APPLICATION OF EXPERT SYSTEM BASED ON NEURAL NETWORK IN MINING THE GENTLE INCLINED THICK SEAM

This paper presents a new method for the correct selection of mining methods and pre-diction of main technological and economic indexes of the face in the gentle inclined thick seams with the application of the artificial neural network theory and the expert system. The theory anal- ysis and calculating results indicate that the method is reliable, practical and precise. This method has strongly capabilities of self-study and non-linear dynamic data process. It is expected to be widely applied in the policy decision and prediction of mining technology in coal mine.

Analysis of the Risk of Water Breakout in the Bottom Plate of High-Intensity Mining of Extra-Thick Coal Seams

In order to clarify the danger of water breakout in the bottom plate of extra-thick coal seam mining, 2202 working face of a mine in the west is taken as the research object, and it is proposed to use the on-site monitoring means combining borehole peeping and microseismic monitoring, combined with the theoretical analysis to analyze the danger of water breakout in the bottom plate. The results show that: 1) the theoretically calculated maximum damage depth of the bottom plate is 27.5 m, and its layer is located above the Austrian ash aquifer, which has the danger of water breakout;2) the drill hole peeping at the bottom plate of the working face shows that the depth of the bottom plate fissure development reaches 26 m, and the integrity of the water barrier layer has been damaged, so there is the risk of water breakout;3) for the microseismic monitoring of the anomalous area, the bottom plate of the return air downstream channel occurs in the field with a one-week lag, which shows that microseismic monitoring events may reflect the water breakout of the underground. This shows that the microseismic monitoring events can reflect the changes of the underground flow field, which can provide a reference basis for the early warning of water breakout. The research results can provide reference for the prediction of sudden water hazard.

Depillaring of total thickness of a thick coal seam in single lift using cable bolts：A case study

Explaining fundamentals of application of cable bolting for a thick seam depillaring,this paper summarizes the results of field studies conducted during adoption of this approach in more than fifteen panels of Madhusudanpur 7 pit and incline mine.Nearly 7.0 m thick Kajora top coal seam of this mine is developed on pillars along the floor horizon to an average height of 3.0 m,leaving a coal band of around 4.0 m along the roof.Analysis of procured core samples showed that roof strata are easily caveable with a caveability index value of around 2000 only.Easily caveable overlying strata and shallow depth of cover alleviated most of the expected strata mechanics problems of the thick seam mining.However,extraction of total thickness at shallow cover caused differential-subsidence and cracks on the surface.These manifestations were immediately tackled to avoid creation of a breathing path for spontaneous heating in the extracted area.

Gas Drainage Technology in Fully Mechanized Caving Face with Horizontal Sublevel Mining in Steep and Extra-Thick Coal Seam

This paper analyzes the gas source of the horizontally sectioned fully mechanized caving face in the steeply inclined and extra-thick seam of Adaohai Coal Mine, and numerically simulates the stress distribution and pressure relief of the lower section coal after the upper section working face is mined. It theoretically analyzed the reasonable layout of the drainage boreholes, and designed the drainage borehole layout accordingly. In the upper and lower section of the working face, the actual drainage effect of the boreholes was inspected, and the air exhaust gas volume in the working face was statistically analyzed. It was confirmed that the layout of boreholes was reasonable, the gas control effect of working face was greatly improved and fully met the needs of safe mining. The control effect was greatly improved and the need for safe mining was fully met, and thus a gas drainage technology suitable for the coal seam storage conditions and mining technology of the Adaohai Coal Mine was found. That is to say: the gas emission from the working face of the section mining mainly comes from its lower coal body. Pre-draining the lower coal body of the section and depressurizing gas interception and drainage are the key to effectively solve the problem of gas emission from the working face. Drainage boreholes in the working face of the section should be arranged at high and low positions. The high-level boreholes are located about 2 m from the top of the working face, and the high-level boreholes are about 9 m away from the top of the working face. Through the pre drainage of high and low-level boreholes in advance and the interception and pressure relief drainage, the gas control in the horizontal sublevel fully mechanized caving mining face in steep and extra thick coal seam can realize a virtuous cycle.

“3-Section” Technology of Full-Dimension Mining in Flat Thick-Seam

To raise coal recovery ratio and solve the key problem of full-dimension mining, a new “3-section” technology of full-dimension mining is put forward in flat thick-seam according to the theory and mining practice. This technology is proved to be rational and feasible in rodway layout system of stagger arrangement.

