scholarly journals Instability Model of a Coal Wall with Large Mining Height under Excavation Unloading Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Lei Li ◽  
Feng zhang
Keyword(s):  
Stress Field ◽  
Instability Mechanism ◽  
Intersection Angle ◽  
Working Face ◽  
Coal Wall ◽  
Large Mining Height ◽  
Wedge Structure ◽  
Supporting Force ◽  
Mining Height ◽  
Safe Mining

On the basis of the stress field characteristics of surrounding rocks at a coal wall on a working face with a large mining height, the theories of unloading rock mass mechanics and fracture mechanics were used to establish a model of the excavation unloading field effect of the coal wall, and its instability mechanism under the action of unloading stress field was analyzed. Results show that the coal mining process is the unloading process of coal and rock masses, and the stress field of surrounding rocks at the coal wall turns into an unloading stress field that consists of original and unloading stresses. Under the action of unloading stress field, cracks in the coal wall will undergo instability, propagation, and combination in the form of composite-type cracks and will gradually evolve into a wedge structure. The wedge stability is inversely related to roof pressure P 0 , unloading force T , and intersection angle φ of structural planes. Elevating the wall-supporting force P h , the initial supporting force of supports on the working face and the cohesion C of coal body can effectively control the occurrence of coal wall caving accidents and contribute to the safe mining of working faces with a large mining height.

Numerical Simulation of Strata Behavior in Super-Long and Large Mining Height Working Face

2013 ◽  
Vol 634-638 ◽  
pp. 3428-3432 ◽  
Author(s):  
Zhi Hua Li ◽  
Xin Zhu Hua ◽  
Ruo Jun Zhu ◽  
De Sheng Zhou
Keyword(s):  
Abutment Pressure ◽  
Roof Displacement ◽  
Mining Depth ◽  
Working Face ◽  
Face Length ◽  
Coal Wall ◽  
Large Mining Height ◽  
Strata Behavior ◽  
Behavior Characteristics ◽  
Mining Height

In order to study the strata behavior characteristics in super-long and large mining height working face, the FLAC-3D software was used to study the roof displacement and the abutment pressure distribution laws of working faces. The results indicate that: ① the influence range is larger of front abutment pressure in Liuzhuang coal mine 171301 super-long large mining height working face, and reaches to 60m. ② the maximum roof displacement increases with the increase of mining depth and working face length, the increase in magnitude decreases gradually, while the maximum roof displacement sharply increases due to the increase of mining height. ③ the peak abutment pressure increases with the increase of mining depth and mining height, the location of peak abutment pressure transfer to ahead of the coal wall. ④ the effect of working face length on abutment pressure is very feeble, so, the strata behavior characteristics remain almost constant with the increase of face length.

scholarly journals The Effect of Joint Damage on a Coal Wall and the Influence of Joints on the Abutment Pressure on a Fully Mechanised Working Face with Large Mining Height

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Weibin Guo ◽  
Shengwei Zhang ◽  
Yuhui Li
Keyword(s):  
Abutment Pressure ◽  
Limit Equilibrium ◽  
Technical Problem ◽  
Damage Variable ◽  
Joint Spacing ◽  
Working Face ◽  
Coal Wall ◽  
Large Mining Height ◽  
Dip Angle ◽  
Mining Height

Coal wall spalling is regarded as a key technical problem influencing safe and efficient mining of large-mining-height working faces while the distribution of abutment pressure within the limit equilibrium zone (LEZ) influences coal wall spalling within a large-mining-height working face. This research attempted to explore the distribution characteristics of abutment pressure within the LEZ in a large-mining-height working face. For this purpose, the influences of the orientation of joints on mechanical characteristics of coal with joints and on the distribution of abutment pressure within the LEZ in the large-mining-height working face were analysed by theoretical analysis and numerical simulation. Research results show that the damage variable of coal with joints first rises, then decreases, and finally increases with increasing dip angle of the joints; as the azimuth of the joints increases, the damage variable first declines, then increases; the damage variable gradually declines with increasing joint spacing; an increase in the dip angle of joints corresponds to first reduction, then growth, and a final decrease of the abutment pressure at the same position in front of the coal walls; on certain conditions, the abutment pressure at the same position within the LEZ first rises, then declines as the azimuth of joints increases; with the growth of the joint spacing, the abutment pressure at the same position within the LEZ rises. The dip angle and azimuth of joints marginally affect the abutment pressure within the LEZ.

