Investigation of a non-explosive directional roof cutting technology for self-formed roadway

Traditional explosives have characteristics of high risk,large vibration,and poor directional fracturing.Consequently,an instantaneous expander with a single crack surface(IESCS),which is a novel nonexplosive directional rock-breaking technique,has been developed.The directional roof-cutting mechanism of the IESCS method,driven by high-pressure gas,was theoretically analyzed.Laboratory experiments and numerical simulations proved the directional slitting effect of the IESCS method to be excellent.Compared with shaped-charge blasting,the charge of IESCS was reduced by 8.9%,but the crack rate increased by 9%in field tests.After IESCS pre-splitting,the roof directionally collapsed along the cutting line,and the gangue filled the goaf.Moreover,the directional roof cutting by the IESCS could decrease roadway stress.The average pressure of hydraulic supports on the cutting side of the roof was 31%lower than that on the non-cutting side of the roof after pre-splitting.After the self-formed roadway constructed by the IESCS was stabilized,the final relative displacement of the roof and floor was 157.3 mm,meeting the required standard of the next working face.Thus,the IESCS was effectively applied to directional roof pre-splitting.The results demonstrate the promising potential of IESCS in the mining and geotechnical fields.

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.

Wide pillar roadway retained in the deep high gas coal seam

According to the geological and mining conditions of deep high gas coal seam,this paper established the mechanical model of stope surrounding rock,and analyzed the stress distribution and deformation failure mechanism of working face and coal pillar.The research determined the arrangement mode that adjacent working faces retain wide pillar,and the reasonable support method of roadway that the combined support of roof and grouting combined together.The reasonable time of reinforced roadway was determined.Through analyzing the mechanical model of the ways of roadway supporting,this research drew the conclusions as follows:the combined support of roof and working slope improved the support strength and range of surrounding rock,optimized the support by adjusting the angle of anchor,and reached the support requirements by using cement grouting in working slope and chemical grout in roof.The technology was applied in 15104 working face of Baoan Mine,and obtained good results.

Joint Bearing Mechanism of Coal Pillar and Backfilling Body in Roadway Backfilling Mining Technology

In the traditional mining technology,the coal resources trapped beneath surface buildings,railways,and water bodies cannot be mined massively,thereby causing the lower coal recovery and dynamic disasters.In order to solve the aforementioned problems,the roadway backfilling mining technology is developed and the joint bearing mechanism of coal pillar and backfilling body is presented in this paper.The mechanical model of bearing system of coal pillar and backfilling body is established,by analyzing the basic characteristics of overlying strata deformation in roadway backfilling mining technology.According to the Ritz method in energy variation principle,the elastic solution expression of coal pillar deformation is deduced in roadway backfilling mining technology.Based on elastic-viscoelastic correspondence principle,combining with the burgers rheological constitutive model and Laplace transform theory,the viscoelastic solution expression of coal pillar deformation is obtained in roadway backfilling mining technology.By analyzing the compressive mechanical property of backfilling body,the time formula required for coal pillar and backfilling body to play the joint bearing function in roadway backfilling mining technology is obtained.The example analysis indicates that the time is 140 days.The results can be treated as an important basis for theoretical research and process design in roadway backfilling mining technology.

Characteristics of stress distribution in floor strata and control of roadway stability under coal pillars

给在煤支柱下面在车道支持遇到的困难，我们在车道稳定性上学习了压力分发和他们的效果的特征，用理论分析和数字模拟。当水平应力减少时，结果证明在一个煤支柱下面，在一个地板阶层的垂直应力增加。我们断定垂直、水平的应力之间的增加的差别是为包围岩石的变丑和在煤支柱下面的车道的失败的一个重要原因。基于这，我们在一个煤支柱下面建议一条车道的包围岩石的控制技术例如高力量和高对的门栓支持，打电报加强支持，单个水力由包围岩石的 grouting 与横梁支持和加强支撑，它成功地在一个煤支柱下面在一条车道的一个稳定性控制工程被使用了。

Roadway layout for recycling residual coal pillar in room-and-pillar mining of thick coal seam

In the context of a room-and-pillar mining gob in Shanxi province in China,this paper numerically investigates the stress distribution and deformation rules of roadway surrounding rocks at various locations of residual coal pillars in room-and-pillar mining gobs using software FLAC3 D.It is found that the concentrated stress beneath coal pillars distributes in a shape of ellipse.A reasonable roadway layout is then proposed.In this design,it is indicated that roadways should be designed to avoid the supporting zones of pillars with increasing compression and take into account the roof falling and crushing in the upper gob.According to the surrounding rock deformation characteristics and mining roadway locations as well as the supporting principles of timely support,rock reinforcing,piecewise management and suiting local conditions,a new asymmetric shield supporting plan is proposed.The field surveying results show that this supporting plan can effectively control the roadway rock deformation,thus guarantee the safe and smooth construction of roadways.

