scholarly journals Research on the First Breaking Mechanism of the Main Roof of Coal Seam with High Dip Angle

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Xinyu Hu ◽  
Jinlong Cai
Keyword(s):  
Numerical Simulation ◽  
Mechanical Model ◽  
Main Roof ◽  
Distribution Characteristics ◽  
Coal Seams ◽  
Working Face ◽  
Elastic Thin Plate ◽  
Breaking Mechanism ◽  
Dip Angle ◽  
Clamped Edges

In order to study the mechanism and characteristics of the first breaking of the roof in thick coal seams with high dip angles, a mechanical model of elastic thin plate with four clamped edges of the roof was established, and the expressions of the deflection and stress of the roof were obtained by the energy method. The influence of the change in seam dip angle on the first breaking distance of the roof was presented. Based on the stress solution, the roof breaking criterion was proposed, and the breaking distance of the roof was calculated. Combined with numerical simulation, the stress distribution characteristics of the upper and lower surfaces of the stope roof were analyzed. The results show that the first breaking distance of the roof is inversely proportional to the seam dip angle. Broken morphology of roof in high dip seam is different from the “O-X” morphology of horizontal roof. The roof breaking order of the seam with high dip angle is middle-middle upper-middle lower-upper-lower. These research results have certain theoretical guiding significance for the study of the first breaking mechanism of the main roof of highly inclined working face of coal seams.

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 Surrounding Rock Movement of Steeply Dipping Coal Seam Using Backfill Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Wenyu Lv ◽  
Kai Guo ◽  
Jianhao Yu ◽  
Xufeng Du ◽  
Kun Feng
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Surrounding Rock ◽  
Maximum Deflection ◽  
Coal Seams ◽  
Physical Similarity ◽  
Working Face ◽  
Rock Structure ◽  
Backfill Mining ◽  
The Stability

The movement of the overlying strata in steeply dipping coal seams is complex, and the deformation of roof rock beam is obvious. In general, the backfill mining method can improve the stability of the surrounding rock effectively. In this study, the 645 working face of the tested mine is used as a prototype to establish the mechanical model of the inclined roof beam using the sloping flexible shield support backfilling method in a steeply dipping coal seam, and the deflection equation is derived to obtain the roof damage structure and the maximum deflection position of the roof beam. Finally, numerical simulation and physical similarity simulation experiments are carried out to study the stability of the surrounding rock structure under backfilling mining in steeply dipping coal seams. The results show the following: (1) With the support of the gangue filling body, the inclined roof beam has smaller roof subsidence, and the maximum deflection position moves to the upper part of working face. (2) With the increase of the stope height, the stress and displacement field of the surrounding rock using the backfilling method show an asymmetrical distribution, the movement, deformation, and failure increase slowly, and the increase of the strain is relatively stable. Compared with the caving method, the range and degree of the surrounding rock disturbed by the mining stress are lower. The results of numerical simulation and physical similarity simulation experiment are generally consistent with the theoretically derived results. Overall, this study can provide theoretical basis for the safe and efficient production of steeply dipping coal seams.

scholarly journals Evolution Laws of Mining-induced Stress in Floor Strata and Its Influence on the Stability of a Floor Roadway Affected by Overhead Mining

2020 ◽  
Vol 24 (1) ◽  
pp. 45-54 ◽  
Author(s):  
Pu Wang ◽  
Lishuai Jiang ◽  
Changqing Ma ◽  
Anying Yuan
Keyword(s):  
Numerical Simulation ◽  
Mechanical Model ◽  
Scientific Basis ◽  
Pull Out ◽  
Induced Stress ◽  
Working Face ◽  
Geological Conditions ◽  
Evolution Laws ◽  
The Stability

The study of evolution laws of the mining-induced stress in floor strata affected by overhead mining is extremely important with respect to the stability and support of a floor roadway. Based on the geological conditions of the drainage roadway in the 10th district in a coalmine, a mechanical model of a working face for overhead mining over the roadway is established, and the laws influencing mining stress on the roadway in different layers are obtained. The evolution of mining stress in floor with different horizontal distances between the working face and the floor roadway that is defined as LD are examined by utilizing UDEC numerical simulation, and the stability of roadway is analyzed. The results of the numerical simulation are verified via on-site tests of the deformation of the surrounding rocks and bolts pull-out from the drainage roadway. The results indicate that the mining stress in floor is high, which decreases slowly within a depth of less than 40 m where the floor roadway is significantly affected. The mining stress in the floor increases gradually, and the effect of the mining on the roadway is particularly evident within 0 m ≤ LD ≤ 40 m. Although the floor roadway is in a stress-relaxed state, the worst stability of the surrounding rocks is observed during the range -20 m ≤ LD < 0 m, in which the negative value indicates that the working face has passed the roadway. The roadway is affected by the recovery of the abutment stress in the goaf when -60 m ≤ LD <20 m, and thus it is important to focus on the strengthening support. The results may provide a scientific basis for establishing a reasonable location and support of roadways under similar conditions.

