Behaviors of overlying strata in extra-thick coal seams using top-coalcaving method

Accidents such as support failure and excessive deformation of roadways due to drastic changes in strata behaviors are frequently reported when mining the extra-thick coal seams Nos.3e5 in Datong coal mine with top-coal caving method,which significantly hampers the mine's normal production.To understand the mechanism of strata failure,this paper presented a structure evolution model with respect to strata behaviors.Then the behaviors of strata overlying the extra-thick coal seams were studied with the combined method of theoretical analysis,physical simulation,and field measurement.The results show that the key strata,which are usually thick-hard strata,play an important role in overlying movement and may influence the mining-induced strata behaviors in the working face using top-coal caving method.The structural model of far-field key strata presents a 'masonry beam' type structure when'horizontal O-X' breakage type happens.The rotational motion of the block imposed radial compressive stress on the surrounding rock mass of the roadway.This can induce excessive deformation of roadway near the goaf.Besides,this paper proposed a pre-control technology for the hard roof based on fracture holes and underground roof pre-splitting.It could effectively reduce stress concentration and release the accumulated energy of the strata,when mining underground coal resources with top-coal caving method.

Monitoring strata behavior due to multi-slicing top coal caving longwall mining in steeply dipping extra thick coal seam

For studying the strata behavior due to multi-slicing top coal caving longwall mining along-the-strike direction in steeply dipping extra thick coal seams,the shield support pressures of the upper and lower slices of panel 37220 in Dongxia Coal Mine were monitored using the KJ513 dynamic monitoring system.The set up rooms adopted the "horizontal line-arc segment-inclined line" form and used different types of shield supports.The results show that the strata pressure of upper slice panel 37220-1 changed slightly along the strike direction,while along the dip direction it exhibited strong to weak pressure from bottom to top.The first weighting interval of lower slice panel 37220-2 was about 60.8 m,and the average periodic weighting interval were about 22.6 m.The strata behavior of panel 37220-2 exhibited a spatiotemporal characteristic in that periodic weighting occurred first in the middle-upper part,followed by the middle and upper parts,arc segment,and finally the lower part.During the periodic weighting,the weighting interval and intensity also exhibited strong space characteristics.The average dynamic load coefficient was 1.48 and the maximum lateral load of the side shield was 20-25 MPa.

Strata behavior in extra-thick coal seam mining with upward slicing backfilling technology

Based on the character of upward slicing backfilling mining and the condition of Gonggeyingzi coal mine in Inner Mongolia,this paper describes the studies of the strata behavior and the stress distribution in the process of backfilling mining in extra-thick coal seams.This was achieved by setting up and analyzing the elastic foundation beam model using the ABAQUS software.The results show that:(1) With the gradual mining of different slices,the roof appears to bend continuously but does not break.The vertical stress in the roof decreases and the decreasing amplitude reduces,while the tensile stress in the roof grows with the mining slices and the maximum tensile stress will not exceed the allowable tensile stress.(2) The front vertical stress at the working face exceeds the rear vertical stress and both show a trend of decrease with decreasing amplitude of decrease.(3) The slices mined early have more influence on the surrounding rock than the later ones.Similarly,the strata behavior experiences the same trend.The field measured data show that the roof does not break during the mining process,which is consistent with the conclusion.

Regularity of Strata Behaviors of Tailentry of Longwall Face in Deep Colliery

Based on the dividing of derormation zones of tailentry in working face and the classification of driving metbods, toking the way of field measurement, this paper fiuds out some changing regularities of main deformation parameters of a tailentry in 2# coal seam in Suncun Colliery with the incrcasing of mining depth, and puts forward some layout methods to protect the tailentry in deep mining.