THE RELATION BETWEEN THE CHAIN PILLAR WIDTH AND THE SURROUNDING ROCK DEFORMATION OF ROADWAY

Based on the analysis and research into ground pressure behavior law and surrounding rock deformation of a large number of roadways affected by mining activity,this paper proposed a relation between the surrounding rock deformation during mining ,the surrounding rock deformation rate during stable stage of mining and the chain pillar width. Moreover,it established the relation between the total amount of surrounding rock deformation during service period of roadway and the chain pillar width,which provides a principal basis for choosing the chain pillar width.

SELECTION OF HORIZONTAL DISTANCE X BETWEEN ROADWAY AND THE EDGE OF ITS UPPER PILLAR

The horizontal distance X between roadway and the edge of its upper pillar is considered as an important parameter for layout of roadway in floor strata or in the adjacent coal seam. Based on the research achievements of rockstrata pressure, this paper illustrates the quantitative relationship among the mining situation of upper searn, the rockstrata properties around roadway, the vertital distanee Z (between roadway and its upper pillar), and the horizontai distance X (between roadway and the edge of its upper pillar), and provides a main basiS for the selection of value X and the relative location between roadway and its upper seam.

Evaluation of roof cutting by directionally single cracking technique in automatic roadway formation for thick coal seam mining

Automatic roadway formation by roof cutting is a sustainable nonpillar mining method that has the potential to increase coal recovery,reduce roadway excavation and improve mining safety.In this method,roof cutting is the key process for stress relief,which significantly affects the stability of the formed roadway.This paper presents a directionally single cracking(DSC)technique for roof cutting with considerations of rock properties.The mechanism of the DSC technique was investi-gated by explicit finite element analyses.The DSC technique and roof cutting parameters were evaluated by discrete element simulation and field experiment.On this basis,the optimized DSC technique was tested in the field.The results indicate that the DSC technique could effectively control the blast-induced stress distribution and crack propagation in the roof rock,thus,achieve directionally single cracking on the roadway roof.The DsC technique for roof cutting with optimized parameters could effectively reduce the deformation and improve the stability of the formed roadway.Field engineering application verified the feasibility and effectiveness of the evaluated DSC technique for roof cutting.

相邻空区影响下三软巷道变形破坏规律与煤柱留设宽度研究

为了探究相邻空区影响下三软煤层巷道掘进时不同煤柱宽度下巷道围岩变形破坏规律,采用理论计算、数值模拟、物理相似模拟与现场实测相结合的研究方法,分析存在临空区后不同区段煤柱宽度下巷道围岩应力演化规律、塑性破坏范围以及位移分布特征。结果表明:临空区是造成巷道掘进后非对称破坏的主要原因,使煤柱主应力方向与垂向夹角增大,巷道两帮应力呈煤柱侧大于实体煤侧的非对称分布特征;三软巷道破坏形式以剪切破坏为主,破坏主体为两帮,随着煤柱宽度增大,主应力方向与垂向夹角减小,巷道围岩破坏程度降低,临空区对巷道不同位置的影响程度不同,巷道中部围岩破坏程度大于端头处且煤柱侧破坏程度大于实体煤侧;煤柱宽度增大对巷道围岩应力以及煤柱破坏的改善程度有限,现场结果显示当煤柱宽度为20 m时巷道正常维护满足需求。

煤层群下行开采底板应力演化规律与合理巷道错距研究

为解决近距离煤层开采遗留煤柱下伏回采巷道合理布置工程问题,采用理论分析、数值模拟和现场实测相结合的方法,基于半无限平面体理论建立遗留煤柱底板岩层应力分布力学模型,系统研究了遗留煤柱下伏底板岩层应力分布特征及减压区相对位置关系,提出遗留煤柱非均布载荷影响的底板水平/垂向距离判别方法,揭示了遗留煤柱水平/垂向间距对下伏煤层回采巷道应力变化率的影响程度。结果表明:垂直应力集中是导致下伏巷道失稳的主控因素,以垂直应力变化量0.2γH作为评判应力影响程度的临界指标,探究了不同因素影响下的应力扰动程度,随着遗留煤柱尺寸、煤层间距、埋深与岩层垮落角逐渐减小,底板岩层应力影响深度呈递减趋势;随着水平错距增大,巷道围岩垂直应力值、应力变化率差值不断减小,界定两者数值低于0.2γH与0.01时,围岩达到可控稳定状态;现场试验21320回风巷采用外错式25 m进行实测验证,优化布置后巷道顶板相对位移量控制在45 mm以内,服务期间巷道围岩工况稳定,验证了所得安全错距的合理性。

