共查询到20条相似文献，搜索用时 31 毫秒
1.
The presence of hard and massive sandstone above the coal seam in underground coal mines often leads to delay in caving of overlying rock beds thereby causing excessive load on supports and posing danger to underground workings. The problem is more prominent in blasting gallery (BG) as well as longwall mining methods in Indian coal mines. Induced caving by blasting is a promising means for hard roof management in underground coal mines. Based on extensive studies and data collected from different mines in India, a Blastability Index (BI) has been developed which can be used for the classification of roof according to the degree of ease in caving by induced blasting. Different charge factors have also been suggested based on the Blastability Index. Due to wide change in the method of extractions, ??Cavability Index?? for longwall panel was found ineffective in case of BG method of working as well as bord and pillar working. For this reason, this proposed Blastability Index would be of immense help for caving of hard roof by induced blasting. 相似文献
2.
Most coal mines in China use the longwall mining system. High stresses are frequently encountered around development entries at deep mines. This paper presents an alternate longwall mining layout for thick coal seams to minimize ground control problems. In a conventional longwall panel layout, development entries on both ends of the panel are located along the floor, and a coal pillar (chain pillar) is left between adjacent panels to ensure stability. Gateroads on either end of a longwall panel using the layout proposed in this paper are located at different vertical levels within a thick coal seam or in a geologically split coal seam for improved stability. The headgate entry/ies are driven along the floor while the tailgate entry/ies are driven along the roof. Therefore, a longwall face has a gradually elevated or curved section on one end of the panel. For the adjacent panel, the development entry may be located directly below the development entry of the previous panel or may be offset horizontally with respect to it. Based on physical and numerical modeling approaches, it is demonstrated that the stress environment for development entries employing the longwall layout is significantly improved; ground control problems are therefore minimized. 相似文献
3.
Hamid Mohammadi Mohammad Ali Ebrahimi Farsangi Hossein Jalalifar Ali Reza Ahmadi 《Rock Mechanics and Rock Engineering》2016,49(1):303-314
In this paper a geometric computational model (GCM) has been developed for calculating the effect of longwall face on the extension of excavation-damaged zone (EDZ) above the gate roadways (main and tail gates), considering the advance longwall mining method. In this model, the stability of gate roadways are investigated based on loading effects due to EDZ and caving zone (CZ) above the longwall face, which can extend the EDZ size. The structure of GCM depends on four important factors: (1) geomechanical properties of hanging wall, (2) dip and thickness of coal seam, (3) CZ characteristics, and (4) pillar width. The investigations demonstrated that the extension of EDZ is a function of pillar width. Considering the effect of pillar width, new mathematical relationships were presented to calculate the face influence coefficient and characteristics of extended EDZ. Furthermore, taking GCM into account, a computational algorithm for stability analysis of gate roadways was suggested. Validation was carried out through instrumentation and monitoring results of a longwall face at Parvade-2 coal mine in Tabas, Iran, demonstrating good agreement between the new model and measured results. Finally, a sensitivity analysis was carried out on the effect of pillar width, bearing capacity of support system and coal seam dip. 相似文献
4.
Jin-wang Zhang Jia-chen Wang Wei-jie Wei Yi Chen Zheng-yang Song 《Arabian Journal of Geosciences》2018,11(5):96
Steep coal seam mining activities will frequently occur during the next few decades in China. In this study, both experimental and numerical methods are employed to investigate the coal drawing from thick steep seam with longwall top coal caving mining. A series of analyses is performed to investigate the features of the drawing body, the distribution of top coal recovery ratio and the shape of the rock flow under steep conditions. The results indicate that the drawing body of top coal develops prior to upper side of the panel face obviously, and the top coal in the central part of the panel has a higher recovery ratio than that in the lower and upper parts in steep coal seam with caving mining method. The flow paths of the fragmented top coal are nearly straight lines moving towards the drawing window, and the fastest path maintains a constant angle with the plumb line. The spatial shape of the rock flow indicates “bidirectional asymmetry,” which results from the presence of the shield beam and dip angle of the coal seam; thus, this is the root cause of the appearance of the drawing body’s prior development towards the upper side of the panel. The field observation data indicates the same distribution of top coal recovery as that in the physical experiment and numerical simulation. Furthermore, suggested measurements are proposed to improve top coal recovery in steep seam mining based on the engineering practice of Dayuan coal mine. 相似文献
5.
