scholarly journals Investigation on the Movement and Fracture Characteristics of an Extra-Thick Hard Roof during Longwall Panel Extraction in the Yima Mining Area, China

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Hongwei Wang ◽  
Daixin Deng ◽  
Ruiming Shi ◽  
Guozhen Yang ◽  
Shuo Xu ◽  
...  
Keyword(s):  
Main Roof ◽  
Mining Area ◽  
Hard Roof ◽  
Induced Stress ◽  
Physical Experiments ◽  
Longwall Panel ◽  
Numerical Simulation Methods ◽  
Sudden Decrease ◽  
Coal Bursts ◽  
Sudden Collapse

As an extra-thick hard roof is a significant contributing factor to frequently induced sudden roof collapse accidents and coal bursts, this study investigates the relationship between extra-thick hard roof movement and mining-induced stress using physical experiments and numerical simulation methods based on mining activities in a longwall panel in the Yima mining area, Henan province, China. The results suggested that the movement and failure processes of the extra-thick roof could be divided into three main periods: the undisturbed, movement stabilization, and sudden collapse periods. The roof displacement remained essentially unchanged during the undisturbed period. During the movement stabilization period, the displacement gradually increased into the upper roof. However, the extra-thick main roof remained undisturbed until the immediate roof experienced its fourth periodic caving in the physical model. Consequently, the displacement expanded rapidly into the extra-thick main roof during the sudden collapse period and the strain energy was violently released when it accumulated in the extra-thick main roof. Additionally, the mining-induced stress was characterized by a sudden decrease in the gradual increase trend when the extra-thick roof instantly collapsed. The deformation and fracture of the extra-thick roof could cause a sudden decrease in the mining-induced stress and lead to continuous and unstable subsidence pressure exerted on the mining panel and roadway. This significantly contributes to the occurrence of coal bursts.

scholarly journals Rebound Mechanism and Control of the Hard Main Roof in the Deep Mining Roadway in Huainan Mining Area

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Denghong Chen ◽  
Chao Li ◽  
Xinzhu Hua ◽  
Xiaoyu Lu ◽  
Yongqiang Yuan ◽  
...  
Keyword(s):  
Slope Angle ◽  
Bending Moment ◽  
Main Roof ◽  
Mining Area ◽  
Calculation Model ◽  
Surrounding Rock ◽  
Tensile Failure ◽  
Damage Area ◽  
Critical Range ◽  
Working Face

Taking the occurrence conditions of the hard main roof in the deep 13-1 coal mining roadway in Huainan mining area as the research object, based on the mechanical parameters of the surrounding rock and the stress state of the main roof obtained by numerical simulation, a simply supported beam calculation model was established based on the damage factor D, main roof support reaction RA, RB, and critical range C (9 m) and B (7 m) at the elastoplastic junction of the solid coal side and mining face side (hereinafter referred to as “junction”). Considering that the damage area still has a large bearing capacity, the vertical stress of the main roof at the junction is K1γH (0.05γh, 0.15γh, and 0.25γh) and K2γH (0.01γh, 0.10γh, and 0.2γh). The maximum deflection is 21 mm, 324 mm, and 627.6 mm, respectively. According to the criterion of tensile failure, the maximum bending moment of the top beam is 209 mN·m at the side of the working face 3.1 m away from the roadway side when K1 = 0.15 and K2 = 0.10, and the whole hard main roof is in tensile failure except the junction. To control the stability of the top beam and simplify the supporting reaction to limit the deformation of the slope angle, RC and RD are used to construct the statically indeterminate beam. By adding an anchor cable and advance self-moving support to the roadway side angle, the problem of difficult control of the surrounding rock with a large deformation of the side angle roof is solved, which provides a reference for roof control under similar conditions.

scholarly journals New Method to Design Coal Pillar for Lateral Roof Roadway Based on Mining-Induced Stress: A Case Study

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Feng Wang ◽  
Shaojie Chen ◽  
Jialin Xu ◽  
Mengzi Ren
Keyword(s):  
Stress Distribution ◽  
Coal Pillar ◽  
In Situ Stress ◽  
New Method ◽  
Maximum Deformation ◽  
Induced Stress ◽  
Stress Contour ◽  
Longwall Panel ◽  
Overlying Strata

The traditional method to design coal pillar for lateral roof roadway was established based on the mining-induced strata movement contour which is considered as a straight line, while ignoring the variations of the internal strata deformation law as well as stress distribution characteristics. In order to make up for this deficiency, in this study, evolution of mining-induced stress in the overlying strata was simulated using physical and numerical simulations, and a method to design coal pillar for lateral roof roadway based on mining-induced stress was proposed. The results indicate that the stress of the overlying strata is redistributed during excavation, and the stress distribution can be divided into a stress-relaxation area, a stress-concentration area, and an in situ stress area. The contour line of 1.05 times the in situ stress is used to define the mining-induced stress contour. Stress inside the contour is redistributed while outside the contour the overlying strata are still within the in situ stress area. Mining-induced stress contour presents a concave-upward type from coal seam to the overlying strata that cannot be merged into a straight one due to their different characteristics of movement and deformation. With this in mind, this study proposed a method to design the width of coal pillar for lateral roof roadway according to the mining-induced stress contour. According to mining-induced stress contour, the width of coal pillar for lateral roof roadway of longwall panel 31100 is 160 m, and the maximum deformation of the roadway is 270 mm. The new method can definitely meet engineering demands.

scholarly journals Case study on the mining‐induced stress evolution of an extra‐thick coal seam under hard roof conditions

