Laboratory results of a 3rd generation roof bolter canopy air curtain for respirable coal mine dust control

Testing was completed on an earlier roof bolter CAC that used slots to provide a perimeter airflow. NIOSH tested it due to its unique design that differed from canopies that provided uniform airflow. Based upon NIOSH recommendations from the earlier testing, a 3rd generation roof bolter CAC has been developed by J.H. Fletcher & Co. The changes to this CAC involve design modifications to the plenum outlets, using a single row of outlets on the perimeter and a different material for the plenum. This laboratory testing was a continuation of the original perimeter slotted CAC design. Using gravimetric and instantaneous sampling of respirable dust concentrations underneath and outside of the CAC. the laboratory testing was completed using three different blower fans that delivered differing airflows. The maximum plenum airflow velocities ranged from 2.34 to 3.64 m/s (460-716 fpm). Results showed plenum respirable dust concentrations ranging from 34.6% to 49.3% lower than respirable dust concentrations outside the plenum protection zone, thus showing an improvement in protection for the roof bolter operators.

Field study results of a 3rd generation roof bolter canopy air curtain for respirable coal mine dust control

A 3rd generation roof bolter canopy air curtain(CAC)has been developed and constructed by J.H.Fletcher&Co.,Inc.As with the previous generation of the CAC,this design uses the principle of providing uniform airflow across the canopy area as recommended by the National Institute for Occupational Safety and Health.The new modifications include a plenum that is constructed of a single flat aluminum plate,smaller-diameter airflow openings,and a single row of perimeter nozzles designed to prevent mine air contaminated by respirable dust from entering the CAC protection zone.Field testing was conducted on this new 3rd generation design showing reductions in coal mine respirable dust exposure for roof bolter operators.Dust control efficiencies for the CAC for the left bolter operator(intake side)ranged from approximately 26%–60%,while the efficiencies for the CAC for the right bolter operator(return side)ranged from 3%to 47%.

Application of new void detection algorithm for analysis of feed pressure and rotation pressure of roof bolters

Roof and rib instability is an important issue in underground mining. To optimize ground support design,enhance ground stability, and reduce the possibility of roof or rib failure with minimal use of artificial ground support, it is essential to have an accurate understanding of ground conditions. This includes the location of voids, cracks, and discontinuities, as well as information about the different strata in the immediate roof. This paper briefly introduces ongoing research on void detection by using the roof bolter feed and rotation pressure. The goal of this project is to improve the sensitivity of detection programs to locate smaller joints and reduce the number of false alarms. This paper presents a brief review of the testing procedures, data analysis, logic, and algorithms used for void detection. In addition, this paper discusses the results of preliminary laboratory tests and statistical analysis of the data from these two drilling parameters used for void detection.

A field study of a roof bolter canopy air curtain(2nd generation)for respirable coal mine dust control

A 2nd generation roof bolter canopy air curtain(CAC)design was tested by National Institute for Occupational Safety and Health(NIOSH)at a Midwestern underground coal mine.During the study,the roof bolter never operated downwind of the continuous miner.Using a combination of personal Data Rams(pDR)and gravimetric samplers,the dust control efficiency of the roof bolter CAC was ascertained.Performance evaluation was determined using three methods:(1)comparing roof bolter operator concentrations underneath the CAC to roof bolter concentrations outside the CAC,(2)comparing roof bolter operator concentrations underneath the CAC to the concentrations at the rear of the bolter,and finally,(3)using the gravimetric data directly underneath the CAC to correct roof bolter operator concentrations underneath the CAC and comparing them to the concentrations at the rear of the bolter.Method 1 dust control efficiencies ranged from 53.9%to 60.4%.Method 2 efficiencies ranged from 150.5%to 52.2%,and Method 3 efficiencies ranged from 40.7%to 91%.Reasons for negative and low dust control efficiencies are provided in this paper and include:incorrect sampling locations,large distance between CAC and operator,and contamination of intake air from line curtain.Low dust concentrations encountered during the testing made it difficult to discern whether differences in concentrations were due to the CAC or due to variances inherent in experimental dust measurement.However,the analyses,especially the Method 3 analysis,show that the CAC can be an effective dust control device.

