯卸压动态过程,综合考虑吸附瓦斯的解吸补充作用、煤体有效应力突增作用、气压动力作用及各部分之间的相互影响,将瓦斯解吸扩散方程作为裂隙系统瓦斯流动控制方程汇源项,重新定义了煤体变形控制方程中煤体损伤演化方程、煤体有效应力演化方程,构建了含瓦斯煤体的气固耦合动力学模型。将新模型导入COMSOL Multiphysics对瞬间揭露诱发突出模拟试验进行了模拟,模拟结果与试验结果完全一致,证明了新模型可以更加准确描述煤体瓦斯卸压动态过程与致突机制,同时也证明了煤体瓦斯卸压损伤致突机制的科学性:瓦斯卸压诱发的突出是瓦斯瞬间解吸、瓦斯卸压动力作用和卸压瞬间煤体有效应力突增三种作用耦合、不断演化的结果。(5)基于煤体瓦斯卸压损伤致突机理,提出了将煤层瓦斯压力、煤体应力状态、煤体温度、巷道瓦斯动态指标、声发射、微震等物理信息作为普适性的突出前兆预警指标;研发了一种低渗透性岩层相似材料,克服了高压瓦斯赋存及巷道掘进真实模拟难题;依托于该材料及“巷道掘进揭煤诱导煤与瓦斯突出模拟试验系统”,以典型突出案例为原型,成功开展了巷道掘进诱发的煤与瓦斯突出模拟试验,监测并揭示了普适性预警指标的演化趋势及突出前兆特征,确定了突出普适性指标的敏感性由高到低依次是煤层温度、巷道内气体浓度、巷道内温度、煤层应力、煤层气压。研究成果有益于煤与瓦斯突出机理深化及突出精准预警防控。更多还原

【Abstract】 Coal and gas outburst is a very complex mine dynamic accident,which often causes numerous casualties,bad social impact and heavy economic losses.It has become a obstacle to the healthy development of China’s coal industry.Only by revealing the breeding,development,evolution and disaster-causing mechanism of coal and gas outburst,and making accurate prediction and early warning,can outburst accidents be effectively prevented.However,due to the complexity of the outburst process and the diversity of the factors involved,the existing researches on the outburst mechanism still can not accurately interpret the mechanism of each factor in the outburst and quantitatively describe the effect of each factor with the mathematical model.In addition,the development of precursory information research methods is not balanced.While physical model test is still in a weak position in various methods,the research on precursory information law and the theoretical technology of early warning are still not able to meet the needs of safety production.In this thesis,by means of laboratory test,theoretical analysis,numerical simulation and model test,starting with the key disaster-causing factor of gas pressure relief,the disaster-causing mechanism of gas pressure relief of coal and gas outburst under simple working conditions was studied and analyzed.We focused on the laws concerning desorption and diffusion of adsorbed gas,damage and degradation of coal body induced by gas impact dynamic action,and effective stress change of coal body.A gas-solid coupling dynamic model was constructed to accurately describe the dynamic process.Based on the mechanism of gas pressure relief,a universal early warning index of outburst was proposed.The simulation test of coal and gas outburst induced by roadway excavation was carried out,and the sensitivity,evolution trend and outburst precursor characteristics of universal early warning indicators were monitored and revealed.The main achievements are as follows:(1)A new instrument for the measurement of coal particle gas emission characteristic was independently developed,which met the requirements of coal sample gas adsorption and desorption characteristics test in complex storage environment.This instrument was used to carry out gas desorption tests of coal samples under different ambient air pressure and different damage conditions,which help us figure out the influence law of key variables in the process of pressure relief on dynamic parameters of gas desorption.1)The gas desorption speed and quantity decrease with the increase of the ambient air pressure;2)The influence of ambient air pressure on diffusion coefficient is time-dependent,which has little effect at the initial stage and gradually increases after 4000 s;3)With the increase of coal damage,the path of gas diffusion seepage changes,and the amount of gas desorption increases obviously,showing a linear relationship.Based on the test data,a more applicable gas desorption diffusion model is constructed.(2)The "dynamic static combined loading test system of gas bearing coal" was developed,which realized the visualized study of deformation and failure mechanism of gassy coal under the combined loading of "static stress+dynamic impact disturbance" and "static stress+instantaneous relief pressure disturbance".This instrument was used to carry out the pressure relief test of adsorbed coal under the conditions of different damage state、gas pressure relief rate and gas type,and the damage and degradation rule of coal induced by the impact of gas pressure relief was obtained.1)The dynamic action impact of gas pressure relief can cause obvioug irreversible damage to the coal body,which leads to the sudden increase of the damage variable of the coal body,even the tensile damage;2)Based on the generation and increment of the irreversible damage of the coal body in the process of gas pressure relief,the damage state of the coal body can be divided into three stages:no influence stage,stable influence stage and unstable influence stage;3)The larger the amount of desorption gas is,the larger the increment of gas pressure relief induced damage is;4)The damage increment of coal body increases linearly with the gas pressure release rate.Based on the mathematical relationship between the rate of change of damage variables and the influencing factors,a mathematical model of coal damage evolution considering the impact of gas pressure relief is established.