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Coal-gas outburst is a violent phenomenon of energy release and strong dynamics is generated in underground coal mining. Coal-gas outbursts are accompanied by strong coal pulverization, and the gas desorbed by pulverized coal will in turn promote the development and spread of outbursts. Quantitative study on the role desorption gas played can improve the disaster-causing mechanism of coal-gas outburst and guide the work of outburst prevention and disaster reduction. Based on established gas emission model, the gas desorption is combined with the outburst process and its dynamic characteristics in this paper. The energy contribution and outburst dynamics with desorption gas are quantitatively studied under various desorption conditions, verified by outburst experiments. The results indicate that the energy contribution of desorption gas is 15.49–58.59% for JG71 coal, 4.49–57.26% for JG82 coal. The coal pulverization in the JG82 coal seam has a great influence on the energy contribution of desorption gas. After correction of gas desorption, the energy contribution increases by ∼20%. The maximum energy release rate (MERR) of the outburst with 0.075–0.15 mm JG71 coal sample reaches is 2.87 times that of the 1–2.36 mm coal sample at 3 MPa, and even 5.72 times that of the JG82 coal sample. For the outburst experiments, the energy contribution of desorption gas is 31.97–40.06% with 1–2.36 mm coal, 50.29–52.76% with < 0.25 mm coal. This paper presents a novel quantitative study defining the role of gas desorption in outburst energy and dynamics, applicable to disaster risk assessment and an accurate method to derive the energy contribution of desorption gas in experiments is proposed. [ABSTRACT FROM AUTHOR]

Analyzing the causes of accidents, excavating accident paths, and applying accident prevention are important tasks in safety management. Focusing on coal and gas outburst accidents, this study examined the primary accident path and conducted applied research on the reasoning of the accident case. First, combined with the obtained accident causes, a coupling analysis of the causes of coal and gas outburst accidents was conducted. Second, using the method of data mining coupled with Apriori algorithm, the coupling relationship between each cause module of the coal and gas outburst accident was obtained, and consequently, a path map of the coal and gas outburst accident was drawn. Third, a Bayesian network model for the causes of coal and gas outburst accidents was established based on the accident path map and the probability of occurrence of each cause. Finally, considering the safety concept element (SC1) as an example, the Bayesian network model was used to conduct a sensitivity analysis of accident causes. Thereafter, considering the coal and gas outburst accident of the Sanjia Coal Mine in Guizhou Province as an example, probabilistic reasoning research on the cause of the accident was conducted. The application results showed that (1) under normal conditions, there are approximately 797,280 accident paths for coal and gas outbursts. Following data mining, 188 main accident paths were found. (2) Sensitivity analysis determined 19 factors that were sensitive to safety concept elements (SC1), of which the three most sensitive factors were (i) resource management system procedures (SM7), (ii) safety policy (SM1), and (iii) safety training system procedure (SM8). 13 paths exhibited a sensitivity ≥0.5%, of which 7 exhibited strong sensitivity. (3) The absolute accuracy rate of accident cause reasoning in the Sanjia Coal Mine in Guizhou Province was 71.43%, while the relative accuracy rate was close to 100%. Thus, it was concluded that: (1) the accident path mining method proposed in this paper is feasible for main accident path mining. (2) The Bayesian network model for the causes of coal and gas outburst accidents established in this study can be practically applied for the sensitivity analysis of accident causes and exhibits high reliability in the probabilistic reasoning of accident causes. The results of this study is expected to aid in the prevention of coal and gas outburst accidents, and provide reference and help for the path mining of other accident causes and the probabilistic reasoning of accident causes. [ABSTRACT FROM AUTHOR]

