Disasters of gas-coal spontaneous combustion in goaf of steeply inclined extra-thick coal seams

In light of the escalating global energy imperatives,mining of challenging-to-access resources,such as steeply inclined extra-thick coal seams(SIEC),has emerged as one of the future trends within the domain of energy advancement.However,there is a risk of gas and coal spontaneous combustion coupling disasters(GCC)within the goaf of SIEC due to the complex goaf structure engendered by the unique mining methodologies of SIEC.To ensure that SIEC is mined safely and efficiently,this study conducts research on the GCC within the goaf of SIEC using field observation,theoretical analysis,and numerical modeling.The results demonstrate that the dip angle,the structural dimensions in terms of width-to-length ratio,and compressive strength of the overlying rock are the key factors contributing to the goaf instability of SIEC.The gangue was asymmetrically filled,primarily accumulating within the central and lower portions of the goaf,and the filling height increased proportionally with the advancing caving height,the expansion coefficient,and the thickness of the surrounding rock formation.The GCC occurs in the goaf of SIEC,with an air-return side range of 41 m and an air-intake side range of 14 m,at the intersection area of the“<”-shaped oxygen concentration distribution(coal spontaneous combustion)and the“>”-shaped gas concentration distribution(gas explosion).The optimal nitrogen flow rate is 1000 m3/h with an injection port situated 25 m away from the working face for the highest nitrogen diffusion efficacy and lowest risk of gas explosion,coal spontaneous combustion,and GCC.It has significant engineering applications for ensuring the safe mining of SIEC threatened by the GCC.

Research on the mechanism of rockburst induced by mined coal-rock linkage of sharply inclined coal seams

In recent years,the mining depth of steeply inclined coal seams in the Urumqi mining area has gradually increased.Local deformation of mining coal-rock results in frequent rockbursts.This has become a critical issue that affects the safe mining of deep,steeply inclined coal seams.In this work,we adopt a perspective centered on localized deformation in coal-rock mining and systematically combine theoretical analyses and extensive data mining of voluminous microseismic data.We describe a mechanical model for the urgently inclined mining of both the sandwiched rock pillar and the roof,explaining the mechanical response behavior of key disaster-prone zones within the deep working face,affected by the dynamics of deep mining.By exploring the spatial correlation inherent in extensive microseismic data,we delineate the“time-space”response relationship that governs the dynamic failure of coal-rock during the progression of the sharply inclined working face.The results disclose that(1)the distinctive coal-rock occurrence structure characterized by a“sandwiched rock pillar-B6 roof”constitutes the origin of rockburst in the southern mining area of the Wudong Coal Mine,with both elements presenting different degrees of deformation localization with increasing mining depth.(2)As mining depth increases,the bending deformation and energy accumulation within the rock pillar and roof show nonlinear acceleration.The localized deformation of deep,steeply inclined coal-rock engenders the spatial superposition of squeezing and prying effects in both the strike and dip directions,increasing the energy distribution disparity and stress asymmetry of the“sandwiched rock pillar-B3+6 coal seam-B6 roof”configuration.This makes worse the propensity for frequent dynamic disasters in the working face.(3)The developed high-energy distortion zone“inner-outer”control technology effectively reduces high stress concentration and energy distortion in the surrounding rock.After implementation,the average apparent resistivity in the rock pillar and B6 roof substantially increased by 430%and 300%,respectively,thus guaranteeing the safe and efficient development of steeply inclined coal seams.

Stability of roof structure and its control in steeply inclined coal seams

To improve the effectiveness of control of surrounding rock and the stability of supports on longwall topcoal caving faces in steeply inclined coal seams, the stability of the roof structure and hydraulic supports was studied with physical simulation and theoretical analysis. The results show that roof strata in the vicinity of the tail gate subside extensively with small cutting height, while roof subsidence near the main gate is relatively assuasive. With increase of the mining space, the caving angle of the roof strata above the main gate increases. The characteristics of the vertical and horizontal displacement of the roof strata demonstrate that caved blocks rotate around the lower hinged point of the roof structure, which may lead to sliding instability. Large dip angle of the coal seam makes sliding instability of the roof structure easier.A three-hinged arch can be easily formed above both the tail and main gates in steeply inclined coal seams. With the growth in the dip angle, subsidence of the arch foot formed above the main gate decreases significantly, which reduces the probability of the roof structure becoming unstable as a result of large deformation, while the potential of the roof structure's sliding instability above the tail gate increases dramatically.