This study investigates the flow and caving characteristics of top coal and roof rock, as well as top coal loss pattern in the fully mechanized top coal caving mining of extra thick coal seams. The two dimensional discrete element numerical simulation software program, particle flow code (PFC), is used for the simulation of top coal caving and the inversion analysis. The original locations, distribution, and migration pattern of caved top coal and lost coal were obtained. The analysis shows that in the initial site of caving, the caved bodies are in the form of arc shaped strips in front of the working face. During the caving, caved bodies of different heights move towards the lower rear of the face at different speeds. The lost coal and caved roof rock are originally located at the interface between coal seam and roof, the lost coal is mainly distributed in the goaf on the floor. Behind the support, the caved top coal bodies originally are arc shaped strips, with the highest points located at the midline of the caving opening. The strips are more curved near the goaf than those near the support. During top coal caving, the strips successively cave, with the adjacent outer strip replacing the caved one. The variations of top coal loss and waste rock ratio with time reflect the different phases of top coal caving. In order to improve coal recovery and limit the amount of caved roof rock, the waste rock ratio should be controlled below 10 %. When the waste rock ratio reaches this value, the caving opening should be closed. This paper provides theoretical bases for the improvement of top coal recovery in the fully mechanized top coal caving mining of extra thick coal seams. 相似文献
6.
With hard roof conditions and the influence of side and front abutment pressures, pressure bump and large deformations periodically occur in the advanced support area of longwall face gob-side gateroads. To control the strong strata behaviours in gob-side gateroads, “directional hydraulic fracturing, to cut off the roof hanging over the adjacent gob area, and pre-fracturing of the roof, located behind the working face being extracted,” are performed. The directional initiation of hydraulic fracturing is controlled by pre-slotting, and this action guides the propagation of hydraulic fractures in three-dimensional space. The oriented fractures meet engineering requirements by cooperating with both the in situ ground stresses and the mining-induced stresses, as well as the technology of hydraulic fracturing. In field applications, hydraulic fracturing has proven to be a viable option for weakening hard roofs, destressing the side and front abutment pressures at the mining face and also transferring in situ and mining-induced stresses. Successful field tests in the Tongxin coal mine, Datong district, as well as other coal mines, show that hydraulic fracturing in both a hanging roof over an adjacent gob area and in the gob area behind the advancing working face controls the behaviour of strong strata material on the gob-side of gateroads in longwall mining and also guarantees safe extraction at the working face. 相似文献
7.
The paper discusses the concept and methodologies for the development of longwall face stability index (LFSI). LFSI is used
for estimation of chock-shield pressure and face convergence. The index comprises of engineering properties of main roof,
depth of mining, different support capacities and mechanical properties of coal seam being mined and provides a numerical
value in the range of −6.17 to 8.13. In this study, 324 finite element models of longwall panel are developed based on various
combinations of geomining conditions of Indian coal measure strata. The LFSI is an outcome of the results from finite element
models. This paper illustrates a real life example for the estimation of chock shield pressure and face convergence based
on LFSI. Validation of the LFSI based calculation is carried out with the field monitored data and found that the LFSI based
approach is sufficient to forecast face stability parameters at longwall face. 相似文献
8.
新疆托克逊县雨田煤矿含煤地层为侏罗系下统八道湾组,3-3号煤层厚度大、结构简单,为该矿的主采煤层。由于受坚硬顶板条件的制约,一直沿用"刀柱式采煤法",不仅回采率低,同时存在重大的安全隐患。根据煤层顶板物理力学性质测定结果,结合矿井3-3号煤层的赋存条件,确定工作面的顶板管理采用"超前工作面深孔预爆破控制坚硬顶板"的方式。该技术有效的提高了回采的安全性,顶板基本随采随冒,工作面无明显冲击来压现象,支架载荷变化平缓,资源回收率大幅提高。 相似文献
9.
