scholarly journals Analysis of the Influence Characteristics of the Support Stability of a Fully Mechanized Coal Mining Face under the Hard Roof Mining Pressure

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Jiaxin Dang ◽  
Min Tu ◽  
Xiangyang Zhang ◽  
Qingwei Bu
Keyword(s):  
Numerical Simulation ◽  
Load Bearing ◽  
Hard Roof ◽  
Working Face ◽  
Cantilever Length ◽  
Mining Face ◽  
Mining Pressure ◽  
Group B ◽  
Coal Reserves ◽  
Two Sides

The conditions of the hard roof in my country vary greatly, ranging from a few meters to tens of meters or even hundreds of meters in thickness. The coal reserves under the hard roof account for about one-third of the total reserves. At present, nearly 40% of fully mechanized mining faces that belong to the hard roof working face has the problem of mining in the hard roof working face. This has a serious impact on the load-bearing stability of the fully mechanized support, and it is urgent to solve the problem of strong underground pressure dynamic disaster under the condition of the hard roof. Based on the research background of 11129 working face in Zhangji Coal Mine in Huainan, this paper constructs a mechanical model of the interaction between the cantilever beam of the hard roof of the stope and the support and then the force distribution equation of the bearing capacity of the supports at different positions of the roof during the periodical rotation of the working face is obtained, which is combined with numerical simulation and engineering site to verify. The research results show that the bearing stability of the support is significantly affected by factors such as the buried depth H, the roof elastic modulus E, the roof thickness h, and the roof cantilever length l0, but most of the influencing factors belong to the geological occurrence conditions of the coal seam itself. Presplit blasting of the roof in advance can effectively destroy the integrity of the roof itself and reduce the periodic breaking distance, thereby improving the apparent environment of roof rock pressure and reducing the force on the working face support. According to the specific geological environment of the 11129 working face, the cutting plan of the cut hole is given out, along the groove 0∼200 and 200∼700 m of the concrete presplitting blasting. The stent force of the top-cutting section fluctuates in the range of 3360.8–4347.9 kN in the range of control top distance (5275∼6175 mm). The load-bearing pressure of the stent before top-cutting is about 1.8 times of that after top-cutting. The pressure distribution of the hydraulic support in the numerical simulation stope is approximately “Λ” in the middle and the low on the two sides. The simulated value is slightly smaller than the theoretical calculation value. The reason is that the goaf is backfilled during the simulation process, and the roof has a certain ability to bear the load. Real-time understanding of the “roof-support” mechanical relationship can effectively ensure the safe and efficient mining of the 11129 working face and also provide experience for the subsequent mining of group B coal in the later period.

scholarly journals Support design of main retracement passage in fully mechanised coal mining face based on numerical simulation

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yalong Li ◽  
Mohanad Ahmed Almalki ◽  
Cheng Li
Keyword(s):  
Numerical Simulation ◽  
Coal Mine ◽  
Surrounding Rock ◽  
Control Measures ◽  
Coal Face ◽  
Support Design ◽  
Working Face ◽  
Surrounding Rock Control ◽  
Mining Face ◽  
Mining Pressure

Abstract For the comprehensive mechanised coal mining technology, the support design of the main withdrawal passage in the working face is an important link to achieve high yield and efficiency. Due to the impact of mining, the roof movement of the withdrawal passage is obvious, the displacement of the coal body will increase significantly, and it is easy to cause roof caving and serious lamination problems, and even lead to collapse accidents, which will affect the normal production of the mine. In this paper, the mining pressure development law of the main withdrawal passage support under the influence of dynamic pressure is designed, the most favourable roof failure form of the withdrawal passage is determined, and the action mechanism and applicable conditions of different mining pressure control measures are studied. The pressure appearance and stress distribution in the final mining stage of fully mechanised coal face are studied by numerical simulation. The deformation and failure characteristics and control measures of roof overburden in the last mining stage of fully mechanised coal face are analysed theoretically. Due to the fact that periodic pressure should be avoided as far as possible after the full-mechanised mining face is connected with the retracement passage, some auxiliary measures such as mining height control and forced roof blasting are put forward on this basis. The relative parameters of the main supporting forms are calculated. The main retracement of a fully mechanised working face in a coal mine channel is put forward to spread the surrounding rock grouting reinforcement, reinforcing roof, and help support and improve the bolt anchoring force, the main design retracement retracement channels in the channel near the return air along the trough for supporting reinforcing surrounding rock control optimisation measures, such as through the numerical simulation analysis, the optimisation measures for coal mine fully mechanised working face of surrounding rock is feasible. Numerical simulation results also show that the surrounding rock control of fully mechanised working face of coal mine design improvements, its main retreat channel under the roof subsidence, cribbing shrank significantly lower, and closer, to better control the deformation of surrounding rock, achieved significant effect, to ensure the safety of coal mine main retracement channel of fully mechanised working face support.

