scholarly journals Physical simulation of upper protective coal layer mining with different coal seam inclinations

2020 ◽  
Vol 8 (9) ◽  
pp. 3103-3116 ◽  
Author(s):  
Feng Fang ◽  
Cai Shu ◽  
Hongtu Wang
Keyword(s):  
Coal Seam ◽  
Physical Simulation ◽  
Coal Layer

scholarly journals Key Stratum Structure and Support Working Resistance of Longwall Face with Large Mining Height in the Shallow Coal Seams, China

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Qingxiang Huang ◽  
Jinlong Zhou ◽  
Jian Cao
Keyword(s):  
Coal Seam ◽  
Physical Simulation ◽  
Longwall Face ◽  
Beam Structure ◽  
Key Stratum ◽  
Immediate Roof ◽  
Large Mining Height ◽  
Shallow Coal Seam ◽  
Working Resistance ◽  
Mining Height

The fully mechanized mining with large mining height is the main method for high yield and efficient coal mining in China. The key stratum structure (KSS) is the basis of revealing the mechanism of roof weighting and determination of support working resistance of the longwall face with large mining height (LFLMH) in the shallow coal seam. The height of the caving zone at LFLMH is large, the thick immediate roof forms the “short cantilever beam” structure commonly, and the hinge layer of the overlying key stratum will move upward to the higher position. The “high position oblique step voussoir beam” structure of single-key stratum (SKS) and “oblique step voussoir beam and voussoir beam” structure of double-key stratum (DKS) in the shallow coal seam were proposed with physical simulation and Universal Distinct Element Code (UDEC). The analysis of the KSS and numerical simulation reveals the mechanism of strong roof weighting at the SKS longwall face and large-small alternate periodic weighting at the DKS longwall. It is concluded that the large static load caused by the “equivalent immediate roof (EIR)” is the basic load, and the instability load of the KSS is the additional dynamic load of support. Besides, the calculation methods of the reasonable support working resistance at LFLMH were obtained and verified with engineering applications.

scholarly journals Research on Roof Fracture Characteristics of Gob-Side Entry Retaining with Roof Cutting and Non-pillar Mining in Thick Coal Seam, China

2021 ◽  
Author(s):  
Mengye Zhao ◽  
Lei Zhu ◽  
Qingxiang Huang ◽  
Kai Xu ◽  
Yuyi Wu ◽  
...  
Keyword(s):  
Coal Seam ◽  
Physical Simulation ◽  
Structural Characteristics ◽  
Thick Coal Seam ◽  
Fracture Characteristics ◽  
Microseismic Events ◽  
Entry Roof ◽  
Control Layer ◽  
P Mining ◽  
Basic Roof

AbstractBased on the S1201-2 large height mining in the 2–2 coal seam of Ningtiaota colliery with on-site microseismic measurement, physical simulation and theoretical analysis methods, this paper explores the rule of roof movement in thick coal seams with roof cutting and non-pillar (hereinafter referred to as RCN-P) mining, so as to obtain scientific and effective theoretical basis for entry support and to summarize the regional structural characteristics and dynamic periodic fracture characteristics. As can be seen from microseismic events, the entry roof is featured by "two zones and one line" along the horizontal direction, namely, the crack generation area, the roof movement area. Additionally, and the obvious lateral breaking of the entry roof on the coal wall is a typical feature of the thick coal seam with RCN-P mining. The roof is vertically divided into "three zones", the crack generation area, the roof movement area and the crack development area. The roof cutting activity mainly affects the overburden activity within the basic roof height range, which is also the roof movement area. In addition, the distribution frequency and the intensity of microseismic events indicate the roof periodic breaking characteristics. The "breaking pressure relief,” “advanced crack development,” and “the limit breaking state” of roof breaking corresponds to the initial, middle, and final stage of breaking in the periodic weighting process, respectively. Compared with the normal mining, the RCN-P mining reduces the periodic weighting length and increases the pressure strength. As is shown in the physical simulation experiment, the basic roof and the cutting control layer in the "regional structural characteristics" constitute the “large” and “small” structures with RCN-P mining. The basic roof key layer is the core to control the stability of the strata, and the breaking process from the cantilever beam to the short masonry beam of the roof-cutting control layer is the main cause of the entry stress. Correspondingly, the basic structure model of “short masonry-hinged” roof was proposed and the calculation method of support was established for the entry with RCN-P mining in thick coal seam, providing a research foundation for scientific and effective rock formation control.