The coalbed methane energy resources waste, environmental pollution and miner's health remain challenging problems in worldwide mining operations accompanied by coal-gas outbursts; thus, the safe and efficient yield of these resources plays a vital role in the world's energy market. The tectonic coal development is a significant geological feature of coal and gas outburst sites, and the study of coal and gas outburst mechanism should be based on more precise geological occurrence characteristics. In this paper, the geological characteristics of coal and gas outburst sites were analyzed. The failure law of coal body under the stratified occurrence of tectonic coal and raw coal seam with different thickness was studied. The mechanical equilibrium equation of non-synchronous deformation of tectonic coal and raw coal was constructed, the initiation criterion of coal and gas outburst was established based on the support body model, and a case study was carried out. The results show that with the thickness increase of the tectonic coal seam, the peak displacement of the driving face increases. The outburst start-up and development of coal and gas outburst, coal and gas extrusion outburst and coal and gas collapse outburst were deeply analyzed, as well as the internal reasons of the occurrence of coal-gas outburst portent are explained, based on the support body model. The development process from the start to the end of coal and gas outburst is revealed, and a new perspective is proposed for the prevention and control of coal and gas outburst: improving the strength of support body is also of great significance for the prevention and control of coal and gas outburst. • Asynchronous deformation induced coal-gas outburst mechanism. • The initiation criterion of coal and gas outburst was established. • The start and development process of the three types outburst were revealed. • New theoretical method and direction into dynamic disaster monitoring. [ABSTRACT FROM AUTHOR]

Mining protective coal seams is an effective approach for coal and gas outburst control, but a large amount of gangue is usually produced when mining a thin protective seam and dealing with the gangue can be a challenging task. In the paper, a novel integrated mining system by extracting two panels simultaneously was demonstrated in the 12th coal mine of the Pingdingshan coalfield: one panel was mined in the thin protective coal seam, and the other one was mined in the protected coal seam. The thickness of the protective seam was only 0.8 m, but the mining height reached 1.8 m, indicating that there was about 1 m thick roof stone being mined. An underground coal preparation plant was built, and the mixture of coal and gangue from the protective panel was sorted underground. The sorted coal was delivered to the surface stockpile, while the waste rock was directly backfilled into the gob of the panel in the protected coal seam. Thus, waste rock did not need to be lifted up to the surface, which can reduce material handing cost and minimise mining footprint on the surface. In order to prevent the migration of pressure relief gas into the working areas of the protective coal seam, the main reasons causing gas exceedance in the upper corner of U-shaped ventilation system were investigated, and then the Y-shaped ventilation system and various gas extraction boreholes were implemented to effectively control the pressure relief gas. Numerical models were developed to assess the effect of applying gob backfilling during the extraction of two panels in parallel. The results show that the gob backfilling can reduce the surface subsidence and horizontal movement, which is very helpful for the protection of ground water and surface infrastructures. [ABSTRACT FROM AUTHOR]

For the characteristics of high frequency and strong suddenness of dynamic disasters in deep coal mines, the traditional detection and evaluation techniques applied to shallow coal mine failed to accurately judge the risk degree of disasters. Therefore, it is of great significance to use advanced detection technologies and appropriate evaluation methods to improve the accuracy and efficiency of risk assessment in the process of coal mining. The present paper applies the rapid detection and multi-source dynamic detection technologies used in the field of mining with the purpose of improving the reliability of detection technologies for typical dynamic disaster. In this study, the data fusion technology was used to analyze data obtained from laboratory experiments, engineering survey, detection and historical data, so as to form the final dynamic and static indicators. Then, the new combined evaluation models with time series of coal and gas outburst as well as rock burst were established respectively to carry out the comprehensive risk evaluation using the least-squares method and the time-varying weight method. After the comprehensive analysis on the results of the above two evaluation models, the risk areas of the typical dynamic disasters were judged and classified. Finally, the evaluation models were coded to build an early-warning software platform that could achieve automatic evaluation and the actual 3D visualization of coal mining areas. The early-warning software platform was applied to risk assessment of dynamic disasters in Gengcun Coal Mine in Yima City, Henan Province, China. The results of the 6-month experiment showed that the risk assessment accuracy and reliability of the proposed evaluation models was 100% and 90% respectively, which indicates that the newly developed approach is reliable and can be recommended for applying in more coal mines to improve the process safety risk control. [ABSTRACT FROM AUTHOR]

