Characteristics of Gas Emission at Super-Length Fully-Mechanized Top Coal Caving Face

Characteristics of gas emission at the K8206 working face in the Third mine of the Yangquan Coal Group were investigated. The effects of strata movement,advancing velocity of working face,production capacity of working face and gas extraction capability of strike high-level entry on gas emission at K8206 working face were analyzed. A regression equation,reflecting the relationship between relative gas emission rate and the production capacity of work-ing faces,was established. Another regression equation showing the relationship between the gas emission rate from adjacent layers when the working face was advancing for one metre and advancing velocity was derived. It can be con-cluded that,1) the amount of gas emitted at the K8206 working face is far greater than that of ordinary top coal caving faces with a dip length of 180-190 m; 2) the dynamic process of gas emission from adjacent layers during the initial mining stage is controlled by the movement of key strata; 3) the amount of gas emitted that needs to be forced out by air is greatly affected by the capability of gas extraction; 4) when the advancing velocity is between 3.5-5.5 m/d or when the output is up to 8-12 kt/d,the gas emission from adjacent layers is almost constant.

Analysis on distribution law of the abutment pressure of the integrated coal beside the road-in packing for gob-side entry retaining in fully-mechanized caving face

The three-dimensional damage constitutive relationship of coal is established and distribution law of the abutment pressure of the integrated coal beside the road-in packing for gob-side entry retaining in fully-mechanized caving face under the effect of given deformation of the main roof is analyzed by the damage mechanics theory. And the relationship between distribution of the abutment pressure and thickness of coal seam is explored. The presented result is of great theoretical significance and practical value to the study on stability control of the surrounding rock of road-in packing for gob-side entry retaining in fully-mechanized caving face.

Analysis and key control technologies to prevent spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines

In order to prevent spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines in China,we have analyzed the characteristics of spontaneous coal combustion and explain theoretically the factors affecting spontaneous coal combustion,such as rock bursts,high temperatures,high ventilation resistance,slow advancing speed and large obliquity mining.Key technologies to prevent spontaneous combustion occurring in sharply inclined seams in deep mines are proposed;these include pouring water,stopping leakage in upper and lower corners of the working face,choking off the goaf and covering the coal.CO concentrations were controlled within two years to less than 15×10-6 at the upper corner by applying these technologies at the 1410 working face of the Huafeng coal mine.Our method has significant theoretical value and is of practical importance in controlling spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines.

Deformation mechanism of surrounding rocks and key control technology for a roadway driven along goaf in fully mechanized top-coal caving face

The variation of the stress in the bolted surrounding rocks structure of the roadway driven along goaf in a fully mechanized top coal caving face with moderate stable conditions are studied by using numerical calculation. The essential deformation characteristics of the surrounding rocks in this kind of roadway are obtained and the key technology of bolting support used under these conditions is put forward.

Statistic constitutive equation of top-coal damage for fully mechanized coal face with sublevel caving

Under the action of abutment pressure in front of fully mechanized coal face with sublevel caving(CFSC),top-coal over CFSC deformed.In the process of whole de- formation of top-coal,it changed from continuum elastic mass to non-continuum plastic mass contained fissures,become a loose body.According to its bearing characteristics and mechanical properties,top-coal mass can be divided into four deformation zones along the winning direction of CFSC,i.e.initial stress zone,elastic zone,plastic zone and loose zone.Top-coal in plastic zone located in the post-peak zone of the stress-strain curve for top-coal.With equivalent strain principle of damage mechanics and mathemati- cal theory of statistic,combining the movement law of top-coal,set up a constitutive equa- tion with damage statistics for top-coal in different position in CFSC.The equation illus- trated the mathematical relationship among top-coal bearing capacity,horizontal confining pressure along the winning direction of CFSC and mechanical properties of top-coal mate- rial.The conclusions not only provide a basis for numerical computer simulations on damage deformation and failure mechanism for top-coal,but also further promote the ap- plication of damage mechanics in CFSC.

