scholarly journals Research on The Evolution Law of Spatial Structure of Overlying Strata and Evaluation of Rock Burst Risks in Deep Well Strip Mining

2021 ◽  
Author(s):  
Jinglin Wen ◽  
Zhengxing Yu ◽  
Haitao Ma ◽  
Quande Wei
Keyword(s):  
Spatial Structure ◽  
Rock Burst ◽  
Calculation Model ◽  
Control Surface ◽  
Support Pressure ◽  
Strip Mining ◽  
Coal Seams ◽  
Index Method ◽  
Evolution Law ◽  
Overlying Strata

Abstract Strip mining in mines is one of the main mining methods to control surface subsidence and protect the ecological environment. In recent years, strip mining has induced frequent rock burst accidents due to the increase in mining intensity and mining depth. Based on two typical deep strip mining accidents, the characteristics of the changes in spatial structure of the overlying strata caused by strip mining are studied, and the influencing factors of the occurrence of strip mining rock burst are analyzed. A support pressure calculation model is proposed, and estimated and verified in a mine after an analysis of the change law of the overlying strata structure in strip mining and research on the distribution and evolution law of support pressure. Based the above research, a risk evaluation model of the strip mining face is proposed based on the possibility index method, the 4203 working face of a mine is evaluated. Compared with the numerical simulation results, this method is well consistent with the theoretical calculation model. It can be seen that this method has strong practicability and is of great significance for studying the rock burst characteristics of coal seams in strip mining and evaluating the risk of rock burst of coal seams.

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

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhen Wei ◽  
Ke Yang ◽  
Xiaolou Chi ◽  
Wenjie Liu ◽  
Xinyuan Zhao
Keyword(s):  
Shear Stress ◽  
Coal Seam ◽  
Main Roof ◽  
Stability Control ◽  
Calculation Model ◽  
Coal Seams ◽  
Overburden Pressure ◽  
Dip Angle ◽  
Basic Roof ◽  
Overlying Strata

The fracture instability mechanism of the basic roof is the key to support selection and surrounding rock stability control, and it is also the guarantee of safe and efficient coal mining. By means of theoretical analysis and numerical calculation, the calculation model of basic roof of steeply dipping coal seams (SDCS) under linear load is established, the stress distribution expression of basic roof plate is deduced, the inclination effect of stress evolution of steeply dipping coal seams (SDCS) workface is analyzed, and the “sequential” weighting mechanism of workface is revealed. Based on the numerical simulation test, the evolution laws of vertical stress release and shear stress concentration of overlying strata in workface with different coal seam dip angles are obtained. The results show that there is shear stress arch in the overlying strata. With the increase of coal seam dip angle, the overlying strata are suddenly damaged under the action of shear stress. 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.

scholarly journals The Impact of the Coexistence of Methane Hazard and Rock-Bursts on the Safety of Works in Underground Hard Coal Mines

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 128
Author(s):  
Justyna Swolkień ◽  
Nikodem Szlązak
Keyword(s):  
Rock Burst ◽  
Methane Concentration ◽  
High Energy ◽  
Hard Coal ◽  
Coal Seams ◽  
Safety Level ◽  
Methane Drainage ◽  
Innovative Methods ◽  
Hard Coal Mining ◽  
The Impact

Several natural threats characterize hard coal mining in Poland. The coexistence of methane and rock-burst hazards lowers the safety level during exploration. The most dangerous are high-energy bumps, which might cause rock-burst. Additionally, created during exploitation, safety pillars, which protect openings, might be the reason for the formation of so-called gas traps. In this part, rock mass is usually not disturbed and methane in seams that form the safety pillars is not dangerous as long as they remain intact. Nevertheless, during a rock-burst, a sudden methane outflow can occur. Preventing the existing hazards increases mining costs, and employing inadequate measures threatens the employees’ lives and limbs. Using two longwalls as examples, the authors discuss the consequences of the two natural hazards’ coexistence. In the area of longwall H-4 in seam 409/4, a rock-burst caused a release of approximately 545,000 cubic meters of methane into the excavations, which tripled methane concentration compared to the values from the period preceding the burst. In the second longwall (IV in seam 703/1), a bump was followed by a rock-burst, which reduced the amount of air flowing through the excavation by 30 percent compared to the airflow before, and methane release rose by 60 percent. The analyses presented in this article justify that research is needed to create and implement innovative methods of methane drainage from coal seams to capture methane more effectively at the stage of mining.

