Stability analysis of longwall top-coal caving face in extra-thick coal seams based on an innovative numerical hydraulic support model

The relationship between support and surrounding rock is of great significance to the control of surrounding rock in mining process.In view of the fact that most of the existing numerical simulation methods construct virtual elements and stress servo control to approximately replace the hydraulic support problem,this paper establishes a new numerical model of hydraulic support with the same working characteristics as the actual hydraulic support by integrating numerical simulation software Rhino,Griddle and FLAC3D,which can realize the simulation of different working conditions.Based on this model,the influence mechanism of the supporting strength of hydraulic support on surrounding rock stress regulation and coal stability in front of the top coal caving face in extra thick coal seam were researched.Firstly,under different support intensity,the abutment pressure of the bearing coal and the coal in front of it presents the “three-stage”evolution characteristics.The influence range of support intensity is 15%–30%.Secondly,1.5 MPa is the upper limit of impact that the support strength can have on the front coal failure area.Thirdly,within a displacement range of 2.76 m from the coal wall,a support strength of1.5 MPa provides optimal control of the horizontal displacement of the coal.

Mechanisms and Kinematics of Hydraulic Support for Top-Coal Caving

The structure and characteristic of new type of hydraulic support for top coal caving were discussed. The mechanism and kinematics of the hydraulic support were analyzed. The formulas were deduced to calculate the velocity and acceleration of top beam, shield beam, front and back legs, which give the solution to the design and research for hydraulic support.

Hydraulic support stability control of fully mechanized top coal caving face with steep coal seams based on instable critical angle

Analyzed the support instable mode of sliding,tripping,and so on,and believed the key point of the support stability control of fully mechanized coal caving face with steep coal seams was to maintain that the seam true angle was less than the hydraulic support instability critical angle.Through the layout of oblique face,the improvement of support setting load,the control of mining height and nonskid platform,the group support system of end face,the advance optimization of conveyor and support,and the other control tech- nical measures,the true angle of the seam is reduced and the instable critical angle of the support is increased,the hydraulic support stability of fully mechanized coal caving face with steep coal seams is effectively controlled.

Longwall Top-Coal Caving in Thinner Thick-Seam and Research on Light Hydraulic Support

The application of light hydraulic support highlights the advantages of longwall top-coal caving (LTC) in thinner thick-seams (3. 0~ 5. 0 m). Considering the problems in practice, the developing of its new series will promote the mining of LTC with light hydraulic supports. Some relevant technical problems of the caving technology and the future of this series of supports are analyzed in this paper with several new opinions.

Key technologies and equipment for a fully mechanized top-coal caving operation with a large mining height at ultra-thick coal seams