Experimental investigation on behaviors of bolt-supported rock strata surrounding an entry in large dip coal seam

In order to investigate the behaviors and stability of rock strata surrounding an entry with bolt supporting in large dip coal seams (LDCSs) dipping from 25° to 45°, a self-developed rotatable experimental frame for similar material simulation test was used to build the model with the dip of 30°, based on analyses of geological and technological conditions in Huainan mine area, Anhui, China. The strata behaviors, such as extracting- and mining-induced stresses development, deformation and failure modes, were synthetically integrated during working face advancing. Results show that the development characteristics of mining-induced stress and deformation are asymmetrical in the roadway. The strata behaviors are totally different in different sections of the roadway. Because of asymmetrically geometrical structure influenced by increasing dip, strata dislocating, rock falling and breaking occur in roof. Then, squeezing, collapsing and caving of coal happen in upper- and lower-rib due to shearing action caused by asymmetrical roof bending and dislocating. Owing to the absence of supporting, floor heaving is very violent and usually the zone of floor heaving develops from the lower-rib to upper-rib. Engineering practices show that, due to the asymmetrical characteristics of rock pressure and roadway configuration, it is more difficult to implement bolt supporting system to control rock stability of roadways in LDCSs. The upper-rib and roof of entries are the key sections. Consequently, it is reliable to use asymmetrical bolt-mesh-cable supporting system to control rock stability of roadways based on the asymmetrical characteristics of roadway configuration and strata behaviors.

两次采动影响下小煤柱巷道切顶卸压围岩控制技术

为解决多次采动影响下留小煤柱巷道矿压显现剧烈、围岩变形量大的问题,提出了“切顶卸压+顶、帮锚索补强”联合控制技术。以贾家沟煤矿10115运输巷为工程背景,分析了切顶卸压位置、高度与巷道围岩垂直应力分布的关系,给出切顶卸压关键参数,并研究了留小煤柱巷道在切顶卸压后受两次采动影响下的矿压显现规律。结果表明:切顶卸压后,煤柱上的应力峰值随切顶深度的增加呈指数降低;10115运输巷在邻近工作面一次采动过程中巷道围岩变形依次呈现出无变形、缓慢变形、快速变形和围岩稳定的变化规律,本工作面二次采动过程中巷道围岩变形依次呈现出明显变形和剧烈变形的规律;巷道围岩在受二次采动影响时变形更加剧烈,巷道变形量为一次采动时的3.0~7.5倍。

顶板疏水条件下矿压显现规律及防治对策

顶板疏水带来矿压显现,影响矿井安全生产。为降低顶板疏水对工作面回采的影响,在分析顶板疏水条件下矿压显现规律的基础上,提出了针对性的防治措施。防治措施主要包括:大直径钻孔卸压和加强巷道支护,通过改变煤岩变形系统控制量,提高矿压显现的临界应力;控制回采速度和顶板深孔预裂爆破,降低煤岩变形系统外部实际应力,降低矿压危险性。可以为顶板疏水引起的矿压显现防治提供一定的技术参考。

浅埋近距离煤层过斜交区段煤柱开采矿压规律研究

为了探究浅埋近距离煤层工作面开采过不同斜交角度煤柱的矿压规律,保障工作面安全高效回采,采用现场实测和数值模拟相结合的方法,分析了11°、30°、45°、60°和75°斜交角度的采动应力演化特征,揭示了工作面过不同斜交角度煤柱的应力变化规律。结果表明:根据过11°斜交煤柱矿压规律实测,工作面来压位置随煤壁与斜交煤柱叠加区而移动,在工作面中部压力最大,机尾次之,机头最小;工作面机尾过煤柱时应力集中最明显;中部过斜交煤柱时,随着斜交角的增大,超前煤壁峰值应力自30°以内为中部宽缓单峰,45°~75°为中部斜交区和机尾双峰,且机尾峰值较大;机尾最大超前应力峰值随斜交角的减小而增大,峰值越靠近机尾;斜交角超过45°时工作面中部出现应力峰值,表现为双峰,该研究可为类似工作面过斜交煤柱开采提供借鉴意义。