Rock characterization while drilling and application of roof bolter drilling data for evaluation of ground conditions

Despite recent advances in mine health and safety, roof collapse and instabilities are still the leading causes of injury and fatality in underground mining operations. Improving safety and optimum design of ground support requires good and reliable ground characterization. While many geophysical methods have been developed for ground characterizations, their accuracy is insufficient for customized ground support design of underground workings. The actual measurements on the samples of the roof and wall strata from the exploration boring are reliable but the related holes are far apart, thus unsuitable for design purposes. The best source of information could be the geological back mapping of the roof and walls, but this is disruptive to mining operations, and provided information is only from rock surface.Interpretation of the data obtained from roof bolt drilling can offer a good and reliable source of information that can be used for ground characterization and ground support design and evaluations. This paper offers a brief review of the mine roof characterization methods, followed by introduction and discussion of the roof characterization methods by instrumented roof bolters. A brief overview of the results of the preliminary study and initial testing on an instrumented drill and summary of the suggested improvements are also discussed.

Development of a roof bolter drilling control process to reduce the generation of respirable dust

The drilling operation in the roof bolting process,especially in hard rock,generates excessive respirable coal and quartz dusts,which could expose the roof bolting operator to continued health risks.Previous research has shown that the amount of respirable dust produced is dependent on the main drilling parameters,specifically the drilling rotational and penetration rate.In this paper,a roof bolter drilling control process was proposed to reduce the generation of respirable dust.Based on the analysis of laboratory drilling test results,a rational drilling control process(adjusting rotational and penetration rates)to achieve the optimal drilling parameter for different rock types was proposed.In this process,the ratio between specific energy and rock uniaxial compressive strength was used as the index to determine the optimal operation point.The recommended drilling operation range for the rock type used in the experiment was provided,and the reduction in respirable dust generation was demonstrated.By following this control process,the drilling efficiency can be monitored in real time,so the system can stay in a relatively high-energy efficiency with less respirable dust production from the drilling source.This algorithm is targeted to be incorporated into the current roof bolter drilling control system for drilling automation so that a safe and productive drilling operation can be conducted in a healthy working environment.

“三软”厚煤层回采巷道掘锚一体机工艺优化及应用

“三软”厚煤层回采巷道围岩整体强度低,且岩层结构组合普遍变化较大,造成掘进工作面悬露顶板稳定性差异明显,部分顶板稳定性较差区域无法直接采用掘锚一体机及配套施工工艺,造成掘进工作面频繁停工,整体掘进效率下降。针对此类问题,以沙吉海煤矿“三软”厚煤层回采巷道为工程背景,采用现场调研、理论分析、数值模拟等综合研究方法,阐明了掘进工作面悬露顶板漏冒、掘锚一体机陷入底板或跑偏、煤壁片帮是制约掘锚一体机在“三软”厚煤层回采巷道中应用的关键制约因素;考虑悬露顶板厚度、扰动影响系数、顶板各岩层强度及各岩层完整性等参量的影响,建立和推导了掘进工作面悬露顶板极限跨距计算公式;形成了以掘进工作面悬露顶板极限跨距计算为主导的巷道围岩稳定性分级方法,将“三软”厚煤层回采巷道围岩划分为极稳定、稳定、中等稳定、不稳定、极不稳定5个级别;提出了不同稳定性级别围岩条件下掘锚一体机装备及施工工艺分类优化方案,并从截割滚筒位态调整、底板接地处理、巷帮作业平台增设等方面给出了困难作业环境下掘锚一体机应用对策。研究成果在沙吉海煤矿B1003W05工作面巷道进行了工程应用,其分类优化方案可有效保障掘锚一体机在“三软”厚煤层中的正常运行,相比邻近巷道采用悬臂式掘进机综掘工艺,掘进速度提升了1.0~1.8倍。

矿用自动液压锚杆钻机可靠性分配研究

针对自动液压锚杆钻机可靠性数据缺乏、结构复杂、工作环境恶劣的问题,优选了代数分配法作为其可靠性分配方法。通过结构功能分析,将钻机划分为8个组元并建立了可靠性分析模型。依据MT/T 688-1997《煤矿用锚杆钻机通用技术条件》计算了钻机故障率。运用代数分配法完成了钻机可靠性分配,研究结果表明控制系统等4个组元为薄弱环节。从提升关键部件可靠性和钻机加载试验两方面提出了钻机可靠性提升建议,对于自动液压锚杆钻机研发具有参考价值。

