Comparison of large deformation failure control method in a deep gob-side roadway: A theoretical analysis and field investigation

Under the dual influence of the mining disturbance of the previous working face and the advanced mining of the working face,the roadway is prone to large deformation,failure,and rockburst.Roadway stabilization has always significantly influenced deep mining safety.In this article we used the research background of the large deformation failure roadway of Fa-er Coal Mine in Guizhou Province of China to propose two control methods:bolt-cable-mesh+concrete blocks+directional energy-gathering blasting(BCM-CBDE method)and 1st Generation-Negative Poisson’s Ratio(1G NPR)cable+directional energy-gathering blasting+dynamic pressure stage support(πgirder+single hydraulic prop+retractable U steel)(NPR-DEDP method).Meantime,we compared the validity of the large deformation failure control method in a deep gob-side roadway based on theoretical analysis,numerical simulations,and field experiments.The results show that directional energy-gathering blasting can weaken the pressure acting on the concrete blocks.However,the vertical stress of the surrounding rock of the roadway is still concentrated in the entity coal side and the concrete blocks,showing a’bimodal’distribution.BCM-CBDE method cannot effectively control the stability of the roadway.NPR-DEDP method removed the concrete blocks.It shows using the 1G NPR cable with periodic slipping-sticking characteristics can adapt to repeated mining disturbances.The peak value of the vertical stress of the roadway is reduced and transferred to the deep part of the surrounding rock mass,which promotes the collapse of the gangue in the goaf and fills the goaf.The pressure of the roadway roof is reduced,and the gob-side roadway is fundamentally protected.Meantime,the dynamic pressure stage support method withπgirder+single hydraulic prop+retractable U steel as the core effectively protects the roadway from dynamic pressure impact when the main roof is periodically broken.After the on-site implementation of NPR-DEDP method,the deformation of the roadway is reduced by more than 45%,and the deformation rate is reduced by more than 50%.

Roof filling control technology and application to mine roadway damage in small pit goaf

To recover coal resources that have been damaged by traditional mining methods and ensure stability of the lower roadway in a small pit goaf,the goaf area must be filled and reinforced.In this research,the 1202 working face of the Hanzui mine is considered as an example for classifying the roof of the mining tunnel under the small kiln destruction zone,the effect of the goaf on the roadway is determined based on the radio tunnel penetration method,a mechanical model to determine the roof filling control mechanism was established,and the duct foaming system and roof filling process were designed.The results show that the scope and degree of influence of the goaf on the mining lane are large,but safe tunneling can be ensured through the use of a steel shed and advanced grouting techniques.When the roof conditions are not similar,materials with different filling heights and filling strengths can be used to control the roof filling of the roadway.By combining field experience and laboratory tests,it was determined that a high-foaming material with a water-cement ratio of 1:0.6,a suitable high-foaming additive,and a water volume ratio of 1:30 is cost-efficient for filling and meets the filling strength requirements.Finally,the reliability of the proposed technology was verified by field experiments,which provide a reference for filling operations in similar mines.

Comparative study of model tests on automatically formed roadway and gob-side entry driving in deep coal mines

Automatically formed roadway(AFR)by roof cutting with bolt grouting(RCBG)is a new deep coal mining technology.By using this technology,the broken roadway roof is strengthened,and roof cutting is applied to cut off stress transfer between the roadway and gob to ensure the collapse of the overlying strata.The roadway is automatically formed owing to the broken expansion characteristics of the collapsed strata and mining pressure.Taking the Suncun Coal Mine as the engineering background,the control effect of this new technology on roadways was studied.To compare the law of stress evolution and the surrounding rock control mechanisms between AFR and traditional gob-side entry driving,a comparative study of geomechanical model tests on the above methods was carried out.The results showed that the new technology of AFR by RCBG effectively reduced the stress concentration of the roadway compared with gob-side entry driving.The side abutment pressure peak of the solid coal side was reduced by 24.3%,which showed an obvious pressure-releasing effect.Moreover,the position of the side abutment pressure peak was far from the solid coal side,making it more beneficial for roadway stability.The deformation of AFR surrounding rock was also smaller than the deformation of the gob-side entry driving by the overload test.The former was more beneficial for roadway stability than the latter under higher stress conditions.Field application tests showed that the new technology can effectively control roadway deformation.Moreover,the technology reduced roadway excavation and avoided resource waste caused by reserved coal pillars.