scholarly journals Mining-Induced Stress Control by Advanced Hydraulic Fracking under a Thick Hard Roof for Top Coal Caving Method: A Case Study in the Shendong Mining Area, China

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1405
Author(s):  
Kaige Zheng ◽  
Yu Liu ◽  
Tong Zhang ◽  
Jingzhong Zhu
Keyword(s):  
Stress Transfer ◽  
Mining Area ◽  
Fracture Networks ◽  
Horizontal Fracture ◽  
Hard Roof ◽  
Working Face ◽  
Huge Impact ◽  
Mining Pressure ◽  
Impact Kinetic Energy ◽  
Mining Height

Fully mechanized top-coal caving mining with high mining height, hard roofs and strong mining pressure are popular in the Shendong mining area, China. The occurrence of dynamic disasters, such as rock burst, coal and gas outburst, mine earthquakes and goaf hurricanes during the coal exploitation process under hard roof conditions, pose a threat to the safe production of mines. In this study, the characteristics of overburden fracture in fully mechanized top-coal caving with a hard roof and high mining height are studied, and the technology of advanced weakening by hard roof staged fracturing was proposed. The results show that the hard roof strata collapse in the form of large “cantilever beams”, and it is easy to release huge impact kinetic energy, forming impact disasters. After the implementation of advanced hydraulic fracturing, the periodic weighting length decreases by 32.16%, and the length of overhang is reasonably and effectively controlled. Ellipsoidal fracture networks in the mining direction of the vertical working face, horizontal fracture networks perpendicular to the direction of the working face, and near-linear fracture planes dominated by vertical fractures were observed, with the accumulated energy greatly reduced. The effectiveness of innovation technology is validated, and stress transfer, dissipation and dynamic roof disasters were effectively controlled.

scholarly journals Determination of Reasonable Width of Filling Body for Gob-Side Entry Retaining in Mining Face With Large Cutting Height

2021 ◽  
Author(s):  
Shijiang Pu ◽  
Gui yi Wu ◽  
Qinzhi Liu ◽  
Yuliang Wang ◽  
Qiang Li ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Mechanical Model ◽  
Vertical Displacement ◽  
Vertical Stress ◽  
Body Width ◽  
Minimum Width ◽  
Mining Face ◽  
The Stability ◽  
Cutting Height ◽  
Two Sides

Abstract When gob-side entry retaining is adopted in mining face with large cutting height, due to large stope space, strong dynamic pressure and other reasons, the filling body is usually broken and unstable due to improper width of filling body, and the stability of surrounding rock of roadway is poor. Therefore, this paper will take Shaqu mine as the engineering background to study the reasonable filling body width of gob-side entry retaining in mining face with large cutting height. Firstly, the stability factors of gob-side entry retaining in mining face with large cutting height are analyzed, and the mechanical model of bearing structure of gob-side entry retaining is established based on the lateral pressure and overlying load of filling body, and the reasonable width of filling body is obtained quantitatively; Numerical simulation is used to analyze the evolution of vertical stress, vertical displacement and plastic zone of working face with the change of filling body width. Finally, combined with the deformation observation results of 24207 gob-side entry retaining roof, two sides and filling body, the rationality of filling body width is verified. The results show that: the setting of the width and strength of the filling body plays an important role in the stability of gob-side entry retaining. According to the mechanical model, the minimum width of the filling body is 2.2m in the lateral direction and 3.9m in the vertical direction; Numerical simulation shows that when the width of filling body is too small, with the increase of filling body width, the vertical stress of filling body increases gradually. When the width of filling body reaches a certain value, the vertical stress decreases with the increase of width, and the stress concentration area will change from symmetrical type to eccentric load type, from the middle of filling body to the side of filling body near gob. If the width of the filling body is too small, the filling body will be too broken to bear the load, resulting in too small vertical stress and too large vertical displacement of the roadway roof. The larger the width of the filling body is, the greater the cutting resistance is, the more timely the side roof of the gob can be cut off, the less the stress of the roadway and the filling body, and the more stable the retained roadway is. Finally, through the observation of 24207 gob-side entry retaining, the total deformation of two sides and roof and floor of roadway tends to be stable after 665mm and 597mm respectively. The roof of roadway does not appear severe subsidence and obvious cracking, and the floor does not appear too large floor heave. The effect of roadway retaining is good, which indicates that 4m support can meet the needs of practical engineering.