Reliability analysis of the velocity matching of coal cutting and caving in fully mechanized top-coal caving face

The matching relationship between coal cutting and caving in fully mechanized top-coal caving face is analyzed in detail from the angle of reliability. The coupling equation of reliability is established correspondingly, and the mathematical equation of the coefficient of velocity matching of coal cutting and caving is obtained, which meets a certain reliability demand for making the working procedure of coal caving not influence coal cutting of coal-cutter. The results show that the relationship between the coefficient of the velocity matching and the reliability of coal cutting and caving system is linear on the whole when R <0.9. It is pointed out that different numerical value should be selected for different coal face according to different demand for reliability.

Back-and-forth mining for hard and thick coal seams—research about the mining technology for fully mechanized caving working face of Datong Mine

The article introduced the key technology, mining process, and back-and-forth mining method for the caving working face of hard-thick coal seams in Datong mine, and researched this innovations process, optimized the systemic design and working face out-play, tried to perfect the caving mining technology of hard-thick coal seams further.

Study of mechanical principle of floor heave of roadway driving along next goaf in fully mechanized sub-level caving face

Abstract On the basis of analyzing floor strata mechanical circumstance of the roadway, the mechanical model was established. The relative displacement of roadway floor, narrow pillar floor coal mass and floor strata was calculated, the results showed that the high abutment pressure on coal mass beside the roadway was the main reason to lead to relative displacement of floor strata. And the roadway floor heave come mainly from three aspects. Firstly, the roadway floor strata is easily fractured by the stretch stress. Secondly, because the high abutment pressure is greater than the uniaxial compressive strength of floor strata, when the roadway floor strata are fractured, the coal mass floor strata at the same depth will be fractured, and broken rock will fluid into the open roadway. Thirdly, comparing with the coal mass floor, the roadway floor is relative ascending.

Ground pressure and overlying strata structure for a repeated mining face of residual coal after room and pillar mining

To investigate the abnormal ground pressures and roof control problem in fully mechanized repeated mining of residual coal after room and pillar mining,the roof fracture structural model and mechanical model were developed using numerical simulation and theoretical analysis.The roof fracture characteristics of a repeated mining face were revealed and the ground pressure law and roof supporting conditions of the repeated mining face were obtained.The results indicate that when the repeated mining face passes the residual pillars,the sudden instability causes fracturing in the main roof above the old goaf and forms an extra-large rock block above the mining face.A relatively stable ‘‘Voussoir beam" structure is formed after the advance fracturing of the main roof.When the repeated mining face passes the old goaf,as the large rock block revolves and touches gangue,the rock block will break secondarily under overburden rock loads.An example calculation was performed involving an integrated mine in Shanxi province,results showed that minimum working resistance values of support determined to be reasonable were respectively 11,412 kN and 10,743 kN when repeated mining face passed through residual pillar and goaf.On-site ground pressure monitoring results indicated that the mechanical model and support resistance calculation were reasonable.

两次采动影响下小煤柱巷道切顶卸压围岩控制技术

为解决多次采动影响下留小煤柱巷道矿压显现剧烈、围岩变形量大的问题,提出了“切顶卸压+顶、帮锚索补强”联合控制技术。以贾家沟煤矿10115运输巷为工程背景,分析了切顶卸压位置、高度与巷道围岩垂直应力分布的关系,给出切顶卸压关键参数,并研究了留小煤柱巷道在切顶卸压后受两次采动影响下的矿压显现规律。结果表明:切顶卸压后,煤柱上的应力峰值随切顶深度的增加呈指数降低;10115运输巷在邻近工作面一次采动过程中巷道围岩变形依次呈现出无变形、缓慢变形、快速变形和围岩稳定的变化规律,本工作面二次采动过程中巷道围岩变形依次呈现出明显变形和剧烈变形的规律;巷道围岩在受二次采动影响时变形更加剧烈,巷道变形量为一次采动时的3.0~7.5倍。

