scholarly journals Reasonable Determination of Terminal Mining Lines Using the Stress Field with Seismic Wave Excitation in Deep Coalfaces

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Guang-an Zhu ◽  
Huan Liu ◽  
Bo-ru Su ◽  
Qi-peng Jiang ◽  
Hai-yang Liu
Keyword(s):  
Stress Field ◽  
Theoretical Analysis ◽  
Rock Burst ◽  
Seismic Wave ◽  
Coal Mine ◽  
Evaluation Method ◽  
Coal Pillar ◽  
Field Observations ◽  
Wave Excitation ◽  
Rock Burst Risk

Many field observations have shown that rock bursts occur frequently near the terminal mining line (TML) and dip coal pillar area in deep coalfaces. Taking the “7.26” rock burst in coalface 3302 in Xingcun Coal Mine as an example, the rock burst mechanism was investigated based on theoretical analysis and field observations, and a combined evaluation method using the stress field under seismic wave excitation was established to determine the reasonable TML of coalface 3302. Firstly, the static geological data revealed during roadway excavation were used for preevaluation of rock burst risk at the working face. By theoretically analyzing the stress transfer mechanism of the two types of the roof structure, the computational model of abutment pressure was established and the calculation method giving the abutment stress was proposed. Subsequently, a dynamic evaluation method that adopts microseismic and stress online monitoring system to monitor dynamic information, such as mine tremors and stress during coalface mining, was developed to define stress anomaly areas and then dynamically determine the TML. Finally, the proposed model was used to optimize the position of the TML of LW3302 in Xingcun Coal Mine; findings obtained in this study provide theoretical guidance for safe coal mining. Combined with the results of theoretical analysis (255 m), online stress monitoring (200 m), microseismic (MS) monitoring (262 m), and passive seismic velocity tomography (220–250 m), it can be finally determined that the width of the protective coal pillar for the TML of coalface 3302 should be at least 262 m.

scholarly journals GA-Based Early Warning Method for Rock Burst with Microseismic and Acoustic Emission in Steeply Inclined Coal Seam

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Yarong Xue ◽  
Dazhao Song ◽  
Zhenlei Li ◽  
Jianqiang Chen ◽  
Xueqiu He ◽  
...  
Keyword(s):  
Genetic Algorithm ◽  
Rock Burst ◽  
Coal Mine ◽  
Early Warning ◽  
Characteristic Parameter ◽  
Control Measures ◽  
Risk Level ◽  
Parameter System ◽  
Fitness Value ◽  
Rock Burst Risk

Aiming at problem of low efficacy of early warning of rock burst in coal mine, a multisystem and multiparameter integrated early warning method based on genetic algorithm (GA) is proposed. In this method, firstly, the temporal-spatial-intensity information of energy incubation process of rock burst is deeply mined, and the multidimensional precursory characteristic parameter system of rock burst is constructed. Secondly, the genetic algorithm is used to train the historical monitoring data to obtain the optimal critical value and fitness value of each precursory characteristic parameter, and then the early warning index WC of each monitoring system is calculated. Finally, the integrated rock burst early warning index IC is obtained by synthesizing the early warning index WC of each system. The value of IC corresponds to the specific rock burst risk level of the mine. This method is applied to Wudong coal mine in Xinjiang, China. Based on the actual situation of the mine, a multidimensional precursory characteristic parameter system of rock burst is constructed, which includes energy deviation (DE), frequency ratio (Fr), frequency deviation (DF), degree of dispersion (DS), and total high value of energy deviation (DH). After analyzing the rock burst danger status and risk level in the monitoring area, the early warning capability of this method is found to reach 0.896. Combining with the specific prevention and control measures corresponding to different rock burst risk levels, it can provide effective guidance for the field work.

scholarly journals Study on the Mechanism and Control of Rock Burst of Coal Pillar under Complex Conditions

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Xingping Lai ◽  
Huicong Xu ◽  
Jingdao Fan ◽  
Zeyang Wang ◽  
Zhenguo Yan ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Rock Burst ◽  
Coal Mine ◽  
High Stress ◽  
Coal Pillar ◽  
Vertical Stress ◽  
Body Area ◽  
High Stress Concentration ◽  
Solid Coal ◽  
Working Face