非对称载荷作用下倾斜区段煤柱稳定性分析及控制技术

为解决工作面回采及巷道掘进影响下倾斜区段煤柱稳定性劣化的复杂问题,运用弹性力学半逆解法及摩尔-库伦准则建立力学模型,结合三维有限元数值模拟,深入分析了倾斜区段煤柱一侧受载结构形态特征,明确了倾斜煤柱失稳致灾力源及载荷的分布特性,探究了采掘扰动下倾斜区段煤柱塑性变形-失稳-破坏的动态演化过程,揭示了非对称载荷作用下倾斜区段煤柱临界失稳致灾机理,以此为基础优化了倾斜煤柱及周围巷道稳定性控制技术。结果表明:区段煤柱因煤层倾角导致的倾斜形态是煤柱所承受载荷呈非对称状的关键诱因,这一特性致使倾斜煤柱最底端区域覆载最大,且当此区域失稳破坏时,呈现由煤柱下端底角塑性区向煤柱上端底角塑性区扩展的运移过程,并因此得出倾斜区段煤柱临界尺寸随煤层倾角增大而增加的演化规律。由此,针对大南湖一矿倾斜区段煤柱及周围巷道变形失稳的问题,采用支护优化及注浆加固等措施,降低了倾斜区段煤柱侧巷道的变形速率,为类似矿井的煤柱稳定性控制提供了借鉴。

胀锁型锚索双向加固窄煤柱试验研究与工程应用

针对沿空掘巷窄煤柱非对称变形问题,提出了对穿锚索双向加固窄煤柱技术,设计了伸长型和胀锁型两种对穿锚索结构及工艺,开展了对穿锚索拉拔试验,试验表明两种锚索结构均满足抗拉要求,从锚索破坏形态、施工便捷性和材料经济性等方面对比分析,确定胀锁型对穿锚索为窄煤柱双向加固的首选。进一步通过相似模型试验与数值模拟研究了不同加固方式下煤柱承载变形规律和对穿锚索受力特征。结果表明:双排紧密型对穿锚索加固试件较未加固试件峰值荷载提高了96.04%,且随着锚索排数及数量的增加,窄煤柱双向加固稳定性越来越高,胀锁型对穿锚索提高了煤柱破坏前的能量储存量和临界破坏点。最后,在济宁三号煤矿123_(下)04工作面运输巷开展胀锁式对穿锚索加固窄煤柱工程试验,监测显示对穿锚索锚固力超过220 kN,锚索加固区煤柱帮鼓量降低70%,窄煤柱整体稳定性好,窄煤柱双向加固技术可行,为沿空掘巷工程提供了新技术途径。

区段煤柱下大断面回采巷道不同成巷方式分析研究

为了探究在区段煤柱下大断面巷道在掘进时受到扰动最小的一种成巷方式,以乌兰色太煤矿掘进52202工作面运输顺槽为研究背景,针对该工作面实际地质资料,通过数值模拟分析了大断面巷道在不同成巷方式条件下的塑性区形态、应力场及位移场分布规律。结果表明,先掘进5.4 m宽正常巷道,后扩帮2 m的成巷方式为最优成巷方式,将其应用于工程实践,为同类型区段煤柱下大断面巷道提供参考依据。

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。

深部特厚煤层综放沿空掘巷煤柱优化及巷道支护

为研究深部大采高综放工作面窄煤柱沿空掘巷巷道矿压控制问题,以国能宁煤集团枣泉煤矿2^(-2)特厚煤层130203大采高综放工作面回风巷道为背景,基于实用矿山压力理论,建立了巷道围岩内、外应力场动态结构力学模型,运用理论计算和数值计算针对不同尺寸煤柱煤体应力对比分析,将原留设15 m护巷煤柱缩小至5 m进行了煤柱优化。结果表明:在稳定的内应力场掘巷有利于巷道的稳定性,避免了顶板事故及冲击地压相关灾害的发生,现场5 m小煤柱护巷工程应用中,130203回风巷道小煤柱侧变形量为1050 mm,实体煤帮变形量为400 mm,两帮呈现不对称性变形,底板局部底鼓量为1400 mm;深部特厚煤层综放开采沿空掘巷采用5 m小煤柱护巷方案设计正确,极大改善了巷道围岩的应力环境,整体设计满足生产要求,现场应用良好。130203工作面小煤柱沿空掘巷技术成功应用,为矿井开采提供了可靠的科学依据。