新型泵控液压锚杆钻机的能耗分析与高精度控制

现有的阀控锚杆钻机系统存在严重的节流与溢流损失,导致整机效率低下,为解决这一问题,提出了一种新型闭式泵控锚杆钻机系统。通过理论分析与联合仿真结合的方法,首先,对比研究了新型锚杆钻机与阀控锚杆钻机的能耗特点;其次,设计了一种基于压力反馈的自动调速方法;最后,针对泵控系统非线性严重、控制精度低的缺陷,设计了模糊自适应PID来对推进油缸进行闭环位置控制。结果表明,与传统的阀控锚杆钻机相比,新系统的动力源功率显著降低、整机效率获得了大幅度提高,节能效果显著;回转马达可依据压力的变化实现自动调速,误差不到1%;与PID控制相比,采用所设计的模糊PID,稳态时,可使钻机的定位误差减小70%以上。

大采高掘锚一体机升降操作平台的设计及应用

结合大采高煤巷锚杆支护现状,设计了一种机载升降操作平台,解决大采高断面锚杆支护难的问题,减轻工人劳动强度。现场使用表明,该升降操作平台极大提高了锚杆支护效率,具有一定的推广价值。

EJM270/4-2(E)掘锚一体机电机智能保护装置设计

为提升EJM270/4-2(E)掘锚一体机在斜沟煤矿的作业效率,设计了适合该机型的电机智能保护装置。重点分析了以DSP、ARM双处理器为核心的保护装置的硬件、软件设计方案并完成了试验分析。分析结果表明:设计的掘锚一体机电机智能保护装置满足设计要求,能够实时、准确地触发保护动作,为掘锚一体机高效、安全、稳定运行奠定了基础。

煤巷锚杆支护施工装备现状及发展趋势

锚杆支护施工装备是煤巷锚杆支护成套技术的重要组成部分,直接影响锚杆支护速度与质量。经过长期发展,我国煤矿开发出多种形式的锚杆支护施工装备,包括单体锚杆钻机、锚杆钻车、掘锚机、掘锚一体机、锚杆转载机及跨骑式锚杆钻车等。系统分析了6类锚杆支护施工装备的发展历程、技术性能、技术参数、适用条件及最新进展。单体锚杆钻机轻便、灵活、技术成熟,形成系列化产品,得到广泛应用。机载锚杆钻臂可集成于不同平台,形成各种集成化施工装备:锚杆钻车形成了从两臂到九臂的多种机型,可紧跟掘进装备、与掘进装备交替作业,多臂协同、多臂平行作业完成锚杆支护施工;将机载锚杆钻臂配置于悬臂式掘进机上,开发出多种形式的掘锚机,实现了掘进与锚杆支护施工2个功能;掘锚一体机实现了国产化,研制出支护平台前移的掘锚一体机、护盾式掘锚一体机及钻锚一体化掘锚一体机;研制出从两臂到七臂的锚杆转载机、十臂跨骑式锚杆钻车,实现了锚杆支护与掘进、运输分区作业。介绍了钻锚一体化锚杆支护技术与装备,包括钻锚一体化锚杆、泵注锚固剂、钻锚一体化钻臂、钻箱、锚杆仓、锚固剂泵注系统及智能控制系统,将传统锚杆施工6道工序简化为1道连续工序,实现了“一键打锚杆”自动化作业,显著提高了锚杆支护速度和自动化程度。指出了煤巷锚杆支护施工装备发展趋势:数智化锚杆钻臂;锚杆钻臂定位、位姿自主调节及多钻臂协同控制技术;锚杆(索)结构与材料优化、锚注材料升级及施工设备完善;环境动态感知及随掘围岩稳定性判别;锚杆支护施工装备故障诊断技术;巷道围岩变形与支护体受力在线监测;建立大数据平台,实现锚杆支护自动化、智能化。