scholarly journals Numerical Investigation of Gob-Side Entry Retaining through Precut Overhanging Hard Roof to Control Rockburst

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Xiaoming Sun ◽  
Li Gan ◽  
Zhao Chengwei ◽  
Tang Jianquan ◽  
He Manchao ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Abutment Pressure ◽  
Feasibility Studies ◽  
Main Roof ◽  
Surrounding Rock ◽  
Distribution Characteristics ◽  
Hard Roof ◽  
Working Face ◽  
Stress Fluctuation ◽  
Peak Value

Gob-side entry retaining through precut overhanging hard roof (GERPOHR) method is one of the commonly used methods for nonpillar mining. However, feasibility studies of controlling rockburst by this method are few. Rockburst occurs in hard thick strata with a higher probability, larger scale, and higher risk. To better understand the GERPOHR method is beneficial for rockburst mitigation. In this paper, the design of GERPOHR was first introduced. And the layout of the working face was optimized. Then, based on the numerical simulation, the stress and displacement distribution characteristics were compared under the condition of conventional mining and GERPOHR method. The research shows that the intervals of main roof weighting could be decreased through the precut overhanging hard roof method. And the peak value of abutment pressure decreased. Meanwhile, the energy accumulation and the stress fluctuation could be alleviated in roadway surrounding rock.

scholarly journals Numerical Simulation of Coal Wall Cutting and Lump Coal Formation in a Fully Mechanized Mining Face

2020 ◽  
Author(s):  
Yong Yuan ◽  
Shengzhi Wang ◽  
Wenmiao Wang ◽  
Cheng Zhu
Keyword(s):  
Numerical Simulation ◽  
Cutting Force ◽  
Cutting Process ◽  
Working Face ◽  
Secondary Damage ◽  
Coal Wall ◽  
Statistical Analysis Method ◽  
Mining Face ◽  
Lump Coal ◽  
Cutting Model

Abstract It is difficult to accurately calculate the lump coal rate in a fully mechanized mining face. Therefore, a numerical simulation of the coal wall cutting process, which revealed the crack expansion, development, evolution in the coal body and the corresponding lump coal formation mechanism, was performed in PFC. Moreover, a correlation was established between the cutting force and lump coal formation, and a statistical analysis method was proposed to determine the lump coal rate. The following conclusions were drawn from the results. (1) Based on a soft ball model, a coal wall cutting model was established. By setting the roller parameters based on linear bonding and simulating the roller cutting process of the coal body, the coal wall cutting process was effectively simulated, and accurate lump coal rate statistics were provided. (2) Under the cutting stress, the coal body in the working face underwent three stages—microfracture generation, fracture expansion, and fracture penetration—to form lump coal, in which the fracture direction was orthogonal to the cutting pressure chain. Within a certain range from the roller, as the cutting depth of the roller increased, the number of new fractures in the coal body first increased and then stabilized. (3) Under the cutting stress, the fractured coal body was locally compressed, thereby forming a compact core. The formation and destruction of the compact core caused fluctuations in the cutting force. The fluctuation amplitude was positively related to the coal mass. (4) Because the simulation did not consider secondary damage in the coal, the simulated lump coal rate was larger than the actual lump coal rate in the working face; this deviation was mainly concentrated in large lump coal with a diameter greater than 300 mm.

scholarly journals Deformation Mechanism and Control Technology of the Surrounding Rock of the Floor Roadway under the Influence of Mining

