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.

Mechanism of gas pressure action during the initial failure of coal containing gas and its application for an outburst inoculation

Faced with the continuous occurrence of coal and gas outburst(hereinafter referred to as“outburst”)disasters,as a main controlling factor in the evolution process of an outburst,for gas pressure,it is still unclear about the phased characteristics of the coupling process with in situ stress,which induce coal damage and instability.Therefore,in the work based on the mining stress paths induced by typical outburst accidents,the gradual and sudden change of three-dimensional stress is taken as the background for the mechanical reconstruction of the disaster process.Then the true triaxial physical experiments are conducted on the damage and instability of coal containing gas under multiple stress paths.Finally,the response characterization between coal damage and gas pressure has been clarified,revealing the mechanism of action of gas pressure during the initial failure of coals.And the main controlling mechanism during the outburst process is elucidated in the coupling process of in situ stress with gas pressure.The results show that during the process of stress loading and unloading,the original gas pressure enters the processes of strengthening and weakening the action ability successively.And the strengthening effect continues to the period of large-scale destruction of coals.The mechanical process of gas pressure during the initial failure of coals can be divided into three stages:the enhancement of strengthening action ability,the decrease of strengthening action ability,and the weakening action ability.The entire process is implemented by changing the dominant action of in situ stress into the dominant action of gas pressure.The failure strength of coals is not only affected by its original mechanical strength,but also by the stress loading and unloading paths,showing a particularly significant effect.Three stages can be divided during outburst inoculation process.That is,firstly,the coals suffer from initial damage through the dominant action of in situ stress with synergy of gas pressure;secondly,the coals with spallation of structural division are generated through the dominant action of gas pressure with synergy of in situ stress,accompanied by further fragmentation;and finally,the fractured coals suffer from fragmentation and pulverization with the gas pressure action.Accordingly,the final broken coals are ejected out with the gas action,initiating an outburst.The research results can provide a new perspective for deepening the understanding of coal and gas outburst mechanism,laying a theoretical foundation for the innovation of outburst prevention and control technologies.

Dynamic behavior of outburst two-phase flow in a coal mine T-shaped roadway:The formation of impact airflow and its disaster-causing effect

The study of the dynamic disaster mechanism of coal and gas outburst two-phase flow is crucial for improving disaster reduction and rescue ability of coal mine outburst accidents.An outburst test in a T-shaped roadway was conducted using a self-developed large-scale outburst dynamic disaster test system.We investigated the release characteristics of main energy sources in coal seam,and obtained the dynamic characteristics of outburst two-phase flow in a roadway.Additionally,we established a formation model for outburst impact flow and a model for its flow in a bifurcated structure.The results indicate that the outburst process exhibits pulse characteristics,and the rapid destruction process of coal seam and the blocking state of gas flow are the main causes of the pulse phenomenon.The outburst energy is released in stages,and the elastic potential energy is released in the vertical direction before the horizontal direction.In a straight roadway,the impact force oscillates along the roadway.With an increase in the solid–gas ratio,the two-phase flow impact force gradually increases,and the disaster range extends from the middle of the roadway to the coal seam.In the area near the coal seam,the disaster caused by the two-phase flow impact is characterized by intermittent recovery.In a bifurcated roadway,the effect of impact airflow on impact dynamic disaster is much higher than that of two-phase flow,and the impact force tends to weaken with increasing solid-gas ratio.The impact force is asymmetrically distributed;it is higher on the left of the bifurcated roadway.With an increase in the solid-gas ratio,the static pressure rapidly decreases,and the bifurcated structure accelerates the attenuation of static pressure.Moreover,secondary acceleration is observed when the shock wave moves along the T-shaped roadway,indicating that the bifurcated structure increases the shock wave velocity.

