Failure mechanism and control technology of longwall coalface in large-cutting-height mining method

The stability control of longwall coalface is the key technology of large-cutting-height mining method.Therefore,a systematic study of the factors that affect coalface stability and its control technology is required in the development of large-cutting-height mining method in China. After the practical field observation and years of study,it was found that the more than 95% of failures in coalface are shear failure. The shear failure analysis model of coalface has been established,that can perform systematic study among factors such as mining height,coal mass strength,roof load,support resistance,and face flipper protecting plate horizontal force. Meanwhile,sensitivity analysis of factors influencing coalface stability showed that improving support capacity,cohesion of coal mass and decreasing roof load of coalface are the key to improve coalface stability. Numerical simulation of the factors affecting coalface stability has been performed using UDEC software and the results are consistent with the theoretical analysis. The coalface reinforcement technology of large-cutting-height mining method using the grouting combined with coir rope is presented. Laboratory tests have been carried out to verify its reinforcement effect and practical application has been implemented in several coal mines with good results.It has now become the main technology to reduce longwall coalface failure of large-cutting-height mining method.

Rational cutting height for large cutting height fully mechanized top-coal caving

Large cutting height fully mechanized top-coal caving is a new mining method that improves recovery ratio and single-pass production. It also allows safe and efficient mining. A rational cutting height is one key parameter of this technique. Numerical simulation and a granular-media model experiment were used to analyze the effect of cutting height on the rock pressure of a fully mechanized top-coal caving work face. The recovery ratio was also studied. As the cutting height increases the top-coal thickness is reduced. Changing the ratio of cutting to drawing height intensifies the face pressure and the top-coal shattering. A maximum cutting height exists under a given set of conditions due to issues with surrounding rock-mass control. An increase in cutting height makes the top-coal cave better and the recovery ratio when drawing top-coal is then improved. A method of adjusting the face rock pressure is presented. Changing the cutting to drawing height ratio is the technique used to control face rock pressure. The recovery ratio when cutting coal exceeds that when caving top-coal so the face recovery ratio may be improved by over sizing the cutting height and increasing the top-coal drawing ratio. An optimum ratio of cutting to drawing height exists that maximizes the face recovery ratio. A rational cutting height is determined by comprehensively considering the surrounding rock-mass control and the recovery ratio. At the same time increasing the cutting height can improve single pass mining during fully mechanized top-coal caving.

大采高综采工作面矿压显现及顶板活动特征研究

为了得到唐山某煤矿综采工作面的矿压显现及顶板活动特征,基于关键层理论、“悬臂梁-砌体梁”力学模型,通过现场观测、理论分析、数值模拟的方法对9煤层矿压显现特征、顶板结构、支架工作阻力开展了深入研究,建立了覆岩结构力学模型,得到了工作面支架工作阻力的合理计算式。研究结果表明:工作面来压步距和来压大小均有一定的规律性,呈现一大一小的周期来压现象,来压期间中部测区支架荷载最大,两边偏小;通过直接顶关键层判别方法,确定了第2层岩层和第7层岩层分别为亚关键层1和亚关键层2。亚关键层1破断后以“悬臂梁”结构形态垮落进入采空区,亚关键层2破断后形成了稳定的“砌体梁”结构,此时亚关键层1与亚关键层2共同组成了“悬臂梁-砌体梁”结构;第2层岩层和第7层岩层组成的双关键层结构的破断运移规律导致了工作面呈现一大一小的周期来压现象。当双关键层同步破断时,支架工作阻力为13 688 kN。

