Coupling effects of coal pillars of thick coal seams in large-space stopes and hard stratum on mine pressure

Concerning the issue of mine pressure behaviors occurred in fully mechanized caving mining of thick coal seams beneath hard stratum in Datong Mining Area, combined with thin and thick plate theory, the paper utilizes theoretical analysis, similar experiments, numerical simulations and field tests to study the influence of remaining coal pillars in Jurassic system goaf on hard stratum fractures, as well as mine pressure behaviors under their coupling effects. The paper concludes the solution formula of initial fault displacement in hard stratum caused by remaining coal pillars. Experiments prove that coupling effects can enhance mine pressure behaviors on working faces. When inter-layer inferior key strata fractures, mine pressure phenomenon such as significant roof weighting steps and increasing resistance in support.When inter-layer superior key strata fractures, the scope of overlying strata extends to Jurassic system goaf, dual-system stopes cut through, and remaining coal pillars lose stability. As a result, the bottom inferior key strata also lose stability. It causes huge impacts on working face, and the second mine pressure behaviors. These phenomena provide evidence for research on other similar mine strata pressure behaviors occurred in dual-system mines with remaining coal pillars.

Measurement and numerical analysis of influence of key stratum breakage on mine pressure in top-coal caving face with super great mining height

To analyze the influence of movement in shallow-buried working faces with large mining heights on mine pressure manifestation, the key stratum at a working face was categorised using the 1313 top-coal caving face with super great mining height under cover as a case study. The research combined theoretical analysis, field measurement, and numerical simulation to analyze the influencing mechanism of key stratum. Moreover, the research results were verified by numerical simulation and indicate that the sub-key stratum is prone to be broken to form a "cantilever beam" structure rather than a stable hinged structure during the excavation of working faces with super great mining heights. When the "cantilever beam" structure is unstable, a low pressure will occur on the working face, and the overlying strata will subside simultaneously with the sub-key stratum to induce the breakage of the primary key stratum: the breakage will further trigger the periodic breakage of sub-key stratum, causing a greater load on the working face. Finally, steps, and strength of weighting in the working face vary to be great or small alternatively. This is the main reason explaining why the 1313 working face shows strong mine pressure manifestation. The results provide theoretical and practical experience for forecasting and controlling mine pressure manifestation.

Mining pressure monitoring and analysis in fully mechanized backfilling coal mining face-A case study in Zhai Zhen Coal Mine

Fully mechanized solid backfill mining(FMSBM) technology adopts dense backfill body to support the roof. Based on the distinguishing characteristics and mine pressure control principle in this technology, the basic principles and methods for mining pressure monitoring were analyzed and established. And the characteristics of overburden strata movement were analyzed by monitoring the support resistance of hydraulic support, the dynamic subsidence of immediate roof, the stress of backfill body, the front abutment pressure, and the mass ratio of cut coal to backfilled materials. On-site strata behavior measurements of 7403 W solid backfilling working face in Zhai Zhen Coal Mine show that the backfill body can effectively support the overburden load, obviously control the overburden strata movement, and weaken the strata behaviors distinctly. Specific performances are as follows. The support resistance decreases obviously; the dynamic subsidence of immediate roof keeps consistent to the variation of backfill body stress, and tends to be stable after the face retreating to 120-150 m away from the cut. The peak value of front abutment pressure arises at 5-12 m before the operating face, and mass ratio is greater than the designed value of 1.15, which effectively ensures the control of strata movement. The research results are bases for intensively studying basic theories of solid backfill mining strata behaviors and its control, and provide theoretical guidance for engineering design in FMSBM.

Deformation and failure study of surrounding rocks of dynamic pressure roadways in deep mines

In order to understand the change rules of stress-displacement in surrounding rocks of dynamic pressure roadways in deep mines and to obtain a theoretical basis for analyses of roadway stability and designs of support, we established a coupling equation of adjacent rock strength, mining stress and supporting resistance on the basis of an elastic-plastic theory of mechanics. We obtained an analytical solution for stress and displacement distribution of elastic and plastic regions in surrounding rock of dy-namic pressure roadway.. Based on this theory, we have analyzed the changes in stress-displacement in elastic and plastic regions of surrounding rocks of dynamic pressure roadways in the Haizi Coal Mine. The results show that: 1) radial and tangential stress change violently within the first 4 m from the inner surface of a roadway after excavation; radial stress increases while tangential stress decreases within a range of about 6 m from the inner surface of the roadway as a function of q3; 2) radial and tangential stress increase with an increase in the mining pressure coefficient k; the increase in the rate of tangential stress is greater than that of ra-dial stress; 3) the radial displacement of the inner surface of roadways decreases with an increase in q3, provided that k remains unchanged.

