Outburst Accidents Research Articles

Accidents analysis and prevention of coal and gas outburst: Understanding human errors in accidents

Coal is an important energy resource internationally. However, accidents have severely restricted the clean and safe production of coal resources. Among such accidents, coal and gas outburst accidents are a kind of coalmine disaster with high destructive power. Previous research on coal and gas outburst accidents mainly focused on gas factors but ignored the role of human factors. This paper analyses the coal and gas outburst accidents in China from 2008 to 2018 and studies its macroscopic laws. To better understand the causes of coal and gas outbursts, this paper uses the 24modelel to analyse coal and gas accidents and suggest measures for accident prevention from the two aspects ‘gas’ (risk control) and ‘humans’ (behavioural safety). Macroscopic law research found the following: (1) March, May, July, and August are the predominant months for accidents. (2) The second to fourth hours of the working hours and the first hour before the end of work are the peak periods for accidents. (3) Guizhou, Hunan, Henan, Sichuan, Yunnan, and Chongqing are the provinces with the most coal and gas outburst accidents. (4) An overall 75.82 % of accidents occurred in the driving face, and 81.08 % of accidents occurred in coal and gas outburst mines. (5) Blasting, drilling, driving, and coal falling are the main inducing factors. Case analysis of accidents found the following: (1) Human error is the leading cause of accidents. Among the errors, the lack of strict enforcement of outburst prevention measures, illegal command, and the illegal operation of miners are the main unsafe acts. (2) Safety knowledge and awareness of miners is not generally high, and serious habitual violations and unsafe psychologies exist. (3) The gas comprehensive prevention system and supervision system in the coal mine safety management system (SMS) can be easily operated improperly, and the safety training system and emergency management system can be absent. (4) Coalmine enterprises seriously lack safety culture.

Research on Application of Hydraulic Fracturing Enhanced Technology in Coal Mine

Coal and gas outburst accident is one of the critical disasters restricting the safety production of coal enterprises in China. To solve the problems of low permeability and difficulty in gas extraction, a hydraulic fracturing test was carried out according to the occurrence characteristics of coal and rock gas in Pingdingshan Coal Mine No. 12; and the change law of the gas concentration and flow rate after hydraulic fracturing were obtained through long-term monitoring. Based on the test results, the effect of hydraulic fracturing on gas permeability enhancement of coal and rock was analyzed. The results have shown that the gas content decreases obviously and yet the water content increases since the hydraulic fracturing test completed, which makes the effect of gas displacement remarkably. It not only provides a reference for implementing hydraulic permeability enhancement and enhanced extraction in deep high outburst mines but also provides safe and efficient production in mining.

Experimental investigations of stress‐gas pressure evolution rules of coal and gas outburst: A case study in Dingji coal mine, China

AbstractCoal and gas outburst is a potentially fatal risk during the mining of gassy coal seams, which seriously threatens the safe mining of collieries. To understand the outburst mechanism and evolution rules, a new apparatus (LSTT) was developed to conduct simulated experiment. In the context of an outburst accident in Dingji coal mine, the authors launched an authentic outburst experiment to replay the outburst accident. Experimental apparatus, similar criterion, coal‐like materials and gas sources, and experimental design were discussed systematically in this paper. Experimentally, the study analyzed the geo‐stress has significant influence on the outburst evolution. At the driving face, the stress concentration possibly caused gas outburst, under the influence of mining‐induced stress. After the outburst occurred, the stress balance of the coal changed, resulting in the instability of the coal. Furthermore, the elastic energy, gas enthalpy, and gravitational potential energy were released rapidly. The experimental result stated that outburst coal has the sorting characteristics, in line with the field outburst law. The intensity prediction model has been built based on the energy model. Moreover, the factors that impact outburst intensity were analyzed. In the process of coal and gas outburst, the gas enthalpy of gas and the elastic potential of coal are the main energy sources. This study provides guidance for the development of the outburst mechanism and outburst mine management.