Thick and ultra-thick coal seams are main coal seams for high production rate and high efficiency in Chinese coal mines, which accounts for 44 % of the total minable coal reserve. A fully mechanized top-coal caving mining method is a main underground coal extraction method for ultra-thick coal seams. The coal extraction technologies for coal seams less than 14 m thick were extensively used in China. However, for coal seams with thickness greater than 14 m, there have been no reported cases in the world for underground mechanical extraction with safe performance, high efficiency and high coal recovery ratio. To deal with this case, China Coal Technology ＆ Engineering Group, Datong Coal Mine Group, and other 15 organizations in China launched a fundamental and big project to develop coal mining technologies and equipment for coal seams with thicknesses greater than 14 m. After the completion of the project, a coal extraction method was developed for top-coal caving with a large mining height, as well as a ground control theory for ultra-thick coal seams. In addition, the mining technology for top-coal caving with a large mining height, the ground support technology for roadway in coal seams with a large cross-section, and the prevention and control technology for gas and fire hazards were developed and applied. Furthermore, a hydraulic support with a mining height of 5.2 m, a shearer with high reliability, and auxiliary equipment were developed and manufactured. Practical implication on the technologies and equipment developed was successfully completed at the No. 8105 coal face in the Tashan coal mine, Datong, China. The major achievements of the project are summarized as follows： 1. A top-coal caving method for ultra-thick coal seams is proposed with a cutting height of 5 m and a top-coal caving height of 15 m. A structural mechanical model of overlying strata called cantilever beam-articulated rock beam is established. Based on the model, the load resistance of the hydraulic support with a large mining height for top-coal caving method is determined. With the analysis, the movement characteristics of the top coal and above strata are evaluated during top-coal caving operation at the coal face with a large mining height. Furthermore, there is successful development of comprehensive technologies for preventing and controlling spalling of the coal wall, and the top-coal caving technology with high efficiency and high recovery at the top-coal caving face with a large mining height. This means that the technologies developed have overcome the difficulties in strata control, top-coal caving with high efficiency and high coal recovery, and enabled to achieve a production rate of more than 10 Mtpa at a single top-coal caving face with a large mining height in ultra-thick coal seams; 2. A hydraulic support with 5.2 m supporting height and anti-rockburst capacity, a shearer with high reliability, a scraper conveyor with a large power at the back of face, and a large load and long distance headgate belt conveyor have been successfully developed for a top-coal caving face with large mining height. The study has developed the key technologies for improving the reliability of equipment at the coal face and has overcome the challenges in equipping the top-coal caving face with a large mining height in ultra-thick coal seams; 3. The deformation characteristics of a large cross-section roadway in ultra-thick coal seams are discovered. Based on the findings above, a series of bolt materials with a high yielding strength of 500-830 MPa and a high extension ratio, and cable bolt material with a 1 × 19 structure, large tonnage and high extension ratio are developed. In addition, in order to achieve a safe roadway and a fast face advance, installation equipment for high pre-tension bolt is developed to solve the problems with the support of roadway in coal seams for top-coal caving operation with a large mining height; 4. The characteristics of gas distribution and uneven emission at top-coal caving face with large mining height in ultra-thick coal seams are evaluated. With the application of the technologies of gas drainage in the roof, the difficulties in gas control for high intensive top-coal caving mining operations, known as ＂low gas content, high gas emission＂, are solved. In addition, large flow-rate underground mobile equipment for making nitrogen are developed to solve the problems with fire prevention and safe mining at a top-coal caving face with large mining height and production rate of more than 10 Mtpa. A case study to apply the developed technologies has been conducted at the No. 8105 face, the Tashan coal mine in Datong, China. The case study demonstrates that the three units of equipment, i.e., the support, shearer and scraper conveyor, are rationally equipped. Average equipment usage at the coal face is 92.1%. The coal recovery ratio at the coal face is up to 88.9 %. In 2011, the coal production at the No. 8105 face reached 10.849 Mtpa, exceeding the target of 10 Mtpa for a topcoal caving operation with large mining height performed by Chinese-made mining equipment. The technologies and equipment developed provide a way for extracting ultra-thick coal seams. Currently, the technologies and equipment are used in 13 mining areas in China including Datong, Pingshuo, Shendong and Xinjiang. With the exploitation of coal resources in Western China, there is great potential for the application of the technologies and equipment developed.

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.

6~10 m厚煤层超大采高液压支架及其工作面系统自适应智能耦合控制

厚煤层储量及产量占我国原煤总储量及产量的一半,通过梳理厚煤层开采历史沿革,总结了我国厚煤层开采40年来的技术及装备研发实践,系统分析了以高端大采高液压支架及围岩智能耦合理论为代表的6~10 m大采高综采高效智能化综采技术及装备研究进展,提出了大采高支护理论及围岩智能耦合控制的突破是厚煤层一次开采高度突破的首要因素,完善的感知体系建立是液压支架自适应支护的前提,数字技术的应用为大采高工作面高效推进及装备智能协同控制提供了新的技术途径;阐明了大采高综放液压支架与围岩耦合关系,剖析了采高增加对硬煤层冒放性的有利影响,提出了基于煤矸识别、放煤机构控制的“纯煤段记忆放煤+煤岩分界模糊段人工反馈式干预放煤”的智能放煤控制策略;分析了大采高开采“采–运”协同智能耦合控制关键技术,构建了基于采煤机牵引速度与刮板输送机链速间联动调节的工作面装备间多机异构耦合自适应协同控制模型;研发了厚煤层开采中10 m超大采高液压支架,分析了厚煤层开采不断突破开采高度极限的新认识,从开采装备、控制系统等方面提出厚煤层一次开采高度的突破的研发方向。

基于支架结构运动学的放煤机构精准控制研究

放煤机构的精准控制是实现智能化、无人化放顶煤开采的重要基础,放煤机构与后部刮板输送机的空间关系及支架姿态对空间关系的影响规律是构建放顶煤支架控制模型的关键。以ZF17000/27.5/42D型低位放顶煤支架为研究对象,阐述了支架顶板和底板不同俯仰姿态下放煤机构与后部刮板输送机的空间关系;基于液压支架放煤机构开口度控制逻辑,搭建了支架姿态感知系统,提出了液压支架放煤机构末端运动学分析方法;建立了基于D-H矩阵的低位放顶煤液压支架放煤机构末端运动学模型,并据此构建了液压支架放煤机构开口度计算模型,平均计算误差仅为1.71%,满足现场应用精度要求;提出了基于姿态反馈的支架放煤机构闭环控制方法,并将基于放煤机构开口度计算模型开发的放煤决策模型应用于现场。应用效果表明:自动放煤时各支架平均放煤时间的均方差仅为0.13 min,较人工放煤方式整体放煤效率提高20%~43.9%;顶煤采出率达89%,后部刮板输送机负载更加均衡,过载率仅为0.73%。