Elimination mechanism of coal and gas outburst based on geo‑dynamic system with stress–damage–seepage interactions

Coal and gas outburst is a complex dynamic disaster during coal underground mining.Revealing the disaster mechanism is of great signifcance for accurate prediction and prevention of coal and gas outburst.The geo-dynamic system of coal and gas outburst is proposed.The framework of geo-dynamic system is composed of gassy coal mass,geological dynamic environment and mining disturbance.Equations of stress–damage–seepage interaction for gassy coal mass is constructed to resolve the outburst elimination process by gas extraction with boreholes through layer in foor roadway.The results show the occurrence of outburst is divided into the evolution process of gestation,formation,development and termination of geo-dynamic system.The scale range of outburst occurrence is determined,which provides a spatial basis for the prevention and control of outburst.The formation criterion and instability criterion of coal and gas outburst are established.The formation criterion F1 is defned as the scale of the geo-dynamic system,and the instability criterion F2 is defned as the scale of the outburst geo-body.According to the geo-dynamic system,the elimination mechanism of coal and gas outburst—‘unloading+depressurization’is established,and the gas extraction by boreholes through layer in foor roadway for outburst elimination is given.For the research case,when the gas extraction is 120 days,the gas pressure of the coal seam is reduced to below 0.4 MPa,and the outburst danger is eliminated efectively.

In-situ gas contents of a multi-section coal seam in Sydney basin for coal and gas outburst management

The gas content is crucial for evaluating coal and gas outburst potential in underground coal mining. This study focuses on investigating the in-situ coal seam gas content and gas sorption capacity in a representative coal seam with multiple sections (A1, A2, and A3) in the Sydney basin, where the CO_(2) composition exceeds 90%. The fast direct desorption method and associated devices were described in detail and employed to measure the in-situ gas components (Q_(1), Q_(2), and Q_(3)) of the coal seam. The results show that in-situ total gas content (Q_(T)) ranges from 9.48 m^(3)/t for the A2 section to 14.80 m^(3)/t for the A3 section, surpassing the Level 2 outburst threshold limit value, thereby necessitating gas drainage measures. Among the gas components, Q_(2) demonstrates the highest contribution to Q_(T), ranging between 55% and 70%. Furthermore, high-pressure isothermal gas sorption experiments were conducted on coal samples from each seam section to explore their gas sorption capacity. The Langmuir model accurately characterizes CO_(2) sorption behavior, with ft coefcients (R^(2)) greater than 0.99. Strong positive correlations are observed between in-situ gas content and Langmuir volume, as well as between residual gas content (Q_(3)) and sorption hysteresis. Notably, the A3 seam section is proved to have a higher outburst propensity due to its higher Q_(1) and Q_(2) gas contents, lower sorption hysteresis, and reduced coal toughness f value. The insights derived from the study can contribute to the development of efective gas management strategies and enhance the safety and efciency of coal mining operations.

1950-2022年中国煤与瓦斯突出事故的时空分布规律

为厘清煤与瓦斯突出事故的发生规律,从时间和空间2个维度,对1950-2022年中国煤与瓦斯突出事故进行统计分析并提出防突措施与建议。研究结果表明:1950-2022年中国煤与瓦斯突出事故的时间分布特征可划分为大幅上升时期(1950-1980年)、持续好转时期(1981-2000年)和稳定下降时期(2001-2022年)。空间分布特征为范围广、较集中、南多北少、南重北轻。煤与瓦斯突出事故发生次数随时间逐渐减少,死亡人数与煤矿事故总死亡人数之比随时间波动上涨。煤与瓦斯突出矿井的空间分布总体呈南多北少的特点。研究结果为中国煤与瓦斯突出事故防治提供参考。

