Surrounding rock control of gob-side entry driving with narrow coal pillar and roadway side sealing technology in Yangliu Coal Mine

Gob-side entry driving can increase coal recovery ratio, and it is implied in many coal mines. Based on geological condition of 10416 working face tailentry in Yangliu Coal Mine, the surrounding rock deformation characteristics of gob-side entry driving with narrow coal pillar is analysed, reasonable size of coal pillar and reasonable roadway excavation time after mining are achieved. Surrounding rock control technology and effective roadway side sealing technology are proposed and are taken into field practice. The results showed that a safer and more efficient mining of working face can be achieved. In addition, results of this paper also have important theoretical significance and valuable reference for surrounding rock control technology of gob-side entry driving with narrow coal pillar under special geological condition.

Failure laws of narrow pillar and asymmetric control technique of gob-side entry driving in island coal face

In allusion to the problems of complex stress distribution in the surrounding rock and deformation failure laws, as well as the difficulty in roadway supporting of the gob-side entry driving in the island coal face, 2107 face in Chengjiao Colliery is researched as an engineering case. Through physical mechanical test of rock, theoretical and numerical simulation analyses of rock, the analysis model of the roadway overlying strata structure was established, and its parameters quantified. To reveal the deformation law of the surrounding rock, the stability of the overlying strata structure was studied before, during and after the roadway driving. According to the field conditions, the stress distribution in coal pillar was quantified, and the surrounding rock deformation feature studied with different widths of the pillars in gob-side entry driving. Finally, the pillar width of 4 m was considered as the most reasonable. The research results show that there is great difference in support conditions among roadway roof, entity coal side and narrow pillar side. Besides, the asymmetric control technique for support of the surrounding rock was proposed. The asymmetric control technique was proved to be reasonable by field monitoring, support by bolt-net, steel ladder and steel wire truss used in narrow pillar side.

Cable-truss supporting system for gob-side entry driving in deep mine and its application

In order to solve the large deformation controlling problem for surrounding rock of gob-side entry driving under common cable anchor support in deep mine, site survey, physical modeling experiment, numerical simulation and field measurement were synthetically used to analyze the deformation and failure characteristics of surrounding rock. Besides, applicability analysis, prestress field distribution characteristics of surrounding rock and the control effect on large deformation of surrounding rock were also further studied for the gob-side entry driving in deep mine using the cable-truss supporting system. The results show that, first, compared with no support and traditional bolt anchor support, roof cable-truss system can effectively restrain the initiation and propagation of tensile cracks in the roof surrounding rock and arc shear cracks in the two sides, moreover, the broken development of surrounding rock, roof separation and extrusion deformation between the two sides of the roadway are all controlled; second, a prestressed belt of trapezoidal shape is generated in the surrounding rock by the cable-truss supporting system, and the prestress field range is wide. Especially, the prestress concentration belt in the shallow surrounding rock can greatly improve the anchoring strength and deformation resisting capability of the rock stratum;third, an optimized support system of ‘‘roof and side anchor net beam, roof cable-truss supporting system and anchor cable of the narrow coal pillar" was put forward, and the support optimization design and field industrial test were conducted for the gob-side entry driving of the working face 5302 in Tangkou Mine, from which a good supporting effect was obtained.

Stability of coal pillar in gob-side entry driving under unstable overlying strata and its coupling support control technique

Considering the situation that it is difficult to control the stability of narrow coal pillar in gob-side entry driving under unstable overlying strata, the finite difference numerical simulation method was adopted to analyze the inner stress distribution and its evolution regularity, as well as the deformation characteristics of narrow coal pillar in gob-side entry driving, in the whole process from entry driving of last working face to the present working face mining. A new method of narrow coal pillar control based on the triune coupling support technique (TCST), which includes that high-strength prestressed thread steel bolt is used to strain the coal on the goaf side, and that short bolt to control the integrity of global displacement zone in coal pillar on the entry side, and that long grouting cable to fix anchor point to constrain the bed separation between global displacement zone and fixed zone, is thereby generated and applied to the field production. The result indicates that after entry excavating along the gob under unstable overlying strata, the supporting structure left on the gob side of narrow coal pillar is basically invalid to maintain the coal-pillar stability, and the large deformation of the pillar on the gob side is evident. Except for the significant dynamic pressure appearing in the coal mining of last working face and overlying strata stabilizing process, the stress variation inside the coal pillar in other stages are rather steady, however, the stress expansion is obvious and the coal pillar continues to deform. Once the gob-side entry driving is completed, a global displacement zone on the entry side appears in the shallow part of the pillar, whereas, a relatively steady fixed zone staying almost still in gob-side entry driving and present working face mining is found in the deep part of the pillar. The application of TCST can not only avoid the failure of pillar supporting structure, but exert the supporting capacity of the bolting structure left in the pillar of last sublevel entry, thus to jointly maintain the stability of coal pillar.