scholarly journals Characteristics of the Roof Behaviors and Mine Pressure Manifestations During the Mining of Steep Coal Seam

2017 ◽  
Vol 62 (4) ◽  
pp. 871-891 ◽  
Author(s):  
Tu Hong-Sheng ◽  
Tu Shi-Hao ◽  
Zhang Cun ◽  
Zhang Lei ◽  
Zhang Xiao-Gang
Keyword(s):  
Coal Seam ◽  
Field Measurement ◽  
Main Roof ◽  
Mine Pressure ◽  
Steep Seam ◽  
Working Face ◽  
Geological Conditions ◽  
Depth Study ◽  
Dip Angle ◽  
Similar Simulation

Abstract A steep seam similar simulation system was developed based on the geological conditions of a steep coal seam in the Xintie Coal Mine. Basing on similar simulation, together with theoretical analysis and field measurement, an in-depth study was conducted to characterize the fracture and stability of the roof of steep working face and calculate the width of the region backfilled with gangue in the goaf. The results showed that, as mining progressed, the immediate roof of the steep face fell upon the goaf and backfilled its lower part due to gravity. As a result, the roof in the lower part had higher stability than the roof in the upper part of the working face. The deformation and fracture of main roof mainly occurred in the upper part of the working face; the fractured main roof then formed a “voussoir beam” structure in the strata’s dip direction, which was subjected to the slip- and deformation-induced instability. The stability analysis indicated that, when the dip angle increased, the rock masses had greater capacity to withstand slip-induced instability but smaller capacity to withstand deformation-induced instability. Finally, the field measurement of the forces exerted on the hydraulic supports proved the characteristics of the roof’s behaviors during the mining of a steep seam.

scholarly journals Numerical Simulation of the Volumetric Strain Distribution of a Protected Coal Seam

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Hengyi Jia
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Strain Distribution ◽  
Volumetric Strain ◽  
Distribution Characteristics ◽  
Permeability Enhancement ◽  
Working Face ◽  
Coal Pillars ◽  
Definition Of ◽  
Seam Mining

To investigate the deformation characteristics of protected coal seams, the numerical simulation of the mining of an upper protective coal seam was carried out in the present study. Based on the basic definition of strain, a method for the extraction of the strain data of the protected coal seam was proposed, and the strain distribution characteristics were obtained. It was found that the x -direction strain is mainly distributed near the coal pillars on both sides and inside the goaf, the y -direction strain is mainly distributed at the working face, the initial mining line, and inside the goaf, and the z -direction strain is mainly distributed at the working face, the initial mining line, the coal pillars on both sides, and inside the goaf. The distribution characteristics and the value of volumetric strain were found to be basically consistent with the z -direction strain. As the working face advances, the protected coal seam undergoes compression and damage expansion in turn. The turning point between compression and damage expansion is approximately 15 m in front of the working face. The variation law of gas drainage in the boreholes of the protected coal seam is closely related to the distribution characteristics of volumetric strain. The results of this research are of great significance for the comprehensive investigation of the effects of pressure relief and the permeability enhancement of protective coal seam mining.

scholarly journals Study on strata behavior law of deep inclined coal seam

2021 ◽  
Vol 248 ◽  
pp. 03031
Author(s):  
Chen Zhengwen
Keyword(s):  
Numerical Simulation ◽  
Stress Distribution ◽  
Surrounding Rock ◽  
Rock Deformation ◽  
Coal Seams ◽  
Working Face ◽  
Support Resistance ◽  
Strata Behavior ◽  
The Law ◽  
Surrounding Rock Deformation

In order to understand and grasp the law of roof pressure on the working face of deep inclined coal seams, the law of support resistance distribution, the law of leading support stress distribution and the law of surrounding rock deformation of the two roadways, the 94101 working face of Zhangshuanglou Coal Mine was taken as the engineering background. Through a combination of field measurement, numerical simulation, theoretical analysis, etc, this paper analyzes the laws of roof migration and rock pressure manifestation in deep inclined coal seams.