放煤过程中液压支架顶梁动态载荷演化特征试验研究

接触式煤矸识别需要研究综放开采液压支架顶梁承载特性,但现有研究大多重点关注放煤前后的支架承载特性或在给定载荷情况下支架的力学响应特征,忽略了对放煤过程中载荷变化的深入探究。针对上述问题,搭建了放顶煤支架动态载荷相似模拟试验平台,借助散体颗粒模拟破碎煤矸块体,反演了综放工作面放煤过程,利用薄膜压力传感器采集支架顶梁压力,分析了放煤过程中顶梁动态载荷演化特征。试验结果表明:①顶煤的放出对支架顶梁载荷产生了较为明显的影响,即随着顶煤放出,支架顶梁载荷整体呈先增大后减小最终稳定的演化规律。②沿顶梁长度方向,支架顶梁距离掩护梁越远的位置受顶煤放出的影响越小,主要表现在距离掩护梁越远,顶梁载荷峰值相较初始值的增幅越小,且达到载荷峰值所需的时间越长。③沿顶梁宽度方向,由于顶煤的放出过程受到了约束边界或流动过程不均衡性的限制,顶梁不同位置的载荷峰值具有差异性,顶梁载荷峰值相较初始值的增幅最大值达到了最小值的2.4倍。

孤岛综放工作面小煤柱沿空掘巷围岩控制技术研究

为提高同宝煤业15106孤岛工作面煤炭资源回收率,提出采用留小煤柱沿空掘巷技术施工辅运顺槽。通过理论计算和数值模拟分析确定了小煤柱宽度为8m,并提出了“锚网索+煤柱侧锚索梁加固+破碎区段煤柱侧巷帮注浆加固”的联合支护方案。应用结果表明:煤柱帮和实体煤帮最大位移量分别为223.56 mm、68.36mm,顶板最大下沉量为216.52mm,底鼓量最大值为172.54mm,沿空巷道围岩变形控制效果显著。此外,采用小煤柱沿空掘巷技术后,区段煤柱宽度由25m缩小至8m,可多回收煤柱资源约10.15万t,经济效益显著。

大坡段俯斜开采综放工作面运输机窜动及防倒架管理

为了研究运输机窜动控制及防倒架管理方法,分析、探讨控制运输机窜动的主要原因,结合综放工作面设备结构和采场条件,研究综放工作面运输机上窜下滑控制及架型调整的具体方法。结果表明,除了常用的“伪斜法”辅以“单向推溜法”控制运输机窜动以外,还要做好日常架型的管理,以及介绍架型管理及防倒架的具体方法,对综采工作面运输机上窜下滑、架型管理及防倒架管理具有借鉴意义。

ZF14000/25/38D型液压支架液压系统设计研究

通过对某煤矿3203综放工作面液压支架设备配套情况分析,针对工作面低位放顶煤液压支架运动情况,设计了ZF14000/25/38D型电液控放顶煤液压支架液压系统。从液压支架使用情况分析,针对不同执行元件的动作,对液压回路进行设计,为放顶煤开采提供安全保证。

松软煤层工作面片帮分析及防治技术研究

以5102采煤工作面为研究对象,对煤壁片帮的内在及外在因素展开了详细的分析,并制定了一系列防治措施,以增强松软煤壁自身的承载能力和降低顶板下沉对煤壁的影响。通过“超前大范围注水+局部注浆”的方式可以提高松软煤体的强度,采用ZF 2600/17/26型液压支架不仅能够增强顶板管理效果,还能够减少顶板下沉量,给煤壁提供一定的支护作用力。工程应用后,5102采煤工作面后续回采期间片帮发生率明显降低,实现了松软煤层片帮的有效防治。

掩护式前部放顶煤液压支架选型设计与可靠性研究

为解决土耳其IMBAT矿使用的四柱低位放顶煤支架出现的放煤效果不理想、拔后柱严重、外形尺寸大下井受限、前部顶板冒顶严重、顶板管理难度大等问题,结合矿方地质条件,提出一种适应此类地质条件的掩护式前部放顶煤液压支架。介绍了该液压支架的选型过程以及主要参数和结构特点,并对整架进行了偏转和扭转有限元分析。经样机研制及26000次压架试验,验证了该支架布局及结构的合理性,丰富了具备此类地质条件的综放开采液压支架应用案例。