Gas Drainage Technology in Fully Mechanized Caving Face with Horizontal Sublevel Mining in Steep and Extra-Thick Coal Seam

This paper analyzes the gas source of the horizontally sectioned fully mechanized caving face in the steeply inclined and extra-thick seam of Adaohai Coal Mine, and numerically simulates the stress distribution and pressure relief of the lower section coal after the upper section working face is mined. It theoretically analyzed the reasonable layout of the drainage boreholes, and designed the drainage borehole layout accordingly. In the upper and lower section of the working face, the actual drainage effect of the boreholes was inspected, and the air exhaust gas volume in the working face was statistically analyzed. It was confirmed that the layout of boreholes was reasonable, the gas control effect of working face was greatly improved and fully met the needs of safe mining. The control effect was greatly improved and the need for safe mining was fully met, and thus a gas drainage technology suitable for the coal seam storage conditions and mining technology of the Adaohai Coal Mine was found. That is to say: the gas emission from the working face of the section mining mainly comes from its lower coal body. Pre-draining the lower coal body of the section and depressurizing gas interception and drainage are the key to effectively solve the problem of gas emission from the working face. Drainage boreholes in the working face of the section should be arranged at high and low positions. The high-level boreholes are located about 2 m from the top of the working face, and the high-level boreholes are about 9 m away from the top of the working face. Through the pre drainage of high and low-level boreholes in advance and the interception and pressure relief drainage, the gas control in the horizontal sublevel fully mechanized caving mining face in steep and extra thick coal seam can realize a virtuous cycle.

Underground pressure appearance laws analysis for fully mechanized top coal slice caving on high-dipping thick coal seams

Taking Adaohai Coal Mine as the example, underground pressure appearance laws of fully mechanized top coal slice caving on high-dipping and thick coal seams. Through site visit, theoretical analysis and discrete element calculation, the research shows that, as the mining deepens, underground stress of lower sublevels is more obvious and higher than that of upper sublevels and is higher in the air return roadway than that in the air intake roadway in the area that is near to the top coal. Because the top coal is thick and gangue is caved above the support, underground pressure to the working face is relatively gentle. Immediate roof will mainly fall down along the floor. Main roof and the rock bed above the main roof will move to the mined out area along the fault in the early stage and then fall down with the mined out area later. In addition, roof pressure mainly periodically appears in two directions along the trend and the dip.

Study on Supporting of Seam Roadways in Deeply Inclined Coal Seams

Based on the present problems of the support method of gateways in complex surrounding rock in steeply inclined seams, this paper discusses the support selection of lasting gateways in steeply inclined seams, and evaluates the support effects. It draws the conclusion that the support of bolt-mesh-anchor is the most effective support of this sort of gateways by using scale model simulation in lab and practice application.The support effects of practice application are satisfactory. It will give a beneficial reference to other analogical mine and has an extensive application prospect.

Development and prospect on fully mechanized mining in Chinese coal mines

Fully mechanized mining(FMM)technology has been applied in Chinese coal mines for more than 40 years.At present,the output of a FMM face has reached 10-million tons with Chinese-made equipment.In this study,the new developments in FMM technology and equipment in Chinese coal mines during past decades are introduced.The automatic FMM technology for thin seams,complete sets of FMM technology with ultra large shear height of 7 m for thick seams,complete sets of fully mechanized top coal caving technology with large shear height for ultra-thick seams of 20 m,complete sets of FMM technology for complex and difficult seams,including steeply inclined seams,soft coal seams with large inclination angle,and the mechanized filling mining technology and equipment are presented.Some typical case studies are also introduced.Finally,the existing problems with the FMM technology are discussed,and prospect of FMM technology and equipment applied in Chinese coal mines is put forward.