锚杆钻车串并联冗余机械臂的运动学研究

锚杆钻车机械臂的自动定位打孔可进一步提高巷道支护工艺的自动化作业程度。本文针对某锚杆钻车的串并联混合8自由度冗余机械臂的逆运动学问题展开研究。该机械臂有两大特点,一是串并联混合机构,臂在整体上为串联开链机构,但其大臂存在一个四边形的并联结构;二是冗余自由度,导致逆运动学存在无穷解。针对前者,为便于使用D-H法建立运动学模型,推导了并联结构的运动表达式,将其用一个等效的串联结构来替代。针对后者,详细分析了机械臂的结构与实际工况,设置了逆解的3个条件:1)为保证推进器获得最大打孔行程,设置定位油缸为最大伸长量;2)根据不同类型锚杆孔设定大臂四边形形状,可实现姿态补偿;3)优先使用中臂进行位置补偿,以尽量减少大臂的运动。在以上约束下提出基于位姿分离的逆运动学求解方案,得到的逆解结果充分利用了机械臂的设计特点,且兼顾人工操作过程的直观、方便性。为验证算法,针对一个矩形巷道断面的锚杆孔设计,通过计算机进行了逆解计算,计算精度与速度均有满意的结果;将算法部署到PLC上,在模拟巷道自动打孔试验,结果满足工程要求。

钻锚一体化锚杆钻机控制系统设计与研究

针对钻锚一体化锚杆的施工工艺,提出了一种钻锚一体化锚杆钻机控制系统,设计并阐述了系统总体架构、系统硬件和软件设计方案。针对锚杆钻机外置传感器故障率高的问题,提出基于压力阈值判断钻机工作状态,控制系统仅采用液压压力传感器即可实现锚杆自动化施工。针对片状钻头易磨损和断裂的问题,提出钻机进给恒压控制方法,通过压力值滤波算法、目标值滤波算法及PID算法实现进给压力的稳定恒压控制。煤矿现场试验结果表明,采用钻机恒压控制方法时钻机进给压力波动最小,进给压力方差为0.18,平均值3.3 MPa,能保证基于压力阈值判断钻机工作状态的可行性。钻锚一体化锚杆钻机控制系统可实现锚杆钻机的自动化运行,具有较高的可靠性和稳定性,为掘进工作面智能支护技术提供有效的技术支撑。

新型矿用机载锚杆钻机全液压自动控制系统的设计

针对某进口四臂锚杆钻车钻机液压控制回路复杂、液压阀规格繁杂、故障排查难度大以及阀块流道复杂、体积笨重、加工设计难度大等问题,设计了新型钻机全液压自动控制系统。控制系统以负载传感多路阀作为主控制阀,通过特定设计的控制模块、进给模块、定位模块等液压逻辑控制回路,实现了锚护作业一个工作流程内钻箱旋转、进给、返回、水阀启闭自动控制。该控制系统有助于提高机载锚钻装置的自动化水平,降低工人劳动强度,提高锚杆支护效率,同时具有阀组体积重量小、功能划分清晰、无需电气防爆元件、故障易排查等优点。

液压锚杆钻机转速的无模型自适应控制

大多数液压锚杆钻机转速控制主要依赖于工程技术人员的现场经验,在人工钻进不同岩层时,多采用固定转速,导致作业效率低、设备故障率高。本研究提出了钻机转速的无模型自适应控制算法。该算法仅利用系统的I/O数据,而不需要系统的精确机理模型信息,其可适应钻孔过程中岩层的变化以及快速性的要求。文中分别对无外界干扰和存在外部扰动两种情况进行仿真验证,结果表明:本研究所提出的无模型自适应控制方法能够实现对期望转速的快速跟踪,相比于PID控制,具有更好的控制性能和较强的鲁棒性。

