Rock pressure relief is the basic alternative for sustainable underground mining

Retreat longwall mining is the most productive system for underground extraction of tabulated deposits. However, the steady growth of the mining depth dramatically increased the ground pressure in chain pillars protecting the longwall entries. Therefore, several coal industries have tried to shift to pillarless mining and practiced maintenance of the head or tail entry behind the longwall in the stress relief zones using the backfill bodies in the thin coal seams. We modernized the pillarless variant of the retreat longwall system introducing the third roadway, which is driven in the consolidated goaf behind the moving longwall in a stress relief zone. We used a computer code FLAC3D to simulate stress redistribution during pillarless extraction of adjacent panels that assisted to determine optimal parameters of mining layout. This modernized technology provides for sustainable mining due to enhancement of transport, ventilation, safety conditions, and a comfortable environment because of the stability of the underground roadways, which serve the high productive longwalls.

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Analysis of the Relative Position of the Slope and Underground Mining Area and its Influence Properties

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.634-638.3277 ◽

2013 ◽

Vol 634-638 ◽

pp. 3277-3281 ◽

Cited By ~ 1

Author(s):

Shi Guo Sun ◽

Hong Yang ◽

Chun Sheng Li ◽

Bao Lin Zhang ◽

Jia Wang ◽

...

Keyword(s):

Slope Stability ◽

Underground Mining ◽

Mining Area ◽

Open Pit ◽

Stability Factor ◽

Mining Depth ◽

Extracellular Region ◽

Geological Conditions ◽

Slope Rock ◽

The Stability

The stability state of slope rock mass is relating to each other’s relative location during the transformation from open-pit to underground mining, it’s the most disadvantageous influence on the slope stability when the underground mining area is located in the toe of slope, and it’s the best influence as in the slope extracellular region. Slope stability factor changes with the geometric dimensions of underground mining increased, but not in direct proportion. Under the condition of constant geometric dimensions of mining area, the influence on slope stability is changing with the mining depth increased. Thus indicating that the influence on slope stability by underground mining has its spatial property, and to determine the specific influence value requires a combination of many factors, such as the relationship of relative spatial position, the geometric dimensions of mining area, engineering geological conditions and so on.

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Ground surface subsidence as effect of underground mining of the thick coal seams in the Jiu valley basin / Osiadanie gruntów wskutek wybierania pokładów o dużej miąższości w kopalniach zagłębia w dolinie Jiu

Archives of Mining Sciences ◽

10.2478/v10267-012-0036-z ◽

2012 ◽

Vol 57 (3) ◽

pp. 547-577 ◽

Cited By ~ 2

Author(s):

Ilie Onica ◽

Dacian Marian

Keyword(s):

Surface Deformation ◽

Longwall Mining ◽

Underground Mining ◽

Ground Surface ◽

Surface Subsidence ◽

Coal Seams ◽

Elasto Plasticity ◽

Ground Surface Subsidence ◽

Time Dependent Analysis

Abstract In the case of the thick and gentle coal seam no. 3 of the Jiu Valley Coal Basin (Romania), the mining methods are by use of the longwall mining technologies with roof control by caving or top coal caving. In this paper, it is presented the analysis of the complex deformations of the ground surface, over time, as a consequence of the coal mining in certain mining fields of the basin. Also, it is analysed the ground surface subsidence phenomenon using the CESAR-LCPC finite element code. The modelling is made in the elasticity and the elasto-plasticity behaviour hypothesis. Also, the time dependent analysis of the ground surface deformation was achieved with the aid of an especial profile function. The obtained results are compared with the in situ measurements data basis.

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Optimization of Stope Structural Parameters in Phosphorite Mine and its Stability Analysis

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.580-583.1268 ◽

2014 ◽

Vol 580-583 ◽

pp. 1268-1272 ◽

Cited By ~ 1

Author(s):

Xiang Xing Li ◽

Ke Gang Li

Keyword(s):

Structural Parameters ◽

Simulation Method ◽

Surrounding Rock ◽

Room And Pillar Mining ◽

Rock Stability ◽

Mining Depth ◽

Ground Pressure ◽

Pillar Mining ◽

Phosphate Deposit ◽

The Stability

A mine plans to exploit the low dip thin phosphate deposit by room-and-pillar mining. But a township highway is just above the orebody, and its distance is only 80m, in order to better control the ground pressure in stopes and ensure the operation security, the size of room and pillar must be reasonably designed to maintain the stability of stopes and surrounding rock. The 3D-σ numerical simulation method was applied to analyze the surrounding rock stability in different stope structure parameters. The results show that when holding the size of pointed prop unchanged, the surrounding rock stability would decline with the increase of room width and pillar spacing, for security, the mining plan, the pointed prop is 3×3 m, the stope width and pillar spacing is not more than 9 m, were considered to be one of the optimal. In addition, it is important to emphasize that if the mining depth exceeds 300m, some methods, such as decreasing the spacing of stope and pointed props or increasing the pillar size, need to be taken to avoid the stope instability caused by greater ground pressure.