Stability influence factors analysis and construction of a deep beam anchorage structure in roadway roof

Deep beam anchorage structures based on spatial distribution analysis of the cable prestressed field have been proposed for roadway roof support, Stability and other factors that influence deep beam structures are studied in this paper using mechanical calculations, numerical analysis and field measurements, A mechanical model of deep beam structure subjected to multiple loading is established, including analysis of roof support in the return airway of S1203 working face in the Yuwu coal mine, China, The expression of maximum shear stress in the deep beam structure is deduced according to the stress superposition criterion, It is found that the primary factors affecting deep beam structure stability are deep beam thickness, cable pre-tension and cable spacing, The variation of maximum shear stress distribution and prestressed field diffusion effects according to various factors are analyzed using Matlah and FLAC3DTM software, and practical support parameters of the S1203 return airway roof are determined, According to the observations of rock pressure, there is no evidence of roof separation, and the maximum values of roof subsidence and convergence of wall rock are 72 and 48 mm, respectively, The results show that the proposed roof support design with a deep beam structure is feasible and achieves effective control of the roadway roof,

Numerical research on stability control of roofs of water-rich roadway

In order to study the strength-weakening law of roofs of water-rich roadway, this study used FLAC software, and simulated and analyzed the failure characteristics of the surrounding rock of water-rich roadway under the condition of different cross sections and support parameters, finally obtained the stress distribution of the principle stress of the roadway as well as the displacement variation of its surrounding rock. Results indicate that the roof stability of roadway with semicircular cross section is better than the roadway with inclined rectangular cross section under water-rich condition. Besides, the surrounding rock deformation of roadway under the action of water shows a pronounced increase compared to the roadway without the action of water due to the fact that water will obviously weaken the surrounding rock of roadway, especially its roof. It is very beneficial to control roof stability of water-rich roadway and guarantee the roadway stability during its service life by improving the pretension of bolt and cable as well as decreasing inter-row spacing of the bolt.

Study of dynamic pressure roadway supporting scheme under condi- tion of thick composite roof

This paper analyzed the strata behaviors of solid-coal roadway, gob-side entry driving and deformation law of surrounding rock in depth under high stress and thick composite roof based on the dynamic pressure roadway as engineering background in Fengcheng mining area, Jiangxi province. The results, both field measurement and numerical simulation show that gob-side entry driving results the deformation of coal roadway main wall, however, entity-coal roadway driving results deformation of main roof and floor. The maintenance state of gob-side entry driving is better than entity-coal roadway, this situation is relevant to thick composite roof layered and easy collapse characteristics. At the same time, this paper put fox＇ward and proved proper dynamic pressure roadway supporting scheme under the surrounding rock condition and stress environment.

Mechanism and practice of rock control in deep large span cut holes

Deep large span cut holes are difficult to stabilize. The 7801 cut hole in the Lu'an Wuyang Mine was used as this project's background. The main factors affecting large span cut hole stability are analyzed. Pre- stressed bolting theory was used to design a roof control method for a large span roadway. By reducing the span and applying equal strength coordinated supports the rock could be stabilized. The control prin- ciples and methods are given herein along with the analysis. A double micro arch cross section roadway is defined and its use in solving the current problem is described. Beam arch theory was used to build a model of the double micro arch cross section roadway. A support reverse force model for the arch foot intersection was also derived. A support method based upon reducing the width of the large span in the cut hole is presented. These results show that the reduced span of the roadway roof plus the use of cable anchors and single supports gives an effective way to control the large span cut hole. On site monitoring showed that the reduced span support from the double micro arch cross section roadway design had a significant effect. The roadway surface displacement was small and harmful deformation of the cut hole was effectively controlled. This will ensure its long term stability.