scholarly journals Study on Fracture and Stress Evolution Characteristics of Ultra-Thick Hard Sandstone Roof in the Fully Mechanized Mining Face with Large Mining Height: A Case Study of Xiaojihan Coal Mine in Western China

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Feng Ju ◽  
Meng Xiao ◽  
Zequan He ◽  
Pai Ning ◽  
Peng Huang
Keyword(s):  
High Strength ◽  
Western China ◽  
Stress Evolution ◽  
Working Face ◽  
Mining Condition ◽  
Evolution Characteristics ◽  
Large Mining Height ◽  
Evolution Laws ◽  
Mining Face ◽  
Mining Height

Ultra-thick hard sandstone roofs present high thickness, poor delamination, and wide caving range. The strata pressure of the working face during actual mining increases, having a significant influence on the safe mining of the working face. Especially, in the mining areas of western China, the fully mechanized mining faces with high mining height and high-strength mining are more prominent. Understanding the fractures and stress evolution characteristics of the ultra-thick hard sandstone roof during actual mining is of high significance to control the dynamic pressure on the working face. In this paper, the typical ultra-thick hard sandstone roof of the Xiaojihan coal mine was taken as an example. The structural and chemical composition characteristics were analyzed. Besides, the fracture characteristics of ultra-thick hard roof during the working face mining were analyzed. Moreover, the fracture structure consistency was verified through physical simulation and a field measurement method. Finally, the stress evolution laws in the ultra-thick hard sandstone roof fracture were studied through numerical simulation. The findings demonstrated that (1) the ultra-thick hard sandstone roof was composed of inlaid coarse minerals, which had compact structure, while the Protodyakonov hardness reached up to 3.07; (2) under the high-strength mining condition of fully mechanized mining face with large mining height, the ultra-thick hard sandstone roof had the characteristics of brittle fracture, with a caving span of 12 m; (3) under the high-strength mining condition of fully mechanized mining face with large mining height, the ultra-thick hard sandstone roof followed the stress evolution laws that were more sensitive to the neighboring goaf. Therefore, it was necessary to reduce the fracture span or layering of ultra-thick hard sandstone roof through the manual intervention method adoption or increase either the strength of coal pillar or supporting body, to resist the impact generated during ultra-thick hard sandstone roof fracture.

scholarly journals Determination of Optimal Extrication Location of High Extraction Roadway of Large-Mining-Height Fully Mechanized Face

2018 ◽  
Vol 2018 ◽  
pp. 1-7
Author(s):  
Xue-bo Zhang ◽  
Ming Yang
Keyword(s):  
Gas Extraction ◽  
Horizontal Distance ◽  
High Position ◽  
Working Face ◽  
Extraction Site ◽  
Large Mining Height ◽  
Porosity And Permeability ◽  
Permeability Distribution ◽  
Mining Height

Determining the optimal extrication location of the high extraction roadway can improve the gas extrication effect of highly gassy mine and solve the problem of gas concentration overrun at the upper corner, which is of great significance to safety and efficient mine production. According to the actual situation of mine, the gas gushing amount in the goaf, pressure difference at both ends of the working face, the 3D porosity, and permeability distribution of the caving zone and fissure zone were obtained by field measurement and numerical calculation. Through theoretical calculation, the proper extraction site of a high-position alley was determined. On this basis, the optimal extraction site of a high-position alley was determined by numerical analysis of the gas extraction effect at different sites. The results show that as the perpendicular distance between high-position alley and goaf floor increases, the gas extraction amount increases first and then decreases. The concentration of extraction gas gradually increases, and the increasing trend is gradually diminished. With the increase of the horizontal distance between the air return way and the high-position alley, the gas extraction amount and gas extraction concentration increase first and then decrease. The optimal extraction site of a high-position alley should be 39 m vertically away from the goaf floor and 30 m horizontally away from the air return way.