Control mechanism of a cable truss system for stability of roadways within thick coal seams

Cable truss systems have been widely applied in roadways with complicated conditions, such as the large cross-sections of deep wells, and high tectonic stress. However, they are rarely applied to roadways with extremely thick coal seams because the control mechanism of the system for the deformation of the roof and the separation between coal rock segments is not completely understood. By using the relationship between the support system and the roof strata, a mechanical model was established to calculate the deformation of the roof in a thick coal seam with bedding separation under different support conditions: with an anchor truss support and without support. On this basis, the research was used to deduce a method for computing the minimum pre-tightening forces in the anchor truss, the maximum amounts of subsidence and separation with, and without, anchor truss support under the roof, and the maximum subsidence and the decreasing amounts of the separation before and after adopting the anchor truss. Additionally, mechanical relationships between the minimum pre-tightening force and the anchoring force in the anchor were analyzed. By taking a typical roadway with thick coal roof as an example, the theoretical results mentioned above were applied in the analysis and testing of a roof supporting project in a roadway field to verify the accuracy of the theory: favorable experimental results were achieved. In addition, the relationships among other parameters were analyzed, including the minimum pre-tightening forces applied by the anchor truss, the angle of inclination of the anchor cable, and the array pitch. Meanwhile, the changing characteristics of the amounts of roof separation and subsidence with key parameters of the support system(such as array pitch, pre-tightening force, and inclination angle) were also analyzed. The research results revealed the acting mechanism of the anchor truss in control of roadway stability with a thick coal seam, providing a theoretical basis of its application in coal mining.

Overburden fracture evolution laws and water-controlling technologies in mining very thick coal seam under water-rich roof

Considering the danger of water inrush in mining very thick coal seam under water-rich roof in Majialiang Coal Mine,the universal discrete element(UDEC)software was used to simulate the overburden fracture evolution laws when mining 4#coal seam.Besides,this study researched on the influence of face advancing length,speed and mining height on the height of the water flowing fractured zones(HWFFZ),and analyzed the correlation of face advancing length and change rules of aquifer water levels and goaf water inflow.Based on those mentioned above,this research proposed the following water-controlling technologies:draining the roof water before mining,draining goaf water,reasonable advancing speed and mining thickness.These water-controlling technologies were successfully used in the feld,thus ensured safely mining the very thick coal seam under water-rich roof.

Behaviors of overlying strata in extra-thick coal seams using top-coalcaving method

Accidents such as support failure and excessive deformation of roadways due to drastic changes in strata behaviors are frequently reported when mining the extra-thick coal seams Nos.3e5 in Datong coal mine with top-coal caving method,which significantly hampers the mine's normal production.To understand the mechanism of strata failure,this paper presented a structure evolution model with respect to strata behaviors.Then the behaviors of strata overlying the extra-thick coal seams were studied with the combined method of theoretical analysis,physical simulation,and field measurement.The results show that the key strata,which are usually thick-hard strata,play an important role in overlying movement and may influence the mining-induced strata behaviors in the working face using top-coal caving method.The structural model of far-field key strata presents a 'masonry beam' type structure when'horizontal O-X' breakage type happens.The rotational motion of the block imposed radial compressive stress on the surrounding rock mass of the roadway.This can induce excessive deformation of roadway near the goaf.Besides,this paper proposed a pre-control technology for the hard roof based on fracture holes and underground roof pre-splitting.It could effectively reduce stress concentration and release the accumulated energy of the strata,when mining underground coal resources with top-coal caving method.

Top coal caving mining technique in thick coal seam beneath the earth dam

It is important to study the mining technology under structures for raising the coal resources recovery ratio. Based on the geological and mining conditions, the top coal caving harmonic mining technique in thick coal seam beneath the earth dam was put forward and studied. The 5 factors such as the panel mining direction, panel size, panel location, panel mining sequence and panel advance velocity were taken into account in this technique. The dam movement and deformation were predicted after the thick coal seam mining and the effects of mining on the dam were studied. By setting up the surveying stations on the dam, the movement and deformation of the dam were observed during mining. By taking some protective measures on the dam, the top coal caving mining technique in thick coal seam beneath the earth dam was carried out successfully. The study demonstrates that harmonic mining in thick coal seam is feasible under the dam. The safety of the earth dam after mining was ensured and the coal resources recovery ratio was improved.