基于截割顶底板高度预测模型的采煤机自动调高技术

传统的煤层截割路径规划通过几何控制、规划计算等方式对采煤机滚筒高度进行预测,但存在预测的数据误差较大、无法适应地质条件变化的问题。针对上述问题,提出了一种基于截割顶底板高度预测模型的采煤机自动调高技术。首先,分析了影响截割顶底板高度的因素,指出影响顶底板高度的主要因素包括煤层的起伏变化数据、历史截割数据、刮板输送机的高程数据及人工操作记录,将上述4类数据融合处理,建立以长短期记忆(LSTM)模型和灰色马尔可夫模型为基础的截割顶底板高度预测模型,通过算法模型预测出截割顶底板的高度。然后,以截割顶底板的高度数据为基础,结合采煤机位姿和空间坐标,建立计算滚筒高度的几何模型,同时依据刮板输送机上窜下滑量及是否执行加减刀工艺等因素进行修正,最终将顶底板高度序列转换为滚筒高度序列,即将截割顶底板高度转换为采煤机滚筒的目标高度,由采煤机执行到目标高度,实现滚筒自动调高工业性试验结果表明:(1)在自动调高技术的控制下,顶滚筒和底滚筒的预测高度与实际高度偏差值有90%的数据量均在10 cm以内,滚筒的预测高度和实际高度具有明显的一致性。(2)与传统手动控制方式相比,中部截割一刀煤的人工干预调高次数由49次下降为21次,说明截割顶底板的高度预测模型和计算滚筒高度的几何模型是准确合理的,采煤机滚筒的自动调高技术是可行的。

基于工况触发的采煤机滚筒截割高度模板生成方法

针对采煤机在工作过程中易受不同工况条件的影响导致滚筒调高精度低的问题,提出了一种基于工况触发的采煤机滚筒截割高度模板生成方法。对采煤机历史传感器数据进行预处理和特征提取,选择影响滚筒高度调节的截割电动机电流、截割电动机温度、俯仰角、横滚角、牵引速度5维特征数据,构建用于生成滚筒截割高度模板的补偿回声状态网络(C−ESN)模型;建立工况触发机制,将采煤机传感器实时数据输入C−ESN模型,以测试误差为判断准则,识别当前采煤机的工况为正常区域、三角煤区域或异常工况;最后,C−ESN模型生成相应的滚筒截割高度模板。当三角煤区域和正常区域测试误差都大于阈值时,采用迁移学习方法对测试误差小的截割高度模板参数进行修正,以保证异常工况下截割高度模板的精度。基于现场采煤机实际数据的实验结果表明:左右滚筒截割高度模板与实际截割高度相比,在正常区域的最大误差分别为11.47,9.96 cm,在三角煤区域最大误差分别为12.91,7.94 cm,能够满足工程实际要求;与传统回声状态网络和径向基函数网络模型相比,C−ESN模型的精度在正常区域分别提升了54%和57%,在三角煤区域分别提升了10%和69%。

激光切割调高器微距测量传感器设计

该文针对现有的激光切割调高技术需求,提出一种基于电容器原理的非接触式微距测量方法,该方法是通过克拉泼振荡电路将激光切割喷嘴与工件之间形成的电容器电容信号调制转化为一定频率的高频正弦波信号,并基于电流反馈型的运算放大器和波形转化电路实现高精度、无失真、极低时滞的信号放大与波形转化。最后通过实验分析,该传感器满足信号输出稳定、重复性良好、分辨率高和量程合适等要求,达到激光切割调高技术需求的理想测距效果。

煤矿爆破切顶卸压沿空留巷开采技术应用

该文以某煤矿的回采工作面为例,探究爆破切顶卸压沿空留巷开采技术的应用策略。采用双向聚能爆破技术进行顶板预裂,通过合理设计切顶高度、切顶角度以及炮孔间距等关键参数,提高爆破预裂效果,保证巷道围岩的稳定性。在完成爆破后进行煤层开采,使用锚索支护和U型钢支护,提高巷内支护效果;使用工字钢和U型钢档矸支护,防止矸石对围岩的侧向冲击,为煤矿安全作业创造有利环境。

综采工作面切顶卸压沿空留巷技术应用

为解决护巷煤柱留设造成资源浪费及上覆采空区煤柱处应力集中的问题,余吾煤业研究应用切顶卸压沿空留巷技术,通过理论计算得出切顶钻孔高度、角度,采用聚能管定向爆破技术产生预裂面,同时对留巷段采用高强支护技术,工作面回采过后采空区侧顶板沿预裂面顺利切落。切顶卸压沿空留巷技术的成功应用,直接减少1条回采巷道的施工,减少护巷煤柱的留设,为类似条件下矿井的沿空留巷提供借鉴。