scholarly journals Research on Surface Failure Law of Working Faces in Large Mining Height and Shallow Buried Coal Seam

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Zhenhua Li ◽  
Yingkun Pang ◽  
Yongsheng Bao ◽  
Zhanyuan Ma
Keyword(s):  
Near Field ◽  
Mining Area ◽  
Surface Cracks ◽  
Large Space ◽  
Key Strata ◽  
Key Stratum ◽  
Surface Failure ◽  
Working Face ◽  
Large Mining Height ◽  
Mining Height

In the process of high-intensity and large-space mining in Shendong mining area, various surface cracks are generated on the surface, resulting in serious damage to the surface buildings and the local ecological environment. To study the influence of overlying rock movement on surface failure of near-field single key strata of near-shallow buried and large mining height working face, the relationship between overburden movement, strata pressure appearance, and surface failure at working face 52307 in Daliuta mining area was analyzed by field measurement and numerical simulation. The results show the following: (1) there is only one thick and hard key stratum in the overburden of large mining height and near-shallow buried working face. Under the condition of presplitting roof blasting, the first weighting step is still as high as 95 m, and the periodic breaking step of roof is 20–30 m. During the weighting, the working resistance of support is still close to the rated resistance. (2) The single key stratum plays an obvious role in controlling overburden movement. After the first weighting of the working face, a stepped subsidence crack appears on the surface within a short time, and the crack lags behind the working face for about 5 m. (3) During each periodic weighting process, the breaking and subsidence of key blocks are accompanied by surface cracks.

scholarly journals Control of Gob-Side Roadway with Large Mining Height in Inclined Thick Coal Seam: A Case Study

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Xie Fuxing
Keyword(s):  
Numerical Simulation ◽  
Coal Pillar ◽  
Simulation Software ◽  
Surrounding Rock ◽  
Mine Pressure ◽  
Thick Coal Seam ◽  
Working Face ◽  
Rock Structure ◽  
Large Mining Height ◽  
Mining Height

The gob-side roadway of 130205, a large-mining-height working face in the Yangchangwan coal mine, was investigated in terms of the mine pressure law and support technology for large mining heights and narrow coal pillars for mining roadways. The research included field investigations, theoretical analysis, numerical simulation, field tests, and other methods. This paper analyzes the form of movement for overlying rock structure in a gob-side entry with a large mining height and summarizes the stress state and deformation failure characteristics of the surrounding rock. The failure mechanism of the surrounding rock of the gob-side roadway and controllable engineering factors causing deformation were analyzed. FLAC3D numerical simulation software was used to explore the influence law of coal pillar width, working face mining height, and mining intensity on the stability of the surrounding rock of the gob-side roadway. Ensuring the integrity of the coal pillar, improving the coordination of the system, and using asymmetric support structures as the core support concept are proposed. A reasonably designed support scheme for the gob-side roadway of the working face for 130205 was conducted, and a desirable engineering effect was obtained through field practice verification.

scholarly journals Research on Overburden Movement Characteristics of Large Mining Height Working Face in Shallow Buried Thin Bedrock

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4208 ◽  
Author(s):  
Qingxiang Huang ◽  
Yanpeng He
Keyword(s):  
Physical Simulation ◽  
Mining Area ◽  
Engineering Problem ◽  
Dynamic Crack ◽  
Working Face ◽  
Time Space ◽  
Movement Distance ◽  
Large Mining Height ◽  
Thin Bedrock ◽  
Mining Height

