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1.
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
2.
侧向支承压力分布、资源回收率以及煤柱和巷道的稳定性是大采高综放面区段煤柱宽度留设要兼顾的因素,为了确定大采高综放面区段煤柱宽度,以某矿8103面为工程背景,首先,采用理论计算和现场应力监测等方法确定大采高综放工作面倾向支承压力分布规律,得出应力降低区宽度约为8 m,原岩应力区为巷帮侧28 m外。其次,采用工程类比方法确定大采高综放工作面巷帮外侧煤体严重破裂区宽度约为4 m。最后,采用FLAC3D数值软件分析了下区段工作面回采时窄煤柱（6、8 m）和宽煤柱（28、30 m）的应力场、位移场及塑性区特征,获得不同煤柱宽度时巷道和煤柱力学特征。研究表明：当煤柱宽度6 m和8 m时,在采动支承压力下煤柱几乎无承载能力,且巷道变形量较大;当煤柱宽度28 m和30 m时,在采动支承压力下煤柱中央仍有一定的弹性核,煤柱保持稳定且巷道变形量较小。综合考虑资源回收、巷道稳定性、次生灾害控制等因素,确定大采高综放工作面区段煤柱宽度为28 m。 相似文献
3.
Summary The Bureau of Mines is investigating methods for evaluating and optimizing shaft designs for deep metal mines. This paper describes one such project at the Homestake Mine in Lead, SD. To determine a safe approach for the extraction of ore from the Ross Shaft pillar at Homestake, a basic rock mechanics approach has been taken that involves laboratory testing, field measurements, and computer modelling. The results of the study show that ore bodies in the Ross pillar can be mined safely and that the shaft will remain in elastic rock. On the basis of this work, other mines can develop finite-element modelling to evaluate the stability of mine openings and increase resource recovery. 相似文献
4.
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
5.
Monitoring the performance of rock reinforcement 总被引：5，自引：0，他引：5
A rock mechanics program has been developed and implemented in order to achieve a safe and economical room and pillar extraction of the shallow dipping orebodies at the McArthur River Mine in Australia. Three closely spaced tabular orebodies have been targeted for extraction over the life of the mine and due to economics the lowermost number 2 orebody is being mined first. This paper formulates the calculation of the 2 Orebody hangingwall spans and the appropriate rock reinforcement design for the long-term stability of the room and pillar excavations. The field trials suggested that a rock beam was formed within the hangingwall of the room and pillar operations, arresting any vertical movement of the roof. The results indicated that the weight of the beam is transferred to the pillars via an arching process and there is no need for deep-anchored reinforcement. 相似文献
6.
A number of pillars are left developed in some of the Chinese metal mines due to careless mining and lack of proper planning. There are pillars in such mines which do not contribute much in supporting the covered rock mass. Re-exploitation of these standing (non-supporting) pillars can be an efficient method for resource recovery if the remaining pillars ensure the stability of the covered host rock. In this study, a tungsten mine in Jiangxi Province, China, was chosen as a case for studying this pillar recovery scheme. Based on accurate in situ stress measurement data in the original and disturbed host rock, the storage energy in the rock mass could be estimated by numerical simulation methods. After comparing the storage energy to the sum of the fractured energy consumption and friction energy consumption (obtained from lab tests), the recyclable pillars can be identified by a cyclic judgment programming process. 相似文献
7.
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
8.
Qing Yu Jinrong Ma Hideki Shimada Takashi Sasaoka 《Geotechnical and Geological Engineering》2014,32(4):821-827
In order to find the relationship between the shaft lining stability and the coal extraction operation, a 3D numerical model of strata layers and shaft lining was established for simulating the influence of coal extraction operation on shaft lining. Certain factors including mining depth, safety pillar width, mining width and mining height were taken as the influence factors in the simulation. The results indicated that the coal extraction could lead to the initiation of the failure in the aquifer and rock layers. As the mining depth increases, the shear strain increment in aquifer becomes small. In this case, the distance between mining panel and aquifer should be larger than 220 m and the safety pillar width should not <70 m. The maximum principal stress in aquifer had a little relation to mining operations. The mining panel width should not exceed 50 m without any support. 相似文献
9.
条带开采煤柱稳定性的试验模拟与数值分析——以山东省济宁市太平煤矿为例 总被引：1，自引：0，他引：1
以山东省济宁市太平煤矿为例，采用煤柱模拟试验和数值分析手段，对薄基岩条带开采时所留设煤柱的应力应变状态、煤柱强度结构及煤柱长期稳定性进行了深入的分析与研究，揭示了煤柱稳定性及煤柱应力分布与条采尺寸、采出率、覆岩特征的相互关系，进行了条带煤柱的稳定性评价，为工程实践提供了理论依据。 相似文献
10.