In order to explore the mechanism of coal pillar rock burst in the overlying coal body area, taking W1123 working face of Kuangou Coal Mine as the engineering background, the full mining stage of W1123 is simulated by FLAC3D. It is found that the high stress concentration area has appeared on both sides of the coal pillar when W1123 does not start mining. With the advance of the working face, the high stress concentration area forms X-shaped overlap. There is an obvious difference in the stress state between the coal pillar under the solid coal and the coal pillar under the gob in W1123. The concrete manifestation is that the vertical stress of the coal pillar below the solid coal is greater than the vertical stress of the coal pillar below the gob. The position of the obvious increase of the stress of the coal pillar in the lower part of the solid coal is ahead of the advancing position of the working face, and the position of the obvious increase of the stress of the lower coal pillar in the gob lags behind the advancing position of the working face. At the same time, in order to accurately reflect the true stress environment of coal pillars, the author conducted a physical similarity simulation experiment in the laboratory to study the local mining process of the W1123 working face, and it is found that under the condition of extremely thick and hard roof, the roof will be formed in the gob, the mechanical model of roof hinged structurer is constructed and analyzed, and the results show that the horizontal thrust of roof structure increases with the increase of rotation angle. With the development of mining activities, the self-stable state of the high stress balance in the coal pillar is easily broken by the impact energy formed by the sudden collapse of the key strata. Therefore, the rock burst of coal pillar in the overlying coal body area is the result of both static load and dynamic load. In view of the actual situation of the Kuangou Coal Mine, the treatment measures of rock burst are put forward from the point of view of the coal body and rock mass.

Microseismic Precursory Characteristics of Rock Burst Hazard in Mining Areas Near a Large Residual Coal Pillar: A Case Study from Xuzhuang Coal Mine, Xuzhou, China

2016 ◽  
Vol 49 (11) ◽  
pp. 4407-4422 ◽  
Author(s):  
An-ye Cao ◽  
Lin-ming Dou ◽  
Chang-bin Wang ◽  
Xiao-xiao Yao ◽  
Jing-yuan Dong ◽  
...  
Keyword(s):  
Rock Burst ◽  
Coal Mine ◽  
Coal Pillar ◽  
Mining Areas ◽  
Burst Hazard ◽  
Residual Coal

Rock burst risk in an island longwall coal face by stress field

2018 ◽  
Vol 22 (4) ◽  
pp. 609-622 ◽  
Author(s):  
Guangjian Liu ◽  
Zonglong Mu ◽  
Jianjun Chen ◽  
Jing Yang ◽  
Jinglong Cao
Keyword(s):  
Stress Field ◽  
Rock Burst ◽  
Coal Face ◽  
Rock Burst Risk

scholarly journals Investigation on Rock Strata Fracture Regulation and Rock Burst Prevention in Junde Coal Mine

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Fengnian Wang ◽  
Gan Li ◽  
Chi Liu
Keyword(s):  
Rock Burst ◽  
Coal Mine ◽  
Coal Pillar ◽  
Energy Concentration ◽  
Pressure Relief ◽  
Rock Stratum ◽  
Mechanics Model ◽  
Bending Elasticity ◽  
Mine Roadway ◽  
Rock Strata

Through the establishment of structural mechanics model, this paper analyzes the fracture of super thick rock stratum. Through the model, it can be seen that the fracture of low-level super thick rock stratum produces large elastic energy release and dynamic load, which is easy to produce disasters such as rock burst. The numerical calculation shows that under the influence of low hard and thick rock stratum, the leading area of coal mine roadway will produce energy concentration, and the coal pillar will also produce energy accumulation. Thick rock stratum is in bending state and has large bending elasticity. Coal pillar has large compression elasticity, which is the main reason for rock burst. The accumulation of elastic properties of overburden and rock burst caused by coal pillar energy storage can be effectively controlled by using advanced presplitting blasting, coal seam drilling pressure relief, and strengthening support.

scholarly journals Mechanism and Evolution Control of Wide Coal Pillar Bursts in Multithick Key Strata

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Wenhao Guo ◽  
Anye Cao ◽  
Chengchun Xue ◽  
Yang Hu ◽  
Songwei Wang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Stress Concentration ◽  
Theoretical Analysis ◽  
Coal Mine ◽  
Coal Pillar ◽  
Western China ◽  
Key Strata ◽  
Working Face ◽  
Microseismic Events ◽  
Evolution Control

Coal mine pillar burst frequently occurs in Western China, which seriously restricts safe production. This paper takes the 35 m coal pillar of the 3102 working face of MKQ coal mine as the engineering background. The mechanism and evolution control of pillar bursts in multithick key strata are studied using field investigation, theoretical analysis, and numerical simulation. The mechanism of dynamic and static stress-induced pillar bursts was revealed combining the “O-X” broken features for key strata and numerical simulation of pillar stress evolution. A prevention scheme is put forward for strata presplit blasting and adjusting coal pillar width to minimize the dynamic and static stresses. The results demonstrate the following. (1) In the multithick strata, the first and second near-field subkey strata have perpendicular “O-X” broken features, whereas the third far-field subkey has parallel “O-X” broken features. The working face has three kinds of periodic weighting phenomena: long, medium, and short. (2) The simulated vertical stress curve of 35 m coal pillar goes through three states: two-peak, asymmetric trapezoidal and symmetrical trapezoidal shape with the different advancing position of working face. The stress concentration is extensively promoting a high-risk area for rock burst. (3) The coal pillar burst was induced by the superposition of energy released by the key strata breaking and the elastic energy accumulated in the wide coal pillar. (4) The monitoring data showed that the long, medium, and short periodic weighting steps of multithick key strata are 141.6 m, 43.2–49.6 m, and 17.6–27.2 m, respectively. The microseismic events energy, frequency, and stress of hydraulic support increment are the highest during the long periodic weighting, and the spatial distribution of microseismic events coincides with the stress concentration area. The theoretical analysis is confirmed with the field practice.

