Controlling the Deformation of a Small Coal Pillar Retaining Roadway by Non-Penetrating Directional Pre-Splitting Blasting with a Deep Hole: A Case Study in Wangzhuang Coal Mine

In longwall mining of coal mines, the large deformation of small pillar retaining roadways creates difficulties for the safe and efficient retreating of the mining panel. Based on the engineering background of a small coal pillar retaining roadway in Wangzhuang coal mine, pressure relief technology for non-penetrating directional pre-splitting blasting with a deep hole ahead was proposed. The influence of the non-penetrating fracture length on the pre-splitting effect was studied by numerical simulation. The results showed that the vertical stress in the coal pillar center, the small pillar retaining roadway deformation, and the energy accumulation on the pillar decreased with an increase in the non-penetrating fracture length. The vertical stress at the working face end increased with an increase in the non-penetrating fracture length. The field application and monitoring results indicated that non-penetrating directional pre-splitting blasting could effectively control the deformation of small pillar retaining roadways. The roof-to-floor and rib-to-rib maximum convergences of the 6208 tail entry were reduced by 53.66% and 52.62%, respectively, compared to the results with no blasting. The roadway section met the demands of mining panel high-efficiency retreating, thereby demonstrating the rationality of the technical and numerical simulation results. The research results shed light on the improvement of small coal pillar retaining roadway maintenance theory and technology.

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

Shock and Vibration ◽

10.1155/2021/6687244 ◽

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.

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Study on the Mechanism and Control of Rock Burst of Coal Pillar under Complex Conditions

Geofluids ◽

10.1155/2020/8847003 ◽

2020 ◽

Vol 2020 ◽

pp. 1-19

Author(s):

Xingping Lai ◽

Huicong Xu ◽

Jingdao Fan ◽

Zeyang Wang ◽

Zhenguo Yan ◽

...

Keyword(s):

Stress Concentration ◽

Rock Burst ◽

Coal Mine ◽

High Stress ◽

Coal Pillar ◽

Vertical Stress ◽

Body Area ◽

High Stress Concentration ◽

Solid Coal ◽

Working Face

In order to explore the mechanism of coal pillar rock burst in the overlying coal body area, taking W1123 working face of Kuangou Coal Mine as the engineering background, the full mining stage of W1123 is simulated by FLAC3D. It is found that the high stress concentration area has appeared on both sides of the coal pillar when W1123 does not start mining. With the advance of the working face, the high stress concentration area forms X-shaped overlap. There is an obvious difference in the stress state between the coal pillar under the solid coal and the coal pillar under the gob in W1123. The concrete manifestation is that the vertical stress of the coal pillar below the solid coal is greater than the vertical stress of the coal pillar below the gob. The position of the obvious increase of the stress of the coal pillar in the lower part of the solid coal is ahead of the advancing position of the working face, and the position of the obvious increase of the stress of the lower coal pillar in the gob lags behind the advancing position of the working face. At the same time, in order to accurately reflect the true stress environment of coal pillars, the author conducted a physical similarity simulation experiment in the laboratory to study the local mining process of the W1123 working face, and it is found that under the condition of extremely thick and hard roof, the roof will be formed in the gob, the mechanical model of roof hinged structurer is constructed and analyzed, and the results show that the horizontal thrust of roof structure increases with the increase of rotation angle. With the development of mining activities, the self-stable state of the high stress balance in the coal pillar is easily broken by the impact energy formed by the sudden collapse of the key strata. Therefore, the rock burst of coal pillar in the overlying coal body area is the result of both static load and dynamic load. In view of the actual situation of the Kuangou Coal Mine, the treatment measures of rock burst are put forward from the point of view of the coal body and rock mass.

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Study on Stress Relief of Hard Roof Based on Presplitting and Deep Hole Blasting

Advances in Civil Engineering ◽

10.1155/2020/8842818 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Peng Gong ◽

Yongheng Chen ◽

Zhanguo Ma ◽

Shixing Cheng

Keyword(s):