• 1 Stress distribution was recalculated by stress-softening and prominent dilatancy. • 2 Gas-bearing coal under impact loading was a compaction followed by ruin process. • 3 Measures principles were mainly aimed at fracture and stress-concentration areas. • 4 Preliminary goal-reaching parameter based on principles was proposed and applied. As the increasing demand for coal and the depletion of shallow coal resources, the tendency of coal mining in China is progressively shifting to deeper areas, which brings about a circumstance where the frequency and intensity of coal and gas outburst accidents have further deteriorated. Nowadays, there are many outburst prevention measures being applied on site, while this disaster still occurs from time to time. Therefore, to better improve the preventing outcome of them, this paper came forward with some principles, based on the mechanical theory of deep mining and damage evolution procedure concerning coal containing gas underneath the impact load. The primary conclusions were as follows: the stresses, strains, and associated widths in the three areas, namely fracture area, plastic area, and elastic area, in front of the working face were recalculated by considering stress-softening and dilatancy of coal mass. The damage evolution of gas-bearing coal mass under impact loading was displayed in the LS-DYNA numerical simulation as a process of compaction followed by destruction. The proposed principles could be split into two perspectives, one for the fracture area, specifically, to minimize the descending of the coal mass's strength in this area; another for the stress-concentration zone, namely, to abate the thrust due to extrusion and deformation, on the coal body which was located in the front area. According to those principles, a preliminary goal-reaching parameter was proposed and it was implemented for the evaluation of advanced drilling. The results will cooperate to rationalize the design and layout of local outburst prevention measures, thereby enhancing the efficiency of control and ameliorating the deteriorating scenario of outburst disasters. [ABSTRACT FROM AUTHOR]

Coal and gas outburst is a violent mechanical instability of gas-containing coal, and its mechanism is crucial for prevention of gas dynamic disasters. The macroscopic instability of gas-containing coal is the result of the expansion and connection of micro cracks driven by unloading induced tensile stress and gas pressure. This study is aimed at solving the problem of crack instability of gas-containing coal during mining unloading. To this end, first, the governing equations of unloading-induced tensile stress and gas pressure evolutions in cracks were built, and the dynamic evolutions and main controlling factors of tensile stress and gas pressure were revealed. Furthermore, the evaluation indexes of crack stability under tensile stress and shear stress were established, and the variation of crack stability during unloading was investigated. Finally, the phase diagram of crack failure mode was drawn, and the transformation of crack failure mode was analyzed. The results show that unloading-induced tensile stress is generated when θ > 54.73°, and it rises gradually with the increase of original stress, unloading rate, unloading time and crack size and dip angle. Overall, gas pressure in cracks increases first and then decreases during unloading. It increases gradually with the increase of initial gas pressure, gas desorption rate and original stress, while it decreases as the unloading rate gets higher (k from 10−4 to 10−2 s−1) and the dip angle gets larger (θ from 50 to 90°). With the increase of unloading ratio, the crack stability declines slowly first and then plunges rapidly until the crack finally becomes unstable. In addition, burial depth of coal seam, unloading rate, gas desorption rate and mechanical strength of coal have significant effects on this process. Different factors have important influences on the crack failure mode. With the increase of burial depth from 100 to 2000 m, the crack failure mode gradually transforms from tensile failure to shear failure, and the higher the unloading rate is, the more easily tensile failure occurs. With the increase of cohesion (0.1–2 MPa), the scope of the shear failure zone shrinks gradually, and the crack is less prone to shear failure. The desorption rate has a notable effect on the scope of the non-failure zone. Under a higher gas desorption rate, the scope of the non-failure zone becomes smaller, which is due to the greater gas pressure in crack for a given time. The research in this paper has certain reference value for further grasping of the instability failure of gas-containing coal and the mechanism of coal and gas outburst. [Display omitted] • Evolutions of mining-induced tensile stress perpendicular to crack surface and gas pressure in crack were modeled. • Stability of crack under both tensile and shear stresses were evaluated and failure criteria were put forward. • Phase diagram and its evolution with the influencing factors were drawn to present the transformation of crack failure mode. [ABSTRACT FROM AUTHOR]