顶板水平井分段分簇压裂治理掘进巷道瓦斯模式研究

为了解决淮南矿区碎软低渗煤层掘进巷道瓦斯抽采效率低的问题,提出了煤层顶板水平井分段分簇压裂瓦斯治理模式。运用数值模拟方法和物理相似模拟方法研究了煤层顶板水平井水力压裂裂缝扩展过程;运用产能模拟的方法研究了分段分簇压裂的产气效果,对分簇压裂和不分簇压裂进行了剩余瓦斯含量对比分析。裂缝扩展数值模拟结果表明:煤层顶板水平井内的裂缝能够扩展至煤层,将煤层全部压开,且由于煤层的塑性大于顶板砂质泥岩,煤层形成比顶板更为宽泛的压裂缝。裂缝扩展物理相似模拟结果表明:在考虑了泥岩伪顶发育的条件下,水平钻孔布置在碎软煤层顶板的砂岩内,在合理的垂直距离和大排量压裂液施工的环境下,若煤层发育有较薄的泥岩伪顶,裂缝能沿着射孔孔眼穿过直接顶−伪顶界面(粉砂岩−泥岩界面)和伪顶−煤层界面(泥岩−煤层界面),扩展至下伏煤层内,裂缝延伸形成1条弯曲不规则的阶梯型裂缝,能实现对碎软煤层的压裂改造目标。但是,当煤层发育有较厚的泥岩伪顶时,泥岩对水力压裂产生了阻挡作用,导致裂缝难以压开下伏煤层。产能模拟结果表明:在相同的地层环境和施工条件下,经过3 a的抽采,单段不分簇压裂能够产生更大的瓦斯抽采影响范围,但不能均匀降低掘进巷道的瓦斯含量,压裂段之间出现了瓦斯抽采空白带,分簇压裂产生的瓦斯抽采影响范围小,却能够更均匀的降低掘进巷道的瓦斯含量。经过在淮南地区潘谢煤矿的工程验证,在10 m^(3)/min的施工排量下,裂缝长度最长可以达到193.8 m,最大缝高27.0 m,单井日产气量最高达到1490 m^(3)/d,2 a的瓦斯抽采量达到31×10^(4) m^(3),说明煤层顶板水平井分段分簇压裂技术是淮南地区碎软低渗煤层掘进巷道瓦斯高效抽采的有效模式。

托顶煤巷道易片冒顶板变形机理与超前导管预注浆控制技术研究

目的 为探究厚煤层易片冒区域托顶煤巷道顶板变形破坏机理,并对易片冒区托顶煤巷道顶板进行有效控制,方法 以常村煤矿2701工作面皮带运输巷为例,通过等截面梁理论分析托顶煤巷道顶板破断成因,研究托顶煤巷道顶板的稳定性与巷道宽度和顶煤强度的关系。通过极限平衡准则得到巷帮位移的计算公式,证明托顶煤巷道具有帮顶协同变形机制。建立托顶煤巷道数值模型,研究巷道埋深、侧压系数、顶煤厚度和顶煤强度与托顶煤巷道围岩稳定性的关系。结果 结果表明:巷道埋深越大,其对托顶煤巷道两帮稳定性的影响越大;侧压系数的增加对巷道两帮和底鼓量的影响更大,对顶板影响较小;顶板下沉量与顶煤厚度呈正相关,底鼓量则与顶煤厚度呈负相关;顶煤强度的增加使巷道顶板下沉量与两帮移近量均近似呈线性减小趋势,底鼓量基本保持不变。结论 通过幂律型流体柱形渗透注浆扩散理论得到超前导管注浆半径,由此提出托顶煤巷道超前导管预注浆帮顶联合控制技术,成功控制易片冒托顶煤巷道顶板冒落问题,可为类似地质条件的托顶煤巷道顶板控制提供借鉴。

深部矿井软底回采巷道底鼓机理及防治研究

针对山阳煤矿软底回采巷道严重底鼓的难题,采用理论分析、数值模拟和现场应用的方法,基于塑性理论建立了巷道底板岩体滑移线底鼓力学模型。研究表明,巷道底板破坏岩体主要分为3个区,分别为主动极限区、过渡区和被动极限区,推导了巷道底板岩体的最大破坏深度,提出了锚索+卸压槽联合控制底鼓的方法。采用数值模拟的方法验证了联合控制方案的可行性,现场应用效果表明该方法能够有效控制软底巷道底鼓,为相似地质条件底鼓问题的研究提供了一定的帮助。