Study on Close Coal Seam Pressure Behavior Law of Zhong Xing Mine by Physical Model

2012 ◽  
Vol 204-208 ◽  
pp. 1439-1444
Author(s):  
Guang Shun Cai ◽  
Li Qian An ◽  
Xin Xin Zhu ◽  
Ji Li An ◽  
Ling Tao Mao
Keyword(s):  
Stress Distribution ◽  
Coal Seam ◽  
Simulation Model ◽  
Lower Layer ◽  
Shanxi Province ◽  
Overburden Rock ◽  
Geological Data ◽  
Coal Layer ◽  
Working Face ◽  
Similar Simulation

Based on the actual geological data of the 1202 lower layer work face of the Zhong Xing mine, in Shanxi province, a physical similar simulation model has been built to analyze the influence on the lower coal layer after mining the upper layer, and research on the deformation, failure law and the stress distribution of overburden rock. The results show that after mining the upper coal layer, overburden rock experienced subsidence, separation, bending and even breaking down, and the original state of the rock destroyed. The rock's intensity is weaken, and the whole rock has been softened. When the distance of the coal layers becomes smaller, the influence of the mutual exploitation becomes larger. Those results provide a reference for reasonable layout of the mining of the coal seam working face.

scholarly journals Complex Function Solution for Deformation and Failure Mechanism of Inclined Coal Seam Roadway

2021 ◽  
Author(s):  
Xianyu Xiong ◽  
Jun Dai ◽  
Xinnian chen ◽  
Yibo Ouyang
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Failure Mechanism ◽  
Physical Simulation ◽  
Complex Function ◽  
Surrounding Rock ◽  
Simulation Test ◽  
Deformation And Failure ◽  
Stress And Deformation ◽  
The Right

Abstract The stressed environment of the inclined coal seam roadway is complex and changeable, and the damage degree of surrounding rock increases, threatening the safe mining of coal mines. To improve the effectiveness of stability control of surrounding rock of this kind of roadway, the deformation and failure law of the inclined coal seam roadway is analyzed based on the complex function theory. It optimizes the solution process and accuracy of the mapping function coefficient and deduces the analytical solution of surrounding rock stress and deformation inclined coal seam roadway. The deformation and failure mechanism of surrounding rock in inclined coal seam roadway is revealed theoretically and verified by numerical simulation and physical simulation test. The results show that the stress and deformation of roadway surrounding rock in inclined coal seam show obvious asymmetric distribution characteristics. The stress and deformation of roadway surrounding rock on the right side are greater than on the left side. The two sides of the roadway, the right side of the roof and the roof angle of the right side, are the key positions of roadway stress concentration and deformation. According to the variation law of stress and deformation distribution of roadway surrounding rock, roadway cyclic deformation and failure theory is put forward. The numerical simulation and physical simulation test show that the deformation and failure law of roadway is consistent with the theoretical analysis results, and the cyclic deformation and failure mechanism of roadway in inclined coal seam is verified.

scholarly journals Research on Roof Fracture Characteristics of Gob-Side Entry Retaining with Roof Cutting and Non-Pillar Mining in Thick Coal Seam, China

2021 ◽  
Author(s):  
Lei Zhu ◽  
Mengye Zhao ◽  
Qingxiang Huang ◽  
Kai Xu ◽  
Yuyi Wu ◽  
...  
Keyword(s):  
Coal Seam ◽  
Physical Simulation ◽  
Structural Characteristics ◽  
Thick Coal Seam ◽  
Fracture Characteristics ◽  
Microseismic Events ◽  
Entry Roof ◽  
Control Layer ◽  
P Mining ◽  
Basic Roof

