Numerical study on DPM dispersion and distribution in an underground development face based on dynamic mesh

In 2012, the International Agency for Research on Cancer(IARC) classified diesel particulate matter(DPM)as a carcinogen to human. With the increased usage of diesel equipment in underground mines, miners have a high risk of over-exposure to DPM, which has drawn many concerns from the public. This study used computational fluid dynamics(CFD) to analyse the DPM dispersion and concentration distribution characteristics in an underground development face based on an onsite experiment. The DPM emitted from a moving loader under a forcing auxiliary ventilation system was simulated. The motion of the load-haul-dump(LHD) in the tunnel was represented by a dynamic mesh method. The species transport approach was applied to study the DPM behaviours. High DPM concentration zones were then identified based on the simulation results. The results could provide guidelines for work practices and be helpful to an optimum auxiliary ventilation design to reduce underground miner exposure.     

DPM simulation in an underground entry: Comparison between particle and species models

The diesel particulate matter(DPM) emission from diesel powered equipment in underground mines can cause health hazards including cancer to the miners. The understanding of the DPM propagation pattern under realistic mining condition is required for selecting proper DPM control strategies and to improve working practices in underground mines. In this paper, three dimensional simulations of DPM emission from the exhaust tail pipe of a load-haul-dump(LHD) vehicle and its subsequent distribution inside an isolated zone in the typical underground mine are carried out using two different solution models available in Ansys Fluent. The incoming fresh air into the isolated zone is treated as a continuous phase and DPM is treated either as a continuous phase(gas) or as a secondary discrete phase(particle). Species transport model is used when DPM is treated as gas and discrete phase model is used when DPM is assumed to behave like a particle. The distributions of DPM concentration inside the isolated zone obtained from each method are presented and compared. From the comparison results, an accurate and economical solution technique for DPM evaluation can be selected.     

近距离保护层开采采场下行通风瓦斯涌出及分布规律

平煤集团四矿在开采过程中工作面φ（CH4）频繁超限,影响了工作面正常安全生产．通过;理论分析,阐述了采空区内风流流动状况和采用不同通风方式时采空区的瓦斯涌出规律．结合现场实验,探讨了工作面采用下行风时采空区的瓦斯涌出和分布规律．在此基础上,提出了用下行风解决工作面瓦斯超限问题．结果表明,在采用下行通风后,采空区绝对瓦斯涌出量为上行风时的80％,工作面φ（CH4）下降了75％,瓦斯不再超限．     

A review of the health effects and exposure-responsible relationship of diesel particulate matter for underground mines

The increasing use of diesel-powered equipment in confined spaces(underground mines) has the potential to over expose underground miners under the threat of diesel particulate matter(DPM). Miners in underground mines can be exposed to DPM concentrations far more than works in other industries. A great number of animal and epidemiological studies have shown that both short-term and long-term DPM exposure have adverse health effect. Based on reviews of related studies, especially some recent evidence, this paper investigated the long and short-term health effects based on animal studies and epidemiological studies. The exposure-response relationship studies were also explored and compared to the current DPM regulation or standards in some countries. This paper found that the DPM health effect studies specifically for miners are not sufficient to draw solid conclusions, and a recommendation limit of DPM concentration can be put in place for better protection of miners from DPM health risk. Current animal studies lack the use of species that have similar lung functions as human for understanding the cancer mode of action in human. And finally, the DPM health hazard will continue to be a challenging topic before the mode of action and reliable exposure-response relationship are established.     

Application of open-pit and underground mining technology for residual coal of end slopes

Given the conditions of residual coal from the boundary of a flat dipping open-pit mine,which uses strip areas mining and inner dumping with slope-covering,we propose an open-pit and underground integrated mining technology for residual coal of end slopes.In the proposal a conveyance road and ventilation conveyance near the slope are built,corresponding to the pit mining area and the surface coal mine dump,as well as an interval haulage tunnel and air-inlet tunnel.The outcome shows that such mining method may reduce the effect to slope stability from underground mining,it does not affect the dumping advance and has a high recovery rate of residual coal resources.The working face is timbered by single hydraulic props,transported by a scraper conveyor and supported by coal walls.This method of mining is one of layered top coal caving,with high resource recovery,low production cost where positive economic benefit can be realized.     

