scholarly journals Failure Mechanisms and the Control of a Longwall Face with a Large Mining Height within a Shallow-Buried Coal Seam

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Haijun Wang ◽  
Yingjie Liu ◽  
Yuesong Tang ◽  
Hao Gong ◽  
Guoliang Xu
Keyword(s):  
Tensile Stress ◽  
Coal Mine ◽  
Horizontal Displacement ◽  
Longwall Face ◽  
Mining Equipment ◽  
Coal Seams ◽  
Increasing Trend ◽  
Support Force ◽  
Coal Wall ◽  
Mining Height

The capabilities of mining equipment and technology in China have been improving rapidly in recent years. Correspondingly, in the western part of the country, the mining heights of longwall faces in shallow-buried coal seams have shown an increasing trend, resulting in enhanced mining efficiency. However, the problems associated with the possible failure of the coal wall then increase and remain a serious difficulty, restricting safe and efficient mining operations. In the present study, the 12401 longwall face of the Shangwan Coal Mine, Inner Mongolia, China, with a mining height of 8.8 m, is taken as an example to study the mechanisms underlying failure phenomena of coal walls and their control methods. Our results show that the failure region inward of the longwall face is small in shallow-buried coal seams, and the damage degree of the exposed coal wall is low. The medium and higher sections of the coal wall display a dynamic failure mode, while the broken coal blocks, given their initial speed, threaten the safety of coal miners. A mechanical model was developed, from which the conditions for tensile failure and structural instability are deduced. Horizontal displacement in the lower part of the coal wall is small, where no tensile stress emerges. On the other hand, in the intermediate and higher parts of the coal wall, horizontal displacement is relatively large. In addition, tensile stress increases first with increasing distance from the floor and then decreases to zero. Experiments using physical models representing different mining heights have been carried out and showed that the horizontal displacement increases from 6 to 12 mm and load-bearing capacity decreases from 20 to 7.9 kN when the coal wall increases in height from 3 to 9 m. Furthermore, failure depth and failure height show an increasing trend. It is therefore proposed that a large initial support force, large maximum support force, large support stiffness, and large support height of a coal wall-protecting guard are required for the improved stability of high coal walls, which operate well in the Shangwan coal mine.

scholarly journals Study on the Working Resistance of a Support under Shallowly Buried Gobs According to the Roof Structure during Periodic Weighting

2021 ◽  
Vol 13 (19) ◽  
pp. 10652
Author(s):  
Chen Wang ◽  
Cheng Zhu ◽  
Yong Yuan ◽  
Zhongshun Chen ◽  
Wenmiao Wang
Keyword(s):  
Coal Mine ◽  
Dynamic Pressure ◽  
Horizontal Displacement ◽  
Mining Area ◽  
Surrounding Rock ◽  
Structural Morphology ◽  
Key Stratum ◽  
Roof Structure ◽  
Coal Wall ◽  
Working Resistance

The phenomenon of dynamic pressure in the panel under shallowly buried gobs is obvious, resulting in limited and challenging support type selection. In this paper, theoretical analysis, numerical simulation and field measurement were combined to study the reasonable working resistance of the support in panels under shallowly buried gobs. First, the definition of the equivalent main key stratum (EMKS) was proposed. Then, a method of identifying the structure of the EMKS and broken key stratum blocks was given. The roof structure of the panel under a shallowly buried gob (PSBG) during strong periodic weighting could be divided into 12 types. Mechanical models of the roof structure were established, and the method to calculate the working resistance of the support was given. The Bulianta coal mine and Fengjiata coal mine in the Yushenfu Mining Area were taken as research objects. Based on the measured working resistance curve of the support, the structural morphology of key stratum blocks during strong periodic weighting was distinguished. On this basis, the working resistance of the support was calculated. Finally, FLAC2D numerical software was used to test the working resistance of the support. Based on the subsidence of the roof, horizontal displacement of the coal wall and the development range of the plastic zone in the surrounding rock, the working resistance of the support and adaptability of the surrounding rock control were verified and evaluated. The results show that it is reasonable to calculate the working resistance of the support based on the roof structure during strong periodic weighting. The research results can provide a reference for the scientific and rational selection of the support in a PSBG.