急倾斜深埋巨厚煤层掘巷冲击地压前兆特征及其灾害防治

随着冲击地压矿井逐渐向深开采,其巷道掘进伴随的冲击显现愈发强烈。针对巷道掘进过程中的冲击地压有效防治问题,以新疆乌东煤矿急倾斜煤层矿井为例,运用微震监测对巷道掘进的冲击地压时空前兆特征加以分析。结合巷道掘进的应力与能量变化数值模拟分析,揭示巷道掘进的冲击地压发生机理,提出急倾斜巨厚煤层巷道冲击地压防治策略,并完成现场工程实践验证。研究结果表明:急倾斜巨厚煤层巷道掘进的冲击地压发生前第2~5天出现微震总能量极低值,或存在至少4 d的能量潜伏期;冲击地压发生前5 d普遍存在3 d以上的最大能量占比高频波动期。冲击地压发生前存在明显缺震现象,发生位置集中分布在距离掘进工作面较近的微震能量极小值区间范围内,或位于微震能量极值区间附近的微震频次极小值区间范围内,且冲击地压事件位于冲击变形能指数较高区域。急倾斜巨厚煤层水平分段综放开采的坚硬覆岩结构不易破断,使得巷道掘进存在上水平采空区两侧“双翼型”应力集中,掘进工作面前方与巷道底部受顶底板岩层相互挤压的应力集中分布且能量积聚显著,随着巷道掘进深度增加其应力集中与能量积聚进一步增强,容易诱发冲击地压等动力灾害。综合分析形成急倾斜巨厚煤层巷道掘进的工作面爆破卸压、巷道钻孔卸压与补强支护、复杂区域架蓬的冲击地压防治策略。结合冲击地压时空前兆异常为及时加强卸压力度提供时机。通过工作面与巷道卸压使得掘进期间未发生单日累计1×105 J以上微震能量,在对支护优化调整与复杂区域重点防护后,巷道掘进日均微震能量降至2.2 kJ,其1 kJ以上微震事件占比下降且巷道断面整体平整。研究结果为急倾斜巨厚煤层巷道安全掘进提供了科学依据。

急倾斜特厚煤层冲击地压防治探索与总结

急倾斜特厚煤层开采顶板破断运动复杂,应力和能量演化规律特殊,在深部“三高一扰动”影响下,冲击地压防治不容乐观。基于某矿2016年冲击地压事故后急倾斜特厚煤层水平分段开采冲击地压防治经验,从急倾斜特厚煤层水平分段开采冲击地压发生机理、瓦斯突出与冲击地压综合防治和冲击地压管理详细介绍了该矿7年来急倾斜特厚煤层冲击地压防治经验。冲击地压发生机理方面,建立了顶板岩层倾斜悬臂梁模型,揭示了顶、底板覆岩结构破断失稳演化过程,划分了夹持煤体受力状态分区,提出了急倾斜特厚煤层冲击“夹持理论”。瓦斯突出与冲击地压综合防治方面,基于冲击地压灾害控制解危技术的强度弱化减冲理论,结合原有防突措施体系,提出了既能防冲且对防突有利的解危措施,形成了某矿瓦斯/CO_(2)突出-冲击地压“双防”技术体系,建立了适用于某矿急倾斜特厚煤层水平分段开采的冲击地压防治体系,以钻屑量和瓦斯吸解值验证了瓦斯突出防治的强度保障,同时以加强实施卸压措施工作面的微震事件分布及各能级总频次和能量对比,论证说明了卸压方案防治效果的有效性。冲击地压管理方面,形成了预测评价、监测预警、治理预防、效果检验、安全防护和教育培训“六位一体”综合防治架构,基于《煤矿安全规程》和《防治煤矿冲击地压细则》等各项规定,制定了Q/YJMD-—FC 0104-2022《窑街煤电集团有限公司煤矿冲击地压防治第四部分:冲击地压防治技术规范》。

深埋倾斜特厚煤层窄煤柱护巷机理与围岩控制

我国中东部地区采深大、巷道变形和冲击风险大,窄煤柱沿空掘巷技术可改善巷道围岩环境。为掌握窄煤柱护巷机理并形成针对性围岩控制技术体系,以800 m埋深倾斜特厚煤层3 m窄煤柱沿空掘巷为背景,开展了理论分析、现场实测及数值模拟研究,结果表明:①该巷围岩破碎程度及变形煤柱侧比实体煤侧严重,煤柱破碎程度及变形采空区侧比巷道侧大,尽管埋深大,但已稳定采空区承担较大覆岩载荷,高应力已充分向深部岩体分流;②巷道变形非对称,实体煤侧顶板下沉量比煤柱侧大,巷帮以浅部变形为主,煤柱帮上部和实体煤帮中部变形较大;③采空区是掘巷卸荷后主要的形变通道,利于形变能向采空区缓释、降低冲击风险;④卸压区形状由掘巷前三角形扩展为掘巷后平行四边形,掘巷后应力集中区转移至实体煤帮右上方实体煤岩体中;⑤窄煤柱一次和二次剪切破坏的交界面及掘巷右上方实体高应力区为围岩关键控制区,据此提出基于煤柱多重塑性破坏区发育规律的煤柱加固和高应力区精准卸压联合的围岩控制技术体系。研究可为邻近工作面以及其他类似深埋倾斜特厚煤层开采提供理论支撑和科学依据。