Shuai Zhao Shiliang Wu Lulin Yang Hui Wang 《Geotechnical and Geological Engineering》2017,35(1):195-202
A new form of roof—”secondary roof structure” form, according to the characteristics of significant differences existing between the measured roof pressure and the roof pressure calculated by “support-surrounding rock” formulas, exists in working face that was mined under the upper gob at short range in Shendong mining area. The reasons why additional static load of secondary roof came into being were gained through the analysis of main roof weight distribution coefficient. It is that main roof can not transfer all the static load to the front coal wall and the rear caved gangue, and partial weight of the gangue of upper gob served as the additional static load attaching to the roof of working face. The roof parameters of five working faces mining under the upper gob were counted based on the field measurement and theoretical analysis. What is more, here, the relationship between the M/L value and the roof form was analyzed. Also the roof pressure of 21305 working face of 1?2 coal seam was calculated based on the secondary roof structure model, and the additional static load coefficient (T) was used as measurement of the additional static load of secondary roof. Finally, the directions which can be made a breakthrough in theoretical research of secondary roof were introduced. 相似文献
10.
应用覆岩空间结构学术观点对孤岛顶煤综放采场冲击矿压机制及其控制技术进行研究。根据覆岩关键层的岩性、层位、范围等因素,覆岩关键层空间结构分为覆岩空间大结构和基本顶有限矿压结构。孤岛顶煤采场冲击矿压发生机制：①孤岛顶煤综放采场 ? 型空间大结构形成过程是集中压力逐渐增加的过程,是该时间段发生冲击矿压的力源;②采场基本顶形成最下位 ? 型空间结构后,随着工作面推进,基本顶块体产生滑落失稳,造成工作面冲击矿压现象。通过对分段来压理论、基本顶结构失稳理论和坚硬顶板预断裂理论对覆岩关键层空间结构运动的控制作用研究,提出采用覆岩空间结构理论分析、分阶段降低放煤率、坚硬覆岩预爆泄压技术、覆岩坚硬岩层破裂的微地震监测技术等方式方法预防冲击矿压的发生。 相似文献
11.
倾斜煤层沿空半煤岩巷由于围岩结构的非对称性和非均质性,受采掘扰动影响,巷道围岩呈现更严重的变形破坏。为揭示不同基本顶断裂形式对倾斜煤层沿空半煤岩巷围岩稳定性的影响规律,采用数值模拟方法针对该类巷道4种基本顶断裂形式下巷道围岩变形特征进行了研究。结果表明:基本顶断裂线位置对该类巷道围岩稳定性的影响程度由小到大依次为:采空区侧、煤柱上方、实体煤侧、巷道上方;基本顶断裂线位于采空区侧时,煤柱轴向、横向应力增速均小于其他情况,垂直位移也最小,煤柱变形在允许范围内,可保持后期对顶板的支承能力,对巷道维护最有利。在此基础上,以贵州某矿1511工作面回风巷为工程背景进行了工业试验,通过理论计算和现场钻孔探测综合分析得出,为避免基本顶断裂线位于煤柱上方靠巷道侧,下一步掘进时煤柱宽度应由3 m改为5 m。掘采期间断面检测结果显示,断面最大收缩率为23.3％,最大非对称变形率为5.2％,巷道整体均匀协调变形,进一步验证了研究成果的可靠性。 相似文献
12.
针 对综 放 工 作 面采 出 量 用 水分 、灰 分和 含 矸 改 正 后 的 统 计 产 量 代 替 的 诸 多 不 合 理 性 ,利 用 相 同 煤 层 或 煤 层结 构、煤层 顶 底板 条件 相 似的 走向 长 壁、倾 向 分层 开采 的 工作 面采 出 量和 统计 产 量的 历史 资 料来 建立 数 学 关系 ,进 而采 用单 位 统计 产量 法 来计 算综 放 工作 面采 出 量,为综 放工 作 面采 出量 计 算提 供了 一 条新 方法 及 新思 路。 相似文献
13.
