Study on Web Pillar Stability in Open-Pit Highwall Mining

Abstract When highwall mining technology is applied to recover large amounts of residual coal left under the highwall of a big open-pit mine, reasonable coal pillar width is the premise for maintaining the stability of web pillars. By adopting the numerical simulation method, the characteristics of the abutment stress distributions in the web pillars under different slope angles and mining depths are studied, and the function of the stress distribution in the web pillar is established. The relationship between the abutment stress and the ultimate strength of the web pillar under different widths is also analyzed and used in combination with the failure characteristics of the pillar yield zone to explore the instability mechanism of the web pillar. The retaining widths of the web pillars are determined. Based on the modeling results, a mechanical bearing model of the web pillar is established, a cusp catastrophe model of pillar-overburden is constructed, and the formula for the web pillar instability criterion is obtained. By analyzing and calculating the ultimate strength of the web pillar, the formula for calculating the yield zone width at both sides of the pillar is achieved. Using the instability criterion of web pillars in highwall mining, a reasonable pillar width can be deduced theoretically, which provides significant guidance on the application of highwall mining technology.

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The Influence of the Backfilling Roadway Driving Sequence on the Rockburst Risk of a Coal Pillar Based on an Energy Density Criterion

Sustainability ◽

10.3390/su10082609 ◽

2018 ◽

Vol 10 (8) ◽

pp. 2609 ◽

Cited By ~ 4

Author(s):

Yi Xue ◽

Zhengzheng Cao ◽

Feng Du ◽

Lin Zhu

Keyword(s):

Energy Density ◽

Dynamic Instability ◽

Coal Pillar ◽

Optimal Choice ◽

Mining Technology ◽

Pillar Stability ◽

Rockburst Hazard ◽

Density Factor ◽

Coal Pillars ◽

Energy Density Factor

The rockburst hazard has always been an important issue affecting the safety production of coal mines in China. The unreasonable sequencing of roadway driving can lead to the dynamic instability of coal pillars, which subsequently causes rockburst accidents in roadway backfilling mining engineering and poses a serious threat to the safety of the mines. Roadway backfilling mining technology is an effective approach with which to mine corner residual coal resources under buildings, railways, and rivers. An energy density criterion is established and programmed with FISH language using numerical analysis software for the rockburst risk evaluation of coal pillars. On this basis, a numerical simulation model is established based on four scheme types, namely, the sequential mining, one-roadway interval mining, two-roadway interval mining, and three-roadway interval mining schemes. The influence of the backfilling roadway driving sequence on coal pillar stability is investigated, and the change law of vertical stress and energy density factor of coal pillars in different driving sequences in roadway backfilling mining technology are analyzed. According to the research results, the maximum energy density factor value of 21,172 J/m4 for coal pillars in one-roadway interval mining is the lowest among the different schemes. Therefore, the one-roadway interval mining scheme is the optimal choice in roadway backfilling mining technology. The results can be treated as an important basis for the prevention and treatment of coal pillar instability and rockburst in roadway backfilling mining technology.

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Stability Analysis of Rib Pillars in Highwall Mining Under Dynamic and Static Loads in Open-Pit Coal Mine

10.21203/rs.3.rs-1085469/v1 ◽

2021 ◽

Author(s):

Haoshuai Wu ◽

Yanlong Chen ◽

Haoyan Lv ◽

Qihang Xie ◽

Yuanguang Chen ◽

...

Keyword(s):