基于多区组合煤体的煤与瓦斯突出动力学机制

煤与瓦斯突出(以下简称“突出”)严重影响煤炭安全开采,其背后涉及的众多科学问题仍未解决。为降低煤体力学性质各向异性对突出研究的困扰,构建多区组合煤体模型;基于上覆岩层应力分布特征及应力波传播机制确定“弱区”煤体位置,将研究对象由“突出中心体”具体为“弱区”。由于外部动载扰动是导致突出的激发条件,采用冲击试验研究应力波在层状组合煤岩体中的传播规律,构建组合煤岩体应力-应变本构模型。进而明确卸载波作用下,煤体轴向多层层裂是煤体质点内撞击形成加载冲击波在自由面反射形成拉应力波导致的;煤体径向平面,由于泊松效应形成卸载波追赶塑性加载波的情形,生成多个径向裂隙及环向裂隙,得到煤体层裂片厚度动态演化规律。从而明确在外部动载扰动下,煤体“弱区”最先破坏,轴向产生多层层裂、径向平面产生多个径向及环向裂隙的三维损伤路径。基于此,提出一种基于多区组合煤体的突出动力学机制,将突出划分为准备、启动、发展、终止四个阶段。突出准备阶段,煤体上覆岩层应力转移、集中,高瓦斯压力梯度形成,为后续煤体失稳破坏创造条件;突出启动阶段,煤体受外部动载扰动,轴向“弱区”煤体最先发生破坏、形成多层层裂,径向平面形成多个径向及环向裂隙;突出发展阶段,吸附态瓦斯解吸与游离态瓦斯积聚形成高压瓦斯抛出煤体,导致突出继续向深部煤体发展,形成二次损伤;突出终止阶段,积聚形成的瓦斯压力低于煤体抗拉强度,形成稳定的纺锤形突出腔体,突出终止。该机制初步解释了突出过程中“响煤炮”“口小腔大”突出孔洞等动力现象成因,为矿井防突工作提供了新思路。

突出煤层分层切削钻孔瓦斯释放特征及应用研究

【目的】突出煤层钻进过程中的喷孔瓦斯超限是威胁矿井高效生产的安全隐患,分层切削钻进方法有助于在孔内削弱喷孔瓦斯压力,但分层切削形成的梯形钻孔周围瓦斯释放特征不明,限制了分层切削钻具结构设计和应用效果。【方法】以不同层间距、层厚差的分层切削钻孔为研究对象,建立数学模型分析钻孔周围瓦斯流动规律,并定量描述了分层切削钻孔瓦斯流量与层间距、层厚差之间的关系,在此基础上,通过数值模拟分析了分层切削钻具瓦斯释放调控机制,优化了分层切削钻具结构,并开展了现场钻进工业性试验。【结果和结论】结果表明:(1)多次切削成孔方式使钻孔的揭露面积逐渐增大,有效控制了瓦斯释放面积,进而调控了瓦斯释放流量,通过合理设计钻孔层厚差Hj与层间距Li,能够将瓦斯释放流量降低18.3%以上。(2)在一定层间距范围内,双层切削钻具调控效果将优于三层切削钻具,直径为63.5 mm刻槽阻尼钻杆在推力140 kN和扭矩4600 N·m作用下,最小安全系数为3.009,满足强度设计要求。(3)优选双层切削钻具,其揭露直径73 mm,终孔直径113 mm,层间距0.8 m,通过工业性试验,钻遇高压瓦斯富集区时,孔口瓦斯体积分数降低了37.7%,孔口瓦斯体积分数均未超过0.5%。表明分层切削钻具调控钻孔周围煤体瓦斯释放量、削弱瓦斯释放强度的作用显著,为预防钻孔喷孔瓦斯超限问题提供了新的解决思路。

铁路隧道煤与瓦斯突出危险性判定分析

铁路隧道在施工开挖过程中判定具有煤与瓦斯突出危险性,会导致投资增加和工期延长等问题。本文解读了国家煤矿安监局煤安监技装〔2019〕28号文附件《防治煤与瓦斯突出细则》与TB 10120-2019《铁路瓦斯隧道技术规范》中关于煤与瓦斯突出危险性判定的规定。通过对比不同铁路隧道煤与瓦斯突出危险性判定实例,讨论了铁路隧道各阶段煤与瓦斯突出危险性判定的原则。研究发现:勘察阶段钻孔内瓦斯测试数据欠准确的原因主要包括:(1)钻孔内测试深度与施工揭示煤层的深度不一致;(2)钻孔内煤层深度过大影响测试准确性。