浅埋煤层非坚硬顶板强制放顶实验研究 总被引：5，自引：0，他引：5
以南梁煤矿地质资料为依据,通过对不同覆岩条件和不同强制放顶方案的相似材料模拟实验,证明整体性较好的顶板以强制放顶减小工作面初次来压步距是可行的,既可实现工作面连续推进,又可避免顶板大面积垮落带来的安全隐患。实验揭示了地表厚粘土层浅埋煤层单体支柱工作面开采时,顶板活动及矿山压力显现规律;为南梁煤矿单体支柱长壁工作面实现连续开采,提供了可靠依据。 相似文献
14.
Numerical Investigation of the Dynamic Mechanical State of a Coal Pillar During Longwall Mining Panel Extraction 总被引：2，自引：1，他引：1
Hongwei Wang Yaodong Jiang Yixin Zhao Jie Zhu Shuai Liu 《Rock Mechanics and Rock Engineering》2013,46(5):1211-1221
This study presents a numerical investigation on the dynamic mechanical state of a coal pillar and the assessment of the coal bump risk during extraction using the longwall mining method. The present research indicates that there is an intact core, even when the peak pillar strength has been exceeded under uniaxial compression. This central portion of the coal pillar plays a significant role in its loading capacity. In this study, the intact core of the coal pillar is defined as an elastic core. Based on the geological conditions of a typical longwall panel from the Tangshan coal mine in the City of Tangshan, China, a numerical fast Lagrangian analysis of continua in three dimensions (FLAC3D) model was created to understand the relationship between the volume of the elastic core in a coal pillar and the vertical stress, which is considered to be an important precursor to the development of a coal bump. The numerical results suggest that, the wider the coal pillar, the greater the volume of the elastic core. Therefore, a coal pillar with large width may form a large elastic core as the panel is mined, and the vertical stress is expected to be greater in magnitude. Because of the high stresses and the associated stored elastic energy, the risk of coal bumps in a coal pillar with large width is greater than for a coal pillar with small width. The results of the model also predict that the peak abutment stress occurs near the intersection between the mining face and the roadways at a distance of 7.5 m from the mining face. It is revealed that the bump-prone zones around the longwall panel are within 7–10 m ahead of the mining face and near the edge of the roadway during panel extraction. 相似文献
15.
Navid Hosseini Kamran Goshtasbi Behdeen Oraee-Mirzamani Mehran Gholinejad 《Arabian Journal of Geosciences》2014,7(5):1951-1956
The state of periodic loading and the interval of periodic roof weighting have an important role in geomechanical stability and, hence, in the continuity of longwall mining operations. In this paper, the mechanism of roof caving in longwall mining—together with the effect of engineering and geomechanical properties of surrounding rock masses on the magnitude and timing of periodic loading—is studied. For this purpose, a longwall mine is first modeled using Phase2 software, and then, by simulating the roof caving process, the periodic roof weighting intervals is calculated. Based on the numerical modeling, the first roof weighting interval and the periodic roof weighting interval are calculated as 27.2 and 12.1 m, respectively. Sensitivity analysis is then applied to determine the effect of changes in the mechanical properties of the rock mass, especially in the main roof and immediate roof. The results of the analysis show that as GSI and quality of the immediate roof increases, the periodic roof weighting interval also increases. Hence, the applied algorithm in this research study can effectively be utilized to calculate the periodic roof weighting interval in the longwall mining method. 相似文献
16.
Monitoring of strata control parameters and behaviour of a powered support was carried out during an experimental trial of a mechanized longwall sublevel caving face for exploitation of a 7.5m thick coal seam. Field observations indicated that the requirement of support density for underwinning of top coal by sublevel caving under intact strata is different from that for underwinning under broken and fractured rock mass. Analysis of the leg closure observations and support resistance variations during different mining cycles showed rapid increase of the setting load density of the support in relation to the yield load density. This resulted in a large amount of leg closure during mining cycles of the sub level caving face under broken rock strata. Due to operational constraints, the field observations could not provide enough information to visualize the behaviour of the overlying rock strata. Simulation of the field conditions was therefore performed on a physical model to bridge this gap of information. Results of laboratory investigations on the physical model are combined with those of the field to explain the critical behaviour of the support system during sublevel caving under broken rock strata. 相似文献
17.