胡家河煤矿综放工作面矿压显现规律预测及主控因素研究

现有工作面矿压显现规律预测方法中,基于数值模拟与统计回归的方法无法实现对工作面矿压显现规律的实时精准预测,深度学习方法存在超参数较多且难以设置、模型训练速度慢等问题。针对上述问题,以胡家河煤矿402102回采工作面采动过程中监测到的煤体内部应力变化时序数据为基础,将基于粒子群优化的门控循环单元(PSO-GRU)应用到回采工作面矿压显现规律预测中。采用PSO算法对GRU进行优化,构建PSO-GRU模型,实现对超参数的自动寻优,从而提高GRU的训练速度和预测精度。以预测结果为依据,采用层次分析法建立402102回采工作面矿压主控因素评价指标体系,将顶板条件、回采工艺、煤层赋存、地质构造确定为影响工作面矿压的一级指标,进一步细分出具有代表性的14个二级指标。测试结果表明:(1)与未经优化的GRU模型相比,PSO-GRU模型的均方误差(MSE)降低了83.9%,均方根误差(RMSE)降低了59.8%,平均绝对误差(MAE)降低了59.0%,决定系数R2提升了28.9%。(2)PSO-GRU模型对矿压数据预测的拟合度达0.980以上,具有良好的非线性拟合能力和泛化能力。(3)地质条件中的煤层赋存因素对回采工作面矿压的影响最大,权重为0.47;可人为干预的影响因素中工作面推进速度对矿压的影响最大,权重为0.13。

临空巷道二氧化碳致裂切顶卸压技术应用研究

针对坚硬顶板临空巷道强矿压显现问题,以晋能控股煤业集团有限公司马脊梁煤矿为工程背景,运用理论分析、数值模拟方法进行了临空巷道二氧化碳致裂切顶卸压技术应用研究,并成功完成现场工业性试验。结果表明:二氧化碳致裂切顶卸压技术能够降低应力峰值,应力集中远离巷帮,缓解矿压显现现象,切顶高度和切顶角度对巷道围岩控制有显著影响,切顶高度越大卸压效果越好,但当切顶高度达到一定程度后,继续增加切顶高度对应力降低影响不甚明显;切顶角度大时煤柱内的应力显著降低,切顶角度小时更利于优化巷道附近应力环境;马脊梁煤矿5015巷应用二氧化碳致裂技术切顶卸压,顶底板移近量、两帮变形量、支承压力峰值较未切顶时分别降低22.6%、28.7%、21.8%,显著改善了巷道的应力环境,减小了围岩变形量,有助于解决强矿压显现问题。

杭来湾煤矿30201综采面矿压显现及支架适应性分析

综采面顶板控制是矿井安全生产中面临的关键问题,有必要对综采面矿压显现规律和支架适应性开展研究,以保障综采面安全生产。通过对杭来湾煤矿30201工作面矿压显现规律进行现场观测和分析,发现工作面支架工作阻力整体表现为“中间大、两头小”的分布规律;上、中、下部支架平均工作阻力分别约为31.76 MPa、37.91 MPa和45.44 MPa,平均动载系数分别为1.228、1.413、1.291,支架安全阀平均开启次数分别为7.8、29.5、8.6;建立了工作面正常开采期间与周期来压期间支架-顶板力学模型,给出了相应的支架临界工作阻力计算方法,计算得到正常开采期间支架所需载荷为14700 kN,周期来压期间所需载荷为17050 kN。经验证,30201工作面ZY21000/36/75D号支架能够满足安全生产要求,研究成果可为后续矿井开采设计、顶板控制等提供借鉴。