大采高综采工作面截割湍流风对煤尘侧向逸散的影响机制

大采高工作面内大尺寸的采煤机滚筒在截割煤体时产生更为明显的湍流风,使得工作面局部风速发生变化,粉尘颗粒向人行道区域发生横向扩散。为了明晰大采高工作面截割湍流风对粉尘质量浓度沿程分布的影响机制,针对三道沟85219工作面,运用数值模拟方法构建了风流-粉尘两相耦合数学模型,对工作面风流分布、粉尘运移、呼吸带高度粉尘质量浓度分布进行研究。结果表明;相较于仅系统通风作用下的流场,前后滚筒处及移架处在截割湍流风扰动下横向偏移分速度明显增大,在滚筒附近产生了横向偏移分速度约为-1.06 m/s的“风流偏移区”;在截割湍流风扰动下,前后滚筒处质量浓度超过151.85 mg/m^(3)的粉尘团向人行道区域发生横向逸散,在顺风割煤状态下前滚筒处截割湍流风对截割煤尘横向逸散的诱导能力高于后滚筒处,前滚筒附件人行道呼吸带区域粉尘质量浓度相较于仅系统通风状态下提升了64.77%;将模拟数据与现场实测数据进行比对,相对误差小于12.57%,模拟数据相对准确。基于此,提出一种采煤机含尘气流控尘装置,在现场进行应用并检测其防控尘效果,在工作面人员作业区域呼尘降尘效率超过78.31%,全尘降尘效率超过89.93%。

采煤机调高试验装置的设计

为了充分验证当前煤岩识别和采煤机自适应调高控制技术的应用效果,提出采用采煤机调高试验装置进行模拟试验的思路。在完成采煤机调高试验装置总体设计的基础上,重点对采煤机调高试验装置的截割系统和液压系统进行设计,完成了截割电机、减速装置以及调高油缸的设计,为完成采煤机调高试验装置的研发奠定扎实理论基础。

坚硬顶板工作面切顶卸压参数合理性研究

为研究坚硬顶板工作面切顶卸压参数的合理性,以姜家湾矿11#煤层工作面生产地质条件为研究对象,采用理论与数值模拟分析方法,给出并优化了切顶参数。研究结果为:基于工程条件,通过理论分析,得出切顶高度为11.4 m,切顶角度为1°~9°;结合理论计算,数值模拟得出在切顶角度为10°时的切顶卸压效果最佳;工作面切顶后,工作面顶板的位移相较于未切顶时的位移更大,该状态下的切顶效果较平稳,切顶后工作面应力下降了约20%,此时工作面应力集中范围扩大,并向深处延伸,采空区顶板对工作面挤压作用减小;进行了工程试验,布置了观测站,发现切顶后的顶底板移近量下降了约27%,锚杆受力下降了约24%,切顶后的围岩应力集中现象缓解。

Reconstructing the size of individual trees using log data from cut-to-length harvesters in Pinus radiata plantations: a case study in NSW, Australia

With their widespread utilization, cut-to-length harvesters have become a major source of ‘‘big data’’ for forest management as they constantly capture, and provide a daily flow of, information on log production and assortment over large operational areas. Harvester data afford the calculation of the total log length between the stump and the last cut but not the total height of trees. They also contain the length and end diameters of individual logs but not always the diameter at breast height overbark（DBHOB） of harvested stems largely because of time lapse, operating and processing issues and other system deficiencies. Even when DBHOB is extracted from harvester data, errors and/or bias of the machine measurements due to the variation in the stump height of harvested stems from that specified for the harvester head prior to harvesting and diameter measurement errors may need to be corrected. This study developed（1） a system of equations for estimating DBHOB of trees from diameter overbark（DOB） measured by a harvester head at any height up to 3 m above ground level and（2） an equation to predict the total height of harvested stems in P. radiata plantations from harvester data. To generate the data required for this purpose, cut-to-length simulations of more than 3000 trees with detailed taper measurements were carried out in the computer using the cutting patterns extracted from the harvester data and stump height survey data from clearfall operations. The equation predicted total tree height from DBHOB, total log length and the small end diameter of the top log. Prediction accuracy for total tree height was evaluated both globally over the entire data space and locally within partitioned subspaces through benchmarking statistics. These statistics were better than that of the conventional height-diameter equations for P. radiata found in the literature, even when they incorporated stand age and the average height and diameter of dominant trees in the stand as predictors. So this equation when used with harvester data would outperform the conventional equations in tree height prediction. Tree and stand reconstructions of the harvested forest is the necessary first step to provide the essential link of harvester data to conventional inventory, remote sensing imagery and Li DAR data. The equations developed in this study will provide such a linkage for the most effective combined use of harvester data in predicting the attributes of individual trees, stands and forests, and product recovery for the management and planning of P. radiata plantations in New South Wales, Australia.

