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1.
This paper attempts to relate the lithology and fabric of four main groups of Newcastle Coal Measures rock types to their geotechnical properties and engineering behaviour. The four groups comprise: massive sandstone and conglomerate; claystones and tuffs; mudstone, shale and siltstone; and the coal itself. Although their geological relevance is primarily concerned with underground coal mining, these rocks are exposed at the surface across most of Newcastle and its suburbs, and are thus significant in terms of urban environmental geology. The key mining issues include longwall support design and panel layouts, caving and subsidence mechanisms, soft floors and stiff roofs, water inflows and pillar design. The urban geotechnical issues include landslides and rock falls, shallow abandoned mine workings, reactive and erodible soils, waste disposal and potential sources for geomaterials. 相似文献
2.
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
3.
In underground coal mining any increase in coal recovery rate is dependent on a decrease in pillar size. Backfilling is one way of reducing the required size of pillars and hence the volume of coal left underground. Therefore any comparisons made between a self-supported mine layout and backfill supported mine layout are based directly on pillar design. The most effective way to examine the effect of backfill on pillar support, and subsequently the rate of recovery, would be to incorporate the mechanisms of backfill support directly into the current design procedure for coal pillars. This paper presents a review of the mechanics of backfill support, a method of estimating the magnitude of that support based on earth pressure theory, and an example that incorporates backfill support into current coal pillar design. 相似文献
4.
De-zhong Kong Wei Jiang Yi Chen Zheng-yang Song Zhenqian Ma 《Arabian Journal of Geosciences》2017,10(8):185
Low recovery of longwall top coal caving (LTCC) remains one of the most difficult engineering problems in this mining method and impedes its application. The top coal left in the gob at face end accounts for a large portion of the total coal loss, and the instability of the leftover triangle coal at face end has long been a threat to the safety of miners and the mining equipment. In this paper, based on the engineering background of Ruilong mine, we explore the stability of the roof at the end of the face by using theoretical analysis, numerical simulation, and field measurement. Results reveal that in the inclined longwall top coal caving face, the immediate roof forms an “arch” structure, and the basic roof forms a “masonry beam” structure after the roof collapses; working resistance of the support calculated by the method of ultimate bearing capacity was adequate to meet the requirement of roof load; roof load of coal pillar was related to the length of key block and fracture position; and increasing the size of coal pillar could ensure the stability of both coal pillar and roof. 相似文献
5.
Deyu Qian Nong Zhang Hideki Shimada Cheng Wang Takashi Sasaoka Nianchao Zhang 《Arabian Journal of Geosciences》2016,9(1):82
Goaf-side entry driving in underground coal mines could greatly improve coal recovery rates. However, it becomes more difficult to maintain stability, especially in deep coal mines. Pillar width plays a pivotal role in the stability of goaf-side entry driving. To obtain a reasonable and appropriate narrow pillar width, theoretical calculations of the widths of mining-damaged zone and limit equilibrium zone in the pillar are derived according to limit equilibrium theory. Based on the stability issues of goaf-side entry driving in the first island longwall coal face (LCF) at a depth of 800 m below the surface in Guqiao Coal Mine in China, a numerical model is established by FLAC software to analyze the stability of the surrounding rock of goaf-side entry driving during excavation, using various coal pillar widths and support schemes. The results obtained from theoretical calculations, numerical simulation, and engineering practice indicate that an 8-m-wide coal pillar is relatively reasonable, appropriate, and feasible. Field measurements show that deformations of the surrounding rock could be efficiently controlled 31 days after the support schemes were implemented in goaf-side entry driving with an 8-m-wide narrow pillar along the adjacent goaf side with a compaction duration of 10 months. The mining influence range of the overlying LCF on the stability of goaf-side entry driving is found to be the area from 50 m ahead of the LCF to 70 m behind the LCF as it passes over the measurement point. 相似文献
6.
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
7.