多层坚硬顶板特厚煤层综放工作面小煤柱护巷技术

为研究小煤柱护巷巷道的稳定性及其阻隔同层位邻近采空区灾害的特征,以大同矿区石炭系坚硬顶板特厚煤层开采为工程背景,采用理论分析、实验研究、数值模拟等研究方法,从小煤柱护巷巷道的稳定性和其是否具有阻隔同层位邻近采空区有害气体能力2个角度,综合分析小煤柱的合理尺寸及其在不同采动阶段渗透率的演化特征。针对同忻煤矿石炭系煤层8210工作面沿空掘巷小煤柱开采具体的开采条件,建立了双关键层采场内外应力场叠加的力学模型,推导出双关键层条件下沿空掘巷小煤柱合理尺寸的计算关系式,理论确定8210工作面小煤柱合理尺寸为6.0 m;应用DJG–Ⅱ型煤岩渗流测试装备,研究不同采动阶段小煤柱渗透率演化特征,试验确定在第3采动阶段小煤柱渗透率较初始渗透率增大了23倍,该阶段小煤柱基本失去了阻隔邻近采空区有害气体的能力。根据理论研究结果,现场选取6 m小煤柱进行工业性试验;根据试验研究结果,开采试验过程中对小煤柱进行了改性降透措施,在小煤柱表面及顶板距煤柱帮1500 mm范围内喷射厚层混凝土(100 mm)。实践表明:工作面回采过程中小煤柱护巷的回采巷道发生了一定的变形量,但是巷道变形在安全可控范围之内,巷道稳定,可实现安全回采;开采过程中8210工作面上隅角CH4气体浓度远低于邻近8305工作面采空区CH4气体浓度,表明小煤柱经过改性降透后具备了阻隔同层位邻近采空区有害气体的能力;开采实践也进一步验证了理论和试验研究成果的合理性和科学性。研究成果可以为类似条件下小煤柱护巷技术的推广应用提供参考。

深部沿空掘巷含软弱夹层顶板离层破坏特征及控制研究

含软弱夹层顶板对深部沿空掘巷稳定性具有重要影响,为有效控制深部高偏应力沿空掘巷含软弱夹层顶板离层破坏,基于含软弱夹层组合体试件力学试验及受采动影响下沿空掘巷数值模拟试验,获得了软弱夹层层厚、层数和层位对顶板的影响以及偏应力条件下含软弱夹层顶板离层演化规律,阐释了含软弱夹层顶板沿空掘巷失稳主要原因,结合顶板支护载荷和煤柱支撑载荷下的悬臂梁力学模型,对含软弱夹层顶板控制要点进行分析,进而提出离层控制方法。结果表明:随着软弱夹层厚度和层数增加,对组合体力学特性劣化影响逐渐变大,软弱夹层位于低位时对组合体试件的劣化影响强于高位,组合体试件破裂均由软弱夹层产生,并随着层厚、层数和层位的不同呈现差异化破裂发育特征。沿空掘巷后主剪切破裂带由顶板左肩角产生并与软弱夹层邻近岩层破裂区相互连接,导致软弱夹层离层严重,主剪切破裂带发育形态和顶板非协调变形程度随主应力偏转角度以及软弱夹层层厚、层数和层位变化,揭示了含软弱夹层顶板沿空掘巷失稳机理。推导了顶板支护载荷和煤柱支撑载荷下的巷道顶板离层解析式,发现软弱夹层在锚固区内的离层量比在锚固区外减少79%,离层大小各主控因素影响程度及其控制优化顺序依次为煤柱支撑载荷—顶板支护载荷—顶板弹性模量。针对深部沿空掘巷含软弱夹层顶板的离层规律和控制要点,提出了“提高煤柱承载能力、减少顶板裂隙发育、增加软弱夹层顶板变形协调性”的离层联合控制方法。现场离层监测显示顶板最大离层量为10 mm,表明该方法能有效控制含软弱夹层顶板离层。