The study of rock pillar failure mechanisms is an issue that is faced routinely in mining and civil industries. In mining operation, the establishment of several mining levels is often necessary to ensure adequate production. This result in the formation of pillars that must be recovered under often high stress conditions at later stages of excavation. It is, therefore, beneficial to develop guidelines that can be used in the design of rock pillars. The aim of this paper is to delve into the mechanisms involved in pillar failure as well as to investigate the non-linear behavior of rock pillars. An extensive numerical analysis was carried out to study the pillar deformation and failure process under natural loading conditions. Effects of pillar geometry and pillar strength parameters on pillar behavior were investigated for hard rock material typical of Canadian mining conditions. Numerical data were compared against field data recorded in Canadian mines. A fairly good match was achieved between numerical and field data and the conducted analysis can be used as a qualitative guideline in the design of rock pillars in underground structures. 相似文献
11.
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
12.
Solid backfill mining for coal pillar recovery in industrial squares has to ensure that the mine infrastructure, such as the shafts and substations, is not degraded or has its utility impaired by that mining. At the same time, it is important to recover as much coal as possible. As a result, it is necessary to predict mining subsidence during solid backfilling mining of coal pillars in industrial squares and to optimize the design of the working faces. At the Baishan coal mine in Anhiu province, China, there are thick layers of unconsolidated overburden above the coal seam so it is not appropriate to use the surface subsidence prediction method of equivalent mining height to predict subsidence during the mining of the coal pillars there. In order to find a reasonable coal pillar recovery scheme for the Baishan mine, a numerical simulation method is used to determine the relationships between the compression ratio of the backfilling material and the surface subsidence prediction parameters. Research was done to determine the appropriate parameters, and based on the final prediction parameters and taking the mandated protection standards for buildings and structures into account, surface subsidence is predicted and a backfill mining scheme for pillar recovery is proposed. The results show that of the six mining schemes considered, scheme 5 is the best scheme for coal pillar recovery in the industrial square at the Baishan mine. The research results are significant for similar mines with thick unconsolidated overburden anywhere in the world. 相似文献
13.
J. F. Abel Jr. 《Geotechnical and Geological Engineering》1988,6(3):215-248
Summary Soft rock pillars can be designed by several methods available in the mining literature. All of these methods include the effect of shape, or geometry, on the average strength of specimens and pillars. All of the pillar design methods include some measurement of the strength of specimens of the pillar rock. The most common rock specimen strength property measured is the unconfined compressive strength. However, the average strength of triaxially confined rock specimens is much greater than the unconfined specimen strength, which can be more important to pillar strength. The estimation of the strength of a pillar is complicated by the decrease in rock specimen strength with increase in specimen size.Editor's note: In common with North American engineering practise, the paper uses English units throughout, where feasible conversions are included in the text. Where not, the following factors may be used: 1 inch=25.4 mm; 1 ft=0.3048 m; 1 lbf/in.–2=6.895 kn/m–2; 1Tonf.=8.896 kN. 相似文献
14.
J. F. T. Agapito H. N. Maleki J. R. Aggson L. A. Weakly 《Geotechnical and Geological Engineering》1984,2(2):93-105
Summary The load carrying capacity of oil shale pillars excavated by conventional blasting can be increased significantly by presplit blasting and mechanical mining. Comparisons ofin situ vertical stresses and fractures obtained from overcoring horizontal holes in the Colony Mine, Piceance Creek Basin, Colorado indicate that conventional blasting causes a strength loss in a zone of damage approximately 3 m (10 ft) thick. Presplit blasting reduces damage significantly, and increases the load carrying capacity in the 3 m (10 ft) thick zone by 5.93 MPa (860 psi). Mechanical mining causes little or no rock damage, and an increase of 9.83 MPa (1425 psi) in strength in the same 3 m (10 ft) thick zone. Pillar design using presplit blasting and mechanical mining techniques can increase the extraction ratio by at least 3% and 5%, respectively, as compared to conventional blasting. It is speculated that comparable increases in extraction should also occur due to increases in span dimensions. 相似文献
15.