Stress Distribution ◽

Coal Mine ◽

Coal Pillar ◽

Deep Hole ◽

Hard Roof ◽

Formation Conditions ◽

Coal Pillars ◽

Mining Coal ◽

The Impact ◽

Pillar Size

For the problem that the hard roof causes wider end-mining coal pillar, and the roadway is greatly affected by mining, this paper took Shanxi Luning Coal Mine as the engineering background; based on the stress distribution characteristics of the coal pillar, the calculation method of the limit end-mining coal pillar size was given; considering the formation conditions and transmission forms of the advanced abutment stress, a method combining presplitting and deep hole blasting was proposed to weaken the advanced abutment stress. The numerical simulation was used to analyze the stress distribution of coal pillars, which was verified by on-site industrial tests. The results showed that the presplitting can achieve the blocking of stress. The closer it is to the peak of the abutment stress, the better the blocking effect. Deep hole blasting can weaken the source of the advanced abutment stress and reduce the peak of abutment stress. With the combination of the two blasting methods, the end-mining coal pillar size of Luning Coal Mine can be reduced to 60 m. The method combining presplitting and deep hole blasting can effectively reduce the end-mining coal pillar size and reduce the impact of mining on the deformation of the dip roadway.

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The Parameter Optimization and Field Application of Truss Cable Support System in a Thick Fragmental Coal Seam Roadway

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.524-527.382 ◽

2012 ◽

Vol 524-527 ◽

pp. 382-386

Author(s):

Xiao Kang Zhang ◽

Hong Jun Jiang ◽

Fu Lian He ◽

Ming Yue Weng

Keyword(s):

Numerical Simulation ◽

Coal Seam ◽

Parameter Optimization ◽

Support System ◽

Coal Mine ◽

Field Application ◽

Simulation Software ◽

Surrounding Rock ◽

Set Up ◽

Main Support

For the support problem of set-up room to be 7.8m wide with thick and broken coal roof in Pangpangta coal mine, the truss cable support system is adopted to control the set-up room surrounding rock. The main support parameters, such as cable length, cable angle and distance between orifice and side of the truss cable support system are simulated and optimally designed by using numerical simulation software FLAC3D, by which the support scheme is designed reasonably. The support scheme is successfully tested at set-up room No. 10101 in Pangpangta mine. The set-up room deformation is small, and the support system is safe and reliable. This kind of support technology can be widely used in the similar set-up rooms.

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Mechanism of Coal Burst and Prevention Practice in Deep Asymmetric Isolated Coal Pillar: A Case Study from YaoQiao Coal Mine

Shock and Vibration ◽

10.1155/2021/3751146 ◽

2021 ◽

Vol 2021 ◽

pp. 1-19

Author(s):

Chengchun Xue ◽

Anye Cao ◽

Wenhao Guo ◽

Songwei Wang ◽

Yaoqi Liu ◽

...

Keyword(s):

Numerical Simulation ◽

Coal Mine ◽

Prevention And Control ◽

High Stress ◽

Coal Pillar ◽

Support Pressure ◽

Mining District ◽

Coal Pillars ◽

And Control ◽

The Impact

Coal pillar bursts continue to be a severe dynamic hazard. Understanding its mechanism is of paramount importance and crucial in preventing and controlling its occurrence. The extreme roadway deformations from the asymmetric isolated coal pillars in the central mining district of YaoQiao Coal Mine have responded with frequent intense tremors, with risky isolated coal pillar bursts. The theoretical analysis, numerical simulation, and field measurements were done to research the impact of spatial overburden structure and stress distribution characteristics on the isolated coal pillar area, aiming to reveal the mechanism of coal pillar burst leading to the practice of prevention and control in the asymmetric isolated coal pillar area. The study shows that the overburden structure of the asymmetric is an asymmetric “T” structure in the strike-profile, and the stress in the coal pillar is mostly asymmetric “saddle-shaped” distribution, with the peak stress in the east side of the coal pillar, and the coal pillar is a “high stress serrated isolated coal pillar.” Numerical simulation results showed that the support pressure in the isolated coal pillar area on the strike profile was asymmetrically “saddle-shaped” distribution. The peak vertical stress in the coal pillar area continued to rise and gradually shifted to the mining district's deep part. As a result, the response of the roadway sides to the dynamic load disturbance was more pronounced. They developed a coal burst prevention and control program of deep-hole blasting in the roof of asymmetrical isolated coal pillar roof and unloading pressure from coal seam borehole. Monitored data confirmed that the stress concentration was influential in the roadway’s surrounding rock in the asymmetric isolated coal pillar area, circumventing coal pillar burst accidents. The research outcomes reference the prevention and control of coal bursts at isolated working faces of coal pillars under similar conditions.

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Structure Partition and Reasonable Width Determination of Waterproof Coal Pillar in Strip Mining

Lithosphere ◽

10.2113/2021/3339797 ◽

2021 ◽

Vol 2021 (Special 3) ◽

Author(s):

Rui Wang ◽

Jian-biao Bai ◽

Shuai Yan ◽

Gui-qiang Pan ◽

Dong Zhang ◽

...