[Display omitted] • A non-coagulant long-time sealing material with excellent performance was developed. • The modified component was successfully inserted into the material group. • The sealing performance of the material is much better than the traditional material. Gas is produced during coal formation and is a major threat to the safety of coal mining operations. Gas-related accidents, including gas explosions and coal and gas outbursts, are particularly dangerous. However, gas also has great potential as a clean energy source. Therefore, effective gas extraction is essential for preventing accidents and utilizing its potential. The sealing material used for gas extraction boreholes directly affects the quality of the seal and, consequently, the efficiency of gas extraction. To address the limitations of cement-based and polyurethane sealing materials, this paper presents a novel non-coagulant long-term sealing material. Firstly, the optimal material ratio was determined through experiments involving constant temperature and weightlessness. The optimum proportion of modifier to be added is obtained by constant temperature weight loss experiments. Secondly, microscopic analysis revealed that the modified component was effectively inserted into the group. To simulate the underground gas extraction conditions in coal mines, drainage and plugging experiments were designed. The results showed that the new material had a 100% plugging performance during the observation time, while the plugging performance of cement-based and polyurethane sealing materials significantly decreased under the same experimental conditions. Finally, the non-coagulant long-term sealing material was applied in the gas drainage experiment of tunnel 53,081 at Changping Coal Mine. Compared to the original cement-based sealing material, the gas extraction concentration of the borehole increased by 16.5%. These results suggest that the newly developed sealing material is suitable for gas extraction and has significant potential for practical application. [ABSTRACT FROM AUTHOR]

• Application problems of the Hodot's energy criterion were found. • The characterization methods of coal deformation energy and gas expansion energy were determined. • The influence mechanism of coal deformation energy on outburst was discussed. • A spatiotemporal evolution model of the release of outburst energy was proposed. Coal deformation energy and gas expansion energy are the main power sources for coal and gas outbursts (called outbursts for short). Although the combined effect hypothesis of the outbursts has been widely recognized, the contribution of the coal deformation energy to the outbursts is always despised compared with the gas expansion energy. In this paper, the famous energy criterion for outburst trigger proposed by Hodot was reviewed systematically. It was found that Hodot's energy criterion pays more attention to coal deformation energy and almost ignores gas expansion energy, different from the views in most literatures related to outburst energy. The characterization methods of coal deformation energy and gas expansion energy were summarized. Experimental results show that the deformation energy of tectonic coal with high outburst risk has a power function relationship with stress and the power exponent is between 1 and 2, indicating that the deformation properties of tectonic coal is between soil and elastomer. The releasing mode of the deformation energy of tectonic coal is different from that of intact coal, that is, the deformation energy of intact coal and tectonic coal mainly releases outward and dissipates inward respectively after they are damaged. The coal deformation energy was proved to have the same order of magnitude with the gas expansion energy, about 102 to 103 kJ/t. A new energy release model for whole process of outbursts was established to discuss the role of coal deformation energy in actual outbursts. It was finally determined that the pre-release of deformation energy of tectonic coal is the necessary condition for the accumulation of the free gas expansion energy and outburst trigger. [ABSTRACT FROM AUTHOR]

Composite coal seam is a kind of special coal seam that is formed after complex geological structure action, including a tectonic coal sublayer. Gas can't be drained easily from this coal seam, which cause coal and gas outburst accidents (CGOA) occur frequently. A new hydraulic flushing technology was proposed in this paper to improve gas drainage. Accordingly, a new set of mechanical equipment, technology process, roadway layout system and gas extraction monitoring system are provided by drawing lessons from the Guhanshan coal mine. The stress variation and damage failure were investigated by numerical simulation on the basis of flushed-out coal and borehole geometry. The gas drainage effect, coal seam permeability and outburst risk-sensitive indexes of the special coal seam were obtained by field measurements. According to the results, hydraulic flushing can enlarge the stress unloading and plastic damaged zone around boreholes dramatically, and the coal seam permeability can be increased largely. • A new technology was proposed to enhance gas drainage in the special low-permeability composite coal seam with a tectonic coal sublayer. • The stress damage and permeability increase mechanism of hydraulic flushing were revealed by theoretical analysis and numerical modeling. • Abundant field experiments were carried to investigate and verify the gas drainage effect in the coal seam after hydraulic flushing. [ABSTRACT FROM AUTHOR]

