设置顶板道解决综放工作面瓦斯超限问题的局限性

针对通过设置顶板道来解决综放工作面瓦斯超限技术的广泛应用问题 ,分别较深入地探讨了顶板道和回风巷风量变化与其排放瓦斯量之间的关系。研究表明 ,一般情况下设置顶板道可以较好地解决综放工作面的瓦斯超限问题 ,但瓦斯严重超限时 ,顶板道的排放瓦斯能力难以满足需要 ,在满足回风巷风速及瓦斯浓度均不超限的条件下 ,可通过增大其风量来提高综放工作面总的排放瓦斯能力 .     

阳泉三矿大采长综放工作面瓦斯涌出特征分析

大采长综放工作面单位时间内瓦斯涌出量增大,经常造成工作面回风隅角和回风巷瓦斯质量浓度超限.通过分析综放工作面瓦斯涌出源,可以了解其瓦斯涌出特征.对阳泉三矿大采长K8206综放工作面初采期和回采期的瓦斯涌出规律的分析可知,初采期瓦斯涌出量具有大幅度波动性,其原因主要为采空区瓦斯不断地、周期性地涌入.正常回采期,只要高抽巷的抽放负压足够大,邻近层瓦斯涌入工作面的问题就能解决;而大采长综放工作面本煤层瓦斯涌出量增大,则需要增加通风量或者采用新的通风方式.     

阳泉三矿大采长综放工作面瓦斯涌出特征分析

大采长综放工作面单位时间内瓦斯涌出量增大,经常造成工作面回风隅角和回风巷瓦斯质量浓度超限.通过分析综放工作面瓦斯涌出源,可以了解其瓦斯涌出特征.对阳泉三矿大采长K8206综放工作面初采期和回采期的瓦斯涌出规律的分析可知,初采期瓦斯涌出量具有大幅度波动性,其原因主要为采空区瓦斯不断地、周期性地涌入.正常回采期,只要高抽巷的抽放负压足够大,邻近层瓦斯涌入工作面的问题就能解决;而大采长综放工作面本煤层瓦斯涌出量增大,则需要增加通风量或者采用新的通风方式.     

漳村煤矿设瓦斯巷综放面瓦斯分布及涌出特征

由于综放工作面开采强度大,引起瓦斯涌出量成倍增加,严重制约着工作面的安全生产．针对瓦斯涌出强度大的问题,通过在山西潞安矿务局漳村煤矿综放工作面布置测点、测线,进行现场观测和研究,分析论述了工作面设置排放瓦斯巷解决瓦斯严重超限问题时,综放工作面的瓦斯分布状况及涌出特征．     

高瓦斯综放采煤工作面瓦斯综合治理方案

针对佳新煤矿1504综放工作面瓦斯的实际情况,分析了该工作面的瓦斯主要涌出来源及涌出量,结合该矿通风系统及瓦斯抽采现状,在上下顺槽顺层、上隅角、措施巷道等采用钻孔、高位钻场、埋管、吊管多种方式抽放,以及增加工作面风量和局部风机对上隅角供风等综合措施治理瓦斯,从而解决了上隅角及回风巷瓦斯超限问题,确保了工作面安全高效生产,真正实现了高瓦斯综放工作面的高产高效。     

综放沿空小断面留巷技术研究

随着开采强度的增加，综放工作面的瓦斯超限问题日益突出．以王庄煤矿5201综放面为例，提出采用综放沿空小断面留巷技术，布置J型通风系统，治理综放工作面瓦斯超限．由关键块的分析和数值模拟结果，确定了综放沿空小断面留巷的断面形状，给出了斜梁的合理支护设计．矿压观测结果表明，留巷小断面变形以及留巷煤帮深部位移有较好的收敛性，能够满足工作面抽放瓦斯的需要．     