Abstract Based on the S1201-2 large height mining in the 2-2 coal seam of Ningtiaota colliery with on-site microseismic measurement, physical simulation and theoretical analysis methods, this paper explores the rule of roof movement in thick coal seams with roof cutting and non-pillar (hereinafter referred to as RCN-P) mining, so as to obtain scientific and effective theoretical basis for entry support and to summarize the regional structural characteristics and dynamic periodic fracture characteristics. As can be seen from microseismic events, the entry roof is featured by "two zones and one line" along the horizontal direction, namely, the crack generation area, the roof movement area. Additionally, and the obvious lateral breaking of the entry roof on the coal wall is a typical feature of the thick coal seam with RCN-P mining. The roof is vertically divided into "three zones", the crack generation area, the roof movement area and the crack development area. The roof cutting activity mainly affects the overburden activity within the basic roof height range, which is also the roof movement area. In addition, the distribution frequency and the intensity of microseismic events indicate the roof periodic breaking characteristics. The "breaking pressure relief,” “advanced crack development,” and “the limit breaking state” of roof breaking corresponds to the initial, middle, and final stage of breaking in the periodic weighting process, respectively. Compared with the normal mining, the RCN-P mining reduces the periodic weighting length and increases the pressure strength. As is shown in the physical simulation experiment, the basic roof and the cutting control layer in the "regional structural characteristics" constitute the “large” and “small” structures with RCN-P mining. The basic roof key layer is the core to control the stability of the strata, and the breaking process from the cantilever beam to the short masonry beam of the roof-cutting control layer is the main cause of the entry stress. Correspondingly, the basic structure model of “short masonry-hinged” roof was proposed and the calculation method of support was established for the entry with RCN-P mining in thick coal seam, providing a research foundation for scientific and effective rock formation control.

scholarly journals Investigation on the Ground Pressure Induced by Hard Roof Fracturing at Different Layers during Extra Thick Coal Seam Mining

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Rui Gao ◽  
Jingxuan Yang ◽  
Tiejun Kuang ◽  
Hongjie Liu
Keyword(s):  
Coal Seam ◽  
Physical Simulation ◽  
Similarity Criterion ◽  
Thick Coal Seam ◽  
Failure Characteristics ◽  
Hard Roof ◽  
Ground Pressure ◽  
Working Face ◽  
Seam Mining ◽  
Roadway Deformation

The fracturing of hard roofs in different layers would result in complex ground pressure on the working face, such as supports collapsed and severe roadway deformation. However, the mechanism of the ground pressure induced by hard roof fracturing in different layers is still unclear. In the paper, a physical model of a 20 m extrathick coal seam mined with hard roofs existing was established based on the physical simulation similarity criterion. The overburden fracturing structure, abutment stress distribution, and failure characteristics of the coal body were monitored by a noncontact strain measurement system and resistance strain gauges, to reveal the mechanism of ground pressure induced by hard roof fracturing. Furthermore, on-site measurement was used to monitor and analyze the ground pressure affected by hard roofs in different levels. The results provide a theoretical basis for the control of ground pressure in extrathick coal seam mining with hard roofs.

scholarly journals Research on the Roof Advanced Breaking Position and Influences of Large Mining Height Working Face in Shallow Coal Seam

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1685
Author(s):  
Qingxiang Huang ◽  
Yanpeng He ◽  
Feng Li
Keyword(s):  
Coal Seam ◽  
Field Measurement ◽  
Physical Simulation ◽  
Main Roof ◽  
Key Strata ◽  
Working Face ◽  
Measurement Results ◽  
Large Mining Height ◽  
Shallow Coal Seam ◽  
Mining Height

The large mining height (LMH) in shallow coal seam has been widely applied in the Shenfu coalfield, China. The dynamic load is obvious, and the rib spalling is serious when the LMH working face concerns roof weighting. The advanced breaking position of the roof affects the strength of the ground pressure when the roof is broken. Firstly, based on a large number of actual measurements and physical simulation experiments, the rock formation in the fall zone, where the articulated structure cannot be articulated between the coal seam and the main roof, is called the equivalent immediate roof (EIR). When the mining height increases, the thickness of the EIR increases non-linearly. Next, based on the theory of “elastic foundation beam”, a mechanical model for the advanced breaking of the roof is established in shallow coal seam, and the calculation equation for the advanced breaking position of the roof is given; then, designed and carry out boreholes of the no. 22201 working face in the Zhangjiamao Coal Mine. The theoretical calculation of key strata results (5.6–6.9 m) are in the range of field measurement results (5–8 m). According to the field measurement results, the roof movement of the LMH working face is ahead of the roof weighting. Finally, we define the thickness of EIR and the mining height ratio as the immediate mining ratio ki, which affects the degree of filling of the goaf and determines the structural form of the main roof. When the ki is small, the goaf is fully filled; when the ki is large, the goaf is fully filled. Under the same conditions, different filling rate conditions will form different roof structures. Results of this research can be helpful to control roof weighting and provide early warning of possible safety problems related to the LMH working face in shallow coal seam.