scholarly journals Dynamic Damage Mechanism of Coal Wall in Deep Longwall Face

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Shuaifeng Lu ◽  
Sifei Liu ◽  
Zhijun Wan ◽  
Jingyi Cheng ◽  
Zhuangzhuang Yang ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Tensile Stress ◽  
Damage Mechanism ◽  
Longwall Face ◽  
Stress Generation ◽  
Stress Wave Propagation ◽  
Mining Machinery ◽  
Coal Wall ◽  
The Stability ◽  
Dynamic Damage

The stability of coal wall in deep longwall face has always been a research hotspot. In this study, pure vibration signals in the coal wall during the operation of mining machinery were obtained for the first time, and their energy is mainly concentrated in 7–12 Hz. Besides, based on the law of stress wave propagation, with the coal wall of deep longwall taken as the research object, the theory of dynamic damage in coal wall was put forward from the perspective of dynamics. The results show that the loading and unloading waves generated by the mining machinery disturbance will be reflected and transmitted at the interface with different impedances, resulting in the formation of multiple unloading and loading waves and multiple tensile stress zones and stress concentration zones. These stress concentration zones tend to induce tensile stress generation and coal failure. As a result, the coal undergoes zonal failure and spalling. Through the vibration test of coal, it is found that the crack development of the coal sample can be divided into five stages, and the phenomena of zonal failure and spalling occur, which is consistent with the theory. At the same time, the sample that has gone through a large disturbance cannot be further damaged by a small disturbance, which is verified by the damage statistical constitutive model based on the isotropy hypothesis.

The Properties and Influence of Dirt Band during the Fully Mechanized Top Coal Caving in Thick Coal Seams

2012 ◽  
Vol 204-208 ◽  
pp. 414-417 ◽  
Author(s):  
Jie Shen ◽  
Wei Dong Pan ◽  
Li Lin ◽  
Xiao Meng Li ◽  
Lu Jia Fan
Keyword(s):  
Mechanical Properties ◽  
Sensitivity Analysis ◽  
Coal Mine ◽  
Recovery Rate ◽  
Physical And Mechanical Properties ◽  
Mining Area ◽  
Beam Model ◽  
Coal Seams ◽  
Average Water ◽  
Mining Height

In the coal mine of Huaibei Mining Area, based on the character of thick dirt band in the coal seams and the influences to top coal caving, the physical and mechanical properties of dirt band were analyzed. In order to improve the recovery rate of top coal, the failure mechanism of dirt band was analyzed through the cantilever beam model, and the sensitivity analysis to the length of dirt band overhang was done in the conditions of different mining height and dirt band thickness. The results show that, the average water absorption of dirt band samples is 3.5%, and the soften coefficient is 0.71, which presents that the dirt band have large softening property and poor engineering geological property. When the thickness of dirt band was more than 3.5 m, the top coal could not be caved smoothly. However, the bigger underground pressure would be helpful to the broken of dirt band and top coal seams, and the recovery rate of top coal was improved.

scholarly journals Mechanical characteristics of drum shearer with large mining height under oblique cutting

2021 ◽  
Vol 303 ◽  
pp. 01024
Author(s):  
Tian Ying ◽  
Zhang Runxin ◽  
Zhang Qiang
Keyword(s):  
Dynamic Characteristics ◽  
Feed Rate ◽  
Lower Surface ◽  
Radial Force ◽  
Oblique Cutting ◽  
Cutting Resistance ◽  
Support Force ◽  
Coal Wall ◽  
Large Mining Height ◽  
Mining Height

In order to study the dynamic characteristics of the shearer with large mining height of 8.8 m under Oblique cutting, the spatial mechanical model of the Shearer under oblique cutting was established, the angle between the drum and the working face, the load of the drum and the dynamic characteristics of the fuselage are analyzed by discrete element method and dynamics. The results show that the maximum feed rate of the front drum is 1940mm, the maximum feed rate of the back drum is 1570mm, and the angle between the front drum and the coal wall reaches a maximum of 8° at 64s, and the cutting resistance of the front drum reaches a maximum at 80s, and finally fluctuates up and down at 3.5×105N, the cutting resistance of the back drum increases with the cutting depth, and finally fluctuates up and down at 3.0×105N. The load of the front drum is 1.2 times of that of the back drum. In the process of Oblique cutting, the support force on the lower surface of the front sliding shoe increases by 3.5×105N, the support force on the lower surface of the rear sliding shoe decreases by 2.5×105N, the support force on the upper surface of the front guiding sliding shoe increases by 1.1×105N, and the support force on the upper surface of the rear guiding sliding shoe decreases by 2.3×105N, the whole machine has the tendency of forward turning and side turning to the coal wall. The average radial force between the front rocker arm and the fuselage pin is about 1.8×106N, the average radial force between the front cylinder and the fuselage pin is about 2.2×106N, and the average radial force between the rear rocker arm and the fuselage pin is about 8.0×105N, the average radial force between the rear cylinder and the PIN shaft is about 1.3×106N, which shows that the radial force at the front of the fuselage, the rocker arm and the height of the pin shaft is obviously larger than that at the rear of the fuselage. The research results are important for the design and development of large mining height shearer.