桃园矿高位钻孔瓦斯抽放参数优化研究

应用RFPA2D软件模拟并确定了桃园煤矿裂隙带的高度,为优化采空区顶板抽放参数提供了依据,并利用优化设计的高位钻孔进行瓦斯抽放,回风巷和上隅角的瓦斯浓度均得到控制,消除了瓦斯超限现象,保证了工作面的安全回采。     

王家岭矿综放工作面上隅角瓦斯体积分数场分布规律研究

针对煤矿综放工作面上隅角瓦斯积聚严重影响安全生产的问题,从综放工作面上隅角瓦斯体积分数场分布规律与上隅角瓦斯抽采的关系出发,采用MATLAB场分析法,以山西中煤华晋能源有限责任公司王家岭矿12318综放工作面的正方形上隅角为研究对象,对上隅角区域的瓦斯体积分数场分布进行了分析。结果表明:12318综放工作面上隅角靠近采空区一侧以及靠近回风巷外侧煤壁处瓦斯体积分数较高,最高可达0. 5%;靠近工作面处瓦斯体积分数较低,仅为0. 10%～0. 25%。这对于合理有效地治理上隅角瓦斯体积分数超限问题具有重要的指导意义。根据研究结果,提出了采用顶板走向定向高位钻孔抽采和埋(插)管抽采等综合瓦斯治理方法,该方法有效地降低了上隅角瓦斯体积分数,即从0. 7%降低至0. 3%左右。     

厚煤层分层开采工作面瓦斯流场分布规律研究

针对厚煤层分层开采工作面回采期间瓦斯涌出治理问题,采用数值模拟计算方法,通过建立采空区瓦斯流场分布的数学模型,对白芨沟矿井首分层0102102工作面回采期间瓦斯流场分布规律进行了研究。结果表明:走向方向上,从工作面往采空区深部,风流速度减小,瓦斯体积分数增大;倾斜方向上,工作面回风巷一侧瓦斯体积分数高于进风巷一侧瓦斯体积分数,工作面上隅角瓦斯容易积聚引起瓦斯超限;垂直方向上,从工作面底板往采空区顶板,瓦斯体积分数逐渐增大;在不采取其他措施前提下,首分层0102102工作面开采前期和后期工作面上隅角以及回风瓦斯均会超限。研究结果为该矿厚煤层分层开采工作面回采期间瓦斯综合治理提供了理论依据。     

“三软”厚煤层瓦斯抽放方法研究

告成煤矿的主采二1煤层属典型“三软”厚煤层,回采工作面隅角和回风流中瓦斯体积分数超限的主要原因是采空区瓦斯涌出过多,采取顶板岩石钻孔的方法对采空区冒落带及冒落裂隙带的瓦斯进行抽放,降低了回采工作面隅角和回风流中的瓦斯体积分数,避免了采煤工作面隅角和回风流瓦斯体积分数超限,同时克服了工作面风速超限的问题.实践表明,顶板岩石钻孔抽放冒落带及冒落裂隙带的瓦斯,是解决“三软”厚煤层瓦斯超限的有效途径.     

Security in gas discharge while unsealing a closed stope

Given the problem of harmful gas discharge in unsealing coal mining faces, we numerically simulated the process of change of gas flows and movements. We have pointed out that, at the moment of unsealing a closed stope, the gas discharge is naturally divided into two parts, i.e., the discharge of gas in the working face and that in the goaf, because of the difference in the spatial medium. The absolute volume of gas discharged has a tendency to decrease from its initial peak value to a final stable value. The rate of decrease and the time needed to reach a stable discharge are related to the scale of the mining stope. The discharge of gas from the working face is closely related to the amount of air distributed in the air return way. The most important thing in un-sealing a stope is to have the initial peak volume of gas discharged well under control. A commonly used method in solving this problem is at first to use a small amount of air and then increasing it gradually. Our study shows that, by extracting gas from the upper corner, we can use a large volume of air at first in order to shorten considerably the discharge time and improve efficiency, thereby making mining activity safer.     

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 working 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 concluded 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.     