Keyword(s):

Plastic Zone ◽

Coal Mine ◽

Water Pressure ◽

Coal Pillar ◽

Mine Pressure ◽

Failure Zone ◽

Core Zone ◽

Zone Width ◽

Elastic Core ◽

Pressure Failure

Abstract Retaining a waterproof coal pillar is the most effective water conservation method for a roadway close to the gob, and determining a reasonable width of the waterproof coal pillar has been a common problem among mining scholars for a considerably long time. Based on the mining of the 15208 mining face in Xinjing Coal Mine, the structure of waterproof coal pillar is divided into a mine-pressure-influenced plastic zone, an effective waterproof elastic core zone, and a water pressure failure zone. The mine-pressure-influenced plastic zone width is determined by using the limit equilibrium theory, the parabolic strength theory, and the separation variable method. The effective waterproof elastic core zone width is determined by the semi-inverse solution method, and the water pressure failure zone width is determined by considering the infiltration and softening of water. After that, combined with the previous theoretical analysis of engineering examples, the theoretical value of waterproof coal pillar width is obtained. In addition, the physical shape distribution of the waterproof coal pillar is measured by ultrasonic detection technology. The results are consistent with the field measured results. The correctness of the model is verified. Finally, the rationality of the model is verified by comparing with the previous classical models. The research results are applied to the design of the waterproof coal pillar in Xinjing Coal Mine, which could provide a theoretical basis for determining the width of the waterproof coal pillar located close to a gob.

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Optimization Coal Pillar Size of Top Coal Caving Face with Dynamic Pressure Impact

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.675-677.1395 ◽

2014 ◽

Vol 675-677 ◽

pp. 1395-1400 ◽

Cited By ~ 1

Author(s):

Wen Zhou Li

Keyword(s):

Numerical Simulation ◽

Coal Mine ◽

Simulation Analysis ◽

Dynamic Pressure ◽

Coal Pillar ◽

Large Error ◽

Working Face ◽

Pressure Impact ◽

Mine Depth ◽

Pillar Size

AH Wilson coal pillar was used widely as it’s simply, but it’s appeared large error for field implementation as its difference assume conditions, mine depth H and mine thickness m. AH Wilson coal pillar formula was studied precisely by in-site stresses test and numerical simulation analysis for N3-5 top coal caving working face of CHANGCUN coal mine in Lu’an coal district of China, then modified AH Wilson formula was put forward as L = 0.008mH + 8.4,then the precise coal pillar size 18m was used in filed implementation, filed testing proved coal pillar size was reasonable.

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Mechanism and Evolution Control of Wide Coal Pillar Bursts in Multithick Key Strata

Shock and Vibration ◽

10.1155/2021/4696619 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Wenhao Guo ◽

Anye Cao ◽

Chengchun Xue ◽

Yang Hu ◽

Songwei Wang ◽

...

Keyword(s):

Numerical Simulation ◽

Stress Concentration ◽

Theoretical Analysis ◽

Coal Mine ◽

Coal Pillar ◽

Western China ◽

Key Strata ◽

Working Face ◽

Microseismic Events ◽

Evolution Control

Coal mine pillar burst frequently occurs in Western China, which seriously restricts safe production. This paper takes the 35 m coal pillar of the 3102 working face of MKQ coal mine as the engineering background. The mechanism and evolution control of pillar bursts in multithick key strata are studied using field investigation, theoretical analysis, and numerical simulation. The mechanism of dynamic and static stress-induced pillar bursts was revealed combining the “O-X” broken features for key strata and numerical simulation of pillar stress evolution. A prevention scheme is put forward for strata presplit blasting and adjusting coal pillar width to minimize the dynamic and static stresses. The results demonstrate the following. (1) In the multithick strata, the first and second near-field subkey strata have perpendicular “O-X” broken features, whereas the third far-field subkey has parallel “O-X” broken features. The working face has three kinds of periodic weighting phenomena: long, medium, and short. (2) The simulated vertical stress curve of 35 m coal pillar goes through three states: two-peak, asymmetric trapezoidal and symmetrical trapezoidal shape with the different advancing position of working face. The stress concentration is extensively promoting a high-risk area for rock burst. (3) The coal pillar burst was induced by the superposition of energy released by the key strata breaking and the elastic energy accumulated in the wide coal pillar. (4) The monitoring data showed that the long, medium, and short periodic weighting steps of multithick key strata are 141.6 m, 43.2–49.6 m, and 17.6–27.2 m, respectively. The microseismic events energy, frequency, and stress of hydraulic support increment are the highest during the long periodic weighting, and the spatial distribution of microseismic events coincides with the stress concentration area. The theoretical analysis is confirmed with the field practice.