迎采动宽煤柱承载特性及矿压显现规律研究

单翼开采矿井为解决采掘接替紧张的问题,常会出现迎采对掘的情况,而迎采动掘巷期间,矿压显现规律和煤柱宽度的确定是巷道掘进及安全回采的关键。以炭窑坪煤业100303运输巷迎采掘巷期间为工程背景,采用理论分析、数值模拟、现场监测等方法,对煤柱的合理宽度及迎采期间的矿压显现规律进行研究分析。主要结论有:通过理论计算,煤柱在受到掘进扰动和工作面采动的双重影响下,确保煤柱不完全发生塑形破坏且存在弹性核的宽度至少为30 m。数值模拟发现,掘进迎头至相遇位置前方20~30 m时,围岩变形开始增大,煤柱帮和回采帮变形量均超过0.5 m。当掘进至采空区后方一定距离后,围岩因同时受掘进扰动与采空区侧向支承应力的叠加影响,变形增幅加快,煤柱帮变形严重,最大变形量超1 m。提出100303运输巷掘进距100302综采工作面70 m时,停止掘进,在迎采扰动范围内,优化支护参数,提高煤柱承载能力。现场监测表明,巷道顶底板和两帮均变形较小均在可控范围内,有效控制了迎采动工作面掘巷的围岩变形。

综采工作面回撤通道围岩控制技术研究

为有效控制3205综采工作面回撤通道围岩变形,通过理论分析确定了回撤通道与采面间煤柱的失稳宽度,同时基于工程类比方式制定了回撤通道围岩控制技术方案。回撤通道掘进时采用锚网索联合支护方式,与采面间距为60 m时采用“架棚(一梁两柱、棚距1 600 mm)+贯通侧煤帮注浆”方式进行补强,在与回撤通道间距为5.25 m时,采用让压等压措施,同时在采面与回撤通道贯通时通过铺网、调整支护方式确保回撤通道围岩的稳定性。工程应用后,采面末采期间回撤通道围岩始终保持稳定,与采面贯通时回撤通道顶底板、两帮最大移近量分别为152、 96 mm,围岩变形量较小,可满足采面设备高效回撤需要。

关于昌泰煤业充填开采技术的分析研究

采煤沉陷会对人类的生存环境造成一系列的消极影响,采煤沉陷区的生态恢复与治理直接关系到矿区的经济、社会和生态环境的可持续发展,是中国矿区所面临的一个亟待解决的难题。对采煤沉陷区进行综合治理,恢复矿区生态环境,同时在煤炭开采时与地表沉陷控制一并考虑,实施绿色开采将是今后中国煤炭开采的重要工作。主要以山西寿阳潞阳昌泰煤业有限公司1508综采工作面为载体,在尽量不影响煤矿主采区域正常生产衔接的前提下,充分利用现有生产系统。通过研究论证,采用膏体充填开采技术,解决地面沉陷、建筑物压煤、采掘衔接等问题,深入分析矿压显现规律,不断探索寻求解决地面零散建(构)筑物压煤问题的新路径。

坚硬顶板工作面水力压裂弱化技术应用

为降低坚硬顶板矿压显现强度,以宏翔煤矿1509工作面地质条件为背景,采用现场试验方法,对水力压裂弱化顶板技术进行了研究应用,结论如下:(1)设计了工作面切眼以及顺槽巷道水力压裂技术方案,切眼水力压裂钻孔深度分别为55 m、30 m、10 m;顺槽巷道顶板水力压裂钻孔深度为30 m、10 m;(2)对水力压裂弱化顶板效果进行了分析,根据工作面推进期间矿压显现结果,1509工作面初次来压步距为32.6 m,周期来压步距平均为15.46 m,来压时工作面支架动载系数平均为1.57,采取水力压预裂弱化顶板措施后,工作面矿压显现强度明显降低。

增子坊煤矿5102回风顺槽支护应用分析

针对增子坊煤矿5102回风顺槽掘进工作面接近断层时遇到的支护失效、巷道变形等问题,为确保施工安全,拟定采用“锚固剂+锚杆+钢带+锚索”联合支护补强支护方案;实践证明,该支护方案能有效地增加工作面围岩的稳定性,巷道顶板变形、下沉以及移近等情况减少,锚索和锚杆支护作用增强,顶板事故明显减少,能够保证矿井安全生产。