Dust removal efficiency of high pressure atomization in underground coal mine

To master theoretical calculation for dust removal efficiency of high pressure atomization in an underground coal mine, the corresponding atomization characteristics and dust removal efficiency were both comprehensively studied in theory by virtue of related theories of hydromechanics and aerosol.According to actual measurements of flow coefficients and atomization angles of X-type swirl nozzle,computational formula was derived for atomized particle sizes of such a nozzle in conjunction with relevant empirical equation. Moreover, a mathematical model for applying high pressure atomization to dust removal in underground coal mine was also established to deduce theoretical computation formula of fractional efficiency. Then, Matlab was adopted to portray the relation curve between fractional efficiency and influence factors. In addition, a theoretical formula was also set up for removal efficiency of respirable dust and total coal dust based on dust size and frequency distribution equations. In the end,impacts of dust characteristic parameters on various dust removal efficiencies were analyzed.

STUDY ON LAWS OF UNDERGROUND PRESSURE APPEARANCEIN THE DEEP ENTRIES OF COAL MINES

Based on a large amount of field investigation and observations, the paper analyzes and summarizes the mining depths and depth distribution of coal mines in China, discusses the characteristics of undrground pressure appearance in the entries of deep mining, points out some characteristics of surtounding rocks when rHo> =0.5, such as obvious rheologital deformation,and puts forward the main principles of supporting the entries in deep

Development of a Combined Flotation and High Pressure Leaching Process for Copper and Nickel Recovery from Mine Tailing

The present study focused on the re-processing of copper and nickel from mine tailings. In this work, recovery of copper and nickel from mine tailing by combined process of flotation and high pressure oxidative leaching were considered. In the first stage, effects of flotation parameters including collector type, collector dosage, and pH and pulp density were examined. The results showed that over 80% copper recovery was achieved under the optimized flotation conditions while nickel recovery was lower than 30% due to its co-ex-istence with gangue minerals of pyrrhotite, pyrite and other clay minerals. In the second stage, key parameters, particularly concentration of sulfuric acid, temperature, pressure and leaching time were investigated to test the leaching efficiency of copper and nickel from the flotation concentrate with high pressure oxidative leaching (HPOL). A comparison was made between the leaching efficiencies of copper and nickel from flotation concentrates and mine tailing.

区段煤柱变形光纤光栅监测应用研究

针对近距离煤层下伏工作面过上覆遗留煤柱时,发生动静载叠加诱发强矿压显现,导致区段煤柱发生变形失稳造成人员伤亡和设备破坏。为探索基于光纤光栅实时监测区段煤柱变形发育特征,分析进、出遗留煤柱阶段矿压显现机理,将FBG、光栅应力计的光测方法相结合,结合现场实测的区段煤柱变形应力应变水平参量变化规律,研究煤柱应变空间分布规律及回采过程中工作面前方煤柱内部应变时域响应特征,验证光测方法在煤体应变水平观测的可行性。结果表明:工作面回采经过上覆遗留煤柱期间,区段煤柱顶板受集中应力影响,上部岩层块体破断并发生回转导致煤柱载荷增加,随着工作面推进覆岩断裂进一步向上传递,关键层断裂回转发生导致工作面来压,最终导致区段煤柱变形失稳。根据现场光栅应变增量幅度判断煤柱内局部变形的剧烈程度,在集中应力作用下,区段煤柱变形时发生最大应变为650×10^(-6),上覆岩层集中应力造成煤柱应变水平峰值位置为煤柱宽度11.5 m,沿煤柱宽度方向应变表现出先增加后减小然后趋于稳定的趋势,内部应变随采动过程中影响范围在5 m左右。综合研究工作面回采经过上覆遗留煤柱时应变对区段煤柱发生变形失稳的特点和规律,以及应变水平变化和煤柱物理力学性质,得到煤柱破坏的前兆特征,在外力作用下达到变形峰值前对煤柱提前进行卸压和防护的安全处理。

基于小波变换的锚杆锚索测力仪设计

针对井下存在的电磁干扰,会对测力仪采集到的运放端的电压信号存在较大的干扰,进而对传感器测得的压力值准确性产生影响的问题;设计了基于小波变换的锚杆锚索测力仪。以国产HC32L176单片机作为主控芯片,对运放端的电压信号进行AD采集;选用合适的小波基函数、分解层数、阈值规则及阈值函数,对含噪信号进行分解,滤除不同层的高频成分,再对信号重构,得到去噪后的信号。Matlab仿真与实际测试结果表明:小波变换可以对采集的电压信号实现很好去噪,提高了锚杆锚索测力仪的可靠性与稳定性。