管道作用下急倾斜煤层稳定性分析

近地表荷载与急倾斜煤层老采空区的“活化”有着紧密的关联,采空区覆岩中裂隙带底部的岩块在荷载作用下极易发生回转失稳和滑落失稳,这些岩块对采空区的稳定性起到至关重要的作用,被称为关键岩块,当荷载作用使得关键岩块失稳时,采空区将发生“活化”。基于采空区覆岩“砌体梁”结构力学模型对关键岩块进行力学分析,构建荷载作用下采空区上覆岩土体失稳判断依据,进而对荷载作用下急倾斜煤层上覆岩体稳定性进行定量分析,研究发现:当作用于土体截面处最大摩擦力大于该土体所受最大剪切力时,该块体不会发生滑落失稳;只有关键岩块与岩块之间的平均挤压应力小于岩块在边角处的挤压强度,关键岩块才不会发生回转失稳。将推导结果应用于广东省某急倾斜煤矿,计算结果表明:在茶山煤矿4煤和6煤采空区上方铺设输气管道并不会引起采空区的“活化”;荷载作用下的关键岩块力学分析在急倾斜煤层上覆岩体稳定性中应用效果较好,对实际工程有一定指导作用。

弱化浅层岩体防治急倾斜特厚煤层冲击地压研究

急倾斜特厚煤层受其特殊的地质、应力和开采技术条件影响,冲击地压防治方法与一般煤层存在较大差异。将理论推导、数值模拟、现场监测等方法相结合,研究了急倾斜特厚煤层的岩层弯曲和煤层能量积聚特征,提出了弱化浅层岩体防治急倾斜特厚煤层冲击地压的方法,得到了防冲关键参数,并进行了工程应用。研究结果表明,急倾斜特厚煤层岩层弯曲时内部岩体破裂释放能量是动载的主要来源,采空区两侧围岩转移、传递至煤层的水平集中应力是静载和能量积聚的主要来源;防治急倾斜特厚煤层冲击地压应弱化工作面浅层岩体的应力传递能力,来降低传递至工作面的动载扰动强度以及转移、传递至煤层的水平集中应力。基于此提出了通过浅孔爆破措施弱化急倾斜特厚煤层浅层岩体的防冲方法。现场工程应用表明,矿井补强浅孔爆破后,工作面微震事件总能量降低了42.38%、总数量增大了471.74%,说明工作面的能量释放由大能量剧烈释放逐渐转为小能量平缓释放,且未再发生过冲击显现,冲击地压危险得到有效控制。研究成果可为类似条件矿井防治冲击地压提供参考。

西南地区急倾斜薄煤层充水采空区地面注浆堵水工艺研究及应用

针对金沙水电站蓄水区南岸的相关煤矿采空区的治理,选择帷幕注浆堵水为治理方案。通过钻孔将水泥浆充填采空区及其上部裂隙,切断金沙江与矿井之间的径流通道,其中帷幕孔注浆采用水泥-水玻璃双液浆注浆工艺,一般注浆孔采用水泥浆单液注浆工艺。室内凝结时间检测试验的结果中,水泥浆的终凝时间随着水灰比的增大而逐渐从500 s以上下降到20 s左右,根据试验结果确定了合适的水泥浆配比。注浆堵水质量检测得到4组水泥芯体的采空区无侧限抗压强度均值分别为1.21、1.21、1.36、1.29 MPa,注浆段波速值为365~384m/s。抗压强度大于1 MPa,横波波速大于350 m/s,表明注浆堵水工艺实施后的质量评价结果整体满足要求,具有可行性与实用性。

煤矿急倾斜煤层柔性掩护支架采煤法开采参数分析

以神角煤矿为例,介绍了1种煤矿急倾斜煤层柔性掩护支架采煤法。通过对煤矿的生产技术条件进行分析,进而计算出作业面主要参数、巷道支护参数、回采工艺参数,确定了最佳的柔性掩护支架采煤技术方案,为煤矿急倾斜煤层的开采提供了支持,明确了根据柔性掩护支架采煤法的开采参数进行煤矿设计,可以提高煤矿的生产效率和经济效益。