基于离散-连续耦合的岩溶隧道防突岩体安全厚度预测

为有效预防岩溶隧道施工中的突涌水灾害,首先,调研近年来国内岩溶隧道突涌水典型案例,总结隧道突涌水形成机理及其影响因素;其次,建立离散-连续耦合模型并采用多元回归理论的方法,明确防突岩体破坏的判定准则,划分岩溶隧道防突岩体破坏模式并提出裂缝发育规律;然后,基于对防突岩体最小安全厚度造成影响的各因素,针对溶洞位于隧道上方、下方及侧方3种情况分别建立防突岩体最小安全厚度预测计算式;最后,依托德庆隧道工程进行验证。结果表明:防突岩体破坏模式主要有弯折破坏、整体剪切破坏和复合破坏3种,可基于裂隙发展速度将其破坏过程分为初始阶段、快速发育阶段、平缓发育阶段3个阶段;各因素按影响显著程度由大到小依次为溶腔内水压、围岩黏结参数、溶腔跨度、溶腔高跨比和隧道埋深;计算得到德庆隧道3处施工段的防突岩体最小安全厚度分别为2.964,5.263和0.961 m,突涌水评估结果准确。防突岩体最小安全厚度预测计算式可用于预测并评估岩溶隧道突涌水风险。

基于径向基网络的堰塞体溃决峰值流量预测研究

堰塞体由天然滑坡堆积而成,受上游来流冲刷和渗透极易发生溃决,给下游人们生命财产造成严重威胁。快速、准确地预测溃决峰值流量是堰塞体抢险工作的重中之重。现有研究基于数据库—统计回归—溃决模型的思想,提出了一系列堰塞体溃决峰值流量预测模型,但均未综合考虑堰塞体冲蚀特性和颗粒组成对溃决流量的影响,且随着数据的不断扩充,预测模型难以取得预期效果。因此,本研究基于国内外2060例堰塞体溃决信息数据库,通过考虑堰塞体几何特征、冲蚀特性和颗粒组成,提炼出堰塞体高度(H_(d))、堰塞体宽度(W_(d))、堰塞体体积(V_(d))、水库库容(V_(l))、溃口深度(H_(w))、溃口平均宽度(W_(b))、堰塞体中值粒径(d_(50))7个影响参数,并将堰塞体冲蚀程度分为5类,构建了考虑冲蚀特性的堰塞体溃决峰值流量预测模型。选取数据齐全的120座堰塞体溃决案例对模型进行验证,均方根误差(RMSE)和相关系数(R2)分别为9581 m^(3)/s与0.965,并和国内外已有典型参数模型进行比较。结果表明,考虑堰塞体冲蚀特性和d50参数的模型可以更好地预测溃决峰值流量,能够为堰塞体溃决抢险进程中的溃决洪水演进、下游受灾区域划分等工作内容提供合理参考。

隧道突出气体特征及形成机理研究

为研究高原隧道不明突出气体特征及形成机理,本文采用资料收集、现场调查测试与监测、室内岩石学、地球化学试验等方法与手段,研究突出气体赋存地质环境,揭示突出气体成分、演化过程及演化规律,结合区域地质条件演化过程,建立突出气体形成、演化模式。研究结果表明:(1)该横洞及周边地区不具备发育大规模油气资源的岩性条件,该突出气体应属有机成因与无机成因混合气范畴;(2)突出气体含量随时间呈逐渐减小趋势,气体储量有限,不具有易燃性,具有微~中等腐蚀性;(3)该横洞突出气体是一类成分多样、形成演化过程复杂的有机成因和无机成因混合气,其形成先后经历有机成因阶段与无机成因阶段,区域地质历史时期活跃的岩浆活动和出气孔处发育的碳酸盐岩为突出气体的无机成因提供了证据。研究成果可为类似高原隧道突出气体研究和评价提供参考。