复式楔形掏槽在马路坪矿切割上山中的应用

为了改善贵州开磷集团马路坪矿地下切割上山的掘进效果,为矿房矿石回采创造良好的自由面和岩石碎胀空间,进而提高切割上山掘进的效率和整个矿房的安全高效回采效率,通过分析独头工作面切割上山不同掏槽方式的作用机理,结合马路坪矿的工程地质和实际生产概况,在以往切割拉槽爆破技术的基础上进行工艺改进,通过对比分析提出了二级复式楔形掏槽技术方法,并在马路坪矿中磷640分层3#底柱北四矿房进行了现场爆破试验.结果证明,该复式楔形掏槽可以提高掏槽爆破中槽腔形成效果,掏槽体积更大,槽腔碎石初始动能大,同时改善了切割上山工作面的安全工作条件,为切割上山掘进工艺改进提供了新的思路.     

用瞬变电磁法探查综放工作面顶板水体的研究

随着机械化综采设备在煤炭开采中的普及,对煤层顶板管理要求愈来愈高,其中煤层顶板水害体的发育将影响综采设备充分发挥效能,甚至会威胁工作面安全回采．提前查明煤层顶板水害体发育位置,为在井下布置探放水钻孔提供依据,是目前矿井地球物理勘探亟待解决的问题．基于地面瞬变电磁法理论及应用技术,根据井下实际应用环境,研究出采用非接触式、多匝数的正方形重叠回线（边长2m左右）装置探测工作面顶板水害体发育位置．依据瞬变电磁场”烟圈效应”理论和物理模拟相似准则,推导出全空间瞬变电磁法视电阻率计算数学模型,并对矿井瞬变电磁探测综放工作面顶板水害技术进行了研究．采用矿井瞬变电磁技术查明综放工作面顶板水害体发育位置,通过井下疏放水钻孔和工作面回采资料验证,该方法探测综放工作面顶板水害体发育的空间位置不仅行之有效,而且明显优越于其它矿井物探方法．     

孤岛煤柱综采工作面旋转开采关键技术

在分析综采工作面旋转式开采现状基础上，结合庞庄煤矿2443和-520西二煤柱开采实际，进行了综采旋转开采回收孤岛煤柱工艺方式、矿压显现规律、旋转区巷道布置和支护技术等方面关键技术研究，在实际生产中取得了较好的技术经济效果，可为在复杂条件下综采开采提供参考。     

CO emission in the air return corner of the working face in shallow burial mining areas

In shallow burial mining areas, abnormal CO emission and the spontaneous combustion of coal are great threats to safety production at a fully-mechanised working face. In order to prevent the CO concentration in the air return corner from exceeding the critical limit, the paper studied the CO emission regularity and characteristics through theoretical analysis, experimental research and field observation. The results show that the main sources of CO emission were the spontaneous combustion of coal in the goaf and the exhaust emissions coming from underground motorised vehicles. The effect factors of CO emission were also investigated, such as seasonal climate changes, the advancing distance and advancing speed of the working face, the number of underground motorised vehicles and some other factors. In addition to these basic analyses, the influence mechanism of each influence factor was also summarised theoretically. Finally, this study researched the distribution and change law of CO concentration in the fully-mechanised working face in two aspects: controlling the change of monitoring points and time respectively. The research results provide a theoretical basis for preventing the CO concentration from exceeding the critical limit in the air return corner and reducing the possibility of spontaneous combustion of coal. Additionally, the results also provide important theoretical and practical guidelines for protecting miners’ health in modern mines featuring high production and high efficiency all over the world.     

工作面复杂构造坑透及反射槽波透明化探测研究

煤矿井下工作面内部发育的复杂地质构造是威胁安全回采的重要因素,为保证工作面安全回采,提高探测精度,达到透明化探测目的,采用坑透和反射槽波两种物探手段相结合对工作面进行了探测研究.首先讨论了坑透和反射槽波的相关理论,分析了电磁波收敛成像算法和弹性波偏移成像算法,研究了坑透场强衰减规律和衰减系数.然后,对反射槽波探测数据进...     

