顶板结构稳定性与顶煤放出率关系探讨

综放采场顶煤放出率控制着采空区的充填状况，从而影响着大厚度坚硬顶板的稳定性。本文建立了周期来压阶段综放采场顶板结构整体变形失稳和局部铰接失稳的力学模型；根据结构稳定理论和强度理论，得到了保持顶板结构整体变形稳定和岩块局部铰接稳定的力学和几何条件，从而建立与顶煤放出率相关的综放采场顶板稳定性判断准则；结合具体采场实例，给出了与顶煤放出率相关的综放采场顶板稳定性判断曲线和方法，为现场针对不同顶板设计合理的顶煤放出率，从而实现顶板的安全控制提供理论依据。     

顶板结构稳定性与顶煤放出率关系探讨

综放采场顶煤放出率控制着采空区的充填状况,从而影响着大厚度坚硬顶板的稳定性。本文建立了周期来压阶段综放采场顶板结构整体变形失稳和局部铰接失稳的力学模型;根据结构稳定理论和强度理论,得到了保持顶板结构整体变形稳定和岩块局部铰接稳定的力学和几何条件,从而建立与顶煤放出率相关的综放采场顶板稳定性判断准则;结合具体采场实例,给出了与顶煤放出率相关的综放采场顶板稳定性判断曲线和方法,为现场针对不同顶板设计合理的顶煤放出率,从而实现顶板的安全控制提供理论依据。     

特厚煤层综放开采顶板岩层控制基本原理

基于无法改变矿井采掘活动中煤岩体的初始赋存状态、缺乏准确获知其赋存特点及工程响应特征的技术手段,采用理论分析对特厚煤层综放开采顶板岩层控制基本原理进行了研究。特厚煤层综放开采顶板岩层具有3个特点,即"暂时稳定性""及时垮落性"以及两种状态的周期性转化,岩层控制的基本原理就是控制工作面回采过程中顶板岩层结构的"暂时稳定性"。维护顶板岩层结构的"暂时稳定性",需要避免上位直接顶"组合短悬臂梁"结构发生滑落失稳以及基本顶"铰接岩梁"结构失稳;通过分析"铰接岩梁"结构两种失稳条件和"组合短悬臂梁"结构3种失稳模式,提出了维护特厚煤层综放开采顶板岩层结构"暂时稳定性"液压支架所受变形压力需满足的条件,得出了可通过外界干预促使"铰接岩梁"结构进一步向上转移、减小"铰接岩梁"断裂步距和"组合短悬臂梁"长度等手段减缓来压强度,维护特厚煤层综放开采顶板结构稳定。现场验证表明:通过外力促使"铰接岩梁"结构进一步向上转移,同时降低"组合短悬臂梁"的长度等措施保障了矿压显现剧烈、多次出现支架损坏综放工作面的接续面在原综放设备不变的前提下实现安全高效回采。     

综放末采期间的矿压特征

在现场实测的基础上，分析了综放末肛期期间的矿压特征及顶板稳定性，提出了提高综放末采期顶煤采出率的顶板控制原则，为进一步减少综放末采损失提供了依据。     

复杂条件综放工作面矿压显现特征

根据乌兰煤矿3^#煤层5343综放工作面的复杂开采条件，采用现场矿压观测和数值模拟方法，对该工作面的矿山压力显现特征进行研究．结果表明，工作面顶板初次来压步距24．2m，周期来压步距9．41m，来压期间支架最大平均载荷2775．5kN／架，支架的侧向挤压力较大，工作面片帮冒顶严重，工作面顶板管理难度大．由于受顶板稳定性较高和煤层倾角较大的影响，与一般的松软煤层综放工作面相比，该工作面的矿山压力显现相对比较剧烈，顶板来压强度较大，工作面存在明显的周期来压现象．     

综放工作面直接顶冒采比及顶板韧性与矿压显现的关系分析

为探索酸刺沟煤矿6上煤层综放工作面非常强烈的矿压显现原因,对工作面顶板结构与岩性进行了分析,提出冒采比和顶板韧性两个概念。通过理论分析计算并结合现场实测,分析了综放工作面直接顶冒采比及顶板韧性与矿压显现的关系,结果表明,在小冒采比和高韧性顶板条件下,综放工作面矿压显现表现出强烈—非常强烈的基本特点,顶板控制难度极大,这是导致酸刺煤矿6上煤层综放工作面矿压显现非常强烈的重要因素。     

综放工作面开采顶板变形控制及灾害事故防治

采场顶板稳定性控制对综放工作面开采至关重要,为了研究综放开采条件下顶板变形特征与稳定性控制,以崔家沟煤矿2305综放工作面为工程背景,采用理论分析、数值模拟等方法,对综放工作面顶板破断特征进行分析,首先分析了综放工作面顶板灾害事故进行分析,利用UDEC数值模拟软件对不同推进距离顶板破断特征,提出了顶板灾害事故的防治措施,并对其进行了顶板灾害事故处理计划方案制定,为崔家沟煤矿综放工作面顶板稳定性控制防治提供了依据。     