2020 ◽  
Vol 8 (9) ◽  
pp. 3174-3185 ◽  
Author(s):  
Cong Li ◽  
Heping Xie ◽  
Mingzhong Gao ◽  
Jing Xie ◽  
Guangdi Deng ◽  
...  
Keyword(s):  
Coal Seam ◽  
Stress Evolution ◽  
Thick Coal Seam ◽  
Hard Roof ◽  
Induced Stress

Study on Technology of Fully-Mechanized Sub-Level Caving Mining Technology in the Datong Permo Carboniferous Coal Seam

2012 ◽  
Vol 616-618 ◽  
pp. 565-568
Author(s):  
Bin Yu ◽  
Jun Zhao ◽  
Hong Chun Xia
Keyword(s):  
Coal Seam ◽  
Mining Area ◽  
Hard Coal ◽  
Control Technology ◽  
Mining Technology ◽  
Hard Roof ◽  
Sublevel Caving ◽  
Seam Mining ◽  
Longwall Top Coal Caving ◽  
And Control

This thesis briefly introduced roof control technology in fully-mechanized sublevel caving mining with hard roof and hard coal seam, Mining technology , gas prevention and comprehensive prevention and control technology in spontaneous combustion of coal, which in longwall top-coal caving face with hydraulic support in thickness seam in the Datong permo carboniferous coal seam . New development directions of fully-mechanized sublevel caving mining technology in the Datong mining area in the next few years.

Development Rule of Full-Mechanized Caving Mining Water-Flowing Fracture Zone in Yanzhou Mining Area

2012 ◽  
Vol 616-618 ◽  
pp. 475-480
Author(s):  
Zhen Li Fan ◽  
Bing Nan Hu
Keyword(s):  
Fracture Zone ◽  
Influence Factors ◽  
Mining Area ◽  
Overburden Rock ◽  
Rock Destruction ◽  
Thick Coal Seam ◽  
Hard Roof ◽  
Mining Depth ◽  
The Face ◽  
Mining Water

The heights of fully-mechanized mining water-flowing fracture zone of Yanzhou mining area were measured by borehole simple hydrology method .In order to confirm the influence degree of the geology and mining factors to the damage height of overburden rock , the paper analyses the measured data by using grey relation analysis theory, and concludes that the face span, mining thickness and mining depth are main influence factors to the height of the water-flowing fracture zone. On this basis, the paper reveals the general rules of fully-mechanized caving mining overburden rock destruction with the on conditions of gentle dip, thick coal seam and hard and medium hard roof by using regression analysis method.

scholarly journals Mechanism of Support Optimization and Confined Blasting of Thick and Hard Rock with a Wedge-Structure Immediate Roof: A Case Study

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Tong Zhao ◽  
Peilin Gong ◽  
Kaan Yetilmezsoy ◽  
Majid Bahramian ◽  
Changyou Liu ◽  
...  
Keyword(s):  
Main Roof ◽  
Hard Roof ◽  
Working Face ◽  
Immediate Roof ◽  
Physical Simulations ◽  
Fracture Size ◽  
Wedge Structure ◽  
Confined Blasting ◽  
Support Optimization ◽  
Strata Behavior

Based on the occurrence conditions of a thick and hard main roof and wedge-structure immediate roof in the Zhuxianzhuang Coal Mine, the fracture characteristics and instability migration law of a thick and hard roof (THR) were examined via physical simulations. Mining zones were divided with respect to the strata behaviors and roof control difficulty levels, and the principles and methods of zonal control under THR were put forward. This study proposed a coordinated control strategy of using confined blasting in water-filled deep holes, and reasonable support optimization, which could effectively reduce the roof fracture size, increases the supporting intensity and eliminate roof-control disasters. The length of confined blasting blocks and supporting intensity were calculated using a mechanical model for roof control in the strong strata behavior zone and less-strong strata behavior zone. These key parameters were determined as 20–25 m and 1.15–1.28 MPa, respectively, and the mining strategy was successfully applied in working face 880, performing high security and reasonable economical efficiency.

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.

Characteristic of stress evolution on fault surface and coal bursts mechanism during the extraction of longwall face in Yima mining area, China

2020 ◽  
Vol 136 ◽  
pp. 104071 ◽  
Author(s):  
Hongwei Wang ◽  
Ruiming Shi ◽  
Daixin Deng ◽  
Yaodong Jiang ◽  
Gang Wang ◽  
...  
Keyword(s):  
Mining Area ◽  
Longwall Face ◽  
Stress Evolution ◽  
Fault Surface ◽  
Coal Bursts

scholarly journals Analytical Analysis and Field Observation of Break Line in the Main Roof over the Goaf Edge of Longwall Coal Mines

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Zhang Guangchao ◽  
He Fulian ◽  
Jiang Lishuai
Keyword(s):  
Analytical Model ◽  
Bending Moment ◽  
Main Roof ◽  
Break Line ◽  
Shanxi Province ◽  
Winkler Foundation ◽  
Analytical Analysis ◽  
Moment Distribution ◽  
Geological Conditions ◽  
Longwall Panel

This paper presents an integrated approach for analytical analysis and field tests to estimate the break line in a main roof over the goaf edge. An analytical model which treated the main roof as a beam seating on the Winkler foundation and subjected to nonuniformity roof loading was established. Further analysis of the bending moment distribution of such a main roof beam was undertaken. Based on the geological conditions pertaining to a case study at Wangjialing coal mine, Shanxi Province, China, the break line in the main roof in a typical longwall panel was calculated in the rib-sides at a distance of 5.6 to 7.4 m from the goaf edge. The influence of main roof flexural rigidity and foundation rigidity and so forth on the bending moment distribution was revealed by a parametric study. Borehole camera detection was employed to further validate the analytical model and its results. The results of the field test demonstrated that the break line detected in the main roof was about 5.5 to 6.8 m away from the goaf edge, which was in good agreement with the analytical model.

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.

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