锚喷注联合支护技术在沿空掘巷工程中的研究与应用

针对邢东矿近千米采深,且1222工作面为单侧临空工作面,其运输巷为沿空掘巷,受高地应力及采空区叠加影响,后路巷道快速失稳,掘进期间巷道后路产生了持续大变形等支护难题,通过钻孔窥视分析围岩结构失稳后的状态特征,并对锚网支护失效的原因进行了分析,提出了在原有支护基础上,变挂网为挂绳,分层喷注与巷帮锚索梁桁架相结合补强煤柱侧原岩强度,进而维持锚网联合体稳定结构的新方法,并将其应用于邢东矿1222运输巷的支护。实践表明,新支护方案使得沿空掘巷后路巷道围岩松散结构得到补强,有效缓解了沿空巷道掘进过程中后路频繁整修的现象,提高了进尺效率。

特厚煤层沿空掘巷围岩支卸协同控制技术

针对特厚煤层小煤柱沿空掘巷大范围塑性全煤巷道锚网索的支护难题,以塔山煤矿8204-2小煤柱工作面为工程背景,采用现场实测、理论分析等方法,揭示了锚杆、锚索对沿空大范围塑性全煤巷道的支护机理。锚杆支护主要作用于浅部二次破碎区煤体,形成浅部连续承载结构;锚索主要作用于深部处于三向受力状态的稳定煤体,形成更大范围的连续稳定承载结构;进一步明确了锚杆、锚索有效长度的计算方法,形成了以高预紧力、高强“锚-网-索”支护为基础,以坚硬顶板井下磨料水射流切顶卸压、巷帮大直径钻孔卸压、底板卸压槽卸压为辅的“支卸协同”小煤柱沿空巷道围岩控制技术体系。工程应用结果表明,试验巷道围岩最大变形量小于700 mm,能够满足使用要求。

综放面“双硬”煤层临空煤柱宽度及承载强度校核

具有“双硬”特征煤层的工作面其护巷煤柱的极限尺寸确定与常规工作面有所不同。以榆树岭煤矿505工作面沿空掘进巷道为背景,首先测试了煤岩样的力学性质和不同高径比煤样的抗压强度,得到了不同高径比煤样峰值强度曲线;其次分析了沿空掘巷覆岩结构模型,建立了沿空掘巷护巷煤柱顶板力学模型,得到了不同宽度煤柱所受的载荷应力;建立了不同高宽比煤柱的数值模型,得到了不同高宽比煤柱的极限强度校核公式;最后通过对比不同宽度煤柱所受的载荷应力和极限强度,得出4m宽度的煤柱即可满足支护要求,并在此基础上提出了沿空掘进巷道支护工艺。现场监测结果表明,煤柱宽度为4m时,巷道整体变形量较小,巷道稳定性得到有效维护。研究结果可为小煤柱护巷宽度的确定提供参考。

深部孤岛充填工作面沿空掘巷围岩偏应力演化与控制

目的 为解决深部孤岛充填工作面沿空掘巷围岩控制问题,方法 以邢东矿12216运料巷为背景,采用FLAC3D数值模拟软件,研究孤岛面临侧采空区在不同充填率条件下沿空掘巷围岩偏应力分布规律,模拟分析孤岛工作面充填开采时,工作面超前段围岩受动压影响时的偏应力演化特征。结果 结果表明:(1)孤岛工作面沿空掘巷巷道煤柱帮受临侧采空区充填效应影响较大,临侧采空区充填率增加使煤柱上偏应力峰值区呈椭圆形并逐步向采空区侧转移;(2)孤岛充填工作面沿空掘巷顶底板偏应力场形成一个朝向采空区侧的弧形低值带;(3)孤岛充填动压扰动时期,最大偏应力区位于实体煤一侧,距工作面前方8 m左右,距巷道4.3 m左右,峰值可达34 MPa。结论 结合数值模拟分析结果,提出采用“高强度锚杆+大直径高延伸率锚索”协同支护方式,现场工程实践表明,该支护方式沿空巷道围岩控制效果良好。