基于压缩感知的液压支架声源定位识别方法

针对当前液压支架放煤过程中落煤时间和落煤量监测主要依赖于人工观察、自动化程度不高的问题,提出了一种基于声源定位的落煤状态识别方法,通过声源的识别与定位得到当前落煤的液压支架位置与落煤状态。设计了基于STM32的声音传感器阵列的数据采集系统。针对传统算法识别宽带信号和多声源定位困难的问题,采用基于压缩感知的多声源宽带定位算法,通过对信号进行分解得到不同频带的定位结果。仿真结果表明,该方法能准确识别170台液压支架落煤声源位置,在信噪比(SNR)为-5 dB时双声源识别率达到98%。

特厚煤层综放工作面超前支护评价分析

针对特厚煤层综放工作面巷道超前支护难题,以古城煤业有限公司Z107综放工作面为工程背景,对该工作面超前支护25 m范围内单体支柱工作压力进行计算分析。分析结果表明,在该工况条件下,工作面超前10 m范围内采用“一梁三柱”支护方式;工作面超前后15 m范围内,采用“一梁两柱”的单体支护形式。经验证,该支护方式满足现场安全生产需求。

特厚煤层综放面超前支护液压支架设计及应用

为了降低特厚煤层综放工作面巷道超前段单体柱支护风险,简化支护工艺,提高作业效率,基于不连沟煤矿特厚煤层地质赋存与综放开采工艺特点,开展了特厚综放工作面巷道超前支护液压支架选型设计,并进行了现场工业性试验。现场试验结果表明,应用ZQL2×6500/27/50D型端头超前液压支架过程中,巷道超前段顶板最大下沉量为127 mm,两帮最大移近量为466 mm,工作面液压支架最大工作阻力为46 MPa,巷道超前段顶板和两帮变形得到了有效控制。现场试验取得了较好的效果,可为特厚煤层综放工作面超前液压支架支护技术提供参考。

综放工作面架间溜煤板装置的研制与应用

铺龙湾煤业回采方法为放顶煤开采,在工作面正常生产期间,移架后产生大量架间浮煤,主要是由支架架间间隙掉落下煤块形成的浮煤。针对此问题,研制出一种能将支架架间间隙掉落下的煤通过U型溜煤板进行收集、最后溜入刮板输送机的装置。实际生产应用表明,95%的架间煤通过该装置落入了刮板输送机内,且不影响机组的割煤,大大减轻了工人的劳动轻度,提高了劳动效率。

煤矿综放工作面矿压显现规律与切顶压架预警指标分析

煤矿特厚煤层综放开采时受技术装备等条件限制,放顶煤时由于顶板松散程度较高难以形成稳定结构,导致工作面顶板更容易大面积切落,瞬间冲击支架,损坏液压支架结构,严重影响矿井安全高效生产。以不连沟煤矿F6218综放工作面为工程背景,通过实测数据分析了工作面支架初撑力、安全阀开启情况及工作阻力频率等支架基本工况,揭示了工作面矿压显现规律,建立了适合该矿的切顶压架灾害预警指标体系。结果表明:不连沟煤矿预警指标界限分别为循环增阻率40 kN/min、安全阀开启率50%、动载系数1.4、活柱下缩量500 mm、支架前柱不低于25 MPa,前柱合格率不低于90%;后柱不低于20 MPa,后柱合格率不低于90%。

综放端头支架与后部输送机配套形式及空间探讨

智能化无人开采是实现煤矿安全高效开采的技术途径,各种设备的自动化及相互间的配套影响着工作面的智能化程度,合理的配套形式及空间是提高开采自动化率的保障。随着工作面开采设备能力的提高,相关配套设备特别是刮板输送机两端的驱动部体积和占用空间不断增大,受设备配套和设备尺寸制约,给工作面的自动化运行与控制带来挑战。对于综放工作面,两端头的端头支架与后部输送机的配套非常关键。为了解决端头支架尾柱与后部输送机电动机间相对位置观察不便、难于控制、发生碰撞损坏电动机、需要人工干预的痛点,通过端头支架底座与后部输送机间限位装置的研究和毫米波雷达的应用,从机械、控制、监测等方面形成了综放工作面两端头后部狭窄空间的设备安全解决方案,此方案的实施,取得了较好的应用效果。