鄂西磷矿岩爆现状及治理措施研究

针对鄂西磷矿,在深入调查苏家坡磷矿、麻坪磷矿、桃郁溪磷矿等矿山地质特征及岩爆现象的基础上,分析了鄂西磷矿岩爆灾害主要发生部位、埋深及岩性等影响因素,提出了适合鄂西磷矿岩爆的治理措施:对鄂西地下磷矿进行地应力测试,根据地应力测试结果,优化回采顺序,减少应力集中区域,并在局部区域开展卸压和支护措施,保障井下安全开采。

Dynamic development characteristics of amounts of gas and levels of pressure in the Pan-1 coal mine of Huainan

The Pan-1 coal mine located in Huainan municipality, Anhui province, is abundant in coal resources. In order to discover the natural conditions of gas in its coal seams, we inverted the burial history of these coal seams using the software of Easy%Ro method and simulated the development process of gas volumes and pressure of the major coal seams using CBM History Simulation Software. Our analysis shows that the devolution of gas volumes and levels of pressure can be divided into four stages: i.e., a biogas stage (P1-P3), a pyrolysis gas stage (T1-T2), an active gas enrichment stage (T3-K1) and a gas dissipating stage (K2-present). Currently, the average amounts of gas and gas pressure in coal seams Nos. 13-1, 11-2 and 8 of the Pan-1 coal mine are 8.18 m3/t and 2.20 MPa; 3.89 m3/t and 2.47 MPa and 6.35 m3/t and 2.89 MPa, respectively. This agrees very well with current mining data.

千米深井切顶卸压自成巷支护技术及应用

为了解决深部复杂条件下的切顶卸压自成巷难题,以红阳三矿703工作面运输巷道为研究对象,从恒阻大变形锚索超前支护、切顶巷内支护、切顶巷旁支护三个方面研究了切顶卸压沿空成巷支护技术,并对现场试验巷道顶板受力以及巷道围岩变形量进行了监测。结果表明:在超前工作面实施爆破切顶能够极大降低巷道所受应力,成巷区巷道顶板整体下沉量较小,巷中顶板最大下沉量约385 mm,平均下沉量约280 mm,巷中底鼓最大值545 mm,碎石巷帮无明显侧鼓现象,实体煤帮无明显片帮现象,满足安全和使用要求,巷道围岩变形在可控范围内,留巷效果良好。

采场全生命周期的矿压危害事件知识图谱表示方法研究

知识图谱是认知智能研究不可或缺的组成部分。针对采场矿压危害事件传统分析方法对煤矿开采过程中应力时空演化过程及隐患演化与风险防控关系等表达存在不足的问题,本文基于采场全生命周期提出一种采场矿压危害事件知识图谱表示方法:首先,从地质灾害的角度,分析采场应力及分布的动态特性,对矿压地质灾害中的各节点进行动态关联,提出顾及时空过程的采场矿压地质灾害知识图谱表示方法。其次,从事故的角度,分析采场矿压事故隐患演化与风险防控过程,将隐患耦合演化与防治措施融入知识图谱表示模型中。最后,运用Neo4j构建矿压危害事件知识图谱。结果表明:依据该表示方法构建的知识图谱,不仅刻画了灾害事件中不同对象的时空演化过程,还描述了隐患耦合演化过程以及对应的风险防控措施,为采场矿压危害的防治提供了智能研究途径。

厚硬覆岩工作面初次放顶矿山压力实测研究

通过分析济宁三号煤矿123_(下)01(南)综放工作面地质条件、直接顶的初垮、基本顶的初垮、微震监测等内容,揭示了影响该工作面出现强矿压显现的主要因素为推进速度、上覆厚硬顶板、开采深度、断层等。该工作面初次放顶期间矿压显现特征:直接顶初次垮落步距21.75 m;基本顶初次来压平均步距51 m;动载系数1.41;初次放顶期间矿压显现程度剧烈,基本顶分层分段来压明显,持续时间7个小班;该工作面本次基本顶初次来压整体呈现“中间小两头大”的运动特征。研究所得结论为厚硬覆岩工作面初次放顶强矿压显现准确解释提供了依据。