Rationality evaluation of production deployment of outburst-prone coal mines: A case study of nantong coal mine in Chongqing, China

The safe and efficient operation of coal mines is inseparable from rational production deployment. As for outburst-prone coal mines, the production deployment is more complicated due to the introduction of gas disaster control processes, which can easily cause continuity tension and even coal and gas outburst accidents. Therefore, it is necessary to establish an evaluation system for the rationality of production deployment of outburst-prone coal mines. In this paper, based on the production experience of coal mines in Chongqing, China and the summaries of experts, a production deployment evaluation system with eleven indices for outburst-prone coal mines is established. In addition, a Bayesian network is used to establish a corresponding evaluation model. The result shows that the evaluation index system for the production deployment rationality of outburst-prone coal mines, which is composed of the excavation advance indices and the validity indices of regional measure engineering, can systematically diagnose the rationality of each link of the production deployment for outburst-prone coal mines. The results of the case study show that the established Bayesian network model can be used to evaluate the deployment rationality of outburst-prone coal mines. The sensitivity analysis shows that the development coal reserve is the most sensitive to the reasonable deployment of outburst-prone coal mines. The accident prediction and cause diagnosis through the posterior probability reasoning indicate that in the absence of other evidence, the most likely reason for the unreasonable mine deployment is the insufficient development coal reserve. The observations and findings in this research have considerable practical significance for the smooth production of outburst-prone coal mines with similar geological conditions.

Geological Control of Fold Structure on Gas Occurrence and Its Implication for Coalbed Gas Outburst: Case Study in the Qinan Coal Mine, Huaibei Coalfield, China

A systematic analysis on gas occurrence in geological structure zone is crucial to coalbed gas exploitation, gas disaster prevention and outburst risk prediction. To study the geological control of fold structure on gas occurrence and its contribution on coalbed gas outburst, a typical case taken from Qinan coal mine was investigated by laboratory tests, theoretical analysis and on-site exploration. Thereby, a comprehensive understanding was made from the influence of fold structure on tectonic stress, coal structure and gas occurrence based on integrated factors outburst hypothesis. The results indicate that burial depth from 470 to 675 m has a slight influence on the fundamental properties of 72 coal seam, whereas the existence of Wanglou anticline is more relevant to affect vitrinite reflectance, gas adsorption and emission capacity with a positive correlation. By comparing the field data of gas content, pressure and emission quantity, it can be discovered that gas occurrence in 81 mining area appears to be primarily controlled by fold structure. Similar trends can be found in drilling cuttings index, indicating that geological stress increases with the distance approaching Wanglou anticline. In this case, a detailed description of tectonic stress in studying area is conceptually presented. Based on physical, pore structure and surface analyses, further knowledge on structural transformation by fold structure demonstrates adsorption and seepage pores are well developed with complex and disordered surface morphology, providing an evidence on the geological formation mechanism of tectonic coal in Wanglou anticline zone. Moreover, a conceptual description is proposed to explain the generation, migration and preservation mechanism of gas occurrence in the fold zone, which is consistent with roof and floor lithological properties as well as gas content data. Additionally, the locations of six gas outburst accidents were investigated to verify the relationship with fold structure. Based on the above results, theoretical analysis for coal mine outburst is discussed, which highlights the effect of tectonic stress on gas occurrence and coal structure as well as their contributions to gas outburst.

Development of a stress-based approach for achieving the risk assessment of fault-related coal and gas outburst

In underground mining, gas accumulation or gas content anomaly caused by geological structures often results in catastrophic coal and gas outburst accidents, this kind of outburst has already been reported for decades and caused thousands of casualties. However, so far there have been very few studies about how to conduct risk assessment for this kind of geological-structure-related outburst. In this study, our aim is to develop an approach to evaluate the risk of fault-related outburst. The approach developed in this study is a stress-based approach and it considers the associated factors including the gas pressure, the fault attitude and the tectonic stresses. The fault-related outburst index proposed in this work not only can be used for evaluating the fault sealing capability but also can be used for quantitatively assessing the risk degree of fault-related outburst. It is a practical approach and can be recommended to apply in more underground engineering. [Received: February 11, 2017; Accepted: August 17, 2017]

The dynamic failure mechanism of coal and gas outbursts and response mechanism of support structure

In view of the common mine disasters such as coal and gas outburst caused by the destruction of gas and coal, the numerical model of RFPA-GAS software was used to establish a numerical model based on a gas outburst accident took place in return roadway of working face 15-17-16041 in Pingdingshan mine. The dynamic failure mechanism of coal and gas outburst under the conditions of different support strengths protection and unsupported conditions was analyzed. Four dynamic processes of coal and gas outburst were discussed, and the dynamic failure mechanism of coal and gas outburst was revealed. The results show that the outstanding effect of the roadway without support treatment is similar to that of the field, and the coal and gas outburst is obviously weakened for supported roadway. Which has effective control of the active support for the protrusion. When the support method is designed, the response mechanism of the coupled support structure should be considered. It provides some theoretical support for the gas outburst control.