Coal seam gas drainage is not only the effective measure for gas outbursts control, but also has the great significance for the use of gas energy and reduction of greenhouse-gas emissions. Coal permeability is the key parameter of gas drainage, and the permeability model of mining-damaged coal has the important theoretical guidance value for gas drainage in low permeability coal seams. In order to better understand the permeability model of damaged coal, the key points during the establishment of permeability model, which are the selection of coal structure, selection of boundary conditions and influencing factors, were first analyzed. Then, the expression and application of permeability models of mining-damaged coal in recent 20 years were reviewed. According to the contribution of new fractures, the permeability models of mining-damaged coal were divided into the empirical permeability models (EPM), volumetric strain permeability models (VSPM), plastic strain permeability models (PSPM) and damage variable permeability models (DVPM). After that, the quantitative characterization of key parameters, scientific issues of permeability models of mining-damaged coal were reviewed and discussed. Finally, the prioritization of 18 indexes affecting the permeability were determined, and the potential research directions of permeability models of mining-damaged coal were pointed out. The results of this paper can provide the theoretical guidance for the improvement of permeability model of mining-damage coal in the future. • The expression and application of permeability models of mining-damaged coal in recent 20 years were reviewed. • The quantitative characterization of key parameters, scientific issues of permeability models of mining-damaged coal were reviewed and discussed. • The prioritization of 18 indexes of factors affecting the permeability were determined. [ABSTRACT FROM AUTHOR]

• The effect of SiO 2 nanofluid with different concentrations on water adsorption capacity of coal is obtained. • The wettability-enhancing effect of SiO 2 nanofluid with different concentrations is investigated by contact angle tests. • The effect of nanofluid concentration on the wettability enhancement of coal is revealed. Water-based SiO 2 nanofluid, a wetting agent, has been proved to be feasible in improving the control effect of coal seam water injection against coal and gas outburst. However, the effect of nanofluid concentration on the control effect is not clear. Therefore, it is necessary to investigate the wettability-enhancing effect of nanofluid with different concentrations. In this paper, firstly, the effect of SiO 2 nanofluid with different concentrations on water adsorption capacity of coal was obtained. Then, the wettability-enhancing effect of SiO 2 nanofluid with different concentrations was investigated by contact angle tests. Finally, the effect of nanofluid concentration on the wettability enhancement of coal was revealed. The results showed that increasing the nanofluid concentration can enhance the water adsorption capacity and wettability of coal. In addition, the wettability-enhancing effect of nanofluid gradually got worse with time, while the stability of wettability-enhancing effect gradually got better. Furthermore, the 0.5 wt% nanofluid had the best sustainability and stability of the wettability-enhancing effect, while 1.0 wt% had the worst sustainability and stability. The research achievements could provide important basis for the selection of nanofluid concentrations in coal seam water injection. [ABSTRACT FROM AUTHOR]

Accurate determination of coalbed methane (CBM) content can not only prevent and control coal and gas outburst disasters in mines, but also facilitate the prediction of coal seam methane resource reserves, which is significant for injecting carbon dioxide to enhance CBM recovery. The freezing core sampling technique proposed in recent years for accurate determination of the CBM content has faced temperature-pressure coupling effects on gas desorption in coalin a low-variable temperature environment. In this paper, we utilized a self-developed high-low temperature alternating adsorption-desorption experimental device to study the gas desorption process in coal under temperature-pressure coupling conditions in a low-variable temperature environment. The experimental results show that the main promotion and inhibition effects of temperature on the gas adsorption and desorption in coal in a low-temperature environment were consistent with those in an ambient temperature environment, i.e., the decrease of temperature promoted coal gas adsorption, while the increase of the temperature promoted coal gas desorption. It is found that throughout the temperature change process (TCP), there existed a 'pseudo-desorption' phenomenon, and the cumulative desorption amount showed a consecutive rising-declining-rising trend and finally stabilized. The whole process can be regarded as consisting of a main desorption process and a retrograde desorption process. In the main desorption process with the same TCP, the cumulative desorption amount and initial desorption rate increased with the increase of initial equilibrium pressure. In the retrograde desorption process, there existed a peak retrograde desorption rate, and the staged retrograde desorption amount conformed to the linear decrease law. A comprehensive analysis of the temperature-pressure coupling effect on gas desorption throughout the TCP was conducted. Thus, we proposed some considerations and precautions for the configuration and supply monitoring of the cold source in the process of the measurement of CBM content using the freeze-coring method. • Temperature-pressure coupling effect is studied at low/ambient variable temperatures. • Gas desorption amount shows a rising-declining-rising trend. • Pseudo-desorption occurs in the temperature change process due to the coupling. • Linear-decreasing stepwise retrograde desorption process shows a peak desorption rate. [ABSTRACT FROM AUTHOR]