scholarly journals Research on the Influence of Mining Height on the Movement Characteristics of Overlying Strata during Extremely Thick Coal Seam Fully Mechanized Sublevel Caving Mining

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Yongkang Yang ◽  
Jie Wei ◽  
Chenlong Wang
Keyword(s):  
Coal Seam ◽  
Physical Simulation ◽  
Quadratic Polynomial ◽  
Tensile Failure ◽  
Thick Coal Seam ◽  
Sublevel Caving ◽  
Height Increase ◽  
Supporting Force ◽  
Mining Height ◽  
Overlying Strata

The study of the effects of mining height on overlying strata movement and underground pressure characteristics during extremely thick coal seam fully mechanized sublevel caving mining is very important for choosing the reasonable mining height and the support. Based on the geological setting and mining conditions at the Xiegou Coal Mine, the results of the physical simulation test and the numerical simulation technology will be used. Some conclusions can be drawn as follows: (1) With the mining height increase, the top coal gradually converted from tensile failure to shear damage, and the coal wall gradually transformed from shear failure to tensile damage. (2) When the mining height is 7.5 m, the full-seam collapse distance, the immediate first weighting interval, and the main roof first weighting length are shorter than that when the mining height is 4m, and the periodic weighting length for the two mining heights is almost the same. (3) With mining height increase, the initial mining stage and the transition stage become shorter, and the production rates become better. (4) The law of the abutment pressure peak and the sphere of influence increase slightly, and the working resistance of support needed to be strengthened. (5) The subsidence quantity of the top coal in the control area increases along with the mining height in a quadratic polynomial way but decreases along with the initial supporting force in a negative logarithmic rule. (6) After assigning the subsidence, the regression relation between the initial supporting force and the mining height is a quadratic polynomial.

scholarly journals Research on the Reasonable Width of the Waterproof Coal Pillar during the Mining of a Shallow Coal Seam Located Close to a Reservoir

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Mengling Hu ◽  
Wenlong Zhao ◽  
Zheng Lu ◽  
Jianxi Ren ◽  
Yanping Miao
Keyword(s):  
Theoretical Analysis ◽  
Coal Seam ◽  
Water Conservation ◽  
Physical Simulation ◽  
Coal Pillar ◽  
Mine Pressure ◽  
Abscission Layer ◽  
Bank Slope ◽  
Seam Mining ◽  
Reservoir Bank Slope

Retaining a waterproof coal pillar is the most effective water conservation method for coal seam mining close to a reservoir, and determining a reasonable width for the waterproof coal pillar has been a common problem among mining scholars for a considerably long time. In case of mining a 4−2 coal seam close to the Changjiagou Reservoir in the Zhangjiamao mine, the research methods of theoretical analysis, physical simulation using similar materials, and numerical simulation have been adopted to analyze the overburden strata mining failure features and the surface subsidence law. Additionally, the influences of the width of the coal pillar on the reservoir bank slope stability have been investigated. The results denote that a coal pillar can be divided into a mine-pressure-influenced zone, an effective waterproof zone, and a water-level-influenced zone with respect to water resistance. Furthermore, the width of the waterproof coal pillar was determined to be 107.41 m by theoretical analysis. The simulation test indicated that when the working face advanced close to the reservoir, the reservoir bank exhibited vertical downward as well as transverse abscission layer fractures and the divided topsoil slipped toward the reservoir. Subsequently, the judgment conditions required for determining the critical width of the waterproof coal pillar were proposed based on the requirements to prevent the reservoir bank slope from instability failure and the water gushing accident in goaf. The maximum width of the waterproof coal pillar when the top point on the slope surface experienced reverse horizontal displacement and several key points produced sharp vertical displacements or when the pore pressure in the coal seam roof and floor suddenly became 0 was considered to be the critical width. Furthermore, the critical width was determined to be 96 m via simulation analysis, verifying the rationality of the theoretical method. These results could provide a theoretical basis for determining the width of the waterproof coal pillar of the coal seam located close to a reservoir.

Sign in / Sign up

Export Citation Format

Share Document