近距离突出煤层群瓦斯治理技术优化的研究

近距离突出煤层群工作面受上下邻近煤层卸压瓦斯的影响,致使回采工作面瓦斯涌出量大、工作面回风隅角及回风巷中的甲烷传感器频繁报警,瓦斯治理消耗大量的人力、物力和时间,严重制约了矿井的安全生产。通过对几种瓦斯治理方案进行分析论证,得出将整个煤层群作为一个治理单元,统筹考虑,将煤层厚度、瓦斯含量相对较小的弱突出煤层作为关键保护层,配合打钻进行立体式抽采,实现上下递进保护,最大限度地抽采邻近煤层的卸压瓦斯的方案。现场实践结果表明,保护层工作面在回采期间瓦斯抽采率高达90%以上,回风隅角瓦斯浓度降至0.6%以下,回风巷风流中瓦斯浓度降至0.2%以下,工作面月平均回采长度由原来的120 m提高至200 m。同时,从根本上解决了被保护层工作面回采期间瓦斯带来的安全威胁。     

高瓦斯综采工作面瓦斯涌出预测与立体防治技术研究

针对高瓦斯低渗透煤层工作面瓦斯抽采与灾害控制难题,以土城矿15311综采工作面为研究对象,首先,初步分析了工作面瓦斯涌出来源,运用分源预测法预测了其瓦斯涌出含量,接着针对性地在3#煤层运用了顺层钻孔、底抽巷穿层钻孔、高位钻场以及采空区埋管等多种抽采方法,并联合工作面配风提出了立体瓦斯防治技术。最后,通过施工底抽巷截留钻孔对底抽巷溢出瓦斯进行截留抽放,考察了抽采效果。结果表明:15311综采工作面瓦斯来源主要为3#煤层和下邻近层,瓦斯抽采总量为45.4 m3/min,瓦斯抽采率为85.33%,回风流中瓦斯浓度未超过1%,瓦斯抽采达标,有效地控制了工作面高瓦斯的涌出。     

Effect of suppressing dust by multi-direction whirling air curtain on fully mechanized mining face

A combined method of numerical simulation and field testing was adopted in this study in the interest of solving the problem of hard to control high concentrate dusts on a fully mechanized mining face.In addition,the dust suppression effect of a multi-direction whirling air curtain was studied in this paper.Under the influence of the wall attachment effect,the compressed air which blows out from the two-phase or three-phase radial outlets on the generator of the air curtain can form a multi-direction whirling air curtain,which can cover the whole roadway section of a fully mechanized mining face.The traditional method of controlling dust is a forcing system with exhaust overlap which has the major disadvantage of lacking a jet effect and consequently results in poor dust control.It is difficult to form the air flow field within the range of L_p5Sr^1/2.However,due to the effect of this novel system,the radial airflow can be turned into axial airflow allowing fresh air to flow through the length of the heading.The air flow field which is good at controlling dust diffusion can be formed 12.8 m from the heading face.Furthermore,the field measurement results show that before the application of a multi-direction whirling air curtain,the dust concentration is 348.6 mg/m³ and 271.4 mg/m³ respectively at the roadway cross-section measurement points which are 5 m and 10 m from the heading face.However,after the application of the multi-direction whirling air curtain,the dust concentration is only 61.2 mg/m³ and 14.8 mg/m³,respectively.Therefore,the dust control effect of a multi-direction whirling air curtain is obvious.     