Study of Energy Release in Failure of Coal and Rock Near Fault on ANSYS

The failure part of 10·20 large coal and rock outburst accidents is analyzed in Daping coal mine of Zhengzhou Coal Group of Henan province by ANSYS finite element software. The amount of energy released is calculated before and after the failure of the rock mass near the fault in the plane strain, and the energy released is 1.0757 × 109 J. Based on the law of conservation of energy, the theoretical ejection velocity of the rock mass in failure is calculated under the energy dissipation (30%) and no energy dissipation. The results show that the numerical calculation results are basically consistent with that of the on-site engineering accidents, indicating that ANSYS and the energy analysis approach are applied to the field of coal mining. Therefore, based on the method of energy analysis, the risk of impact failure of the remaining coal pillars near the fault is evaluated, which provides a scientific basis for coal pillar protection and mine safety.

Risk prediction and factors risk analysis based on IFOA-GRNN and apriori algorithms: Application of artificial intelligence in accident prevention

Risk prediction of disasters is one of the most effective ways to prevent accidents. To solve the problems in multi-factor complex disaster prediction, this paper proposes a new method for risk prediction and factorial risk analysis. Coal and gas outburst accidents were selected as research objects. First, a new coal and gas outburst prediction model was established that consists of 4 levels and 14 factors. Then, the Improved Fruit Fly Optimization Algorithm (IFOA) and the General Regression Neural Network (GRNN) algorithm were combined to establish the IFOA-GRNN prediction model. After that, the sensitivity analysis method was applied to the analysis of the sensitive factors of coal and gas outbursts. Finally, an apriori algorithm was used to mine the disaster information. The method proposed in this paper was applied to the Pingdingshan No. 8 Min. The application results show that the IFOA-GRNN algorithm proposed in this paper has an accuracy rate of 100% for the prediction of accident risk levels. Compared with the Back Propagation (BP), GRNN and FOA-GRNN algorithms, IFOA-GRNN has the characteristics of a smaller prediction error, higher stability and faster convergence. The sensitivity analysis method can judge the sensitive factors of coal and gas outbursts without knowing the mechanisms of the accident. The a priori algorithm can perform good data mining on the combination of high frequency factors leading to accidents and the relationships between the coal and gas outburst levels and factors. The data mining results are very helpful for the prevention and management of coal and gas outbursts.

Structural and evolutionary characteristics of pores-microfractures and their influence on coalbed methane exploitation in high-rank brittle tectonically deformed coals of the Yangquan mining area, northeastern Qinshui basin, China

The Yangquan mining area is an important anthracite production base in China, but various types of tectonically deformed coals (TDCs) are well developed in its mines and gas outburst accidents take place frequently. By using methods such as optical microscope observation, mercury intrusion porosimetry (MIP) and low pressure nitrogen/carbon dioxide gas adsorption (LP-N2/CO2GA), we tested the structural and evolutionary characteristics of pores-microfractures and their influence on coalbed methane exploitation in high-rank (Ro,max = 2.00–2.72%) primary structure coals and brittle TDCs (i.e., cataclastic-, mortor-, and granulitic coals) from the Yangquan mining area. The results show that the tectonic deformation can change the pore-microfracture structure of coals and, thus, their reservoir physical properties. In general, with the enhancement of tectonic deformation, the density of microfractures in coal, which become more and more mussy, gradually increases, the total pore volume (TPV) of coal (pores with a diameter of 5.37–27000 nm) and the pore volume of each pore size range increase, with the greatest increase occurring in pores of 100–1000 nm, and the connectivity between pores is gradually reduced as well. From primary structure coals to granulitic coals, the TPV by the Barret-Joyner-Halenda (BJH) model increases with a greater increase in mesopores, and the specific surface area (SSA) by the Brunauer-Emmett-Teller (BET) model shows a trend of “increase-decrease-increase”, while the average pore diameter changes follow the pattern of “decrease-increase-decrease” in 0.7–206 nm. However, tectonic deformation has little effect on micropores with a diameter of less than 1 nm in brittle TDCs. The difference in pore-microfracture structures of different brittle TDCs indicates that the cataclastic coals distribution area is favorable for coalbed methane (CBM) exploitation, while the granulitic coals distribution area is a gas outburst-prone area.