窄煤柱沿空掘巷非对称支护力学特征与支护参数研究

为了研究窄煤柱沿空掘巷非对称支护下围岩变形与应力分布特征,采用理论分析方法,研究窄煤柱沿空巷道对称支护与非对称支护力学机理;基于马道头煤矿现场工程实践,采用数值模拟与工程效验方法,研究非对称支护下巷道围岩力学特征与稳定性。理论分析结果表明,非对称支护可有效降低巷道顶板弯矩,减小巷道顶底板与两帮变形量。模拟结果表明,煤柱内部压应力增高区与弹性核区保障了煤柱承载性能。现场实测结果表明,采用“锚索+槽型钢”非对称支护,巷道顶板、窄煤柱侧巷帮与实体煤侧巷帮最大变形量分别为100、79、62 mm,巷道松动圈与裂隙发育处于中等水平。

动压影响孤岛工作面巷道围岩“卸-支平衡”协同控制技术

煤矿深部工作面回采过程中,经常受到强开采动压作用影响,矿压显现强烈,巷道围岩变形破坏程度大,尤其对于孤岛工作面,动压影响更加显著,围岩控制难度成倍增加。为了解决深部孤岛工作面强动压影响回采巷道围岩控制问题,以2308工作面为研究背景,采用理论分析、数值模拟、现场验证等方法,首先对巷道围岩结构模型进行分析,确定影响工作面围岩稳定的主要因素;进一步对煤柱宽度和钻孔卸压2种方案进行研究,并根据巷道围岩的实际变形情况,确定巷道围岩的非对称支护参数,实现受强动压影响回采巷道的“卸-支平衡”协同控制方案。经过现场实践验证,2308工作面巷道顶底板移近量为260 mm,两帮移近量为471 mm,巷道围岩的整体性得到增强,变形得到有效控制;采用“卸-支平衡”方案对受动压影响巷道围岩的控制效果显著。

煤矿综采工作面沿空掘巷支护及智能预警技术研究

针对深井综采工作面传统留设宽煤柱方法护巷困难、巷道围岩失稳等问题,以彬县煤炭有限责任公司蒋家河煤矿为工程背景,通过理论分析、数值计算和现场试验的方法研究了原巷道围岩环境以及应力、变形时空演变规律以及巷道应力响应特征,针对性地提出了留设小煤柱沿空掘巷护巷方法,同时对护巷煤柱尺寸进行了适应性分析。现场实践表明,通过对采煤工作面建立监测断面,实现了巷道围岩应力以及支护体的实时监测;通过在地面建立数据分析站对井下各项监测数据进行处理和分析,对超过阈值的数据进行整合评估预警,最终实现沿空巷道围岩智能预警。

强动压松软煤体条件下沿空掘巷护巷煤柱尺寸研究

针对强动压松软煤体条件下综采工作面沿空巷道围岩变形量大、稳定性差的难题,本文以赵庄煤矿5328工作面为研究背景,通过理论计算,得到了沿空掘巷煤柱尺寸的留设范围;然后通过建立数值模拟模型对多种宽度煤柱的围岩应力和塑性区进行分析,确定煤柱的合理尺寸为8 m。现场矿压监测结果表明,留设宽度为8 m的煤柱可以满足工作面安全生产要求。

近距离煤层沿空掘巷围岩稳定性分析

合理的煤柱留设宽度及巷道布置错距不仅能保证煤炭的安全生产,还能提高煤炭资源的产出率,降低巷道支护的难度。以色连二矿近距离煤层群12409工作面为研究背景,采用理论分析得出沿空掘巷煤柱留设宽度,通过数值模拟研究了留设8 m小煤柱时回采巷道的稳定性,并进行现场工业性试验,监测回采期间巷道矿压显现规律。研究结果表明:①基于极限平衡理论及工程经验设计留设8 m小煤柱;②留设8 m小煤柱,测点超前工作面17 m时,煤柱内3.5~5.9 m分布式光纤应变值为-1 470~-7 268,表明煤柱内形成承载区域,利于巷道围岩控制;③回采期间,巷道顶底板及两帮的最大移近量分别为250、123 mm,在可控范围内,保证了矿井安全高效生产。