基于变权模糊理论的掘锚一体机组掘进适用性数学评价

掘锚一体机组具有掘锚钻同体、全宽截割、掘锚平行、锚运同步、多锚平衡等显著技术优势,具备远程操控和地面集中控制,满足日进百米要求,已成为“十四五”时期煤炭行业实现中高级智能化高效掘进、缓解采掘接续的关键装备群。然而,国内近5 a、数十个矿区的应用表明,掘锚一体机组对掘进煤层地质条件有一定的适用性要求,若条件不匹配,其掘进效率、经济性方面相比传统悬臂式掘进机的提升并不明显。因此,针对掘锚一体机组适用性程度的评估是亟需工作,提出了将层次分析、模糊数学以及变权理论等数学原理相结合的方法,基于数十个矿区的应用实践经验建立了掘锚一体机组地质适用性程度评价的数学评价指标框架体系,包括煤层地质赋存特征、掘进巷道特征、地质构造特征、安全影响要素等4个二级指标,并划分确定了21个三级子指标以及这些子指标所对应的特征取值条件,这些取值条件严格遵循并符合表征适用性程度的4种评语子集(“差、中等、较好、好”)要求,然后通过层次分析法得出了子指标的判断矩阵与常权权重,采用模糊数学隶属函数建立了子指标的模糊关系矩阵,引入对数函数与Hadamard矩阵原理实现了常权权重的变权(调低“好”因子权重、调高“差”因子权重,使其更符合实际),最后经过两级综合评判得出最终评价结果值并根据最大隶属原则即选择其最大值所属的评语子集,从而得出其适用性程度。至此,将创建完成的完整的变权模糊层次综合评价模型,引入已经应用掘锚一体机组的3个不同条件的矿井特征值参数(简称为HB矿、HL矿、XZ矿),进行评价模型的准确性验证。结果表明,本研究建立的变权模糊层次综合评价模型,在3个矿条件差异较大的情况下得出的评价结果能很好揭示出各个矿井的指标在不同评语集下的表现与隶属程度,与现场实践的效果吻合,综合评价模型中的权重赋值、矩阵构成、变权方法等计算模型的构建贴近现场实际,变权模糊层次综合评价模型量化表征了掘锚一体机组对某矿井煤层地质条件适用性程度,有助于矿井提前做出决策。

锚杆钻车机载临时支护的优化设计

针对锚杆钻车对破碎顶板的临时支护能力弱的问题,开发了一种复合四连杆形式的临时支护结构,其显著特点是上连杆在升降过程中近似与顶板保持平行,且前后方向移动距离短。为了保证新型临时支护机构升降过程中的上连杆与水平面的夹角波动范围最小,以复合四连杆机构上的3个关键铰点坐标为设计变量,满足空间排布及机构升降行程为约束条件,上连杆与水平面夹角最小为优化目标,采用多体动力学分析软件进行优化设计。优化结果表明,优化目标在整个升降过程中变化范围降低了77.6%。根据优化结果,建立三维模型进行干涉检查及原理验证,确认了结果的可行性。

基于双屏视觉标靶的掘锚机机身位姿测量技术

针对掘锚机在煤矿巷道掘进过程中难以实现机身位姿的实时精确测量,进而导致难以实现定向掘进的问题,提出一种基于双屏视觉标靶的掘锚机导向方法。由2块竖直安装的感光成像屏组成双屏视觉标靶靶面,巷道中的激光器发射指示激光并在前、后靶面上呈现光斑,利用视觉测量、高精度栅格标定等技术,建立光斑质心的图像坐标与三维空间坐标的映射关系,以形成坐标点云数据;再根据栅格索引、坐标变换、欧拉角解算等原理,结合标靶底部的双轴倾角仪来获得掘锚机机身的实时位姿,并解算出机身关键点相对于巷道设计轴线的横向/纵向偏差,为掘进过程中的偏差纠正提供数据支撑。通过构建数学模型对系统脱靶问题进行了分析,同时搭建实验平台验证了该导向方法的有效性。实验结果表明:该方法能够实现机身六自由度空间位姿的精确测量;在9 m测试距离下偏航角重复性测量精度优于0.01º、偏航角绝对测量误差小于0.05º;在15~40 m测量范围内,用全站仪与矿用激光器设置计划线时机身关键点横向/纵向偏差测量误差分别小于5、15 mm。基于该方法研发的导向系统已成功应用于煤矿井下巷道掘进中,满足了巷道施工与掘锚机机身定位的精度要求。该导向方法的误差特性与测试距离无关,且该方法中涉及的所有光学测量功能均在标靶内部实现,可有效屏蔽井下复杂环境对测量功能的影响,大幅提升了现场应用时的抗粉尘干扰能力。

煤矿履带式锚杆机行驶稳定性分析与优化

针对煤矿井下某履带式锚杆机由于重心失衡,导致锚杆机在行驶过程中经常发生“栽头”现象,建立锚杆机在井下纵向、横向坡道上失稳状态的几何模型,分析锚杆机在纵向、横向坡道的行驶稳定性,得知锚杆机不满足稳定性准则要求。研究整机结构,优化设计锚杆机除尘系统及除尘部件的布置,从而优化了锚杆机的行驶稳定性。优化后的设备在神华煤炭集团神东公司哈拉沟煤矿进行了工业性试验,试验结果证明设备可以稳定行驶。