Coal seam water injection is proved an effective method for preventing coal and gas outburst. However, the poor wettability of coal seam has resulted in poor effect of coal seam water injection in preventing coal and gas outburst. In addition, the coal seam is in a state of injected-uninjected cycle due to multiple water injection. Therefore, it is important to study the wettability of coal seam with adding wetting agent under multiple water injection. In this paper, the effect of cyclic water injection on the wettability of coal with different SiO 2 nanofluid treatment times was investigated through contact angle tests. The results showed that increasing the treatment time of SiO 2 nanofluid would enhance the wettability of coal. In addition, the wettability of nanofluid-treated coal samples gradually got worse with the number of cycles increasing. In general, the effect of SiO 2 nanofluid on enhancing the wettability was approximately 2 to 4.5 times better than that of water. However, the difference of wetting enhancement between water and SiO 2 nanofluid became less obvious as the number of cycles increased. Even though, the nanofluid-treated coal samples showed the better wettability than water-treated coal samples after 13th cycle. Furthermore, the potential application of SiO 2 nanofluid in coal seam water injection was proposed, which had important significance for improving the effectiveness of coal seam water injection. [ABSTRACT FROM AUTHOR]

Coal seam water injection is one of the important technical means to prevent mine disasters. It can effectively change the mechanical properties of coal, prevent dust, coal and gas outburst, and reduce gas concentration. In order to expand the range of coal seam water injection, make coal seam water injection more effective in wetting coal mass, and determine the effective type of ionic surfactant required for coal seam water injection, triaxial seepage experiments and spontaneous imbibition experiments are conducted on the long flame coal samples from Houwenjialiang Coal Mine in Ordos City, Inner Mongolia Autonomous Region, China in this paper. Moreover, the effects and mechanisms of different ionic surfactants on the seepage and wetting stages of coal seam water injection are studied, which provides a theoretical basis for on-site coal seam water injection. After analysis and discussion, it is found that the influence of cationic surfactants on the seepage stage of coal seam water injection first decreases and then increases while the influence of anionic surfactants on the seepage stage of coal seam water injection shows a gradually increasing trend. Furthermore, both cationic and anionic surfactants show more significant wetting effects as the concentration of the surfactants increases. In addition, the adsorption of cations to coal molecules is stronger than that of anions, and the water solubility of cations is better than that of anions. [ABSTRACT FROM AUTHOR]

• Release pressure and diameter determined the distribution range of smash district. • Filling level of LCO 2 directly control the distribution range of crack district. • LCO 2 filling parameters can be used to guide LCO 2 -PB field applications. Liquid carbon dioxide phase-transition blasting (LCO 2 -PB) is a promising alternative method for enhanced coalbed methane (ECBM) extraction and prevention of coal and gas outbursts. During the process of the LCO 2 -PB fracturing the coal seam, the improper application of fracturing model will reduce the efficiency of gas drainage and cause gas disasters. To clearly understand the ECBM modes of LCO 2 -PB fracturing coal seam process, this paper employed experiments to investigate the effect of leakage characteristics of the LCO 2 -PB on fracture models of coal cubes, including release pressure (P r), filling level (V), release diameter (D r) and blasting hole diameter (D b). We propose the combination I and II of the LCO 2 -PB leakage parameters and applied two methods to the in-situ tests. The results revealed that the gas flow of the boreholes of the LCO 2 -PB with the combination I is 0.368 m3/min, which is 2.07 times that of the combination II (0.178) in the soft coal seam. Besides, the average methane flow of the boreholes with combination II is 0.796 m3/min, which is 1.78 times the combination I (0.448) in the hard coal seam. The adjustment of leakage parameters of the LCO 2 -PB technology can be helpful for ECBM and reduce the risk of coal and gas outbursts in the soft and hard coal bed. [ABSTRACT FROM AUTHOR]