Tunnelling outburst potential affected by mechanical properties of coal seam

Coal and gas outburst is greatly affected by the stress distribution in front of the heading face when tunnelling in high gassy coal seam. In this paper, the FLAC3D software and Mohr-Coulomb failure criterion are used to study the stress differences in front of the heading face. A total of 31 homogeneous models are built to study the stress differences affected by the coal seam mechanical properties. And another 8 kinds of heterogeneous models are built to study the stress differences affected by the abruptly changes of coal seam mechanical properties.When tunnelling in homogeneous coal seam, the large elastic modulus of coal seam will increase the stress peak value in front of the heading face, but do not change the stress peak position. The small internal friction angle will push the stress peak far away from the heading face. Therefore, the range of stress-relief zone in front of the heading face could significantly increase. The small cohesion of the coal seam will also push the stress peak far away from the heading face, but will result in an increase in the stress peak value. The Poisson ratio and tensile strength of the coal seam have little influence on the value and position of stress peak. As the elastic modulus decreases, cohesion and internal friction angle can greatly increase the displacement of the coal in front of the heading face. Taking into account both the mechanical properties of coal seam and the corresponding stress peaks, gas outburst is not easy to occur in the homogeneous coal seam.When tunnelling in heterogeneous coal seam, the abrupt change of coal seam elastic modulus greatly affects the stress concentration peak. If the cohesion of the coal seams also changes greatly with the elastic modulus, the stress peak will be enhanced. The abrupt change of coal seam cohesion and Poisson ratio have a slight influence on the stress concentration, while the abrupt change of internal friction angle of coal seam have little effect on the stress concentration. An outburst accident is most likely triggered when the cohesion and elastic modulus of the coal seams change greatly at the same time.Outcomes of this study is very beneficial for the prediction and prevention of coal and gas outburst. Meanwhile, this study provides a reference for the setting of mechanical properties of the coal seam and rock layers in the numerical simulation of mining.

Mine safety assessment based on basic event importance: grey relational analysis and bow tie model.

Safety assessments are a crucial first step in preventing coal and gas outburst accidents. The main purpose of this study was to create a new accident prevention technique using a novel safety assessment method based on fault tree basic event importance, grey relational analysis and the bow tie model. The innovation of the proposed method lies in generating the composite importance of a basic event from the fundamental importance via grey relational analysis; bow tie analysis serves to reveal the most critical basic event. First, the minimal cut sets and minimal path sets of a coal and gas outburst accident are determined by fault tree analysis. The role of minimal cut and path sets is determined and the coal and gas outburst occurrence frequency is calculated accordingly. Second, the structure, probability, critical and Fussell–Vesely importance ranked basic events differently due to different aspects of the basic events as investigated. We establish a composite importance to represent single basic events and achieved new ranking results by grey relational analysis. Third, the critical basic event low permeability coefficient is analysed via bow tie model and safety measures are defined which prevent the dangerous consequences of a low permeability coefficient. An actual coal and gas outburst accident is used as a case study to test the feasibility and effectiveness of the proposed method.

The correlation between dynamic phenomena of boreholes for outburst prediction and outburst risks during coal roadways driving

Coal and gas outburst accidents occurring in underground coal mines generally cause great casualties and economic losses, especially in construction areas of coal seams where the outburst risks are not accurately evaluated. Therefore, accurately identifying the outburst risks of coal seams is necessary and critical to prevent and control outbursts. In order to improve the prediction accuracy for outbursts in working faces of coal roadways, a self-designed drilling device that can simulate the in-situ outburst prediction of coal roadways was used in this study. We used the coal samples with different coal ranks to adsorb CO2 and N2 with different pressures in the laboratory, so as to simulate the coal seams with different outburst risks. Finally, boreholes for predicting the outburst risk were drilled in the simulated coal seams to study the correlation between common dynamic phenomena (e.g. gas and coal being ejected from the borehole (GCEB) and drill pipe being stuck by coal mass in the borehole (DPSC)) and outburst risks. The results show that the greater the outburst risks of coal seams, the more frequent the occurrence of GCEB and DPSC is. The GCEB phenomenon for outburst prediction is attributed to small-sized coal and gas outbursts in boreholes, while the occurrence of DPSC phenomenon does not affirm that there definitely are outburst risks on working faces.The DPSC phenomenon indicating outburst risks is generally accompanied with GCEB, which form a linkage system and are triggered successively.