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Qingchong Zhao ◽  
Baojie Fu ◽  
Jiadi Yin
Keyword(s):  
Numerical Simulation ◽  
Surface Displacement ◽  
Surrounding Rock ◽  
Infinite Body ◽  
Maximum Displacement ◽  
Deformation And Failure ◽  
Working Face ◽  
Before And After ◽  
Stress And Deformation ◽  
Two Sides

Deformation and failure mechanism of the surrounding rock of the floor roadway under the influence of working face mining is complicated, and roadway control is difficult. The floor roadway of the 11123 working face in Pan’er Mine is taken as the research object of this study based on semi-infinite body theory of elastic mechanics to establish a mechanical model along the advancing direction of the working face and derive the stress expression of any point in the affected area of floor mining. According to the theoretical results, effective reinforcement and support schemes are then proposed. FLAC3D numerical simulation analyzes the stress and deformation of the surrounding rock of the floor roadway before and after the reinforcement. The numerical simulation results showed that (1) mining abutment pressure of the overlying working face forms a certain range of stress concentration on the roof and two sides of the roadway and will cause deformation and damage to the floor roadway and (2) overall bearing capacity of the surrounding rock of the roadway is significantly improved, and surface displacement of the floor roadway is reduced by 64 mm through the reinforcement and support of the floor roadway. On-site monitoring data of the floor roadway in the 11123 working face of Pan’er Mine showed that the maximum displacement of the roadway roof and two sides is controlled at approximately 80 mm, and the surrounding rock deformation of the roadway is appropriately controlled to meet the needs of safe production.

Laws of Formation and Evolution of Pressure Arch in Coal Mining Adjoining Rock

2011 ◽  
Vol 243-249 ◽  
pp. 2596-2600
Author(s):  
Xiao Li Du ◽  
Hong Wei Song ◽  
Jie Chen
Keyword(s):  
Numerical Simulation ◽  
Coal Mining ◽  
Vertical Direction ◽  
Stress Transfer ◽  
Surrounding Rock ◽  
Coefficient Variation ◽  
Working Face ◽  
Formation And Evolution ◽  
Mining Face ◽  
Adjoining Rock

Based on numerical simulation of computing Software ANSYS, the curve of arching coefficient variation of pressure arch due to actual mining was analyzed aiming to a special mining face, the law of stress transfer and change in surrounding rock was discussed, and the evolving features and characteristics of pressure arch was obtained. The analysis and discussion show the following facts: Arch body will become thicker and stress in the arch body increases with working face’s driving distance increasing; the morphology of pressure arch transits from ellipsoid with long axis in the vertical direction to ellipsoid with long axis in the horizontal direction along the trend of working face; along the tendency of working face, the morphology of pressure arch is a ellipsoid with long axis in the vertical direction.

scholarly journals Research on Physical Similarity Simulation of Mining Uphill and Downhill at the Large-Angle Working Face

2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
Meng Zhang ◽  
Yidong Zhang ◽  
Ming Ji ◽  
Hongjun Guo ◽  
Haizhu Li
Keyword(s):  
Coal Mining ◽  
Large Angle ◽  
Elevation Angle ◽  
Coal Industry ◽  
Physical Similarity ◽  
Working Face ◽  
Geological Conditions ◽  
Mining Face ◽  
Mining Pressure ◽  
Dip Angle

With the development of coal mining and the continuous expansion of mining intensity, large dip angle comprehensive mechanized coal mining as an important development direction and goal has become a worldwide research topic in the coal industry. The working face faces many production problems that need to be solved, such as the large-angle downhill mining, the large-angle uphill mining, and other complicated geological conditions (such as skew, anticline, and fault). In view of the above problems, with the specific conditions of Xinji No. 2 Mine, through the physical similarity simulation, the research on the roof movement law of the fully mechanized mining face under the mining conditions of large dip angle (depression angle and elevation angle are more than 40° and 20°, respectively) is studied. The distribution law of abutment pressure, movement law, and distribution range of water-conducting fracture zone after mining are emphasized. Meanwhile, the paper analyzes and compares the related mining pressure law of inclined longwall fully mechanized mining face under general conditions, forming a systematic, comprehensive, and scientific understanding of the law of mining pressure under such conditions. This achievement is of great significance to the prevention and control of water, support design, safety production, environmental improvement, improvement of enterprise efficiency, and advancement of coal science and technology.

Sign in / Sign up

Export Citation Format

Share Document