Numerical investigation of the effectiveness of radon control measures in cave mines

Ventilation is one of the radon control measures in an underground working environment. However, the dynamics related to the cave mining methods particularly in block/panel cave mines, complicate the design of effective ventilation system, and implementation. Events such as hang ups(in the drawbells),leakage from old workings, and changes in cave porosity lead to differing response of an existing ventilation designs. However, it is difficult to investigate these conditions at the mine or with a laboratory scale study. Therefore, this study develops a discrete model to investigate the impact of different radon control measures in cave mines using computational fluid dynamics techniques. We considered two ventilation conditions for a fully developed cave: with and without the undercut ventilation. For each of the two conditions, we studied four parameters: airflow distribution through the production drifts, radon distribution through the production drifts, the effect of increasing airflow on radon concentration, and the effect of a cave top negative pressure on radon distribution. The results show that: the undercut ventilation significantly increases the radon concentration in the production drift; the growth of radon concentration through the production drift is nonlinear(oscillating pattern); maintaining a negative pressure on top of the cave is more effective at mitigating radon exposure, when the undercut ventilation is active;and increase in air volume flow rate decreases radon concentration in most regions, however, there might be regions with significant radon accumulation due to pressure variation across the drifts. These findings provide vital information for designing an effective ventilation system and for proactive implementation of radon control measures in cave mines.     

Stability of coal pillar in gob-side entry driving under unstable overlying strata and its coupling support control technique

Considering the situation that it is difficult to control the stability of narrow coal pillar in gob-side entry driving under unstable overlying strata, the finite difference numerical simulation method was adopted to analyze the inner stress distribution and its evolution regularity, as well as the deformation characteristics of narrow coal pillar in gob-side entry driving, in the whole process from entry driving of last working face to the present working face mining. A new method of narrow coal pillar control based on the triune coupling support technique (TCST), which includes that high-strength prestressed thread steel bolt is used to strain the coal on the goaf side, and that short bolt to control the integrity of global displacement zone in coal pillar on the entry side, and that long grouting cable to fix anchor point to constrain the bed separation between global displacement zone and fixed zone, is thereby generated and applied to the field production. The result indicates that after entry excavating along the gob under unstable overlying strata, the supporting structure left on the gob side of narrow coal pillar is basically invalid to maintain the coal-pillar stability, and the large deformation of the pillar on the gob side is evident. Except for the significant dynamic pressure appearing in the coal mining of last working face and overlying strata stabilizing process, the stress variation inside the coal pillar in other stages are rather steady, however, the stress expansion is obvious and the coal pillar continues to deform. Once the gob-side entry driving is completed, a global displacement zone on the entry side appears in the shallow part of the pillar, whereas, a relatively steady fixed zone staying almost still in gob-side entry driving and present working face mining is found in the deep part of the pillar. The application of TCST can not only avoid the failure of pillar supporting structure, but exert the supporting capacity of the bolting structure left in the pillar of last sublevel entry, thus to jointly maintain the stability of coal pillar.     

岩体界面效应的物理模拟

根据相似材料模拟试验结果，分析了地下开采后岩体移动的界面效应，研究了界面滑移量与工作面位置、采动程度等的关系，获得了界面滑移函数，为岩体内部移动计算提供了理论基础。     

基于脉动通风原理的局部通风机控制的实现

本文介绍了KJK1- 60/660型矿用局部通风机节能型瓦斯自动排放装置,着重阐述了脉动通风原理以及风机控制所采用的ON- OFF模式及其实现方法,并论述了该装置的软硬件结构及在瓦斯排放和节能方面的效果.     