scholarly journals Urban spatial structure re-identification as an approach to solving urban transport problem (A case study in Malang)

2018 ◽  
Vol 181 ◽  
pp. 10006
Author(s):  
Dadang Meru Utomo ◽  
Septiana Hariyani
Keyword(s):  
Local Government ◽  
Spatial Structure ◽  
Urban Transport ◽  
Urban Spatial Structure ◽  
Spatial Structures ◽  
Index Method ◽  
Centrality Index ◽  
Effective Result

In an effort to solve the congestion problem, the local government of Malang City has taken various steps. However, unfortunately, the result has not been effective. This shows that the efforts that have been taken so far are sectoral, therefore a more comprehensive approach is needed in order to reach a more effective result. This research aims at re-evaluating the determination of Malang City's urban spatial structure through the delineation of narrower units of area using the centrality index method. The research suggests that urban spatial structures have a very clear pattern of association with congestion locations. It can be concluded that the local government of Malang City needs to put more consideration on evaluating the urban spatial structure to solve the problem of transportation which is ever-growing the in second largest urban area in East Java Province.

scholarly journals Research on Evaluation Index and Application of Rockburst Risk in Deep Strip Mining

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Bangyou Jiang ◽  
Hongguang Ji ◽  
Long Fu ◽  
Shitan Gu ◽  
Tong Zou ◽  
...  
Keyword(s):  
Plastic Zone ◽  
Coal Mine ◽  
Coal Pillar ◽  
Width Ratio ◽  
Strip Mining ◽  
Index Method ◽  
Research On Evaluation ◽  
Mechanics Model ◽  
Evolution Characteristics ◽  
Comprehensive Index Method

The practice shows that deep strip mining induces rockburst disaster easily. Accurately evaluating rockburst risk of the strip coal pillar is of great significance for ensuring the safety of deep strip mining. In this paper, the catastrophe mechanics model was used to analyze the abrupt instability condition of strip coal pillar. And the three indicators that are the medium stiffness ratio (k) of the elastic and plastic zone in the coal pillar, the plastic zone width ratio (aY), and the elastic deformation index (Uq) of core zone were put forward with considering the geometry size of coal pillar. Based on the 3202 panel of Gucheng Coal Mine, the evolution characteristics of rockburst risk of coal pillar under different mining widths and coal pillar widths were studied by numerical simulation. The evaluation result shows that the strip coal pillar of the 3202 panel is in danger of strong rockburst, which is more in line with the actual situation than the results of the traditional rockburst tendency identification test and comprehensive index method. These three indicators can be regarded as important indicators to evaluate the rockburst risk in the strip mining engineering field. Based on that, the design principle of strip mining in Gucheng Coal Mine was put forward, which is considered an important reference for similar cases.

Assessment of rigid overlying strata failure in face mining

2010 ◽  
Vol 2 (4) ◽  
Author(s):  
Eva Jiránková
Keyword(s):  
Longwall Mining ◽  
Practical Importance ◽  
Assessment Method ◽  
Coal Seams ◽  
Deep Mine ◽  
Failure Assessment ◽  
Surface Measurements ◽  
Strata Failure ◽  
Simultaneous Assessment ◽  
Overlying Strata

AbstractThe method of overlying strata failure assessment of extracted seams is based upon the simultaneous assessment of surface subsidence and seismic activity, considering the spatiatemporal progress of mining, depending on the character of the rock mass. The rigid overlying strata failure assessment results in finding whether a failure of the firm overlying rocks occurred or whether a strutting arch was formed over the mined-out area. The practical importance of the overlying strata failure assessment consists in determining the size of the mined-out area at which the com-plete failure of the rigid overlying strata occurred and in the assessment of the current stress condition of the overlying strata failure. The assessment method is applicable in deep mine workings where thick coal seams are being mined by means of the method of longwall mining with controlled caving. The results of this method are used to amend contemporary known methods of rock-burst protection, namely (regarding the use of surface measurements for the evaluation) in overlying strata areas.