瓦斯气体水合固化作用影响因素分析

瓦斯与水的水合作用可以促使煤层中的瓦斯气体以水合物的形态固化于煤层之中,为研究外在条件对瓦斯水合物生成的影响,自主搭建了静态水合物合成实验装置,开展了瓦斯水合作用实验,分别考察了促进剂添加量、初始压力对瓦斯水合作用的影响规律,分析了促进剂、初始压力对瓦斯水合物生成促进作用机理。结果表明:促进剂的添加有效增加了水合作用效果但却存在极限浓度,当促进剂浓度介于3 wt%-8.7 wt%时会促进水合作用的进行,浓度达到8.7 wt%时作用效果最佳,而当促进剂浓度在14.4 wt%时,则会减缓水合作用进程;初始压力与水合作用效果呈正相关关系,初始压力越高水合作用的速率越快,水合作用时间越长;通过对反应余气中甲烷组分的监测表明,促进剂和初始压力能够改变水合作用的进程,对于瓦斯水合固化效果起着决定性的作用。

煤矿冲击地压和煤与瓦斯突出事故自动发现与报警方法研究

煤矿冲击地压和煤与瓦斯突出自动感知报警方法是及时发现事故并应急救援,减少人员伤亡,避免或减少瓦斯和煤尘爆炸等次生事故发生,遏制事故迟报、漏报和瞒报的有效措施。煤矿冲击地压事故感知难,目前还没有煤矿冲击地压事故自动发现和报警方法,煤矿冲击地压事故主要靠人工发现。目前仅有基于甲烷、风速和风向传感器的煤与瓦斯突出自动报警方法,但存在响应速度慢、甲烷传感器损毁前监测不到甲烷浓度大幅升高等问题。提出了煤矿冲击地压和煤与瓦斯突出图像感知报警方法:根据煤矿冲击地压和煤与瓦斯突出温度、颜色、深度、掩埋等图像特征,识别煤矿冲击地压和煤与瓦斯突出;再根据巷道空间和采掘工作面的甲烷浓度变化,区分冲击地压和煤与瓦斯突出,如果甲烷浓度大面积迅速升高,则判定为煤与瓦斯突出,否则判定为冲击地压。该方法具有直观、响应速度快、非接触、监测范围广、简单可靠等优点,可直观地记录煤矿冲击地压和煤与瓦斯突出真实情况;当煤矿冲击地压和煤与瓦斯突出事故报警后,调度室值班人员可以通过录像,立即确认事故,及时进行应急救援。提出了减少煤矿冲击地压和煤与瓦斯突出抛出的煤岩对图像感知影响的方法:摄像机多点布置,摄像机设置在较高位置,视频数据及时传输,甲烷传感器多点布置等。