Jixiong Zhang Qiang Sun Nan Zhou Jiang Haiqiang Deon Germain Sami Abro 《Arabian Journal of Geosciences》2016,9(10):558
In China’s western coal mining area, the traditional room mining technology is facing coal pillar instability, mine earthquake, large-area roof subsidence in the goaf, surface subsidence, water and soil loss, vegetation deterioration, and other environmental problems. To solve the aforementioned problems and to improve coal recovery, the roadway backfill coal mining (RBCM) method was proposed as a solution and its technical principle and key equipment were presented in this paper. In addition, the microstructure and mechanical behavior (strain-stress relation in confined compressive test) of aeolian sand and loess backfill materials were studied for a rational backfill design for underground mines. Further, coal pillar stress, plastic zone change, and surface deformation of the RBCM schemes were studied using the FLAC3D numerical simulation software, and a reasonable mining scheme of “mining 7 m and leaving 3 m” was determined. The engineering application in Changxing Coal Mine shows that the RBCM method with loess and aeolian sand as backfill materials allows a stable recovery of coal pillars with a recovery ratio of more than 70 %. The maximum accumulated surface subsidence and the maximum horizontal deformation were measured to be 15 mm and 0.8 mm/m respectively, indicating that the targeted backfilling effect can help protect the environment and also control surface subsidence. 相似文献
8.
Some villages and bridges are located on the ground surface of the working district no. 7 in the Wanglou Coal Mine. If longwall mining is adopted, the maximum deformation of the ground surface will exceed the safety value. Strip mining is employed for the working district no. 7 which is widely used to reduce surface subsidence and the consequent damage of buildings on the ground surface. To ensure the safety of coal pillars and improve the recovery coefficient, theoretical analysis and numerical simulation (FLAC 3D) were adopted to determine the coal pillar and mining widths and to discuss the coal pillar stress distribution and surface subsidence for different mining scenarios. The results revealed that the width of coal pillars should be larger than 162 m, and the optimized mining width varies from 150 to 260 m. As the coal seam is exploited, vertical stress is mainly applied on the coal pillar, inducing stress changes on its ribs. The coefficient of mining-induced stress varies from 2.02 to 2.62 for different mining scenarios. The maximum surface subsidence and horizontal movement increase as the mining width increases. However, when the mining width increases to a certain value, increasing the pillar width cannot significantly decrease the maximum subsidence. To ensure the surface subsidence less than 500 mm, the mining width should not be larger than 200 m. Considering the recovery coefficient and safety of the coal pillar, a pillar width of 165 m is suggested. 相似文献
9.
Summary The demand for increased productivity and the problems associated with mining at greater depths have increased the interest in using the yield pillar concept in the United States. This paper summarizes chain pillar behaviour in a mine that historically experienced coal bumps in both room-and-pillar and longwall sections. Results indicate that, generally, the chain pillars yield as designed, but that yielding occurred either after development or with approach of the longwall face. The Bureau of Mines investigated several yield pillar design approaches to possibly explain observed differences in pillar behaviour. These approaches suggest that very localized conditions, such as coal and rock properties, cover depth, and extraction height, may influence the behaviour of any one pillar. At this mine, yielding chain pillars result in de-stressing of the longwall entries and the transfer of potentially dangerous stress concentrations to adjacent panels. Pre-longwall-mining behaviour indicates the existence of a pressure arch, the width of which increases with depth. Results indicate that use of yield pillars improves stress control, reduces bump potential, and increases resource recovery. 相似文献
10.
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
11.
C. J. Booth E. D. Spande C. T. Pattee J. D. Miller L. P. Bertsch 《Environmental Geology》1998,34(2-3):223-233
Subsidence due to longwall underground coal mining changes the hydraulic properties, heads, yields, and in some cases the
groundwater chemistry of overlying bedrock aquifers. A 7-year study of a sandstone aquifer overlying an active longwall mine
in Illinois has supported a comprehensive model of these impacts. Subsidence caused increases in permeability and storativity
over the longwall panel. These changes initially caused a major decline in water levels in the sandstone, but the aquifer
recovered slightly within a few months and fully within several years after mining. The enhanced hydraulic properties combined
with potentiometric recovery resulted in a zone of greater well yield. However, at sites with very poor transmissivity and
inadequate recharge pathways, recovery may not occur. Also, at the study site, the physical enhancement was accompanied by
a deterioration in groundwater quality from slightly brackish, sodium bicarbonate water to more brackish water with increased
sulfate levels.