浅埋煤层留小煤柱沿空掘巷技术研究与应用

在凤红煤业151302工作面采用沿空掘巷工艺技术,通过理论计算并结合数值模拟,综合分析确定了小煤柱的合理尺寸为5.0 m,同时优化了小煤柱巷道支护参数方案。工程应用结果表明:采用留小煤柱沿空掘巷技术,锚杆索受力远低于破断载荷;巷道顶板下沉位移在200 mm之内,回采帮内位移位小于200 mm,煤柱帮内位移在150 mm之内,巷道围岩和小煤柱皆处于稳定结构状况,整体围岩控制效果良好。

孤岛工作面沿空掘巷支护技术优化

针对孤岛工作面沿空掘巷围岩稳定性差的问题,以山西岳城矿4315工作面条件为背景,采用钻孔窥视方法分析了43152巷围岩变形机理,通过改进锚索长度、架设单体柱与工字钢棚、注浆加固以及喷浆封闭等方式对巷道支护设计方案进行了优化。根据巷道掘进期间围岩变形情况,变形量均在可控范围内,因此优化后的巷道支护方案能够确保巷道稳定。

同忻煤矿窄煤柱宽度留设及围岩控制实践

针对特厚煤层综放开采沿空掘巷时,留设宽煤柱护巷造成煤炭资源丢失严重,以及围岩变形量大、煤壁片帮等问题,以同忻煤矿8311工作面5311回风巷为工程背景,采用理论分析、数值模拟和现场观测相结合的方法,对其沿空掘巷护巷煤柱合理宽度的留设进行了分析。研究表明,理论分析得知留设煤柱宽度为6 m左右时可确保5311回风巷位于沿空边缘煤体支承压力降低区和煤体应力屈服区,有利于巷道围岩的稳定。基于3DEC数值模拟分析,得到留设6 m煤柱5311回风巷的稳定性以及8311工作面回采后沿空掘巷超前段顶板、实体煤帮、煤柱内围岩应力分布和塑性区演化特征。经现场应用,验证了综放开采留设窄煤柱掘巷技术的优越性和可靠性。

浅埋厚煤层综采工作面顶板破断结构及运动形态研究

针对平朔井工一矿浅埋厚煤层开采条件,采用理论分析和数值模拟的方法,对顶板覆岩破断特征及裂隙场演化规律等内容进行研究,得到了煤层开采厚度与覆岩破断结构的关系,井工一矿工作面上覆岩层形成“低位悬臂梁+高位铰接岩梁”结构,低位悬臂梁破断位置距采空区煤壁21.7 m;覆岩断裂位置与区段煤柱垂直应力的关系,当顶板断裂位置位于采空区侧时,侧向支承压力显著增大,应力集中系数约为3.02,此时煤柱稳定性差;工作面回采后,从运动到停止的4个不同阶段侧向支承压力分布特征,14106工作面回采结束92 d后处于支承应力稳定阶段;研究成果可用于指导矿井区段煤柱留设及相似条件煤层开采。

超千米深埋沿空巷道围岩破坏特征及控制技术研究

为解决超千米深埋沿空巷道围岩失稳难题,以平煤股份十一矿具体工程为背景,通过表面位移监测、钻孔窥视、围岩钻孔取芯及拉压剪常规力学试验,分析了典型超千米深埋沿空巷道的围岩损伤破坏规律,提出了以高性能中空钢绞线锚索为基础的厚层预应力全长锚固理论与技术,并通过现场试验对维控效果进行了验证。结果表明:该类巷道围岩属于高应力—节理化复合型软岩,长期维控具有较大挑战。采用厚层预应力全长锚固技术后,巷道顶板及两帮的变形量相比原支护方案降低58.64%、61.65%,巷道掘巷稳定期明显减短,围岩完整性、稳定性及巷道稳定性显著加强,能够满足巷道长期维控的要求。