基于深度特征的煤矿冲击地压和煤与瓦斯突出图像感知报警方法

冲击地压和煤与瓦斯突出容易造成煤矿重特大事故。针对目前煤矿冲击地压和煤与瓦斯突出事故发生主要靠人工发现,结合灾害造成不同于正常工况下采掘工作面和巷道空间的颜色和深度特征,提出了一种基于深度特征的煤矿冲击地压和煤与瓦斯突出图像感知报警方法:在煤矿井下巷道顶板、巷帮靠近顶板以及采掘工作面液压支架顶部或靠近顶部等位置多点布置带有补光灯的彩色双目摄像机,实时采集采掘工作面和巷道空间彩色图像和深度图像;以煤矿井下与灾害抛出煤岩有着鲜明颜色差别的生产设备作为背景,监测识别是否出现彩色图像颜色发生较大变化;如果掘进巷道端头、巷道中间、巷道入口,或回采工作面,或进风巷道入口、巷道中间,或回风巷道入口、巷道中间,或主运输、辅助运输大巷等位置彩色双目摄像机监测到图像颜色发生较大变化,则监测彩色图像平均亮度是否小于设定的亮度阈值;如果平均亮度小于设定的亮度阈值,则以与灾害抛出煤岩有鲜明颜色差别的生产设备为背景,监测深度图像是否发生较大变化;如果深度图像发生较大变化,那么监测导致深度图像发生较大变化物体的移动速度是否大于设定的速度阈值(v>13 m/s);当移动速度大于设定速度阈值时,利用多点布置的甲烷传感器监测监视区域内甲烷浓度,当采煤工作面、掘进工作面、进风巷道、回风巷道、总回风巷道等多个不同地点均监测到甲烷浓度大幅升高或达到报警值,那么进行煤与瓦斯突出报警,反之,则进行冲击地压报警。提出了彩色双目摄像机感知灾害最佳倾角的确定方法,以及导致深度图像发生较大变化物体移动速度的确定方法。在确保安全性的前提下,简化了灾害模拟试验,设计了一套煤矿冲击地压和煤与瓦斯突出颜色和深度特征模拟试验装置:采用与煤岩颜色和比重相近的10 mm橡胶球替代灾害抛出煤岩;利用直径315 mmPVC管模拟煤矿井下巷道受限空间以及与抛出煤岩有着鲜明颜色差异的背景设备;利用轴流式高压鼓风机作为动力装置,进行模拟冲击地压和煤与瓦斯突出发生时大量煤岩抛出造成的采掘工作面和巷道空间颜色和深度异常特征;利用3.4 mm焦距、30FPS、71°×55°视场角的彩色双目摄像机,完成对整个灾害模拟过程的监视与彩色双目图像采集。研究分析表明,提出的方法可识别出灾害发生时颜色和深度特征,验证了基于深度特征的煤矿冲击地压和煤与瓦斯突出图像感知报警方法的可行性与有效性。

基于机器学习的煤与瓦斯突出预测研究进展及展望

我国煤矿安全生产形势不断好转,但煤与瓦斯突出事故仍时有发生。煤与瓦斯突出预测不仅能指导防突措施科学的运用、减少防突措施工程量,在一定程度上也可以确保煤矿工人的作业安全。机器学习(Machine Learning, ML)是一门涉及概率论、统计学和计算机学等领域的交叉学科,可以挖掘突出事故和指标间的非线性关系。将机器学习用于煤与瓦斯突出预测,已得到相对广泛的关注,并随着人工智能和计算机技术的快速进步,其在突出预测领域将发挥更大作用。因此,对机器学习在煤与瓦斯突出预测中的研究进行了全面的综述,分析其在突出预测中面临的难点并展望其发展方向。首先,简述煤与瓦斯突出假说、发生机理与预测指标选择的研究现状;介绍机器学习在煤与瓦斯突出预测领域的主要研究进展,包括支持向量机(Support Vector Machines,SVM)、人工神经网络(Artificial Neural Network, ANN)、极限学习机(Extreme Learning Machines,ELM)和集成学习(Ensemble Learning, EL)等算法的应用,以及特征选择和缺失数据填补在数据处理等方面的创新,同时也指出了目前基于机器学习的突出预测研究面临的挑战及存在的问题,例如事故与非事故样本的不平衡、数据的指标缺失和机器学习中的小样本等;最后,展望了基于机器学习的煤与瓦斯突出预测的未来发展方向,包括改进算法性能、优化特征工程和增加样本量等。随着计算机性能的提升,有望开发出更为复杂、精准的模型,以提高对突出事故的准确预测能力。