Received: 17 March 1997 · Accepted: 9 September 1997 相似文献
12.
Floor design in underground coal mines 总被引：1，自引：0，他引：1
Summary Floor failure and excessive heave in underground coal mines can jeopardize the stability of the whole structure, including the roof and pillars, due to differential settlements and redistribution of stress concentrations. Besides, floor failure is detrimental to haulageway operation and can lead to unacceptable conditions of high deformation. Thus, the design of any underground opening must consider roof/pillar and floor as one structural system.This paper presents guidelines for the design of mine floors, including the necessary field and laboratory investigations and the determination of the bearing capacity of floor strata. The design methodology is based essentially on a modified Hoek-Brown rock mass strength criterion. The main modifications are the introduction of the concept of the point of critical energy release to account for the long term strength, the inclusion of tensile strength and the adoption of a lithostatic state of stress in the rock mass. The determination of the dimensionless parametersm ands result from correlations with the RMR (rock mass rating) of the Geomechanics Clasification. Nine case histories, both in longwall and room and pillar coal mining, were analyzed with the proposed methodology. 相似文献
13.
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
14.
Bali Bonaventura Alves Mangu Mishra Brijes 《Geotechnical and Geological Engineering》2021,39(2):1329-1347
Gas well drilled through longwall mining abutment pillar could potentially face instability issue due to the strata deformation following longwall panel extraction. Therefore, it is imperative to adequately design the pillar size of a longwall mining in order to ensure the stability of the gas well penetrated longwall mining abutment pillar. In this paper, the determination of suitable pillar size for protecting gas well subjected to longwall mining operation was investigated. Two scenarios of longwall gateroad system including the three and four entry system with varying pillar sizes were assessed using numerical modelling approach. The results of this study indicate that the pillar geometry plays an important role on the vertical gas well stability. In addressing the suitable pillar size for the given case study considering three entry system, the suitable chain pillar and abutment pillar size were found to be 80 ft (24.4 m) wide by 120 ft (36.6 m) length and 104 ft (31.7 m) wide by 120 ft (36.6 m) length rib to rib, respectively. Whereas, if four entry system is used, the suitable chain pillar size is 48 ft (14.6) wide by 120 ft (36.6 m) length and the abutment pillar size is 104 ft (31.7 m) wide by 120 ft (36.6 m) length rib to rib. The proposed numerical modelling procedure presented in this paper can be a viable alternative and applied to other similar projects in order to determine an optimal pillar size for protecting gas well in longwall mining area.
相似文献15.
露天底境界顶柱优化是露天转井下过渡时期的重要课题,该优化问题包括多个决策变量和多个评价指标,已有方法的优化效果不够理想。针对露天转井下境界顶柱优化特点,将遗传算法与三维数值模拟相结合,研究了境界顶柱全局优化的进化数值模拟方法,给出优化的指标和步骤,并将该方法用于大杏山铁矿的露天转井下境界顶柱的优化。工程应用表明所提出的井下境界顶柱优化方法是可行的。获得的最优方案对该矿山露天转井下的采矿设计具有指导作用。 相似文献
16.
Summary The paper describes theoretical andin situ studies of tunnel deformation in longwall coal mining. It develops a method to predict tunnel convergence profiles from the faceline in longwall mining. The method accounts for the effect of panel width, extracted seam height, deformation moduli of the goaf material and coal pillar, depth of cover,in situ structural defects, tunnel shape and tunnel size in addition to the strength characteristics of surrounding strata. The analytical technique has been validated by reference toin-situ deformation measurements in 26 face-access tunnels in Cape Breton Coalfield mines. Based on this method a series of vertical convergence profiles for different depths and extracted panel widths have been presented. 相似文献
17.