Outburst mechanism of tunnelling through coal seams and the safety strategy by using “strong-weak” coupling circle-layers

The gas outburst potential is typically high when roadways uncover the gassy coal seams associated with outburst hazards. This paper describes the complex stress and displacement evolution that occurs in roadway tunnelling through coal seams under different original stress conditions, which is helpful for better understanding how the stress leads to an outburst accident, and proposing some relevant control measures.The stress concentration is primarily resulted from the strength difference between coal and rock, and the abutment stress increases gradually as the forward residual rock thickness decreases when the roadway excavation enters a coal seam from rock stratum. When the abutment stress is sufficiently high, the forward residual rock will suddenly be broken after the next cycle, and the stress will decrease rapidly to release elastic energy and generate new fractures. Meanwhile, the coal and rock in front of the heading face will move rapidly towards the free space. Therefore, an outburst accident may occur immediately when the gas pressure in front of the heading face is high enough. Once the outburst accident is triggered, the gas expansion energy and elastic energy distant from the heading face will contribute to developing the accident. The stress perpendicular to the roadway is the primary factor causing such outbursts. The abutment stress concentration will be higher when the maximum original stress is perpendicular to the roadway, which will increase the outburst potential. Therefore, it is suggested that arranging roadways parallel to the maximum original stress, if possible, can also reduce the outburst threat.Outbursts are triggered by the elastic energy near the heading face and developed by the gas expansion energy and elastic energy distant from the heading face. In this study, the method of “strong-weak” coupling circle-layers was proposed to reduce the outburst hazard when roadways excavated through gassy coal seams. This method was proven to be valid by the comparative experiment. The weak circle can be realized by boreholes and hydraulic cutting. It could not only reduce the elastic energy near the heading face but also prevent the distant energy from contributing to the outburst accident. In addition, the strong circle can be made by injecting water slurry and applying anchors. It could help to reduce the strength difference between coal and rock, thereby decreasing the local stress concentration, resisting the residual outburst energy near the heading face, and preventing the outburst from being triggered. The “strong-weak” coupling structure was successfully applied in Bailongshan coal mine when uncovering the #7,8 coal seam. This structure can effectively promote gas drainage, reduce the coal and gas outburst risk. As a result, the mining efficiency improves a lot, and the uncovering time greatly decreases from the expected 2 years to 5 months.

A new combination model for delay outburst of coal and gas

Sudden ejection of coal and gas in a delay outburst accident usually causes even heavier losses than an instantaneous outburst accident. A new combination model composed of outburst-prone soft coal and barrier layer was proposed to better categorise instantaneous outburst and delay outburst. The model offered an explanation for the delay outburst phenomenon, which demonstrates that it is the barrier layer between the work space and the soft coal that defers the occurrence of an outburst accident. Based on this model, delay outburst accidents in China from 2006 to 2016 were investigated. There were 42 delay outburst accidents resulting in 251 deaths, and the frequency of delay outburst accidents during operation of drilling accounted for 38.1%. Furthermore, the delay outburst process was numerically simulated. The simulations show that creep strain increases with the increase of stress, and gas pressure drops with increasing permeability of the barrier layer. [Received: September 30, 2017; Accepted: June 18, 2018]

Coal and gas outburst hazards and factors of the No. B-1 Coalbed, Henan, China

Coal and gas outburst disaster of the No. B-1 Coalbed, Henan, China, have lasted for nearly 60 years, and the threat will become more and more serious as mining depths continuously increase. However, coal and gas outburst characteristics and factors of the coalbed have not been studied in detail. To effectively prevent and control coal and gas outburst, we analyzed the type, intensity, location and precursors of coal and gas outburst occurring in the No. B-1 Coalbed. Moreover, the effects of geological conditions (burial depth, faults, folds, coalbed thickness and dip) and mining disturbances on coal and gas outburst were studied. The results showed that these outburst accidents were mostly typical, small-sized and medium-sized outburst, which mainly occurred at the coal roadway working faces. There were many precursors such as blasting sound, changes in coal structure, and abnormal gas emission prior to the accidents. Within a burial depth of 500 m, the average outburst intensity had a stronger correlation with the burial depth, which was more obvious at a burial depth of 301∼400 m, and less obvious at a burial depth of 401~500 m. However, the distribution of these outbursts barely changed within the burial depth. Up to 99.15% of coal and gas outburst occurred at faults, folds, and areas with changes in coalbed thickness and dip. Up to 68.25% were induced by blasting and 18.04% occurred during shelving, coal-shoveling and no operation. The No. B-1 Coalbed was characterized by delayed outbursts. Moreover, specific suggestions were recommended for the prevention and control of coal and gas outburst. The study is useful to government regulators and staffs engaged in the prevention and control of coal and gas outburst.

