大采高综采工作面片帮加剧机理分析及防治措施

片帮冒顶制约了大采高综采工作面安全高效开采,因此对大采高综采工作面片帮加剧机理进行分析,发现影响工作面片帮的因素有采高、内摩擦角等,运用数值模拟的方法研究了不同采高下的煤壁片帮条件及临界护帮长度,并结合神东矿区的煤层条件,提出提高支架前端的护帮力、支架初撑力和前端支顶力,增加护帮的长度等控制大采高综采工作面片帮的6种措施.     

大采高工作面煤壁片帮力学机制与深度研究

为了揭示大采高工作面煤壁片帮发生机理,确定片帮位置与深度,基于弹性力学、PFC~(2D)数值模拟等方法,对神东矿区补连塔煤矿12511大采高综采工作面片帮机理进行研究;揭示了工作面煤壁渐进劣化特征,建立了工作面"薄板"力学模型与煤壁片帮深度经验计算公式,进而推导出煤壁变形的挠度方程,确定支架护帮结构控制煤壁片帮的技术。结果表明:工作面煤壁片帮失稳位置在采高的0.579倍处;最大煤壁片帮深度0.98~1.61 m;调整工作面支架顶梁前端结构,确定工作面支架的护帮结构平均支护强度应大于0.16 MPa。     

小保当矿大采高工作面煤壁片帮的压杆稳定性分析

针对小保当矿大采高工作面回采期间煤壁片帮剧烈的问题，采用压杆稳定力学理论及MatLab数据分析软件，建立“压杆”结构模型，得到大采高煤壁挠度分布力学表达式，揭示了护帮板提供不同水平载荷及护帮长度时大采高煤壁挠度分布规律及特征，表明了增大护帮板水平载荷及护帮长度可有效控制煤壁片帮，最终论证了小保当矿不同采高〖DK〗(5.5m、6.5m及7.5m〖DK〗)条件下煤壁稳定性，为小保当矿及类似条件矿井大采高工作面防片帮提供一定理论支撑。     

大采高综采工作面煤壁稳定性及控制研究

为研究大采高工作面煤壁片帮问题及其控制方法，以甘肃某煤矿大采高综采工作面条件为研究背景，采用数值模拟和力学分析相结合的研究方法，开展大采高煤壁应力、位移分布特征和煤壁片帮控制研究。由数值模拟结果可知煤壁应力集中系数为2.14,煤壁最大位移位于煤壁上部区域，距离底板3.5～4.2 m,确定煤壁片帮高度2.1 m,约0.33倍的采高。通过建立煤壁梯形滑块力学模型，分析煤壁失稳极限平衡时的受力状态，计算得到煤壁护帮强度不小于0.365 MPa。研究成果可为该矿井及相似条件矿井控制煤壁片帮提供理论指导。     

大采高综采面煤壁片帮特征分析与应用

片帮问题是制约大采高综采面安全高效开采的主要因素之一,为了弄清大采高工作面煤壁片帮特征,采用压杆理论分析完整性较好的煤壁的挠度特征,得到了煤壁容易发生片帮的位置在煤壁的中上部,并与现场实测结果对比分析,得到了大采高综采面两种典型的片帮形式:半煤壁片帮和整个煤壁片帮.现场采取了提高护帮板的使用率,增加支架的实际初撑力和工作阻力,及时移架等片帮综合治理措施,减少了工作面煤壁的大块煤片帮现象.     

大采高综放工作面煤壁片帮与顶煤冒放性影响分析

针对塔山煤矿大采高综放工作面煤壁片帮防治难题,采用理论分析、数值模拟与现场实测相结合的方法,分析了相同机采高度情况下大采高综放工作面煤壁片帮较大采高综采工作面煤壁片帮剧烈的原因,揭示了综放工作面抑制煤壁片帮与提高顶煤冒放性之间的矛盾,研究了液压支架结构参数对煤壁片帮的影响。研究结果表明:由于受塑性破坏区叠加及顶煤冒落放出的影响,相同机采高度情况下,大采高综放工作面煤壁片帮比大采高综采工作面更加剧烈;合理的液压支架初撑力可在缓解煤壁片帮的同时提高顶煤冒放性;整体顶梁比铰接顶梁更有利于抑制煤壁片帮,同时可以通过适当增大液压支架顶梁长度来缓解煤壁片帮与顶煤冒放性的矛盾;护帮板与伸缩梁分体结构作为大采高综放液压支架一种新的护帮结构形式,比护帮板与伸缩梁连体结构更有利于抑制煤壁片帮。     