scholarly journals Prevention and Control Technology for Harmful Toxic Gas Intrusion in High-Fire-Hazard-Risk Areas of Close-Distance Coal Seams

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Wei Wang ◽  
Yuntao Liang
Keyword(s):  
Fire Hazard ◽  
Air Leak ◽  
Coal Seams ◽  
Risk Area ◽  
Hazard Risk ◽  
Working Surface ◽  
Toxic Gas ◽  
Close Distance ◽  
Close Distance Coal Seams ◽  
Overlying Strata

Fire hazard-risk area in small coal pits can be found in the southern part of the Shigetai Coal Mine, a close-distance coal seam mining sector in the Shendong mining area, which is susceptible to the risk of harmful toxic gas intrusion, seriously threatening the safety of mining around the working surface. Aiming at this problem, a numerical model representing the mining activity on the close-distance coal seams was established to simulate the movement pattern of overlying strata and the development process of fractures based on the horizontal stress “normalization” technology. Also, the principal air-leak passageways were detected with the SF6 tracer analysis. On this basis, the influencing pattern of harmful toxic gas intruding into the working surface can be comprehensively analyzed, providing a basis for effectively preventing and controlling gas intrusion disasters. The research findings show that, after a lower coal seam has been mined, the caving zone ranges from 73 m to 94 m in height, and the fractured zone tends to develop all the way to the surface. Furthermore, shear fractures are the major passageways for air leakage, and the occurrence of gas intrusion disasters is basically taking place at the same time frame as the occurrence of roof weighting. Meanwhile, the harmful toxic gas intrudes the working surface through the fractures on the security coal pillars and shear fractures on the overlying strata. To prevent intrusion disasters from occurring, the applications of inorganic foaming and curing materials for filling were studied in combination with the actual engineering conditions. The construction grounds in sections where the fire hazard-risk area in small coal pits have not been stripped were drilled, and filling materials were poured into the goaf to create an isolation belt. As can be observed from the applied areas, constructing isolation belts to block the major air-leak passageways can effectively prevent the harmful toxic gases from intruding into the working surface, ensuring the safety of mining on the working surface.

scholarly journals The Key Stratum Structure Morphology of Longwall Mechanized Top Coal Caving Mining in Extra-Thick Coal Seams: A Typical Case Study

2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Fulian He ◽  
Xiaobin Li ◽  
Wenrui He ◽  
Yongqiang Zhao ◽  
Zhuhe Xu ◽  
...  
Keyword(s):  
Coal Seam ◽  
Cantilever Beam ◽  
Coal Seams ◽  
Key Strata ◽  
Key Stratum ◽  
Structure Morphology ◽  
Coal Wall ◽  
Coal Seam Thickness ◽  
Longitudinal Cracks ◽  
Overlying Strata

Longwall mechanized top coal caving mining (LMTCCM) in extra-thick coal seams has its own characteristics. The law of mining pressure and overlying strata failure height in extra-thick coal seams are much larger than those of medium-thick and thick coal seams. The key stratum structure morphology also has an important influence on the law of overlying strata movement and stability of surrounding rock. Based on the engineering geological conditions, this paper used the method of theoretical analysis and numerical simulation to study the key stratum structure morphology of LMTCCM in extra-thick coal seams. The results show that under the condition of LMTCCM in extra-thick coal seams, the key stratum forms the structure of low cantilever beam and high hinged rock beam. With the increase of coal seam thickness, the breaking position of cantilever beam is closer to the coal wall. Through theoretical calculation, it is obtained that the breaking length of cantilever beam is 31.5 m and the breaking position of cantilever beam is 15.4 m away from coal wall. With the increase of cycle, key strata will undergo the evolution law from the generation of longitudinal cracks to the hinged structure and then to the cantilever beam structure. The breakage of key strata will cause the expansion of longitudinal cracks and the overall synchronous movement of overlying strata. With the increase of coal seam thickness, the distribution of longitudinal cracks will gradually transfer from the upper part of goaf to the deep part of coal body in space and increase in quantity. This research is of great significance for improving the stability of overlying strata and ensuring the safe and efficient mining of extra-thick coal seams.

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