Research on the memory cutting path of shearer based on genetic algorithm

In order to realize the memory cutting of a shearer, made use of the memorizedcutting path and acquisitioned cutting parameters, and realized the teaching and playbackof the cutting path.In order to optimize the memory cutting path of a shearer, took intoaccount the constraints of coal mining craft, coal quality and the adaption faculty of coalmining equipments.Genetic algorithm theory was used to optimize the memory cutting ofshearer and simulate with Matlab, and realized the most valuable mining recovery rate.The experimental results show that the optimization of the memory cutting path of ashearer based on the genetic algorithm is feasible and obtains the most valuable memorycutting path, improving the ability of shearer automatic cutting.

Effects of Anthropometry Variations on Physiological Parameters of Heart Rate, Oxygen Consumption, Aerobic Power While Performing Manual Operation at Fixed Vice Height

This study investigated the effect of fixed height standing-workstation on different people with diverse anthropometry dimensions. Measurements of some anthropometric and physiological parameters are carried out as bases for the calculation of body mass index (BMI) and the determination of the maximum heart rate (HRmax) and aerobic power (VO2max) of individual subject while performing manual cutting operation with hacksaw on fixed vice height of 940 mm. Twenty subjects (S1 to S20) parted 2 mm thick square-pipe of 25 mm × 25 mm. Each subject carried out cutting operation in 5 replicates and their physiological parameters during activities are measured to determine their expended energy (EE) and oxygen consumption rate (VO2). The results showed that subject S4 with BMI of 20.76 kg/m2 has maximum cutting rate of 5.33 stroke/s, while subject S8 with BMI of 23.39 kg/m2 has minimum cutting rate of 0.92 stroke/s. There was a statistically significant effect on the interaction between BMI, EE and Cutting rate, with F = 827.54, P = 0.000, R2 = 0.967 and S = 1.749 units. Subject S11 was discovered to have VO2 (28.54 l/min) and VO2max (24.36 ml/min/kg), with highest value of EE (2.94 kcal/min). Wear rates of 1.86 teeth/s and 9.55 teeth/s have the same energy cost (EE = 0.87 kcal/min) but different cutting time of 36.65 s (S18) and 10.89 s (S20) respectively. This could explain in-part that excess 25.76 s utilized in operation time by subject S18 is responsible for keeping approximately 7.7 teeth intact as regards tool management. EE and Tool Wear Rate in one-way analysis of variance, were statistically significant (F = 45.87, P = 0.000, R2 = 54.69% and S = 1.617 units) at 0.05 level.

刈割高度对美国高丹草生长动态及产量的影响研究

为了解不同刈割高度对高丹草生长动态及产量的影响,达到合理利用的效果,本研究设刈割高度分别为5、10、15、20和25 cm 5个处理,并进行了比较试验。结果表明,高丹草茎孽数、株高和叶面积指数随着刈割高度的增加而增加;高丹草叶龄、再生速度随着刈割高度的增加而下降;刈割高度为20 cm的处理,高丹草的各项指标表现较为均衡,有益于高丹草收获总鲜草的提高,产量最高为74.19 t/hm^(2),刈割高度25 cm收获的总鲜草产量最少,为55.86 t/hm^(2),两者相差18.33 t/hm^(2)。

钢筋砼烟囱拆除爆破切口高度优选及效果分析

为进一步研究复杂环境下垃圾焚烧厂100 m钢筋砼烟囱的最佳爆破切口高度,采用有限元软件ANSYS/LS-DYNA分别对爆破切口高度为1.5、2.0和2.5 m 3种工况进行数值模拟,对比分析烟囱爆破倒塌姿态与最大水平位移,结合该烟囱自身结构与现场环境,采用上半部57 m拆除爆破、下半部43m机械拆除的方式。结果表明,爆破最优切口高度为2.0 m;通过对烟囱倒塌和解体过程图像分析可知,烟囱的爆破倒塌解体过程较为理想且符合工程实际,数值模拟结果与实际爆破效果高度吻合,可为同类拆除爆破提供经验。