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Stability of "Support-Surrounding Rock" System for Fully Mechanized Longwall Mining in Steeply Dipping Coal Seams

10.21203/rs.3.rs-403141/v1 ◽

2021 ◽

Author(s):

Luo Shenghu ◽

tong wang ◽

Wu Yongping ◽

Huangfu Jingyu ◽

Zhao Huatao

Keyword(s):

Coal Seam ◽

Longwall Mining ◽

Stability Control ◽

Surrounding Rock ◽

Coal Seams ◽

Physical Test ◽

Rock System ◽

Working Face ◽

The Stability ◽

Mining Height

Abstract The key to the safe and efficient longwall mining of steeply dipping seams lies in the stability control of the "support-surrounding rock" system. This paper analyzes the difficulty of controlling the stability of the support during the longwall mining process of steeply dipping coal seams in terms of the characteristics of the non-uniform filled-in gob using a combination of physical test, theoretical analysis and field measurements. Considering the floor as an elastic foundation, we built a "support-surrounding rock" mechanical model based on data obtained on "support-surrounding rock" systems in different regions and the laws of support motion under different load conditions. Our findings are summarized as follows. First, depending on the angle of the coal seam, the caving gangue will roll (slide) downward along the incline, resulting in the formation of a non-uniform filling zone in the deep gob in which the lower, middle, and upper sections are filled, half-filled, and empty, respectively. In addition, an inverted triangular hollow surface is formed on the floor of the gob in the middle and upper sections behind the support. Furthermore, as the angle of the coal seam, length of the working face, and mining height increase, the characteristics of the non-uniform filled-in gob are enhanced. Second, we found that, as a result of support by the gangue, the "support-surrounding rock" system is relatively stable in the lower part of the working face while, in the middle and upper sections of the working face, the contact method and loading characteristics of the support are more complicated, making stability control difficult. Third, the magnitude and direction of the load, action point, and mining height all affect the stability of the support to varying degrees, with the tangential load and action position of the roof load having the most significant impacts on the stability of the support. Under loading by the roof, rotation and subsidence of the support inevitably occur, with gradually increasing amplitude and effects on the inter-support and sliding forces. Finally, we found that it is advisable in the process of moving the support to adopt "sliding advance of support" measures and to apply a "down-up" removal order to ensure overall stability. These research results provide reference and guidance of significance to field practice production.

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Determination of the Parameters of Technological Schemes for the Development of Coal Seams Prone to Spontaneous Combustion using Computer Simulation

E3S Web of Conferences ◽

10.1051/e3sconf/201910501016 ◽

2019 ◽

Vol 105 ◽

pp. 01016

Author(s):

Sergey Meshkov

Keyword(s):

Computer Simulation ◽

Spontaneous Combustion ◽

Longwall Mining ◽

Underground Mining ◽

Fire Hazard ◽

Modern Technology ◽

Coal Seams ◽

Mining Operations ◽

Gas Dynamic ◽

Mining Coal

The study considers thr problem of endogenous fire hazard in underground mining of coal seams prone to spontaneous combustion. The main trends in the development of modern technology of underground coal mining are shown. The interaction of air-gas-dynamic and geomechanical processes in the development of coal seams by longwall mining is considered. The possibilities of computer simulation of air-gas-dynamic processes in the extraction districts of modern coal mines are considered. The significant influence of geological and mining conditions of mining operations on the distribution of air flow in extraction districts and the efficiency of gas emission control in the workings of the extraction districts are shown. The design scheme and the results of numerical studies (methane and oxygen concentration fields) are given. It is concluded that it is necessary to determine the rational parameters of the preparation, ventilation, isolated drainage and degassing schemes when developing gas-bearing coal seams that are prone to spontaneous combustion. Recommendations are given on improvement of the safety in mining coal seams that are prone to spontaneous combustion.

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Research on Stability of Overburden Structure around Longwall Mining Face in Steeply Dipping Seam Group

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.724.100 ◽

2015 ◽

Vol 724 ◽

pp. 100-110

Author(s):

Shi Guang Ren ◽

Yong Ping Wu ◽

Jian Hui Yin

Keyword(s):

Coal Seam ◽

Longwall Mining ◽

Coal Pillar ◽

Beam Theory ◽

Coal Seams ◽

Working Face ◽

Rock Structure ◽

Longitudinal Bending ◽

Mining Face ◽

The Stability

The steeply dipping seam group is defined by the two or more coal seams ,a pitch between 35°~55°. Using masonry beam theory, longitudinal bending theory and “R-S-F” dynamics control theory built a lower area overburden structure mode. Analysed the stability of low position coal seam. The balance requirement and the strength of the structure which is affected by the caving rock and lower coal roof were given. It easily generates two lower position steps rock structure in inclination along working face. Regular breaking of the second structure is the main reason leads to the imbalance of the structure between upper coal pillar and upper coal mining face.The interaction among multiple coal seam panels and overburden structures is the main reason that causes the rock disaster, the unbalance of the lower area may lead to pushing accident, the imbalance of the upper area can generate shock pressure.