The overburden movement of the large mining height working face of shallow buried thin bedrock (SBTB) is a complex engineering problem with “time-space-intension”, which is of great significance to realize efficient and safe mining in the northern Shaanxi mining area. Based on the research object of No. 22201 working face in Zhangjiamao Coal Mine, the roof structure characteristics of large mining height working face in SBTB are researched by field drilling measurement, laboratory test, physical and numerical simulation. The results show that: (1) Based on the measured data of the drillholes, it is concluded that under the mining conditions of SBTB with large mining height, the roof movement is ahead of the weighting of the working face, and the working resistance has a significant time effect. The advanced movement distance is about 20 m, which can be used as an early warning index of the weighting. The lag movement distance in the roof with horizon of 30 m is two periodic weighting intervals, which are about 26 m. (2) The first weighting interval of the working face is 32 m. The roof first break has obvious step sinking phenomenon, and the measured surface appears at a position 45 m away from the transport slot. It is statistically concluded that the periodic weighting interval is 9.5~16.5 m, the average weighting interval is 13 m, which is equivalent to the periodic dynamic crack spacing of the surface. (3) The results of field measurement and physical simulation show that the breaking angle of the roof of the No. 22201 large mining height is about 66°, and the periodic stepping distance of the T-junction suspension area is 6~8m. Along the strike of the working face, the roof breaking is mainly arc arched. The research results ensure the safe and green mining of shallow coal seam.

Study on the Relationship between Hydraulic Support on the Working Face with Large Mining Height and Surrounding Rock

2011 ◽  
Vol 328-330 ◽  
pp. 1671-1674
Author(s):  
Ying Ma ◽  
Sheng Zhong
Keyword(s):  
Coal Seam ◽  
Surrounding Rock ◽  
Hydraulic Support ◽  
Working Face ◽  
Safety Work ◽  
Immediate Roof ◽  
The Face ◽  
Large Mining Height ◽  
The Relationship ◽  
Mining Height

Using unified model and theory of rock pressure, the problems, such as caving of stope roof with large mining height and destruction of support, strata movement and surface subsidence, are unified analyzed and researched. The results show that: pressure shell is dynamic shell, which moves forward with the propulsion of working face; with the increase of mining height on the face, the height of fracture zone in coal seam increases, not continuously, but jumpily; with the increase of mining height, support load rises, but the degree of this rise decreases gradually, increased degree of immediate roof weight should be greater than that of given deformation pressure. The results provide necessary basis for reliability of hydraulic support on the working face with large mining height and safety work in the underground.

Study on Distribution Laws of Abutment Pressure for Fully-Mechanized Top-Coal Caving Face in Deep and Large Mining Height

2013 ◽  
Vol 746 ◽  
pp. 496-500
Author(s):  
De Chao Lu ◽  
Xiao Liu ◽  
Xiao Chen Liang ◽  
Yue Gao
Keyword(s):  
Numerical Simulation ◽  
Theoretical Analysis ◽  
Field Measurement ◽  
Concentration Factor ◽  
Abutment Pressure ◽  
Prevention And Treatment ◽  
Coal Wall ◽  
Large Mining Height ◽  
Distribution Laws ◽  
Mining Height

Based on the geologic and technology condition of 2301 fully-mechanized top-coal caving and large mining height face in Longgu colliery, the paper have comprehensive studied distribution laws of abutment pressure by theoretical analysis, FLAC3D numerical simulation and field measurement. The study draws the trend and inclination distribution range and value and concentration factor of the peak, which of these were impacted by mining height and depth and advance distance, and reveals distribution laws of abutment pressure with face advancing, and also pointed out that laws was in favor of top-coal caving, but not conductive to the prevention and treatment of the rib fall of coal wall; field measurement and numerical simulation and theoretical analysis results can be achieved mainly unified.

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