坚硬顶板切顶卸压技术对巷道围岩变形规律影响

针对特厚煤层坚硬顶板、宽煤柱条件下临空巷道面临的高围岩应力、大变形等问题,以老石旦煤矿16403综放工作面为工程研究背景,从宽煤柱顶板侧向破断结构角度对临空巷道大变形的影响因素进行了理论分析,采用数值模拟方法研究了对16402运输巷实施不同切顶卸压方案时,临近采空区的16403回风巷侧向顶板采动应力传递规律,并在现场施工水力压裂钻孔进行切顶卸压,实现临空巷道围岩变形控制。研究结果表明:“低位坚硬岩层悬臂梁+高位坚硬岩层砌体梁”破断结构是特厚煤层宽煤柱临空巷道大变形的主要原因,可采用切顶卸压技术破坏宽煤柱顶板侧向破断结构来控制临空巷道围岩大变形;切顶角变化可使关键块B长度发生改变,切顶角越大,则关键块B长度越小,临空侧顶板载荷向煤柱传递的程度越弱,临空巷道围岩承受的采动应力越小,切顶角为100°时临空巷道围岩垂直应力与变形量最小;在16402运输巷以切顶角100°施工水力压裂钻孔后,16403回风巷顶底板变形量较未实施切顶卸压的16402回风巷减小86.5%,两帮变形量减小87.1%,临空巷道围岩稳定性得到极大提高。

复采巷道过空巷交叉段围岩控制技术

以宇昌煤业复采区地质条件下回采巷道的围岩控制为工程背景,针对与空巷相交区围岩破碎支护困难的问题,对回采巷道破碎段的围岩控制技术方案及参数进行研究。采用理论计算得出回采巷道煤柱稳定的理论宽度,并通过数值计算得出交叉巷道三角区煤柱弹性核区宽度小于2 m时,需要采用架棚的支护方式维护巷道稳定;通过对掘采期间巷道围岩应力及变形的理论计算及数值模拟分析,确定了合理的架棚支护区域及支护方案;现场实测表明,采用锚网索和工字钢棚联合支护的方式,巷道变形量得到了有效控制。

坚硬顶板高压磨料射流侧向切顶煤柱卸荷技术研究

针对坚硬顶板下临空巷道存在的高应力、大变形、难支护等问题,分析了磨料射流能量分布情况,研究了磨料颗粒及高压水射流的冲击破岩作用。基于“砌体梁”原理,建立不同岩性条件下的岩层周期破断力学模型,研究了巷道侧向切顶条件下上覆岩层断裂情况,采用数值模拟分析切顶前后煤柱应力变化情况,提出了磨料射流侧向切顶煤柱卸荷技术。现场试验结果表明,采用磨料射流切顶后巷道高度变形量减小38.7%,宽度变形量减小45.8%,巷道变形得到有效控制。同时,切顶后每日最大总能量降低85.5%,平均每日总能量降低82.6%。验证了磨料射流侧向切顶对坚硬顶板的弱化效果,为坚硬顶板弱化治理提供了一种新的技术手段。

瑶渠煤矿大巷间煤柱尺寸确定及支护优化

为研究大巷过剥蚀区时大巷间煤柱合理尺寸及围岩稳定性,以瑶渠煤矿西采区Ⅱ回风大巷为研究对象,采用理论分析、数值模拟等研究方法,建立了煤柱尺寸计算模型,揭示了煤柱在8 m、10 m、12 m、14 m条件下巷道围岩应力、位移及塑性区的分布规律,确定了过剥蚀区大巷间煤柱的合理尺寸,并优化了西采区Ⅱ回风大巷的支护参数。研究结果表明,瑶渠煤矿西采区Ⅱ回风大巷与辅运大巷之间煤柱尺寸由14 m减小至8 m时,巷道围岩内的垂直应力由1.381 MPa增加至1.465 MPa、最大位移量增加了12.52%,塑性区逐渐贯通煤柱。当煤柱尺寸为10 m时,煤柱塑性区处于贯通的临界区域,煤柱内部具有一定的弹性核区域,且煤柱尺寸大于理论计算的9.23 m,能够满足巷道围岩的稳定性。综合考虑,确定煤柱最小合理尺寸为10 m。对10 m煤柱尺寸下西采区Ⅱ回风大巷进行支护优化,采用帮部3根锚杆支护后巷道围岩应力、位移和塑性区均显著改善,保证了巷道围岩的稳定性。