深部顶板夹煤层巷道变形破坏分析及其控制

为了探究深部顶板夹煤层软岩巷道大变形破坏问题,以平煤六矿三水平戊二胶带运输巷为工程背景,开展夹煤层巷道围岩破坏分析及控制对策的研究。首先,构建原支护体系组合拱力学模型,推导出直墙半圆拱形巷道稳定判别式;其次,提出“锚网索-梁-注浆-组合砂浆锚索”联合返修控制对策,即沿戊8煤层顶板进行巷道扩刷,采用锚网索、梯子梁完成基本支护,对围岩进行深浅孔注浆加固、顶板及两帮关键部位布置组合砂浆锚索等加强支护,并通过数值模拟分析返修前后应力、位移场分布特征;最后,开展工业性试验,并监测矿压。结果表明:两帮及顶底板最大收敛量分别为93、112 mm,后期变形速率均低于1 mm/d,围岩变形得到有效控制,返修效果良好。

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。

托顶煤切顶留巷围岩控制技术研究

为了解决托顶煤巷道围岩变形难以控制的问题,运用理论分析、离散元数值模拟及现场工业试验相结合的方法对义棠煤业100602工作面切顶成巷围岩控制技术进行研究,分析了不同切顶高度、采高对留巷围岩变形影响规律。研究发现,适当增加切顶高度并降低采高有利于巷道围岩稳定,并确定开采技术参数为切顶高度24 m、采高6 m。现场监测结果显示,在合理的支护策略及开采工艺参数下,托顶煤切顶留巷围岩变形控制效果良好。

新街矿区厚硬顶板条件邻空巷道冲击地压机理与控制

【目的和方法】针对厚硬顶板条件下深部矿井回采巷道冲击地压严重威胁工作面安全生产的问题,以内蒙古新街矿区典型深采矿井3-1103工作面辅运巷为工程研究背景,分析邻空巷道冲击地压频发区域外在主控因素和内在驱动力源;构建基于软化地基与弹性地基假定“岩梁-地基”系统力学特性的顶板断裂前受载力学模型,解析采场覆岩结构演化过程厚硬顶板岩梁能量演化规律及其主控因素;运用FLAC3D模拟并探查邻空巷道冲击失稳高风险区域位置与特征;研究采场覆岩结构优化与围岩应力能量控制方案,制定厚硬顶板破断诱发邻空巷道冲击地压控制方法。【结果和结论】结果表明:(1)邻空巷道冲击地压频发区域易发生以高静载或高静载叠加动载为主导灾变力源的失稳破坏,影响因素主要为顶板厚硬岩层、邻近采空区、区段煤柱。(2)顶板储能总量与覆岩载荷、软化地基系数、顶板岩梁弹性模量及惯性矩、采空区顶板极限跨距、工作面支架参数等有关。其中,覆岩载荷、软化地基系数和采空区顶板极限跨距与岩梁应变能密度呈正相关,顶板岩梁弹性模量及惯性矩、工作面支护参数与岩梁应变能密度呈负相关。(3)回采期间3-1103工作面超前支承压力区及其影响区域内区段煤柱和回采巷道煤体呈现多因素叠加影响,发生应力集中和能量积聚,是冲击失稳高风险区域;该区域较3-1101综采面其围岩应力与能量集中度进一步加剧增大。其中,工作面前方应力和应变能密度峰值增幅最大分别为6.61%、12.04%,区段煤柱应力和应变能密度峰值增幅最大分别为29.06%、65.14%。(4)提出了“卸压爆破预处理高静载区域+深孔爆破或水力致裂预裂厚硬顶板+强化巷道吸能防冲支护”的解决方案,现场应用效果明显。

综采工作面超前巷道变形机制及围岩控制技术研究

针对采煤工作面超前巷道变形量大等问题,研究了采煤工作面端部覆岩运动特性对超前巷道变形的影响,分析了超前巷道切顶卸压机理,确定了合理的切顶参数,进行了现场试验。结果表明:工作面超前巷道的变形的根本原因是工作面推进过程中弧形三角板在工作面推进方向和倾斜方向下沉运动导致其重量及其荷载作用在巷道顶板造成的,并在此过程引起超前支承压力和侧向支承压力的集中。有效切断回采巷道上方顶板与工作面顶板的联动效应后,超前巷道替代了单体架棚支护,超前巷道顶底板累计变形量和两帮累计移近量分别为未切顶的1/5和1/3。