Comparative study of mining methods for reserves beneath end slope in flat surface mines with ultra-thick coal seams

The paper aims to identify a reasonable method for mining ultra-thick coal seams in an end-slope in surface mine, With a case study of Heidaigou surface coal mine(HSCM), the paper conducted a comparative research on three mining methods, namely Underground Mining Method(UMM), Highwall Mining System(HMS) and Local Steep Slope Mining Method(LSSMM). A model was firstly established to simulate the impact that UMM and HMS exert on monitoring points and surface deformation. The way that stripping and excavation amount varies with different slope angle, and the corresponding end slope stability were analyzed in the mode of LSSMM. Then a TOPSIS model was established by taking into account six indicators such as recovery ratio, technical complexity and adaptability, the impact on surface mining production, production safety and economic benefits. Finally, LSSMM was determined as the best mining method for mining ultra-thick coal seams in end slope in HSCM.

Numerical Study on an Applicable Underground Mining Method for Soft Extra-Thick Coal Seams in Thailand

The EGAT Mae Moh Mine is the largest open pit lignite mine in Thailand and it produces lignite about 16 million tons annually. In the near future, the pit limit of the mine will be reached and underground mine will then be developed through the open pit in the depth of 400 - 600 m from the surface. However, due to the challenges for underground mining such as poor geological conditions, extra thickness (20 - 30 m) of coal seams, and weak mechanical properties of coal seams and the surrounding rock, the success possibility of underground mining and an applicable underground mining method is being investigated at the present. The paper discusses the applicability of multi-slice bord-and-pillar method for the soft extra thick coal seams in the Mae Moh mine by means of numerical analyses using the 3D finite difference code “FLAC3D”.

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.

浅埋厚煤层开采地表采动裂缝发育演化规律研究

基于串草圪旦煤矿典型生产工作面覆岩赋存情况及地表采动裂缝发育特征,采用现场实测、理论分析和数值计算相结合,研究了覆岩关键层失稳运动形式及其对地表采动裂缝发育形态的影响,以及基采比对地表采动裂缝演化规律的影响。结果表明:浅埋厚煤层开采过程中,关键层失稳运动对地表采动裂缝发育类型具有控制作用,关键层滑落失稳引起地表产生台阶型裂缝,关键层回转失稳引起地表产生张开型裂缝;覆岩关键层失稳运动过程导致地表采动裂缝尺度参数发生动态变化,随着基采比的增大,地表采动裂缝的垂直错动量呈减小趋势,水平张开量呈增大趋势,裂缝水平张开量与关键层回转角线性相关。

高瓦斯开采复合采空区自燃区域划分技术研究

新疆煤炭资源极其丰富,随着开采强度的不断增大,复合采空区也不断增多,为回采工作增加了大量的难度。因此,通过复合采空区煤自燃“三带”分布规律与大面积复合采空区数值模拟计算,对工作面回采期间,复合采空区煤多次氧化自燃特性、复合采空区注氮置换瓦斯及复合采空区瓦斯与煤火耦合致灾机制及综合防控关键技术,解决工作面进入复合采空区后,准确识别煤自燃危险区域,推算工作面安全推进速度,实现了巨厚煤层下分层的安全回采,提高了煤炭资源回收率,消除因复合采空区遗煤多次氧化引起的煤层自然发火。

Experimental research on coal seam similar material proportion and its application

In this paper, the optimization design of the low strength mechanical test and orthogonal test have been analyzed in order to simulate the mechanical properties of thick and extra-thick coal seam accurately in a similar material simulation test. The results show that the specimen can reach a wider range of strength when cement has been used compared to that of gypsum, suggesting that cement is more suitable for making coal seam in similar material simulation tests. The uniaxial compressive strength is more sensitive to cement than coal or sand. The proportion of coal and sand do not play a decisive role in uniaxial compressive strength. The uniaxial compressive strength and specimen density decrease as the mass percent of coal and aggregate–binder ratio rise. There is a positive correlation between uniaxial compressive strength and density. The No. 5 proportion(cement: sand: water: activated carbon: coal = 6:6:7:1.1:79.9)was chosen to be used in the similar material simulation test of steeply dipping and extra-thick coal seam with a density of 0.913 g/cm^3 and an uniaxial compressive strength of 0.076 MPa which are in accordance with the similarity theory. The phenomenon of overburden stratum movement, fracture development and floor pressure relief were obtained during the similar material simulation test by using the proportion.