驱动力对煤介质中CO_(2)水合物生长动力学的影响

为探究不同驱动力对煤介质中CO_(2)动力学的影响,开展了3种驱动力条件下煤介质中CO_(2)水合物生长动力学实验,获取了CO_(2)水合物生成过程中动力学参数。结果表明:相同粒径体系生成水合物的过程中,3 MPa驱动力的CO_(2)气体消耗量约为2.5 MPa、2 MPa驱动力CO_(2)气体消耗量的1.14、1.34倍;不同粒径体系驱动力增加,体系内气体分子运动加快,气体分子与液面水分子碰撞的次数也会随之增高,CO_(2)水合物结晶成核的机会也随之增加,CO_(2)水合物气体消耗量、生长速率随之加快。在0.150~0.850 mm粒径范围内随着煤介质粒径增大,CO_(2)水合物生长速率逐渐提高;利用线性拟合获取了CO_(2)水合物平均生长速率与驱动力关系式,为预测CO_(2)水合物的平均生长速率提供参考。

基于非稳态扩散的复合煤体能量失稳致灾研究

在我国由于地质构造作用的影响,导致煤层中多存在原生结构煤和构造煤分层的现象;而构造煤的存在导致复合煤层突出危险性急剧增加,这严重制约我国煤矿安全生产。根据软硬复合煤体瓦斯的扩散状态,模拟分析了非稳态扩散复合煤体的力学失稳规律;建立了非稳态扩散的吸附瓦斯膨胀能计算模型,探讨了稳态扩散和非稳态扩散对于吸附瓦斯膨胀能的影响,从能量角度分析了吸附瓦斯膨胀能对突出的控制作用,阐释了非稳态扩散复合煤体的突出失稳致灾机制。结果表明:复合煤层中构造煤的存在能够增加其邻近原生结构煤的塑性破坏程度,提高了原生结构煤塑性区内的瓦斯运移速度,进而增加煤与瓦斯突出危险性;非稳态扩散条件下原生结构煤和构造煤的吸附瓦斯膨胀能是稳态扩散条件的0.50~0.57倍和3.36~3.38倍,复合煤层中由于构造煤的存在导致原生结构煤内部裂隙-基质系统间产生巨大的瓦斯浓度差,使得原生结构煤基质内部的吸附瓦斯迅速解吸,增加邻近原生煤中吸附瓦斯膨胀能,进而使得复合煤层的突出危险性显著增加。

基于应力松弛效应的黏弹性煤层地应力分布模型及在突出煤层中的应用

地应力是控制煤矿瓦斯动力灾害的核心因素,现有地应力模型主要基于弹性煤岩体属性而建立,而对于黏弹性煤层介质不适用,需要建立适合煤层属性的地应力分布模型。煤层尤其是构造煤呈现显著的蠕变和应力松弛特性,基于此,构建了黏弹性煤层分数阶麦克斯韦应力松弛数学模型,对扩展伊顿模型中构造应力项改进为黏弹性煤层的应力松弛项,建立了黏弹性煤层地应力分布模型。结果表明,在地质时间尺度内,煤层黏弹性对差应力有显著影响,煤体蠕变和应力松弛程度随黏性系数和分数阶因子的增加而增加;并随弹性模量下降,泊松比、构造比及瓦斯压力增加,煤层应力特征表现为静水压力状态分布趋势,其中弹性模量和泊松比对垂直主应力与水平应力之间差异贡献较大,构造比对水平应力之间差异贡献较大,瓦斯压力对3个主应力贡献相等,应力松弛效应可改变最大、最小水平主应力相对大小及降低应力各向异性。基于临界应力模型,在不同地应力状态下同样获得了摩擦因数降低及瓦斯压力升高的煤层趋近静水压力分布。构造煤力学属性更有利于在地质时间尺度中趋向于静水压力状态。运用地应力模型验证了现场实测结果,并对构造煤瓦斯富集和渗透率降低提出了新的认识。