顶强帮弱半煤岩巷道围岩变形特性及控制对策

针对“顶强帮弱”半煤岩巷道巷帮围岩塑性破坏范围大、锚杆支护强度不足等围岩控制难题,以某矿8#煤层回采巷道为工程背景,在围岩力学性能测试、钻孔可视化观测及声波法实测巷帮不同高度松动圈的基础上,对该类巷道围岩的力学及宏观变形特征进行了研究,得出巷帮煤层既是影响巷道整体稳定的“短板”,又是支护的“关键”。建立数值模型分析了“顶强帮弱”半煤岩巷道围岩受采动影响的变形特征、应力分布规律及承载特性,提出了强化帮部薄弱部位的围岩控制对策,并进行了工业性试验。结果表明:对“顶强帮弱”半煤岩巷道帮部煤层采用“锚杆+斜拉穿层锚索+强护表构件”的支护对策可使其处于三向压缩受力状态,约束其向巷道内挤出变形,发挥封闭及主动促稳作用。

临空巷道煤柱割缝爆破切顶联合卸压技术研究

坚硬顶板下临空巷道存在着高应力集中、大变形、难支护等问题,以葫芦素煤矿21105工作面为工程背景,分析了坚硬顶板下工作面回采期间上覆顶板破断规律,研究了临空巷道围岩变形机理,提出了临空巷道“顶板爆破+煤柱割缝”联合卸压巷道变形控制方法,采用FLAC3D软件模拟了卸压前后临空巷道围岩应力分布规律。在葫芦素煤矿21105工作面回风巷采取“顶板爆破+煤柱割缝”联合卸压措施后,临空煤柱深基点应力峰值降低36.1%,浅基点应力峰值降低19.1%,试验区域微震日均能量降低67.0%,日均微震总能量降低35.7%,采取卸压措施后临空巷道顶底板移近量减小60.1%,两帮移近量减小41.6%,巷道变形得到有效控制。试验结果表明临空巷道“顶板爆破+煤柱割缝”联合卸压技术可有效降低煤柱应力,减少巷道变形,为坚硬顶板下临空巷道变形控制提供了一种新的治理手段。

坚硬顶板切顶成巷挡矸结构变形与破坏机理研究

针对坚硬顶板切顶成巷过程中挡矸结构易弯曲、偏移问题,以邱集煤矿11煤1105工作面运输巷为研究对象,构建全过程挡矸结构力学模型,并结合ABAQUS数值模拟软件分别模拟了受矸石冲击、挤压时挡矸结构受力变形情况。研究结果表明:坚硬顶板垮落矸石冲压特征明显,易导致挡矸结构横向弯曲,尤其是挡矸结构中工字钢上部变形严重,通过对工字钢顶端施加横向约束力,可有效减小工字钢变形;受矸石挤压作用,金属网发生网兜变形,并对相邻工字钢产生较大的拉应力,易造成整体失稳;工字钢间距800 mm时钢筋网变形量降低明显。提出1种新型挡矸支护方案,经现场实施监测,新方案下矸石帮变形减小了约49%,满足生产安全需要。

深井切眼巷道爆破切顶留巷围岩控制技术研究

预裂爆破切顶留巷技术是现今煤矿开采中实现高效开采的重要手段,切顶效果的好坏直接影响到留巷的安全性和稳定性,而切眼巷道处的围岩情况与控制技术也有其不同点。鉴于此,本文针对朱集西煤矿13402工作面切眼巷道切顶留巷相关问题,从理论分析和数值模拟的角度分析了传统方式留巷和切顶留巷两种技术的差别性,阐明了切顶留巷技术的优越性。根据现场情况,针对性地提出了切眼巷道顶板“锚索补强支护+爆破切顶”,实体煤帮“锚杆索强力支护”、采空区侧“U型钢+挡矸支架护帮+锚杆补强”的围岩控制方案,并且对锚杆索参数、爆破深度和角度、装药结构等参数进行了设计。方案实施后,切眼巷道留巷效果良好,稳定后留巷的顶板下沉量约为225mm,实体煤帮变形量约为150mm,保证了下工作面的安全回采。

深部开采复合顶板巷道围岩支护技术研究

为研究深部开采复合顶板巷道围岩支护技术,以火烧铺矿260303轨道巷为工程背景,分析复合顶板巷道破坏原因,提出深部开采复合顶板巷道围岩支护技术方案。结果表明:通过优化断面形式联合锚索-长短锚杆耦合支护的多级围岩支护方案,可提高巷道断面承载强度及锚杆索的联合支护作用,现场监测顶板下沉量仅为48 mm,两帮移近量稳定为34 mm,表明围岩控制效果较好,能够保证工作面安全生产。