急倾斜特厚煤层冲击地压防治探索与总结

急倾斜特厚煤层开采顶板破断运动复杂,应力和能量演化规律特殊,在深部“三高一扰动”影响下,冲击地压防治不容乐观。基于某矿2016年冲击地压事故后急倾斜特厚煤层水平分段开采冲击地压防治经验,从急倾斜特厚煤层水平分段开采冲击地压发生机理、瓦斯突出与冲击地压综合防治和冲击地压管理详细介绍了该矿7年来急倾斜特厚煤层冲击地压防治经验。冲击地压发生机理方面,建立了顶板岩层倾斜悬臂梁模型,揭示了顶、底板覆岩结构破断失稳演化过程,划分了夹持煤体受力状态分区,提出了急倾斜特厚煤层冲击“夹持理论”。瓦斯突出与冲击地压综合防治方面,基于冲击地压灾害控制解危技术的强度弱化减冲理论,结合原有防突措施体系,提出了既能防冲且对防突有利的解危措施,形成了某矿瓦斯/CO_(2)突出-冲击地压“双防”技术体系,建立了适用于某矿急倾斜特厚煤层水平分段开采的冲击地压防治体系,以钻屑量和瓦斯吸解值验证了瓦斯突出防治的强度保障,同时以加强实施卸压措施工作面的微震事件分布及各能级总频次和能量对比,论证说明了卸压方案防治效果的有效性。冲击地压管理方面,形成了预测评价、监测预警、治理预防、效果检验、安全防护和教育培训“六位一体”综合防治架构,基于《煤矿安全规程》和《防治煤矿冲击地压细则》等各项规定,制定了Q/YJMD-—FC 0104-2022《窑街煤电集团有限公司煤矿冲击地压防治第四部分:冲击地压防治技术规范》。

急倾斜深埋巨厚煤层掘巷冲击地压前兆特征及其灾害防治

随着冲击地压矿井逐渐向深开采,其巷道掘进伴随的冲击显现愈发强烈。针对巷道掘进过程中的冲击地压有效防治问题,以新疆乌东煤矿急倾斜煤层矿井为例,运用微震监测对巷道掘进的冲击地压时空前兆特征加以分析。结合巷道掘进的应力与能量变化数值模拟分析,揭示巷道掘进的冲击地压发生机理,提出急倾斜巨厚煤层巷道冲击地压防治策略,并完成现场工程实践验证。研究结果表明:急倾斜巨厚煤层巷道掘进的冲击地压发生前第2~5天出现微震总能量极低值,或存在至少4 d的能量潜伏期;冲击地压发生前5 d普遍存在3 d以上的最大能量占比高频波动期。冲击地压发生前存在明显缺震现象,发生位置集中分布在距离掘进工作面较近的微震能量极小值区间范围内,或位于微震能量极值区间附近的微震频次极小值区间范围内,且冲击地压事件位于冲击变形能指数较高区域。急倾斜巨厚煤层水平分段综放开采的坚硬覆岩结构不易破断,使得巷道掘进存在上水平采空区两侧“双翼型”应力集中,掘进工作面前方与巷道底部受顶底板岩层相互挤压的应力集中分布且能量积聚显著,随着巷道掘进深度增加其应力集中与能量积聚进一步增强,容易诱发冲击地压等动力灾害。综合分析形成急倾斜巨厚煤层巷道掘进的工作面爆破卸压、巷道钻孔卸压与补强支护、复杂区域架蓬的冲击地压防治策略。结合冲击地压时空前兆异常为及时加强卸压力度提供时机。通过工作面与巷道卸压使得掘进期间未发生单日累计1×105 J以上微震能量,在对支护优化调整与复杂区域重点防护后,巷道掘进日均微震能量降至2.2 kJ,其1 kJ以上微震事件占比下降且巷道断面整体平整。研究结果为急倾斜巨厚煤层巷道安全掘进提供了科学依据。

Experiment Research of Application of FMCCT in Complex-Condition Coal Seams

The fully-mechanized caving coal technique (FMCCT) is a great technique progress of mining method in thick coal seams in China, and it has succeeded in some suitable condition mines. This paper introduces some technical measures and achieved outcomes in gas and fire precaution and support selection for the use of the fully-mechanized caving coal technique in the complex-condition coal seams based on the practice of Weijiadi Coal Mine, in which the technique is used in the gently inclined extremelythick soft coal seam with the dangers of coal and gas outburst and spontaneous combustion.