scholarly journals Microseismic Signals in Heading Face of Tengdong Coal Mine and Their Application for Rock Burst Monitoring

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
JianJu Ren ◽  
Wenlong Zhang ◽  
Zheng Wu ◽  
Ji Li ◽  
Ying Shen
Keyword(s):  
Rock Burst ◽  
Coal Mine ◽  
Early Warning ◽  
Great Influence ◽  
Field Tests ◽  
Vibration Signal ◽  
Propagation Distance ◽  
Large Energy ◽  
Rock Burst Risk ◽  
Interference Signals

Microseismic (MS) monitoring is an important and commonly used geophysical method in coal mines to predict rock burst which has great influence on safety production. MS monitoring technology and analysis method of the whole mine or working face have been matured, but its use in heading faces of coal mine is not mature due to small disturbances and narrow layout spaces. To carry out MS monitoring and early warning in the heading face, signal recognition must be adequately performed first, and monitoring objects and indicators must be obtained. Through field tests of MS systems at the 117 track gateway of Tengdong coal mine, interference signals of equipment operation and effective signals of coal vibration are accurately collected. After analysis, the waveform characteristics, spectrum, and propagation distance of the interference signals and coal vibration signal are different. Some effective signals with small energy (one-channel triggering) cannot be used as early warning indicators because they are concealed by interference signals. Through trial operation, it is found that large energy (three-channel and four-channel triggering) coal vibration events successfully predicted a rock burst. The MS system of 117 track gateway of Tengdong coal mine should be able to remove the interference signals in real time through the algorithm and take the number of large energy coal vibration signal rather than all coal vibration events as the predictor for rock burst risk monitoring.

scholarly journals Research on Coal Pillar Malposition Distance Based on Coupling Control of Three-Field in Shallow Buried Closely Spaced Multi-Seam Mining, China

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 462 ◽  
Author(s):  
Qingxiang Huang ◽  
Jian Cao
Keyword(s):  
Stress Field ◽  
Coal Mine ◽  
Physical Simulation ◽  
Coal Pillar ◽  
Ground Surface ◽  
Theoretical Models ◽  
Coal Pillars ◽  
Seam Mining ◽  
Ground Surface Subsidence

In order to explore the rational coal pillar malposition distance (CPMD) based on coupling control of stress field, displacement field and fracture field (three-field) in shallow buried closely spaced multi-seam (SBCSM-S) mining, and realize coupling control of underground concentrated stress and ground surface fractures, taking the No. 1–2 and No. 2–2 coal seams mining in the northward east area of Ningtiaota coal mine as background, through physical simulation and theoretical analysis, the three-field evolution in SBCSM-S mining was analysed, the effect of different CPMD on coal pillar concentrated stress, ground surface subsidence and fractures development was revealed, and the rational CPMD based on coupling control of three-field was put forward. The results show that the concentrated fractures and concentrated stress are due to the strata’s uneven subsidence by coal pillars. Rational arrangement of CPMD can avoid the superposition of vertical stress caused by upper and lower coal pillars and reduce the development of ground fractures and uneven subsidence. Two theoretical models were established: one was based on the control of a concentrated stress field, the other on the control of the displacement and fracture fields. These results will be applied in a follow-up arrangement at the Ningtiaota coal mine, and can provide a new way for safe and green mining in SBCSM-S.

scholarly journals Directional Hydraulic Fracturing (DHF) of the Roof, as an Element of Rock Burst Prevention in the Light of Underground Observations and Numerical Modelling

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 562
Author(s):  
Marek Jendryś ◽  
Andrzej Hadam ◽  
Mateusz Ćwiękała
Keyword(s):  
Rock Mass ◽  
Hydraulic Fracturing ◽  
Coal Mining ◽  
Rock Burst ◽  
Coal Mine ◽  
Seismic Activity ◽  
Black Coal ◽  
Directional Hydraulic Fracturing ◽  
Before And After ◽  
The Face

The following article analyzes the effectiveness of directional hydraulic fracturing (DHF) as a method of rock burst prevention, used in black coal mining with a longwall system. In order to define changes in seismic activity due to DHF at the “Rydułtowy” Black Coal Mine (Upper Silesia, Poland), observations were made regarding the seismic activity of the rock mass during coal mining with a longwall system using roof layers collapse. The seismic activity was recorded in the area of the longwall itself, where, on a part of the runway, the rock mass was expanded before the face of the wall by interrupting the continuity of the rock layers using DHF. The following article presents measurements in the form of the number and the shock energy in the area of the observed longwall, which took place before and after the use of DHF. The second part of the article unveils the results of numerical modeling using the discrete element method, allowing to track the formation of goafs for the variant that does not take DHF into consideration, as well as with modeled fractures tracing DHF carried out in accordance with the technology used at “Rydułtowy” coal mine.

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