Activation characteristics analysis on concealed fault in the excavating coal roadway based on microseismic monitoring technique

In order to effectively monitor the concealed fault activation process in excavation activities, based on the actual condition of a working face containing faults with high outburst danger in Xin Zhuangzi mine in Huainan, China, we carried out all-side tracking and monitoring on the fault activation process and development trend in excavation activities by establishing a microseismic monitoring system. The results show that excavation activities have a rather great influence on the fault activation. With the working face approaching the fault, the fault activation builds up and the outburst danger increases; when the excavation activities finishes, the fault activation tends to be stable. The number of microseismic events are corresponding to the intensity of fault activation, and the distribution rules of microseismic events can effectively determine the fault occurrence in the mine. Microseismic monitoring technique is accurate in terms of detecting geologic tectonic activities, such as fault activations lying ahead during excavation activities. By utilizing this technique, we can determine outburst danger in excavation activities in time and accordingly take effective countermeasures to prevent and reduce the occurrence of outburst accidents.

Comparative study of HFACS and the 24Model accident causation models

A comparative study is conducted to compare the theory and application effect of two accident causation models, the human factors analysis and classification system (HFACS) and the accident causation “2-4” model (24Model), as well as to provide a reference for safety researchers and accident investigators to select an appropriate accident analysis method. The two models are compared in terms of their theoretical foundations, cause classifications, accident analysis processes, application ranges, and accident prevention strategies. A coal and gas outburst accident is then analyzed using both models, and the application results are compared. This study shows that both the 24Model and HFACS have strong theoretical foundations, and they can each be applied in various domains. In addition, the cause classification in HFACS is more practical, and its accident analysis process is more convenient. On the other hand, the 24Model includes external factors, which makes the cause analysis more systematic and comprehensive. Moreover, the 24Model puts forward more corresponding measures to prevent accidents.

Identification of geological structure which induced heavy water and mud inrush in tunnel excavation: A case study on Lingjiao tunnel

Groundwater and mud inrush during tunneling may cause severe security risk, great economic loss and unrecoverable damage to environment. However, the prediction and prevention still remain as a challenging problem. According to geological survey, Lingjiao tunnel was judged to be safe from danger of large-scale water and mud inrush. Unfortunately, a large (the largest one in China) mud outburst accident happened with bursting mud of more than 40,000m3, leaving a huge collapse pit on the upper surface of the crossed mountain. Moreover, another mud inrush took place right in the paralleling tunnel nearby one year after the first accident, which triggered another follow-up collapse in the same site as the first time, though it has been reinforced with concrete cover. The two mud inrushes accidents were induced by and through the similar geological structure, which was not recognized. In this paper, the mud-inrush processes are expatiated. It is found that geological identification of water-bearing and mud-filling structures is crucial for subsequential effective geophysical or drilling probing, misunderstanding and unable to recognize these crucial geostructures accounts for a lot of hazards. The failure to predict the more than once mud inrushes in Lingjiao tunnel is due to misunderstanding of hazard-inducing geostructure. The water-bearing and mud-filling structure is fracture-induced karstified zone (Epi-Fracture-Karst-Zone, EFKZ) which is formed from the karstification enhanced by fracture zone rather than originally suspected main fault zone. The favorable conditions for EFKZ development and mud filling which include dissoluble rocks, hot, humid climate and dense vegetation, tensile fracture zone, thick soil and abundant rainfall and the mechanism of mud inrush have been identified: The adjacent water-bearing fillings with high pressure in EFKZ surrounding the working face flow into the tunnel when EFKZ is disturbed by blasting, which induced the heavy mud-inrush accident in Lingjiao tunnel.

Gas-solid coupling laws for deep high-gas coal seams

A better understanding of gas-solid coupling laws for deep, gassy coal seams is vital for preventing the compound dynamic disasters such as rock burst and gas outburst. In this paper, a gas-solid coupling theoretical model under the influence of ground stress, gas pressure, and mining depth is established and simulated by using COMSOL Multiphysics software. Research results indicate that under the influence of factors such as high ground stress and gas pressure, the mutual coupling interaction between coal and gas is much more significant, which leads to the emergence of new characteristics of gas compound dynamic disasters. Reducing the ground stress concentration in front of the working face can not only minimize the possibility of rock burst accidents, which are mainly caused by ground stress, but also can weaken the role of ground stress as a barrier to gas, thereby decreasing the number of outburst accidents whose dominant factor is gas. The results have a great theoretical and practical significance in terms of accident prevention, enhanced mine safety, disaster prevention system design, and improved accident emergency plans.