Numerical Simulation ◽

Stability Analysis ◽

Theoretical Calculation ◽

Open Pit ◽

Winkler Foundation ◽

Beam Model ◽

Mining System ◽

Static Loads ◽

Pillar Stability ◽

Highwall Mining

Abstract The highwall miner can be used to mine the retained coal in the end slope of an open-pit mine. However, the instability mechanism of the reserved rib pillar under dynamic and static loads is not clear, which restricts the safe and efficient application of the highwall mining system. In this study, the load-bearing model of the rib pillar in highwall mining was established, the cusp catastrophe theory and the safety coefficient of the rib pillar were considered, and the criterion equations of the rib pillar stability were proposed. Based on the limit equilibrium theory, the limit stress of the rib pillar was analyzed, and the calculation equations of plastic zone width of the rib pillar in highwall mining were obtained. Based on the Winkler foundation beam theory, the elastic foundation beam model composed of the rib pillar and roof under the highwall mining was established, and the calculation equations for the compression of the rib pillar under dynamic and static loads were developed. The results show that with the increase of the rib pillar width, the total compression of the rib pillar under dynamic and static loads approximately decreases in an inverse function, and the compression of the rib pillar caused by static loads of the overlying strata and trucks has a decisive role. Numerical simulation and theoretical calculation were performed in this study. In the Numerical simulation, the coal seam with a buried depth of 122 m and a thickness of 3 m was mined by the highwall miner. According to the established rib pillar instability model of the highwall mining system, it is found that when the mining tunnel width is 3 m, the reasonable width of the rib pillar is at least 1.3 m, and the safety factor of the rib pillar is 1.3. The numerical simulation results are in good agreement with the results of theoretical calculation, which verifies the feasibility of the theoretical analysis of the rib pillar stability. The research results can provide an important reference for the stability analysis of rib pillars under highwall mining.

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Reasonable coal pillar design and remote control mining technology for highwall residual coal resources

Royal Society Open Science ◽

10.1098/rsos.181817 ◽

2019 ◽

Vol 6 (4) ◽

pp. 181817 ◽

Cited By ~ 4

Author(s):

Fangtian Wang ◽

Cun Zhang

Keyword(s):

Remote Control ◽

Coal Pillar ◽

Open Pit Mine ◽

Open Pit ◽

Recovery Ratio ◽

Coal Resources ◽

The Road ◽

Highwall Mining ◽

Geological Conditions ◽

Residual Coal

Highwall mining (HWM) technology is an efficient method for exploiting residual coal resources in Chinese open-pit coal mines. However, on-site personnel and equipment can be damaged by the instability of the highwall mining residual coal pillars and subsidence of final end-walls. This paper considers the geological conditions of an open-pit mine in Shendong Coal Field (China) in order to prevent overlying rock fall accidents; the Mark-Bieniawski formula and the FLAC3D numerical simulation are used to analyse reasonable coal pillar widths outside and under the road, which were determined to be 1.7 m and 1.3 m, respectively. Using the EBH132 cantilever excavator for remote control mining, the field experiment shows that the recovery ratio of highwall residual coal resources was over 67%; hence, safety, efficiency and high recovery ratio of highwall mining were achieved for the residual coal resources of an open-pit mine.

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Simulation Research for the Influence of Mining Sequence on Coal Pillar Stability under Highwall Mining Method

Geofluids ◽

10.1155/2021/8864339 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Jing Huang ◽

Fanbao Meng ◽

Ge Wang ◽

Yingkui Wu ◽

Jinhao Wen

Keyword(s):

Great Influence ◽

Coal Pillar ◽

Simulation Method ◽

Mining Method ◽

Pillar Stability ◽

Simulation Research ◽

Highwall Mining ◽

Mining Sequence ◽

Coal Pillars ◽

Highwall Stability

Highwall mining, which is referred to the technique of extracting coal from the bottom of an exposed highwall, features safety, efficiency, and economy. According to existing highwall mining methods, the mining sequence has a great influence on highwall stability. Based on a highwall mining project in Australia, this study adopted the FLAC3D numerical simulation method to investigate the stability of coal pillars with different mining sequences. The results show that different mining sequences of boreholes exert a great effect on highwall stability. Compared with sequential mining, the skip mining method achieves higher speed of highwall stabilization and smaller plastic zone of coal pillar with its maximum strength decreasing by 12%. By adjusting the mining sequence scientifically, the coal pillar failure and roof collapse caused by the deviation of mining angle can be avoided. The results may provide a new angle for the studies on the coal pillar layout and stability design in highwall mining.

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Key ecological aspects of coal mining technology (in terms of the Bureya open pit coal mine)

MINING INFORMATIONAL AND ANALYTICAL BULLETIN ◽

10.25018/0236-1493-2020-1-0-15-25 ◽

2020 ◽

Vol 1 ◽

pp. 15-25

Author(s):

Yu.A. Ozaryan ◽

◽

Yu.A. Vasyanovich ◽

Keyword(s):

Coal Mining ◽

Coal Mine ◽

Open Pit ◽

Mining Technology ◽

Ecological Aspects

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Automatic Roadway Backfilling of Caving Gangue for Cutting Roofs by Combined Support on Gob-Side Entry Retaining with No-Pillars: A Case Study

Advances in Materials Science and Engineering ◽

10.1155/2019/8736103 ◽

2019 ◽

Vol 2019 ◽

pp. 1-13

Author(s):

Shengrong Xie ◽

Xiaoyu Wu ◽

Dongdong Chen ◽

Yaohui Sun ◽

Junchao Zeng ◽

...