稻鱼共作头季稻栽植密度及留桩高度对水稻产量的影响

通过开展稻鱼共作头季稻不同栽植密度及留桩高度小区对比试验,为进一步优化稻鱼共作“优质稻+再生稻”绿色轻简高效配套技术体系提供科学依据。试验设置6个栽植密度(15万~27万穴·hm^(-2))和5个留桩高度(0~30 cm),对头季稻及再生稻进行了观察记载、分析研究。水稻全年产量以种植密度C处理(21万穴·hm^(-2))最高(9628.50 kg·hm^(-2)),B处理(18万穴·hm^(-2))次之(9614.3 kg·hm^(-2)),处理D (24万穴·hm^(-2))再次之(9555.0 kg·hm^(-2));随着留桩高度的增加,再生稻产量随之增加,以留桩高度25 cm处理产量最高(1988.8 kg·hm^(-2))。在水稻产量构成因素中,对产量的贡献自高至低依次为每公顷有效穗数>每穗实粒数>千粒重;随着留桩高度的降低,水稻齐穗期亦相应推迟(2~9 d);在本试验条件下,留桩高度在20 cm以上的3个处理均能正常灌浆结实。稻鱼共作头季稻栽植密度以18万~21万穴·hm^(-2)为适宜;为了确保水稻能安全避过寒露风并获得高产,留桩高度以20~25 cm为适宜。

粤北地区不同留桩高度下适宜再生稻品种筛选及产量构成分析

【目的】评价不同留桩高度下再生稻生育期和产量表现,筛选适宜粤北地区不同留桩高度下的水稻品种。【方法】以广东省培育或审定的34个水稻品种为供试材料,设中桩和低桩2种留桩高度,研究不同留桩高度下品种间生育期、产量和产量构成的差异。【结果】头季稻产量为5210.9~8566.8 kg/hm^(2),其中黄广华占1号最高;低桩再生季产量为3335.0~6357.3 kg/hm^(2),较中桩(2084.4~5940.5kg/hm^(2))提高16.1%,2种留桩高度下均以青香优19香再生季产量最高。聚类分析表明,中桩条件下,再生季产量和两季总产(头季+再生季)可分为高产、中高产、中产和低产4大类群,二者各类群数量分别为4、7、18、5个和1、14、14、5个;低桩条件下,再生季产量仍分为4大类群,数量分别为2、17、14和5个,两季总产则分为高产(10个)、中产(21个)和低产(3个)3大类群。与中桩再生稻相比,低桩条件下再生季生育期平均延长9.1 d,每穗粒数增加,但有效穗数和结实率降低。倒3节位、倒4节位和倒5及以下节位再生稻对产量的贡献率在中桩条件下分别为4.7%、33.3%和62.0%,在低桩条件下分别为0%、11.9%和88.1%。【结论】以再生季产量属中高产以上类群,同时两季总产属高产类群作为标准,筛选出黄广油占、黄广华占1号、黄广太占、五优粤禾丝苗、广8优金占、恒丰优387、青香优003、青香优132和青香优19香共9个品种适宜作中桩再生稻种植,二广香占3号、黄广油占、黄广华占1号、黄广太占、粤禾丝苗、南晶占、粤泰油占、黄华占、五优粤禾丝苗和广8优金占共10个品种适宜作低桩再生稻种植。中桩再生稻主要来自倒4节及以下节位,低桩再生稻主要来自倒5节及以下节位。

大采高工作面沿空留巷底鼓控制技术研究及应用

为解决端氏煤矿沿空留巷底鼓大变形问题,对巷道底鼓机理进行了分析,提出并应用切顶卸压和顶底板双梁联合支护技术来控制底鼓。切顶减小了采空区上方顶板往实体煤帮传递的应力,使留巷巷道处于卸压区,弱化了实体煤帮的应力集中程度,进而控制实体煤帮和底板的变形。通过采用“单体+π型梁+工字钢梁”一体化顶底板双梁联合支护技术,避免了单体钻入底煤导致支护失效现象,实现了顶板压力的有利转换,通过顶板压力有效控制底鼓。监测结果表明,切顶卸压使超前底鼓量平均降低25.6%;在切顶条件下,使用底梁较未使用底梁留巷底鼓量降低51.7%。切顶卸压及顶底板双梁联合支护技术能有效控制底鼓,解决端氏煤矿沿空留巷底鼓大变形问题,为类似条件下的沿空留巷底鼓控制提供借鉴。