注氮条件下大采高综放工作面采空区自燃“三带”的分布规律

为解决大采高综放工作面因采高大、回采率低、开采扰动强等造成采空区遗煤自燃危险性增大的问题,以宁夏某煤矿大采高综放工作面为研究对象,应用渗透率演变方程和气体流动模型,分析注氮前后氧浓度时空演化规律及采空区自燃“三带”分布特征。结果表明:采空区氧浓度在注氮条件下呈现出中部大,两侧小的倒“U”型分布;在氧浓度划分下,氧化带范围呈现出先增大后减小的半月形,最大宽度由未注氮时的100 m缩小到50 m;在风速划分下,氧化带较未注氮时整体向工作面方向前移了15 m左右,有效降低了自燃危险区范围。

双临空综放面巷道变形能量时空演化机理及防治技术研究

以塔山矿8204-2特厚煤层综放不规则双临空工作面工程地质条件为背景,基于数值模拟揭示了不同煤柱宽度下采动应力及煤柱应变能密度分布特征。结果表明,双临空工作面回采期间,30~60 m宽的煤柱处于高应力状态,峰值超过25.96 MPa,为原岩应力的2.09倍;当煤柱宽度在30~60 m时,煤柱表现出高应力、高应变能密度的“两高”特点,发生强动压的危险性高。为防止三角变宽煤柱动力失稳,现场成功实践了“超深高密大直径卸压钻孔+补丁锚索加强支护”的强动压治理技术,使得巷道掘进和回采期间均未发生冲击地压及显著动压事故,实现了不规则综放面的安全回采。

大倾角综放采场遗留顶煤运移规律及防灭火技术

为研究大倾角综放采场遗留顶煤运移规律及裂隙扩展情况,以王家山煤矿中二401工作面为研究对象,采用物理相似模拟实验与数值模拟实验相结合的方法,深入分析大倾角综放采场遗留顶煤运移及裂隙发育规律。结果表明,大倾角综放采场遗留顶煤破碎和运移具有非对称性,工作面倾斜中下部应力与位移量均大于倾斜上部。遗留顶煤在采空区内沿倾斜方向呈现“顶煤—直接顶—顶煤”交替堆积形态,倾斜下部堆积量大于倾斜中上部。围岩裂隙发育范围广,随工作面推进最终可扩展至3号煤层。针对遗煤特征综合提出此类采场的“两阶段”防灭火技术措施,达到良好的防灭火效果,确保工作面安全高效生产。

大水易淤综放工作面泄水巷煤泥淤积物临界流速研究

高家堡煤矿综放工作面面前淋水,水源主要来自采煤工作面顶板,矿井涌水量达到4000~5000 m^(3)/h。结合开采工作面泄水巷煤泥淤积的特点,利用罗宾诺维奇—莫纳方程和哈根—泊肃叶(Hagen-Poiseuille)等公式,确定了煤泥混合物的流变类型和本构方程;采用大型环管实验法建立了煤—泥—水混合物的流动模型,理论分析了工作面泄水巷煤泥淤积物分别在高低压段和不同剪切速率下的沉降特性;计算得到动水条件下煤泥淤积物发生流动的临界流速为1.1~1.5 m/s,从而得出煤泥淤积物的临界流速。研究煤泥在矿井水流动过程中的淤积机理,可为科学合理的清淤工作提供理论依据。

厚煤层综放工作面区段煤柱合理宽度及巷道支护研究

为解决常村煤矿轨道顺槽护巷煤柱宽度不合理、支护效果差的问题,通过数值模拟、矿压监测、理论分析等手段,研究最优煤柱留设宽度及支护方案,并进行工业性应用试验。结果表明:宽度大于30 m煤柱内存在稳定的弹性区,合理煤柱宽度为30 m,矿压监测结果表明,优化后的煤柱尺寸和支护方案可保证2106轨道顺槽围岩稳定,满足了工作面安全回采的需要。

煤矿大倾角综放工作面采煤参数及采煤工艺优化分析

以A煤矿26514工作面为例,介绍了一种基于有限元分析的煤矿大倾角综放工作面采煤参数及采煤工艺优化方法。该方法根据煤矿大倾角综放工作面参数构建相应的有限元模型,通过有限元模型的分析寻找现有工作面采煤参数与采煤工艺的缺陷,进而以此为基础制定工作面采煤参数与采煤工艺优化方案。研究对大倾角综放工作面的开采具有重要意义。