(3)The pressure relief and deformation tests of triaxial stress adsorption coal samples under different damage conditions、gas pressure and gas adsorption content were carried out by using "triaxial instrument for the measurement of the permeability of gassy coal".Based on the corresponding relationship between the effective stress and the matrix deformation,the change rule of the effective stress of the coal body in the dynamic process of gas pressure relief was obtained:1)With the release of free gas and adsorbed gas,the effective stress of coal increases sharply 2)Due to the difference of damage variables of coal samples,the instantaneous increment of effective stress induced by the release of free gas and adsorbed gas is obviously different;3)The effective stress increment induced by the release of adsorbed gas and free gas has a linear relationship with zero intercept with adsorbed gas content and gas pressure.Based on the test results,the influence mechanism of free gas and adsorbed gas on the effective stress of coal body is proved:The free gas directly shares part of the external load,and the adsorbed expansion stress generated by adsorbed gas offsets the external load borne by the coal body skeleton;Based on the theoretical model of double hole single permeability of coal body,the mathematical model of effective stress of gas bearing coal suitable for dynamic process of gas pressure relief is derived.(4)In view of the dynamic process of gas pressure relief,considering the desorption and supplement of adsorbed gas,the sudden increase of effective stress of coal body,the impact dynamic effect of air pressure and the interaction among various parts,the gas desorption and diffusion equation was taken as the source term of gas flow control equation of fracture system,and the damage evolution equation and effective stress evolution equation of coal body in the control equation of coal body deformation were redefined to construct the gas-so-lid coupling dynamic model of gassy coal.The new model is imported into COMSOL Multiphysics to simulate the coal and gas outburst test induced by driving.The simulation results are completely consistent with the test results,which proves that the new model can accurately describe the dynamic process of gas pressure relief and the mechanism of outburst,and that the mechanism of gas pressure relief is scientific.The outburst induced by gas pressure relief is the result of the coupling and continuous evolution of three functions:instantaneous gas desorption,dynamic effect of gas pressure relief and sudden increase of effective stress of coal body at the moment of pressure relief.(5)Based on the mechanism of gas pressure relief and outburst,the physical information of coal seam gas pressure,coal stress state,coal temperature,roadway gas dynamic index,acoustic emission,micro earthquake and so on were taken as the early warning index of outburst.A low permeability rock similar material was developed,which overcame the problems of high pressure gas occurrence and real simulation of roadway excavation.Relying on the low permeability rock stratum and the "simulation test system of coal and gas outburst induced by roadway excavation" and taking typical outburst cases as the prototype,the simulation test of coal and gas outburst induced by roadway excavation was successfully carried out.The evolution trend and precursory characteristics of the universal early-warning index were monitored and revealed.The sensitivity of the universal early-warning index was determined from high to low as follows:coal seam temperature,gas concentration in the roadway,temperature in the roadway,coal seam stress and coal seam pressure.The research results are beneficial to the deepening of coal and gas outburst mechanism and accurate early warning and control of outburst.更多还原