Numerical simulation of gas migration into mining-induced fracture network in the goaf

Gas extraction practice has been proven for the clear majority of coal mines in China to be unfavorable using drill holes in the coal seam. Rather, mining-induced fractures in the goaf should be utilized for gas extraction. To study gas migration in mining-induced fractures, one mining face of 10 th Mine in Pingdingshan Coalmine Group in Henan, China, has been selected as the case study for this work. By establishing the mathematical model of gas migration under the influence of coal seam mining, discrete element software UDEC and Multiphysics software COMSOL are employed to model gas migration in mining-induced fractures above the goaf. The results show that as the working face advances, the goaf overburden gradually forms a mining-induced fracture network in the shape of a trapezoid, the size of which increases with the distance of coal face advance. Compared with gas migration in the overburden matrix, the gas flow in the fracture network due to mining is far greater. The largest mining-induced fracture is located at the upper end of the trapezoidal zone, which results in the largest gas flux in the network. When drilling for gas extraction in a mining-induced fracture field, the gas concentration is reduced in the whole region during the process of gas drainage, and the rate of gas concentration drops faster in the fractured zone. It is shown that with gas drainage, the gas flow velocity in the mininginduced fracture network is faster.     

Study of 3-D Numerical Simulation for Gas Transfer in the Goaf of the Coal Mining

In order to simulate field distribution rules,mathematical models for 3-D air flows and gas transfer in the goaf of the coal mining are established,based on theories of permeability and dynamic dispersion through porous media. A gas dispersion equation in a 3-D field is calculated by use of numerical method on a weighted upstream multi-element balance. Based on data of an example with a U type ventilation mode,surface charts of air pressure distribution and gas concentration are drawn by Graphtool software. Finally,a comparison between actually measured results in the model test and the numerical simulation results is made to proves the numerical implementation feasible.     

Review of coal and gas outburst in Australian underground coal mines

Outburst of coal and gas represents a significant risk to the health and safety of mine personnel working in development and longwall production face areas. There have been over 878 outburst events recorded in twenty-two Australian underground coal mines. Most outburst incidents have been associated with abnormal geological conditions.Details of Australian outburst incidents and mining experience in conditions where gas content was above current threshold levels are presented and discussed. Mining experience suggests that for gas content below 9.0 m³/t, mining in carbon dioxide (CO₂) rich seam gas conditions does not pose a greater risk of outburst than mining in CH₄ rich seam gas conditions. Mining experience also suggests that where no abnormal geological structures are present that mining in areas with gas content greater than the current accepted threshold levels can be undertaken with no discernible increase in outburst risk. The current approach to determining gas content threshold limits in Australian mines has been effective in preventing injury from outburst, however operational experience suggests the current method is overly conservative and in some cases the threshold limits are low to the point that they provide no significant reduction in outburst risk. Other factors that affect outburst risk, such as gas pressure, coal toughness and stress and geological structures are presently not incorporated into outburst threshold limits adopted in Australian mines. These factors and the development of an outburst risk index applicable to Australian underground coal mining conditions are the subject of ongoing research.     

Numerical simulation to determine the gas explosion risk in longwall goaf areas: A case study of Xutuan Colliery

Underground gassy longwall mining goafs may suffer potential gas explosions during the mining process because of the irregularity of gas emissions in the goaf and poor ventilation of the working face, which are risks difficult to control. In this work, the 3235 working face of the Xutuan Colliery in Suzhou City, China, was researched as a case study. The effects of air quantity and gas emission on the three-dimensional distribution of oxygen and methane concentration in the longwall goaf were studied. Based on the revised Coward’s triangle and linear coupling region formula, the coupled methane-oxygen explosive hazard zones (CEHZs) were drawn. Furthermore, a simple practical index was proposed to quantitatively determine the gas explosion risk in the longwall goaf. The results showed that the CEHZs mainly focus on the intake side where the risk of gas explosion is greatest. The CEHZ is reduced with increasing air quantity. Moreover, the higher the gas emission, the larger the CEHZ, which moves towards the intake side at low goaf heights and shifts to the deeper parts of the goaf at high heights. In addition, the risk of gas explosion is reduced as air quantities increase, but when gas emissions increase to a higher level (greater than 50 m³/min), the volume of the CEHZ does not decrease with the increase of air quantity, and the risk of gas explosion no longer shows a linear downward trend. This study is of significance as it seeks to reduce gas explosion accidents and improve mine production safety.