• The whole safety production accidents of coal mines in Guizhou Province were analyzed. • The time–space dynamic evolution of coal and gas outburst accidents were proposed. • Coal and gas outburst accidents, influence factors and suggestions in Guizhou Province were studied. The safety situation of coal mines in Guizhou has been improving for many years, but coal and gas outburst accidents continue to occur. This paper analyzes the safety situation of coal mines in Guizhou by collecting data on accidents and disasters in the last decade: 2011–2020. The distribution characteristics, time–space dynamic evolution, and factors influencing coal and gas outburst disasters were studied. Countermeasures and safety management suggestions for disaster prevention and control were proposed. Our analysis shows that the primary disasters occurring in coal mines in Guizhou province are gas, roof, and water disasters, which are mainly distributed in the western and northern regions, as well as closely related to the complex geological conditions in the region. Coal and gas outburst is the most serious disaster threatening the safety of coal mines in Guizhou province in the last decade. The occurrence and development of gas outburst accidents presents three stages. The coal and gas outburst disasters mostly occurred in the driving face in the last decade, while their distribution showed obvious regional characteristics. In particular, Liupanshui, Bijie, and southwest Guizhou have a greater risk of coal and gas outbursts. Thus, it is necessary to focus on and formulate strict and effective outburst prevention measures when performing mining operations. Finally, according to hazard analysis, objective factors and management factors underlying coal mine disasters in Guizhou, specific countermeasures, and safety management policy suggestions of government and enterprises are provided. This research has certain significance for the safety supervision by the government and the staff engaged in the prevention and control of coal and gas outbursts. [ABSTRACT FROM AUTHOR]

• A new gas pressure inversion model is established. • The application result of the new model proves the uneven distribution of gas pressure. • The gas pressure value shows an approximate normal distribution law in statistics. • The evolution law of outburst elimination in the coal seam presents the characteristics of non-uniformity. China is one of the countries most seriously affected by coal and gas outburst disasters. Gas pressure is an important parameter to evaluate the risk of coal and gas outburst. In order to solve the problem existing in the traditional gas pressure measurement method, a dynamic inversion model of gas pressure while drilling is established based on the gas emission rule of coal particle and the gas radial migration equation of borehole wall in this paper. Combined with the directional drilling system and the special gas emission measuring device, the dynamic inversion model is applied to measure the gas pressure in the coal seam. The results show that: (1) The theoretical value of gas pressure obtained from the new model has a small error range by comparing with the actual value of gas pressure, which indicates that the new model has good reliability and applicability; (2) The distribution range of gas pressure value is wide, which shows the non-uniformity of gas occurrence in coal seam. The heterogeneity of gas pressure value shows an approximate normal distribution law in statistics; (3) Influenced by the occurrence of original gas in coal seam, the evolution law of outburst elimination in each area of coal seam also presents the characteristics of non-uniformity. The research results have important practical significance to assist the early warning of coal and gas outburst and to achieve coal and gas co-mining with safety mining. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rock outbursts and gas are the most serious natural hazards in underground coal mine. • The outburst sensor detects methane concentration, pressure and acoustic effects. • The dynamic properties of the sensor tested on the measuring bench in laboratory. • Field tests of the outburst sensor were carried out in the experimental mine. • The microphone and the pressure signals appear before of methane concentration. Outbursts of methane and rocks are, similarly to rock bursts, the biggest hazards in deep mines and are equally difficult to predict. The violent process of the outburst itself, along with the scale and range of hazards following the rapid discharge of gas and rocks, require solutions which enable quick and unambiguous detection of the hazard. The paper presents the functions of an integrated outburst detector which was equipped with three measuring and detection elements: a pressure sensor, a microphone and a chamber for constant measurement of methane concentration. A measuring stand for testing the dynamic properties of the integrated methane discharge sensor is described. It has been shown that both the pressure transducer and the microphone react immediately after a change in thermodynamic conditions, and the time constant of the pellistor methane concentration sensor was estimated at a few seconds. Field tests of the integrated sensor were also carried out, the main purpose of which was to verify the dynamic parameters of the sensor in medium scale experimental conditions during methane and coal dust explosions in the testing gallery at an experimental mine. [ABSTRACT FROM AUTHOR]