Analyses of Actual Measurement and Numerical Simulation on Gently Inclined Thin Seam

2011 ◽  
Vol 361-363 ◽  
pp. 130-134
Author(s):  
Jian Xin Tang ◽  
Le Le Sun ◽  
Yue Hua Deng ◽  
Hua Hui Jin
Keyword(s):  
Numerical Simulation ◽  
Dynamic Pressure ◽  
Pressure Coefficient ◽  
River Mouth ◽  
Main Roof ◽  
Simulation Method ◽  
Actual Measurement ◽  
Working Face ◽  
Thin Seam ◽  
Working Resistance

Based on the numerical simulation method and actual measurement analyses, characteristics of working face mineral pressure of the River Mouth Mine has been analyzed and this paper has obtained the following results: First weighting step of the main roof is 23.2 m, the average dynamic pressure coefficient is 1.54~1.74, mine strata behaviors is fiercer; hydraulic prop’s average working resistance is 45.72 KN of each, which indicates hydraulic prop’s working resistance has larger surplus coefficient, some measures should be taken to increase utilization ratio; advanced support length of return airway and mechanical roadway should reach to 30 m, the method and results can be used to improve support pattern of working face and guide safety production.

Forecasting Collapse and Monitoring of the Main Roof Current State in Working Faces of Coal Mines with Shallow Seams

2021 ◽  
pp. 13-18
Author(s):  
A.I. Nedzelskiy ◽  
◽  
I.V. Shnayder ◽  
E.S. Lapin ◽  
◽  
...  
Keyword(s):  
Coal Seam ◽  
Coal Dust ◽  
Coal Mines ◽  
Main Roof ◽  
Coarse Grained ◽  
State Monitoring ◽  
Large Area ◽  
Current State ◽  
Working Face ◽  
Dip Angle

Main roof state monitoring and assessment of the roof hanging influence on the coal seam in working face of the coal mines with medium thickness seams with dip angle varying from 0 to 35° using a long-pillar development system along strike and uprising with roof control by complete collapse and abandonment of inter-main pillars a technically difficult task and currently unsolvable by tools. The main roof, composed of fine-grained gray sandstones, coarse-grained siltstones or interbedding of siltstones with sandstones, with average strengths of layers of about 30–40 MPa, is predicted to be moderately collapsing, and more than 50 MPa as difficult to collapse over a large area of coal seam spread. Hanging of the main roof with subsequent uncontrolled collapse can lead to the displacement of methane accumulating in the waste space into the face and provoke an explosion, fire or other emergency. It should be noted that the urgency of the problem is due to the fact that when large masses of the roof collapse during the lava retreat, an instantaneous release of large volumes of air from the collapsed space, accompanied by the release of methane and coal dust, occurs, which has repeatedly led to accidents. The article discusses the prediction of collapse and main roof current state monitoring in the working faces of coal mines with a shallow bedding by seismic method. Using «Mikon-GEO» as a seismic prediction system in coal mines and pits allows to make risks manageable and accounted.

scholarly journals Dip Angle Effect on the Main Roof First Fracture and Instability in a Fully-mechanized Workface of Steeply Dipping Coal Seams

2020 ◽  
Author(s):  
Zhen Wei ◽  
Ke Yang ◽  
Lou Xiao Chi ◽  
Xin Yuan Zhao ◽  
Xin Lv
Keyword(s):  
Coal Seam ◽  
Main Roof ◽  
Overburden Rock ◽  
Coal Seams ◽  
Overburden Pressure ◽  
Ground Pressure ◽  
Support Resistance ◽  
Angle Effect ◽  
Dip Angle ◽  
And Control

Abstract The study of fracture and instability mechanism of the main roof in steeply dipping coal seams (SDCS) workface is crucial to the proper choice of support type and control of stability of surrounding rock, as well as the safe and effective mining in the coal seam. Based on the established SDCS main roof model, this study derived the stress distribution in the main roof under linear load, analyzed the dip angle effect associated with the evolving stress of SDCS workface, and elaborated the sequential characteristics of the ground pressure mechanism. Besides, an inclined unstable structure model of the main roof based on deformation, fracturing, and rotating of the main roof in the SDCS workface was also proposed here, which explained the impacts of overburden rock's key parameters on sliding and rotatory instability of rock mass. In light of the analysis of the movement rule of overburden rock and loading condition of support, it is found that, when the roof and floor in the workface are stable, the critical support resistance with the absence of sliding and rotating increases as the dip angle of coal seam increases, the roof is in the state of discontinuous movement due to its self-weight and overburden pressure. Support is affected by the discontinuous movement and moved along with the roof. The results of this study can be of theoretical reference to the control of SDCS.

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