松软厚煤层超长综放工作面开采关键技术研究

为实现松软厚煤层超长综放工作面安全高效回采,对三元煤业松软厚煤层1312超长综放工作面开采关键技术进行了研究。通过理论研究、现场数据分析,对三元煤业松软厚煤层362m超长综放工作面开采设备运输、支护强度、矿压显现及煤壁稳定性进行了研究。结果表明:目前装备配套方案能够满足三元煤业松软厚煤层超长综放工作面支护及运输的要求;超长综放工作面回采期间,相对于200m以下长度工作面,顶板活动更加频繁,倾向方向周期来压呈现不同特性,且矿压显现程度较为强烈,顶板管理难度加大;为改善工作面端面顶板及煤壁的稳定性,需保障足够支护强度,采用双回路供液系统保障足够的支架初撑力,同时应适当加快工作面推进速度,并在煤壁及顶板破碎时采用注浆加固技术。     

某矿大采高综放工作面矿压显现规律研究

本文以某矿综放工作面为研究背景,通过记录液压支架测力仪的变化,判定顶板初次来压步距和周期来压步距,揭示大采高综放面的采场矿压显现规律,为综放面顶板控制与支架选型提供参考与借鉴。     

厚煤层综采放顶煤开采矿压显现规律研究

为了分析沁水煤田厚煤层综放开采的矿压规律,以王坡煤矿3309综放工作面为例,利用顶板压力在线监测系统,记录工作面回采过程中周期来压步距、液压支架立柱的工作阻力变化、前后立柱受力及安全阀开启情况,综合分析厚煤层综放工作面顶板周期来压规律,提出了周期来压前工作面的安全防护措施,为王坡煤矿及沁水煤田邻近矿井综放工作面开采的顶板压力控制提供了依据。     

Current situation and future trend of China rare earth luminescent material industry

<正>Rare earth luminescent material is one of the most important application sectors of rare earths.China enjoys the exceptional advantage to develop rare earth luminescent material for its abundant rare earth resources.After several decades'endeavor,China's rare earth luminescent material industry,headed by rare earth phosphor for lamp and LED and high efficient rare earth energy-saving light source,has been gradually developed into a scale industry.China has become a major production base of rare earth phosphor for lamps and rare earth     

China rare earth market review

正June 1~10,2014Rare earth market remained weak.Quoted price of rare earth products was similar to that in May.There was no sign of recovery in downstream market.The market of NdFeB magnetic materials and phosphor was depressed.Catalyst,polishing powder and ceramic industries remained inactive.Demand from downstream industry was soft.Consumers purchased on their needs.Suppliers had strong intention to sell.Prices of rare earth products     

Annual Report analysis of Chinese rare earth-related listed companies in 2013

<正>Chinese rare earth-related listed companies have published their 2013 annual reports.It can be understood from their reports that production and operation activities of Chinese rare earth-related companies were still heavily affected by macro economy and industrial policies.They basically followed the steps of national economy.In 2013,world economy recovered slowly but the economy     

Market opportunities and challenges for rare earth polishing powder

正1.Status of rare earth polishing powder Rare earth polishing powder with high content of cerium oxide began to replace iron oxide for glass polishing and became one of the key materials in glass polishing process since 1940.Compared with traditional iron oxide,rare earth polishing powder has many advantages,such as fast polishing rate,high polishing quality and long service life.It can achieve good surface quality and improve operation conditions.For example,in lens polishing,the polishing work that cerium     

Baotou Research Institute of Rare Earths developed a new RE alloy preparation technology

正Pyrometallurgy Laboratory of Baotou Research Institute of Rare Earths had independently developed a new preparation technology of rare earth alloy for NdFeB.The alloy can remarkably enhance the coercivity of NdFeB magnet but also evidently reduce the production cost of the magnet.The new master alloy was prepared in the kA pilot-scale electrolytic cell by the independent technology.The rare earth master alloy can be used as the raw material for NdFeB.Compared     

Market and recycling of NiMH battery

<正>Market status and future trend of NiMH battery1.Global market of small NiMH battery Global market size of small NiMH batteries declined year on year since 2011.The trend will continue to 2018,at the rate of 5%to 10%annually.Demand for small NiMH batteries will be stable gradually.Many electrical apparatuses are powered by the built-in lithium battery today,which is the main reason for the shrunk market of small NiMH batteries.But,for some products,small NiMH     

China rare earth market review

正September 1-10,2014 Affected by the National Day holiday,rare earth transaction was stagnant and the market showed a weak steady state.As there was no good news for downstream market,some products with flat demand would likely rally slightly for some time to     

2014 second batch of rare earth quota released

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矿用防爆轴流对旋主要通风机叶片ANSYS模态分析及应用

高效节能矿用防爆对旋主要通风机的叶片是主要通风机运行的关键部件,叶片在运行时不断受到气流的作用力,从而使叶片产生振动,当叶片振动的频率与叶片的固有频率接近时,容易产生共振从而导致叶片的断裂。一旦叶片断裂时,对主要通风机的安全运行产生致命的影响,从而导致矿山、化工等企业发生重大事故,将会产生不可估量的损失。基于有限元分析软件ANSYS,对高效节能矿用防爆轴流对旋主要通风机叶片进行模态分析及产生对应的六阶模态频率,对主要通风机叶片的运行频率、固有频率及产生的共振问题进行了原理分析,并且解决了叶片频率共振的问题,从而为主要通风机叶片结构设计提供理论依据,并对主要通风机叶片的安全运行提供保障。     

2013 NdFeB export analysis

<正>China totally exported nearly 24,000 tonsof NdFeB products during 201 3,including 18,825 tons of permanent magnet,valued USD 1.34 billion at an average price of 71.4 USD/kg;3,277 tons of NdFeB magnetic powder,valued USD 1 01 million at an average price of 30.9 USD/kg;1,334 tons of strip casting ribbon,with total export value of USD 74million at an average price of 55.3 USD/kg;and 586