大采高综采工作面矿压显现及顶板活动特征研究

为了得到唐山某煤矿综采工作面的矿压显现及顶板活动特征,基于关键层理论、“悬臂梁-砌体梁”力学模型,通过现场观测、理论分析、数值模拟的方法对9煤层矿压显现特征、顶板结构、支架工作阻力开展了深入研究,建立了覆岩结构力学模型,得到了工作面支架工作阻力的合理计算式。研究结果表明:工作面来压步距和来压大小均有一定的规律性,呈现一大一小的周期来压现象,来压期间中部测区支架荷载最大,两边偏小;通过直接顶关键层判别方法,确定了第2层岩层和第7层岩层分别为亚关键层1和亚关键层2。亚关键层1破断后以“悬臂梁”结构形态垮落进入采空区,亚关键层2破断后形成了稳定的“砌体梁”结构,此时亚关键层1与亚关键层2共同组成了“悬臂梁-砌体梁”结构;第2层岩层和第7层岩层组成的双关键层结构的破断运移规律导致了工作面呈现一大一小的周期来压现象。当双关键层同步破断时,支架工作阻力为13 688 kN。

Surrounding Rock Failure Mechanism and Control Technology of Gob-Side Entry with Triangle Coal Pillar at Island Longwall Panel in 15 m Extra-Thick Coal Seams

Taking the return air roadway of Tashan 8204 isolated island working face as the background, the evolution law of the stress field in the surrounding rock of the widened coal pillar area roadway during the mining period of the isolated island working face is obtained through numerical simulation. The hazardous area of strong mine pressure under different coal pillar widths is determined. Through simulation, it is known that when the width of the coal pillar is less than 20 m, there is large bearing capacity on the coal side of the roadway entity. The force on the side of the coal pillar is relatively small. When the width of the coal pillar ranges from 25 m to 45 m, the vertical stress on the roadway and surrounding areas is relatively high. Pressure relief measures need to be taken during mining to reduce surrounding rock stress. When the width of the coal pillar is greater than 45 m, the peak stress of the coal pillar is located in the deep part of the surrounding rock, but it still has a certain impact on the roadway. It is necessary to take pressure relief measures to transfer the stress to a deeper depth to ensure the stability of the triangular coal pillar during the safe mining period of the working face. This provides guidance for ensuring the stability of the triangular coal pillar during the safe mining period of the working face.

基于微震监测的浅埋8 m超大采高综采面矿压规律现场监测研究

以陕北矿区某矿2203浅埋超大采高综采面为工程背景,采用微震监测技术,对浅埋超大采高综采面矿压规律进行了研究。结果表明:单日微震事件数达到峰值后,综采面继续回采8.25~11 m内,能量大于103J的事件增多,微震事件能量及支架压力达到峰值,随后顶板出现垮落现象。综采面初次来压前,微震总能量为6.40×10^(3)J,矿压显现期间为1.07×10^(4)J,总能量增长67%;由于综采面矿压显现与微震最大能量峰值出现一致,通过2次最大能量峰值时综采面位置可以确定综采面周期来压步距。2203综采面初次来压步距为24.75 m,周期来压步距为27~35.25 m,由此确定,顺槽超前支护距离为36 m,实践表明,2203综采面采用ZCZY10300/31/55D型超前液压支架满足巷道超前支护的要求。微震监测是矿压显现规律分析的有效手段,采用液压支架压力变化与微震能量协同分析的方法研究超大采高综采面的矿压规律是可行的。

基于差分非平稳Transformer的液压支架立柱压力预测

液压支架立柱压力预测是回采工艺决策的重要依据,也是确保围岩稳定的基础信息之一。然而,液压支架立柱压力虽然具有一定的规律性,却无法用简单的数学模型进行预测;且在回采过程中,支架不接顶、顶板破碎、传感器检测误差等带来大量的随机噪声,使得压力数据劣化为非平稳时间序列,给压力的预测带来的很大的困难。本文在Transformer基础上,提出一种差分非平稳Transformer模型,在Transformer的编码器和解码器中分别引入差分归一化和反归一化操作,以提升序列的平稳性。同时,在Transformer中采用去平稳注意力机制,计算序列元素之间的关联关系,以增强模型的预测能力。在真实的煤矿支架立柱数据集上的对比实验表明,本文提出的差分非平稳Transformer的预测效果达到0.674,表现明显优于LSTM、Transformer和非平稳Transformer模型。

灵东煤矿上分层综放开采型煤相似材料模拟试验研究

以灵东煤矿为研究对象,采用室内试验、物理相似模拟、现场监测方法,选取了石膏+石子+水作为型煤相似材料,优化了材料配比,验证了相似材料的合理性。研究结果表明,石膏∶石子=1∶5,石膏∶水=0.6∶1,石子粒径为3~5 mm时,材料强度与原煤强度基本一致;选用该配比制作型煤时,模拟试验与现场监测的基本顶平均周期来压步距分别为11.3、12.2 m,误差仅为7.38%,表明该配比制作型煤进行物理相似模拟试验时可以反映现场覆岩真实变化规律。