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Stability Evaluation and Safety Monitoring of Pressure in Yichang Phosphorus Mine

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.170-173.589 ◽

2012 ◽

Vol 170-173 ◽

pp. 589-592

Author(s):

Yun Xiao ◽

Xian Fu Li ◽

Bin Tian ◽

Jia Guo Wang

Keyword(s):

Underground Mining ◽

Element Model ◽

Automatic Monitoring ◽

Test Collection ◽

Stability Evaluation ◽

Automatic Monitoring System ◽

Ground Pressure ◽

Mining Conditions ◽

The Stability ◽

Matter Element Model

The disasters dynamics and security of phosphate are important problems in Phosphorus ore-deposit mining. So monitoring in unstable, hazardous areas and goaf can effectively focus on the activities of ground pressure. Based on mine-site exploration, engineering test, collection of physical and mechanical parameters for ore, research of geology and mining conditions, the main controlling factors of ground pressure were identified. Combining practical projects, the fuzzy matter-element model of stability evaluation on ground pressure in empty areas was built and analyzed, which showed the good agreement with the evaluation results and measured values. At the same time, based on the stability of underground mining partition, automatic monitoring system of phosphate was constructed, which may provide some useful advices for the safety study of ground pressure in phosphate rock mass.

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Research on the Mechanism of Main Roof Advanced Breaking and Supporting Technology When Long-wall Face Passing Through Abandoned Roadways

10.21203/rs.3.rs-775784/v1 ◽

2021 ◽

Author(s):

Pan Weidong ◽

Deng Cang ◽

Li Boyang ◽

Zhang Kunming ◽

Gao Shan

Keyword(s):

Underground Mining ◽

Coal Pillar ◽

Main Roof ◽

Simulation Method ◽

Critical Value ◽

Ground Pressure ◽

Restricted Problems ◽

Mining Condition ◽

Support Force ◽

The Stability

Abstract Unlike general long-wall mining, the roof activity is more intense when long-wall face passes through the abandoned roadway. Technically, the coal pillar between the abandoned roadway and the long-wall face will suddenly fail with a certain critical value of its width, leading to the roof breaks in advance and other production-restricted problems because of the support loss, which will be a great threat to underground mining activities. In order to guarantee a safe mining condition, therefore, it is greatly necessary to uncover how the roof breaks in advance and how to cope with it. From the stability maintaining of the key block perspective, this paper took for research that the 12404-1 long-wall face of Wulanmulun coal mine, China. The critical value of the coal pillar’s width was determined to be about 5m by theoretical analysis, likely, the appropriate support force of the abandoned roadway’s roof is about 4020KN per meter. Meanwhile, a numerical simulation method was adopted to study the ground pressure when the long-wall face passing through the abandoned roadway. Correspondingly, a compound supporting technology involving the roof presplit technique, anchor cable supporting and pumping pillar supporting were proposed for the roof of the abandoned roadway, and it practically worked well.

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Research on determining the safe mining depth in special geological conditions of Mong Duong coal mine

Journal of Mining and Earth Sciences ◽

10.46326/jmes.2021.62(5).07 ◽

2021 ◽

Vol 62 (5) ◽

pp. 76-83

Author(s):

Chung Van Pham ◽

Dac Manh Phung ◽

Ha Thu Thi Le ◽

Trong Gia Nguyen ◽

Trung Thanh Ngo ◽

...

Keyword(s):

Coal Mine ◽

Underground Mining ◽

Water Bodies ◽

Coal Seams ◽

Mining Depth ◽

Geological Conditions ◽

Mineral Loss ◽

Safe Mining

The displacement and deformation of strata due to underground mining is one of the factors that negatively affect the safety of production activities. The strata displacement and deformation depend on many factors such as mining geological conditions, safe mining depths, and mining technologies. The determination of the safe depths is important for calculating the size of safety pillars to minimize mineral loss. To date, there have been many studies to determine safe mining depths under normal geological conditions. However, not much research has been conducted to determine safe mining depths with special geological conditions such as many folds, breaks, faults, and under water-bearing objects. This research introduces a method to determine the safe mining depths for the reservoir set in special geological conditions with folds and excavating several seams under water bodies. The proposed method employs the principle of the similar geological zone theory to calculate the safe mining depths. The method is applied to the Mong Duong coal mine, with three coal seams numbered 5, 6, and 7 with the depth of 210, 180, and 136 m, respectively. The results of mining depths safe obtained H5= 240m, H6 =192m, H7= 136m, respectively.

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