急倾斜采煤机牵引系统研究

对满足采高1.2~2.0 m、适应最大倾角68°的急倾斜薄煤层采煤机牵引传动系统关键技术进行研究。分别研究了紧凑型大扭矩牵引传动系统总体技术、急倾斜高可靠性行走系统、重载调速和负荷平衡技术三方面关键内容,可有效提高急倾斜薄煤层采煤机的牵引爬坡能力和控制可靠性。该研究成果已在四川达竹集团、川煤集团等国内大型煤炭生产企业推广应用,极大促进了急倾斜采煤机技术的进步和煤矿生产效率的提高,为复杂地质条件下急倾斜薄煤层的安全开采提供了装备技术保障,推广应用前景十分广阔。

基于微震时空信息的近直立煤层致冲因素研究

为掌握近直立煤层冲击地压致灾因素,基于矿井开采布局及现场微震监测数据,从时间和空间多维度对矿井微震事件的分布及历次冲击地压事件进行了深入分析,研究了不同开采深度下的致灾因素的演变规律。结果表明:近直立煤层的冲击地压主要由悬空顶板和中间岩柱对工作面产生的应力集中以及煤岩体破裂产生的动载扰动诱发,日推进度、开采深度及遗留煤柱与冲击地压事件的发生也具有强相关关系,是矿井冲击主要致灾因素;矿井浅部开采时中间岩柱受水平构造应力和自重应力对煤岩体产生的“撬动”作用是导致煤岩体失稳破坏的主控因素,进入深部开采后叠加了悬空顶板的“挤压”作用,冲击致灾因素转变为顶板和岩柱的“压+撬”共同作用,而遗留煤柱等因素影响程度减弱。

基于机器学习的急倾斜巨厚煤层掘进巷道冲击地压预测方法

针对急倾斜巨厚煤层掘进巷道冲击地压前兆信息挖掘不充分的困境,以新疆乌东煤矿急倾斜巨厚煤层掘进巷道的冲击危险预警为背景,探究了多项物理指标的演化规律,采用BP神经网络、随机森林(RF)、支持向量机(SVM)、梯度提升决策树(GBDT)等4种机器学习算法,分别建立了急倾斜巨厚煤层掘进巷道冲击地压的预测模型,并对各模型预测性能进行了验证和实例分析,明确了掘进条件下神经网络算法对急倾斜巨厚煤层各指标的敏感性分布。研究结果表明:机器学习算法能够有效提取出各物理指标发展趋势中蕴含的冲击前兆特征其中BP神经网络算法的建模精度最高,相较于其他模型平均绝对误差分别降低了58.44%55.64%,26.37%;R^(2)分数分别提高了11.25%,8.37%,3.66%;依据BP神经网络算法得到的各物理指标敏感性排序分别为A(b)值、b值、矿震活动度S值、等效能级参数EEM值、缺震值、算法复杂性AC值;应用R值评分法对乌东煤矿急倾斜巨厚煤层掘进巷道的冲击预警进行了效能验证结果表明该模型预测准确率较好,总体预测准确率为90.65%,并成功预测了掘进期间的两次大能量事件,该方法适用于急倾斜巨厚煤层掘进巷道的防冲预警,建立的模型对于冲击地压危险的预测有着较好的潜力,研究结果可为类似条件下急倾斜煤层冲击危险的演化发展提供参考。

大倾角煤层充填开采技术研究

大倾角煤层开采作业中,若不对采空区进行适当充填,极易发生岩层沉陷。就矸石滑移充填开采技术展开研究,建立顶板力学模型,进行受力分析,并在山西省某煤矿3203工作面开展现场矿压监测,得出矸石滑移充填非均匀性、矿压分区性、来压时间时序性等结论。

急倾斜煤层回采参数研究

近年来由于煤炭资源的不断开采,矿井深度增加导致煤层地质条件不断恶化,尤其是急倾斜煤层的回采工作,对开采工艺有着极高的要求。结合当前急倾斜煤层开采工艺现状,通过分析急倾斜煤层回采参数,提出一种新型斜坡短臂采煤工艺,为该类复杂型煤层的开采提供借鉴。

煤矿工作面均压通风技术方案研究与实践

为克服急倾斜煤层的开采过程中出现的氧气浓度偏低、隅角气体聚集等问题,提出了一种均压通风的技术方法及测量方案,保证采空区和工作面之间的风压平衡。经过对回风隅角各类气体在均压通风前后浓度测量,实测表明:回风隅角CH4浓度大致保持在0.5%上下、CO浓度可以保持到0.0024%之内、O_(2)浓度大致保持在18%之上、漏风量可以维持在10 m^(3)/min以下,均压系统比较可靠,确保+575水平45号东翼工作面生产的安全推进。