基于煤壁“拉裂-滑移”力学模型的支架护帮结构分析

针对坚硬厚煤层大采高综采工作面极易发生煤壁片帮的问题,以红柳林煤矿7.0 m大采高综采实践为基础,分析了煤壁片帮的应力路径效应,将硬煤煤壁片帮细分为拉裂破坏与滑移失稳两个阶段,建立了坚硬厚煤层煤壁片帮的拉裂-滑移力学模型,得出了煤壁的拉裂破坏深度、宽度与煤体强度、开采高度的关系及液压支架应具有的"临界护帮力",分析对比了2种液压支架护帮装置的结构特点与力学特性。研究结果表明,煤体发生拉裂破坏只是煤壁片帮的必要非充分条件,煤壁最终是否发生片帮,还取决于拉裂破坏体在液压支架与矿山压力作用下是否发生滑移失稳。液压支架很难抑制煤壁发生拉裂破坏,但可以有效防止拉裂破坏体发生滑移失稳。液压支架护帮装置采用伸缩梁与护帮板分开结构设计,具有对煤壁的支护作用力大、结构强度与可靠性高等显著优点。     

小保当矿大采高综采面煤壁片帮机理及防控技术

为了解决小保当煤矿大采高综采面煤壁片帮问题,采用理论分析与数值模拟的方法,分析了小保当煤矿大采高综采面煤壁片帮机理及影响因素.结果表明:小保当煤矿煤壁片帮主要是由于开采过程中上覆岩层形成"悬壁梁"结构,梁前端位于煤壁处,煤壁承载增大,支承压力大而引起.通过煤壁片帮因素分析得出了控制综采面煤壁片帮的合理工艺参数,2~(-2)煤开采时工作面采高为6.5 m,支架支护强度为1.0~1.5 MPa,护帮板支护强度为1.0 MPa.提出了"控制采高、合理支架支护强度、使用护帮板"的煤壁片帮综合防控措施.     

上湾煤矿8.8 m综采工作面煤壁稳定性分析

随着大采高开采技术、综采设备研发制造水平的不断提高,综采工作面开采高度不断突破,向8 m及以上超大采高发展。大采高开采技术实现了采煤工作面高产高效,提高了煤炭回采率,但是随着开采高度的不断增加,煤壁片帮问题愈发凸显,大采高综采工作面煤壁稳定性已严重制约煤矿安全高效生产。针对上湾煤矿8.8 m工作面开采后的煤壁片帮情况,采用煤壁稳定性分析软件及FLAC^3D软件对影响工作面煤壁稳定性因素进行类比分析、理论分析及数值模拟分析,得出该工作面煤壁较为稳定,但仍需在合理选择支架支护强度的前提下,尽量保证液压支架护帮范围达到5 m,以适应8.8 m超大采高工作面的护壁要求。     

大采高综采工作面煤壁片帮特征及其稳定性分析

为研究大采高综采工作面的煤壁稳定性,采用2种压杆力学模型分析,得出煤壁的失稳位置离顶板的距离为0.35～0.5倍的采高。然后将片帮的煤体简化为单一滑动面模型,通过力学分析,得到衡量煤壁稳定性的稳定系数K。如果K>1,即下滑力大于抗滑力,此时发生片帮现象;如果K=1时,此时煤壁处于极限平衡状态;当K<1时,抗滑力大于下滑力,煤壁稳定。另外由K值的表达式可知,当煤体的内摩擦角和内聚力增大时,煤壁越稳定;当采高和顶板来压增大时,煤壁越易于片帮。通过现场实践分析,注射马丽散等增强煤体的抗剪强度,加强顶板及护帮的支护,加快工作面推进速度,及时移架等措施,有利于减小片帮发生,增强煤壁的稳定性。     

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