深埋倾斜特厚煤层窄煤柱护巷机理与围岩控制

我国中东部地区采深大、巷道变形和冲击风险大,窄煤柱沿空掘巷技术可改善巷道围岩环境。为掌握窄煤柱护巷机理并形成针对性围岩控制技术体系,以800 m埋深倾斜特厚煤层3 m窄煤柱沿空掘巷为背景,开展了理论分析、现场实测及数值模拟研究,结果表明:①该巷围岩破碎程度及变形煤柱侧比实体煤侧严重,煤柱破碎程度及变形采空区侧比巷道侧大,尽管埋深大,但已稳定采空区承担较大覆岩载荷,高应力已充分向深部岩体分流;②巷道变形非对称,实体煤侧顶板下沉量比煤柱侧大,巷帮以浅部变形为主,煤柱帮上部和实体煤帮中部变形较大;③采空区是掘巷卸荷后主要的形变通道,利于形变能向采空区缓释、降低冲击风险;④卸压区形状由掘巷前三角形扩展为掘巷后平行四边形,掘巷后应力集中区转移至实体煤帮右上方实体煤岩体中;⑤窄煤柱一次和二次剪切破坏的交界面及掘巷右上方实体高应力区为围岩关键控制区,据此提出基于煤柱多重塑性破坏区发育规律的煤柱加固和高应力区精准卸压联合的围岩控制技术体系。研究可为邻近工作面以及其他类似深埋倾斜特厚煤层开采提供理论支撑和科学依据。

特厚煤层底板断层破坏与顶板垮断联动效应的CFDEM模拟研究

特厚煤层采场空间大、覆岩扰动范围广,顶板垮断产生的强扰动加卸荷载易导致底板断层破坏加剧。通过数值模拟研究特厚煤层底板断层突水与顶板垮断联动效应机理规律是开展水害防治的基础,关键在于掌握加卸载下岩体渐进破坏与裂隙流耦合特征。构建加卸载下拉、剪损伤演化方程,结合有效偏/球应力为基本变量的屈服准则与塑性势函数,得到完整岩块的塑性损伤本构;建立拉/剪、混合型加卸载过程中塑性位移与强度劣化关系,以平方拉剪应力与B-K准则为初始、完全断裂准则,形成非贯通裂隙断裂本构;提出岩块分离、压缩、剪切判据,结合实验数据建立离散块体间挤压、剪切摩擦本构与剪胀方程。基于质量/动量守恒、状态方程,并结合流体体积与浸没边界方法,形成裂隙岩体气−水二相流模拟理论。由此形成CFDEM数值计算程序,并将加卸载下塑性损伤、断裂、挤压/摩擦、流体属性分别赋予实体单元(岩块)、黏聚力单元(非贯通裂隙)、接触对(贯通裂隙)、欧拉单元(水和气)。根据宁武煤田北部矿区工程地质条件,建立特厚煤层底板断层突水与顶板垮断联动效应数值计算模型。结果表明:①CFDEM耦合程序及相应的理论模型可数值实现特厚煤层覆岩及底板断层从(准)连续体到离散体转化,以及地下水在裂隙中运移;②模拟条件下特厚煤层含断层底板的采动裂隙包络线呈w形,最深处超过55 m位于断层及其上盘,最浅处23 m位于断层下盘,而无构造底板处的破坏深度为24~36 m,已导通奥灰含水层;③特厚煤层底板普遍出现二次破坏现象。表现为无构造底板在超前工作面处破坏深度为24.0~29.3 m,但在采空区内普遍增加至31.5~36.0 m;断层及其上盘在超前工作面处裂隙总开度为0.34~0.86 m,但在采空区内迅速增加至3.6 m,形成突水优势通道。④底板断层突水与顶板垮断联动效应的根源在于覆岩高位关键岩层垮断失稳、砌体梁下沉与二次断裂,并导致底板二次破坏,突水风险加剧。