scholarly journals Methane Content Estimation in DuongHuy Coal Mine

2018 ◽  
Vol 35 ◽  
pp. 01005 ◽  
Author(s):  
Van Thinh Nguyen ◽  
Waldemar Mijał ◽  
Vu Chi Dang ◽  
Thi Tuyet Mai Nguyen
Keyword(s):  
Experimental Data ◽  
Coal Mining ◽  
Coal Mine ◽  
Coal Mines ◽  
Methane Content ◽  
Underground Coal Mining ◽  
Coal Seams ◽  
Underground Coal Mine ◽  
Different Depths ◽  
Quang Ninh

Methane hazard has always been considered for underground coal mining as it can lead to methane explosion. In Quang Ninh province, several coal mines such as Mạo Khe coal mine, Khe Cham coal mine, especially Duong Huy mine that have high methane content. Experimental data to examine contents of methane bearing coal seams at different depths are not similar in Duong coal mine. In order to ensure safety, this report has been undertaken to determine a pattern of changing methane contents of coal seams at different exploitation depths in Duong Huy underground coal mine.

scholarly journals Substantiation of Safe Conditions During Undermining of Hydraulic Waste Disposal

2018 ◽  
Vol 41 ◽  
pp. 01007
Author(s):  
Yuriy Kutepov ◽  
Aleksandr Mironov ◽  
Maksim Sablin ◽  
Elena Borger
Keyword(s):  
Rock Mass ◽  
Waste Disposal ◽  
Coal Mine ◽  
Water Body ◽  
Water Inflow ◽  
Open Pit ◽  
Coal Seams ◽  
Geological Conditions ◽  
Mine Workings ◽  
Mine Dump

This article considers mining and geological conditions of the site “Blagodatny” of the mine named after A.D. Ruban located underneaththe old open pit coal mine and the hydraulic-mine dump. The potentially dangerous zones in the undermined rock mass have been identified based onthe conditions of formation of water inflow into mine workings. Safe depthof coal seams mining has been calculated depending on the type of water body – the hydraulic-mine dump.

scholarly journals Stress Distribution Around Mechanized Longwall Face at Deep Mining in Quang Ninh Underground Coal Mine

2021 ◽  
Vol 1 (2) ◽  
Author(s):  
Manh Tung BUI ◽  
Tien Dung LE ◽  
Trong Hung VO
Keyword(s):  
Stress Distribution ◽  
Sea Level ◽  
Coal Mine ◽  
Coal Mines ◽  
Longwall Face ◽  
Geological Condition ◽  
Deep Mining ◽  
Roof Fall ◽  
The Impact ◽  
Quang Ninh

Quang Ninh underground coal mines are currently in the phase of finishing up the mineralreserves located near the surface. Also, in this phase, a number of coal mines have opened and preparednew mine sites for the extraction of the reserves at greater depth. Several mines have mined at -350 mdepth and are driving opening excavations at -500 m depth below sea level. The mining at greater depthfaces many difficulties, such as a significant increase in support and excavation pressures. The longwallface pressure is mostly manifested in great magnitude that causes support overloaded and jumped andface spall/roof fall. This paper, based on the geological condition of the Seam 11 Ha Lam coal mine,uses the numerical program UDEC for studying the impact of mining depth on stress distribution aroundthe longwall face. The results show that the deeper the mining is, the greater the plastic deformationzone is. The peak front abutment stress moves closer to the coal wall, mainly concentrating on theimmediate roof and top coal. The top coal is greatly broken, and its bearing capacity is decreased. Somesolutions to the stability of roof strata are proposed, and a proper working resistance of support isdetermined. Additionally, the paper suggests that the starting depth for deep mining in Quang Ninhunderground coal mines should be -350 m below sea level.

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