Keyword(s):

Longwall Mining ◽

Control Process ◽

Coal Pillar ◽

Main Roof ◽

Control Effect ◽

Mining Technology ◽

Thick Coal Seam ◽

Immediate Roof ◽

Seam Mining ◽

And Control

Automatic roadways on gob-side entry retaining with no-pillars are used for longwall mining technology. The mining technology with no-pillars can recover coal pillar resources and reduce the amount and cost of roadway excavations. Automatic roadway technology for cutting roofs by combined support on gob-side entry retaining with no-pillars is adopted for the condition of thick immediate roof and medium-thick coal seam mining, cutting off the immediate roof and the main roof on the gob by combined support. The fractured roof forms gangue blocks to fill the gob and loads the overlying strata. The gangue control system is placed on the roadside, which controls the caving gangue to form a gangue rib. In this paper, the viewpoints and key technologies (the roof-cutting technology, the reinforcement and support technology, the gangue rib control technology, and the auxiliary support technology) of automatic roadway technology for cutting roofs by combined support on the gob-side entry retaining with no-pillars are introduced. Furthermore, the formation and control process are explained. The numerical simulation is used to simulate and analyze the roof hanging and the roof cutting structures. In addition, a field engineering test is performed. The field test shows that automatic roadway technology for cutting roofs by combined support on gob-side entry retaining with no-pillars is feasible. This process uses construction techniques and technologies to meet on-site production needs. The combined support has high resistance strength and is shrinkable. In engineering applications, the combined support has a low damage rate. The deformation of the automatic roadway with gob-side entry retaining is small, and the control effect is significant.

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Experiment and Design Method on Cold-Formed Thin-Walled Steel Lipped Channel Columns with Slotted Web Holes Under Axial Compression

The Open Civil Engineering Journal ◽

10.2174/1874149501711010244 ◽

2017 ◽

Vol 11 (1) ◽

pp. 244-257 ◽

Cited By ~ 2

Author(s):

Xingyou Yao

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Ultimate Strength ◽

Test Results ◽

Distortional Buckling ◽

Steel Columns ◽

Cold Formed Steel ◽

Thin Walled ◽

Shell Finite Element ◽

The Web

Background: Cold-formed steel structural sections used in the walls of residential buildings and agricultural facilities are commonly C-shaped sections with web holes. These holes located in the web of sections can alter the elastic stiffness and the ultimate strength of a structural member. The objective of this paper is to study the buckling mode and load-carrying capacity of cold-formed thin-walled steel column with slotted web holes. Methods: Compression tests were conducted on 26 intermediate length columns with and without holes. The tested compressive members included four different kinds of holes. For each specimen, a shell finite element Eigen-buckling analysis and nonlinear analysis were also conducted. The influence of the slotted web hole on local and distortional buckling response had also been studied. The comparison on ultimate strength between test results and calculated results using Chinese cold-formed steel specification GB50018-2002, North American cold-formed steel specification AISI S100-2016, and nonlinear Finite Element method was made. Result: Test results showed that the distortional buckling occurred for intermediate columns with slotted holes and the ultimate strength of columns with holes was less than that of columns without holes. The ultimate strength of columns decreased with the increase in transverse width of hole in the cross-section of member. The Finite element analysis results showed that the web holes could influence on the elastic buckling stress of columns. The shell finite element could be used to model the buckling modes and analysis the ultimate strength of members with slotted web holes. The calculated ultimate strength shows that results predicted with AISI S100-2016 and analyzed using finite element method are close to test results. The calculated results using Chinese code are higher than the test results because Chinese code has no provision to calculate the ultimate strength of members with slotted web holes. Conclusion: The calculated method for cold-formed thin-walled steel columns with slotted web holes are proposed based on effective width method in Chinese code. The results calculated using the proposed method show good agreement with test results and can be used in engineering design for some specific cold-formed steel columns with slotted web holes studied in this paper.

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