多层厚砂岩顶板综采面矿压显现机制及防控技术

多层厚砂岩层条件下工作面开采覆岩结构独特,矿压显现强烈,对煤矿的安全高效生产有很大影响。以俄霍布拉克煤矿11112综采工作面为研究对象,采用理论分析、现场研究及数据统计分析等方法,研究了工作面走向不同阶段覆岩赋存特点及应力分布特征,分析了厚层顶板破断能量聚散规律,阐明了厚层砂岩层条件下综采工作面矿压显现机制,提出了针对性的防治技术参数。研究结果表明:(1)工作面走向上覆岩特征呈现出“厚度小、层间距大和岩层分层明显(砂岩层互层)”和“厚度大、层间距小和岩性较稳定(无互层)”特点较明显的两个阶段;(2)工作面超前支承应力大小及范围受不同层位关键层影响不同,关键层一影响下的应力峰值位于工作面前方5~8 m,不同阶段应力增量分别为1.57 MPa、1.71 MPa及1.77 MPa,关键层三主要对其范围影响较大,不同阶段影响范围分别为72.5 m、86.8 m及126.7 m;(3)关键层一破断能量释放对工作面回采影响最大,第二阶段关键层一整体较完整,其破断传递给煤体的能量为2.11×10~4~2.27×10~4J;(4)根据煤体高应力和顶板破断能量释放两种矿压主要影响因素,制定了综合矿压治理方案。

复杂地质条件下工作面扩安一体化工艺实践

济宁二号煤矿93下10工作面切眼地质条件复杂,压力显现、顶板管理难度大,传统切眼扩刷方式支护难度较大、周期较长,严重影响矿井正常生产接续。通过对比传统的施工工艺,在工艺、费用投入上进行对比分析,探索并实践应用扩安一体化技术,即边扩刷切眼边安装支架。实践结果表明,该工艺降低了支护难度,减轻了职工劳动强度,在很大程度上解决了顶板支护困难以及工作面安装准备周期较长的难题,保障了工作面的快速高效安装,缓解了矿井生产接续紧张,具有一定的推广价值。

不同长度工作面矿压显现规律及支护强度分析

为了研究不同工作面长度对矿压显现规律的影响以及工作面长度变化时支架合理支护强度的变化规律,结合某矿实际地质条件,对不同工作面长度下的矿压显现进行分析计算。结果表明,当工作面长度一定,沿走向方向开挖距离超过450 m时,煤壁片帮和顶板下沉量处于平稳状态,不再受走向开挖距离的影响;以走向一次性开挖450 m计算,沿工作面长度方向,顶板下沉量中部最大,两端最小,呈拱形。随着工作面长度的增加,顶板下沉拱逐渐增大,工作面每增加30 m,顶板下沉量增加率为5%~8%。顶板下沉量能直接反映工作面顶板压力的大小,根据分析计算,工作面每增加30 m,支架合理支护强度应增加5%~8%。

基于深井综采工作面开采的矿压显现规律研究

以钱家营矿2021E工作面地质生产条件为工程背景,开展回采期间工作面的矿压显现规律研究。基于基本顶固支梁模型理论及煤矿三下开采规范,计算确定工作面初次来压步距和周期来压步距分别为37.69m和12.5618.84m,覆岩“三带”中垮落带、裂隙带和弯曲下沉带最大范围分别为11.26m,41.31m和581.39m;利用数值模拟方法对不同采高条件进行模拟分析,确认3m采高时在工作面超前支承应力作用范围、围岩稳定性和位移变形控制方面效果较好;进一步分析3m采高时工作面覆岩顶板运移规律,得到初次来压步距为39m,垮落带高度为11.14m,通过数值模拟分析,上述理论计算的数据得到进一步验证。