Since 1998, BHP Billiton has mined diamonds at the Ekati Diamond Mine™ near Lac de Gras in the Northwest Territories of Canada. Current operations are based on mining multiple pipes by the open-pit method, but as some pits deepen, converting to underground mining is being considered.
As a test of underground mining methods and to provide access to the lower elevations of the Panda and Koala pipes, the Koala North pipe is being developed for underground mining. Initially, the top 40 m of the pipe were mined as an open pit to provide grade information and a prepared surface for the transition to underground mining. Currently, Koala North is being developed as an open-benching, mechanized, trackless operation. Although the method was successfully used at several De Beers diamond operations in South Africa, it has never been tested in an Arctic environment.
This case study describes basic geology, mining method layout and ongoing geological and geotechnical investigation. From the beginning of underground development, geotechnical daily routines have been fully integrated within the technical services department, which supports the operation. Geotechnical, geological and structural information obtained from underground mapping and core logging is compiled, processed, reviewed and analyzed on site by the geotechnical staff. Conclusions and recommendations are implemented as part of the operations in a timely manner. This ongoing “live” process enables the operators to make the most efficient use of resources both for ground support and excavations as well as to address safety issues, which are the top priority. 相似文献
18.
长壁孤岛工作面冲击失稳能量场演化规律 总被引：1，自引：0，他引：1
煤矿冲击地压一直是困扰中国煤矿安全的主要问题,而煤矿开采过程中跳采形成的孤岛工作面由于容易产生应力集中,来压强度提高,极容易发生冲击地压。基于唐山矿T2193下孤岛工作面的地质条件,从数值分析的角度研究了煤岩体材料的非均匀性,揭示了孤岛工作面顶板周期来压时煤岩体能量释放的动态特征,分析了工作面前方能量释放激增机制。数值模拟结果显示,长壁工作面回采过程中直接顶的不断垮落造成了老顶悬空距离的不断增大,工作面周期来压时,积聚于老顶岩层内的弹性应变能将瞬间释放,容易引发工作面及巷道的冲击失稳。孤岛工作面由于其特有的矿压显现特征,老顶周期破断时所释放的弹性应变能将更加剧烈,冲击地压势必愈加强烈。孤岛工作面顶底板和煤层的能量释放激增可以作为判断煤岩体冲击失稳的前兆信息。孤岛工作面前方发生冲击破坏的主要原因是由于工作面回采过程中围岩所积聚的大量弹性能在顶板断裂时所伴随的巨大能量释放而造成的。 相似文献
19.
不同岩性顶板回采工作面矿压分布规律 总被引：4，自引：0，他引：4
采用数值模拟技术和现场矿压观测系统,研究了不同岩性顶板回采工作面矿压分布规律及其显现特征。结果表明,在煤炭开采过程中,不同岩性顶板回采工作面最大支承应力存在一定差异,在强度较高的砂岩顶板岩体中,支承压力大,工作面前方支承压力峰值距工作面距离小,初次来压步距和周期来压步距大,矿压显现强烈;而在强度较低的泥岩顶板区,顶板岩体不能和砂岩骨架层一样抵抗覆岩压力,且支承压力小,支承压力的峰值向回采工作面前方岩体内部推移,初次来压步距和周期来压步距小,矿压显现不明显。 相似文献
20.
为研究深部近距离煤层群下向卸压开采高应力演化的特征,根据潘二煤矿深部近距离煤层群8煤和6煤地质与开采技术条件,设计了下向卸压开采的二维相似材料模拟试验模型,对8煤和6煤开采引起的采动应力进行监测。系统分析了8煤下向开采与6煤开采后的采场围岩采动应力、岩层运移及不规则煤柱对采动应力演化的影响,获得了近距离煤层群8煤下向卸压开采的顶底板采动高应力演化特征及6煤回采期间覆岩运移、采动应力裂隙演化和来压特征,得出了下向卸压开采不规则煤柱对采动应力、裂隙分布的影响规律。研究不仅为以采动高应力演化为主导作用的煤岩动力灾害防治提供了理论基础,也为卸压开采采场参数设计与优化提供了技术支撑。 相似文献