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Roof Cutting Parameters Design for Gob-Side Entry in Deep Coal Mine: A Case Study

Energies ◽

10.3390/en12102032 ◽

2019 ◽

Vol 12 (10) ◽

pp. 2032 ◽

Cited By ~ 24

Author(s):

Deyuan Fan ◽

Xuesheng Liu ◽

Yunliang Tan ◽

Shilin Song ◽

Qingheng Gu ◽

...

Keyword(s):

Numerical Simulation ◽

Coal Mine ◽

Cutting Parameters ◽

Surrounding Rock ◽

Vertical Stress ◽

Deep Mining ◽

Cutting Angle ◽

Working Face ◽

Mining Conditions ◽

Cutting Height

Roof cutting is an effective technique for controlling the deformation and failure of the surrounding rock in deep gob-side entry. The determination of the roof cutting parameters has become a popular research subject. Initially, two mechanical models are established for the non-roof-cutting and roof-cutting of gob-side entry in deep mining conditions. On this basis, the necessity and significance of roof cutting is revealed by analysing the stress and displacement of roadside prop. The Universal Distinct Element Code numerical simulation model is established to determine the key roof-cutting parameters (cutting angle and cutting height) according to the on-site situation of No. 2415 headentry of the Suncun coal mine, China. The numerical simulation results show that with the cutting angle and height increase, the vertical stress and horizontal displacement of the coal wall first increase and then decrease, as in the case of the vertical stress and displacement of roadside prop. Therefore, the optimum roof cutting parameters are determined as a cutting angle of 70° and cutting height of 8 m. Finally, a field application was performed at the No. 2415 headentry of the Suncun coal mine. In situ investigations show that after 10 m lagged the working face, the stress and displacement of roadside prop are obviously reduced with the hanging roof smoothly cut down, and they are stable at 19 MPa and 145 mm at 32 m behind the working face, respectively. This indicates that the stability of the surrounding rock was effectively controlled. This research demonstrates that the key parameters determined through a numerical simulation satisfactorily meet the production requirements and provide a reference for ensuring safe production in deep mining conditions.

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Study on the Pressure-Bearing Law of Backfilling Material Based on Three-Stage Strip Backfilling Mining

Energies ◽

10.3390/en13010211 ◽

2020 ◽

Vol 13 (1) ◽

pp. 211 ◽

Cited By ~ 1

Author(s):

Xiaoping Shao ◽

Xin Li ◽

Long Wang ◽

Zhiyu Fang ◽

Bingchao Zhao ◽

...

Keyword(s):

Numerical Simulation ◽

Thin Plate ◽

Coal Mine ◽

Physical Simulation ◽

Plate Theory ◽

Coal Pillar ◽

Smooth Transition ◽

Main Bearing ◽

Working Face ◽

Rock Load

During strip backfilling mining in coal mines, the backfilling material is the main support structure. Therefore, studying the pressure law of the backfilling material is essential for the safe and efficient mining of coal resources. Based on research into strip backfilling mining at working face number 3216 of the Shanghe Coal Mine, and to smooth transition of overlying strata loads to the backfilling material, this study proposes a three-stage strip backfilling mining method. Based on thin-plate theory, an elastic thin-plate model, a reasonable spacing of strip mining is constructed, and the reasonable mining parameters of “mining 7 m to retain 8 m” at working face number 3216 of the Shanghe Coal Mine are determined. The law of backfilling pressure in three-stage strip backfilling mining is studied through numerical simulation and physical simulation experiments. The results show that field measurement results are basically consistent with the experimental results and numerical simulation results. When three-stage strip backfilling mining is adopted, the stage-one backfilling material is the main bearing body to which the overlying rock load transfers smoothly and gradually, and the structure of the “overburden-coal pillar (or backfilling strip)” in the stope remains stable. In three-stage strip backfilling mining, the overlying rock load is ultimately transferred to the stage-one backfilling material, the stage-two backfilling material is the auxiliary bearing body, and the stage-three backfilling material mainly provides long-term stable lateral support for the stage-one backfilling material.

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