不规则煤层开采容易引发顶板应力集中、矿压显现异常等问题,为探究变面长采场顶板破断规律与结构演化特征,针对工作面斜长由小变大的突变型采场不同开采阶段的几何特征与力学成因,运用小挠度薄板弯曲理论依次建立并解析4种边界条件的顶板结构模型。根据变面长采场顶板矿压分区显现特征,采用MATLAB与FLAC3D数值模拟方法分析顶板破断规律与宏观力学响应。通过系统分析与总结归纳,构建了变长工作面“三场三区三结构”的覆岩结构传递演化模式,提出了“两场两规律”的顶板分区破断效应。并通过典型工程案例的矿压实测进行应用验证。结果表明:变面长采场分为小面采场、变面采场和大面采场,小面采场顶板为缓压型结构,发生的是传统“O?X”形破断;变面采场顶板为突变型结构,顶板断裂产生的延长形与漂移形“O?X”破断裂隙与大面采场增压型结构顶板的裂纹发育特征较为相似,故将二者整合为全大面采场;全大面采场顶板发生的是“X?O”形破断,裂纹继续发展产生延长形破断,形成“两场两规律”的顶板破断理论。研究结论为探明变面长采场的覆岩运移本质,加强深部复杂煤层赋存条件下的顶板灾害防控提供了重要依据。 相似文献
18.
Geological and geotechnical aspects of underground coal mining methods within Australia 总被引：1，自引：1，他引：0
B. Scott P. G. Ranjtih S. K. Choi Manoj Khandelwal 《Environmental Earth Sciences》2010,60(5):1007-1019
About one quarter of the coal produced in Australia is by underground mining methods. The most commonly used underground coal
mining methods in Australia are longwall, and room and pillar. This paper provides a detailed review of the two methods, including
their advantages and disadvantages, the major geotechnical and operational issues, and the factors that need to be considered
regarding their choice, including the varying geological and geotechnical conditions suited to a particular method. Factors
and issues such as capital cost, productivity, recovery, versatility and mine safety associated with the two methods are discussed
and compared. The major advantages of the longwall mining method include its suitability for mining at greater depth, higher
recovery, and higher production rate compared to room and pillar. The main disadvantages of the room and pillar method are
the higher risks of roof and pillar collapse, higher capital costs incurred as well as lower recovery rate. 相似文献
19.
结合延安某拟建水库的工程地质条件及采空区赋存状况,在分析房柱式采空区变形破坏形式及机理的基础上,分析了房柱式采空区对拟建水库坝基的稳定性及渗漏性的影响。稳定性分析认为:拟建场地采空区处于不稳定状态,在坝体荷载作用下,将引起采空区"活化",采空区对坝基及泄水涵洞等附属构筑物的稳定存在严重影响。渗漏分析认为,下伏采空区对拟建水库渗漏存在严重影响。在采空区未发生大面积拱冒、切冒破坏的前提下,采空区引起拟建水库的渗漏量为1 671.9 m3/d,约占水库年平均流域径流量的17.9%。当采空区发生大面积拱冒、切冒破坏条件下时,采空区产生的切冒破坏将引起坝基及两侧坝肩的绕流,在切冒陷落区与不扰动区接触带出现台阶,垂直坝基轴线方向形成上下游贯通裂缝或空洞,形成管涌破坏,导致坝体失稳。鉴于此,应对坝基采空区进行有效治理,以确保建设工程安全。 相似文献
20.
针对多个综放采场出现的支架立柱压爆、油缸变形等异常矿压显现,通过对综放采场上覆岩层的运动范围及运动特点、顶板结构动态稳定性的分析,探讨了综放工作面异常压力产生的机理。得出了顶板结构局部铰接失稳（滑落失稳）是造成异常压力主要原因的结论。由于滑落失稳的原因不同,可分为水浸蚀型、地质构造型和顶板失稳型。通过对综放采场支架作用力的分析,给出了计算异常压力的公式。利用顶板结构动态稳定性判断准则,可对异常压力的类型进行判别,从而进一步确定异常压力的计算方法,为采场支架选型和现场控制异常压力提供理论依据。 相似文献