Summary This paper presents field observations on distribution of vertical stress during an experimental trial of extraction of pillars in four panels in 6.0–8.0m thick coal seam, as a part of a Science and Technology project funded by the Ministry of Coal, Govt of India. Variation of induced stress based on continuous monitoring data for the first time in Indian coal mining scenario showed distinct anomalies and potential for better understanding of strata mechanics and warning of major roof falls during pillar extraction. Numerical model studies based on finite difference code – FLAC were also conducted for stress analysis in idealized pillar mining sequence so that the influence of each stage of extraction could be identified. The numerical model results on stress concentration over the pillars, stooks and ribs showed variation of 3.6%, 8.3% and 6.1%, respectively as compared to the field observations for 7m thick coal seam at a depth cover of 60m from the surface. This indicates validity of the numerical models for stress analysis in the simulated conditions of the present field experiments. 相似文献
16.
The reasons that pillars with small width-to-height ratios fail remain unclear. This study established a mechanical model for the buckling failure of a thin pillar subjected to compressive forces to investigate the stability of reserved thin pillars (RTPs) on both sides of mining units during barrier pillar recovery. The critical buckling stress of the thin pillar was obtained using the energy variational method, and its relationship to the aspect ratio (length-to-width ratio) was investigated. The buckling instability of RTPs can be determined by comparing the RTP stress obtained from numerical simulations with the buckling stress derived from the mechanical model. 相似文献
17.
Investigation of a Limestone Pillar Failure Part 2: Stress History and Application of Fracture Mechanics Approach 总被引：1，自引：0，他引：1
Summary Observed pillar failure could not be explained by comparing pillar strength with stresses on the pillar induced by mining
activities. Instead, the effects of the combined stress history of strata and pillar on the deformational response of rock
mass and rock were assessed. Application of the principles of fracture mechanics, i.e., extension strain and strain energy
release rate criteria gave a reasonable explanation for the observed pillar behavior. The derivation of the required fracture
mechanics parameters from laboratory tests is described, and the necessity of an interdisciplinary approach to rock engineering,
i.e., the use of historical geology, engineering geology, mining engineering and rock mechanics, is mandated. 相似文献
18.
我国西部神府东胜煤田主要赋存浅埋近距煤层,煤层埋藏浅,覆岩上部厚松散层大范围分布,近距煤层开采导致覆岩与地表裂缝发育严重,加剧了原本脆弱的生态环境进一步恶化。为探究浅埋近距煤层开采覆岩与地表采动裂缝发育规律,掌握其控制方法,以柠条塔煤矿1-2煤层和2-2煤层开采为背景,结合实测统计分析、物理模拟和分形理论,掌握浅埋顶部单一煤层开采和重复采动下覆岩与地表裂缝发育特征,揭示煤柱布置对裂缝发育的控制作用。研究表明,煤层开采导致的地表裂缝可分为平行于工作面的动态裂缝和工作面开采边界地表裂缝(切眼边界侧地表裂缝和区段煤柱侧地表裂缝),动态裂缝在开采后能够实现自修复,工作面开采边界的地表裂缝不能自修复。下煤层开采区段煤柱侧覆岩与地表采动裂缝发育严重,其与区段煤柱错距密切相关。1-2煤层开采后,基岩垮落角为60°,土层垮落角为65°,边界煤柱侧地表裂缝的宽度为0.26 m。下部2-2煤层开采,煤柱叠置、错距20、40 m时,区段煤柱侧覆岩采动裂缝宽度分别为0.81、0.45和0.22 m,地表裂缝宽度分别为0.65、0.30和0.12 m。通过确定合理煤柱布置方式,能够有效控制覆岩和地表采动裂缝的发育程度,据此确定柠条塔煤矿1-2煤层和2-2煤层开采的合理煤柱错距应大于40 m。 相似文献
19.
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20.
Chandrani P. Verma John Loui Porathur N. R. Thote P. Pal Roy S. Karekal 《Geotechnical and Geological Engineering》2014,32(2):587-599
Pillar design is of paramount importance to any underground mine design. Oversized pillars may lead to loss of coal while undersized pillars may lead to instability. While underground pillars are mostly square and rectangular, highwall mining pillars are long and narrow, as they are formed after driving parallel entries in the seam from the highwall. These pillars are termed as web pillars. The overall stability of highwall depends upon these pillars as no other supports are provided in the entries. Web pillar differs from usual coal pillars in respect of w/h ratio being <3.0, with an exceptionally longer length compared to its width, to the tune of 50–500 m. Several empirical coal pillar strength equations developed for rectangular pillars are still being used with some modifications to adapt to web pillars. Review and analysis of these empirical approaches for determining web pillar strength along with a numerical approach for web pillar design are discussed in this paper. Their application to some Indian case studies is also discussed. 相似文献