矿山进风井风温变化规律探析

矿井井下气温高低是影响矿井通风方案选择的重要因素之一。通过对矿山通风系统进风井井筒中气温预测模型和预测数值的分析，得出了在一定的围岩热物理条件下，进风井井筒气温随井口气温、风量、井深等因素变化的基本规律。     

Influence of gas ventilation pressure on the stability of airways airflow

Coal mine ventilation is an extremely complicated system that can be affected by many factors. Gas ventilation pressure is one of important factors that can disturb the stabilization of airflow in airways.The formation and characteristics of gas ventilation pressure were further elaborated, and numerical simulations were conducted to verify the role of gas ventilation pressure in the stability of airway airflow.Then a case study of airflow stagnation accident that occurred in the Tangshan Coal Mine was performed.The results show that under the condition of upward ventilation, the direction of gas ventilation pressure in the branch is the same to that of the main fan, airflow of the branches beside the branch may be reversed. The greater the gas ventilation pressure is, the more obvious the reversion is. Moreover, reversion sequence of paralleled branches is related to the airflow velocity and length of the branch. Under the condition of downward ventilation, the airflow in the branch filled with gas may be reversed. Methane in downward ventilation is hard to discharge; therefore, accumulation in downward ventilation is more harmful than that in upward ventilation.     

南温河钨矿区域受控循环通风新技术理论与应用研究

通过对南温河钨矿一采选厂1232m中段南翼通风能力不足、有效风量率低、采空区漏风、局扇布局混乱等问题展开分析,提出了受控循环通风新技术应用的构想,在优化计算了循环系统循环率、循环风量、净化效率等参数的基础上,得出采用受控循环通风系统,可使系统区域有效进风从49.45m3／s增加为84.66m3／s。对比采用传统通风系统,将用风地点的风量由49.45m3／s增加到84.66m3／s所耗功率是原系统的5.021倍,而采用受控循环通风系统时,所耗功率只是原来的1.845倍,相对于一个生产能力为每年450kt的区域而言,应用受控循环通风技术对矿山降低通风能耗具有重要的应用意义,可有望取得较好的经济效益。     

Tests and error analysis of a self-positioning shearer operating at a manless working face

Self-positioning of a shearer is the key technology for mining with a man-less working face. In an underground coal mine all radio navigation; satellite positioning or celestial navigation methods have their limitations. We analyzed an inertial navigation system intended to guide the movement a shearer and designed a self-positioning device for the shearer. Simulation tests were also performed on the system. We analyzed the errors observed in these tests to show that the main reason for the low precision of the self-positioning system is accumulated error in the inertial sensor. A Kalman filtering algorithm used in combination with the shearer motion model effectively reduces the measurement errors of the self-positioning system by compensating for gyroscopic drift. Finally, we built an error compensation model to reduce accumulated errors using continuous correction to provide self-positioning of the shearer within a certain range of accuracy.     

Floor stress evolution laws and its effect on stability of floor roadway

According to the distribution of abutment stress in a stope, this research established the mechanical model of mining abutment pressure transmission in floor base on the theory of semi-infinite plate body in elasticity. This study takes the 762 working face of Haizi Coal Mine as a case in point, and analyzed the dynamic evolution law of seam floor stress during the mining process. With an organic combination of the mining floor stress and surrounding rock stress, the study obtained the change laws of the maximum principle stress and the minimum one for the floor roadway surrounding rock when mining the upper working face. Considering the non-constant pressure force state and the cracks revolution mechanisms of floor roadway surrounding rock, the research built the mechanical model of roadway stress. Simulation results verify the reliability of the above conclusions. Moreover, this model could provide the theoretical basis and technical support for controlling floor roadway surrounding rock.     

金刚煤矿综采支架工作阻力的确定

综采支架工作阻力的大小,直接决定着综采支架的架型和质量,关系到矿井的生产和安全,影响到矿井的经济效益和社会效益。运用国内外对支架阻力的计算方法,借助相似模拟试验,确定了金刚矿3115工作面综采支架工作阻力为2400 kN。现场使用效果表明：使用综合机械化开采经济效益和社会效益明显,不过在确定液压支架工作阻力时,应充分参考同一矿井与拟用综采工作面毗邻区采煤工作面的矿压观测结果,由此获得的工作阻力更加可靠合理,适当降低3115工作面综采支架工作阻力,仍可满足安全生产要求。