Occurrence Of Outbursts Research Articles

Two-dimensional simulations of disks in close binaries

Context. Previous simulations of cataclysmic variables studied either the quiescence, or the outburst state in multiple dimensions or they simulated complete outburst cycles in one dimension using simplified models for the gravitational torques. Aims. We self-consistently simulate complete outburst cycles of normal and superoutbursts in cataclysmic variable systems in two dimensions. We study the effect of different α viscosity parameters, mass transfer rates, and binary mass ratios on the disk luminosities, outburst occurrence rates, and superhumps. Methods. We simulate non-isothermal, viscous accretion disks in cataclysmic variable systems using a modified version of the FARGO code with an updated equation of state and a cooling function designed to reproduce s-curve behavior. Results. Our simulations can model complete outburst cycles using the thermal tidal instability model. We find higher superhump amplitudes and stronger gravitational torques than previous studies, resulting in better agreement with observations.

Infilled lakes (Pampas) of the Cordillera Blanca, Peru: Inventory, sediment storage, and paleo outbursts

Infilled lakes are a prevalent geomorphic feature in the intricate high mountain landscape of the Cordillera Blanca, Peru. Despite their apparent geomorphic, hydrological, and ecological importance, a systematic inventory of these areas has been lacking. This study presents an inventory of infilled lakes in the Cordillera Blanca. A total of 962 infilled lake polygons have been manually mapped, covering an area of nearly 90 km2 (the area of individual mapped polygons ranges from 0.001 km2 to 1.760 km2), more than double the area of existing lakes (40 km2) and the majority of flat areas (62% of areas with slope ≤5°). The study reveals that infilled bedrock-dammed lakes are the most common type (42%), while moraine-dammed lakes account for the majority of the infilled lake area (52%) and sediment volume (52% to 57%). Considering high uncertainty of infilled basins’ morphology, the estimated sediment volume of infilled lakes ranges between 0.9 km3 and 2.3 km3 (compared to 0.79 km3 to 1.15 km3 of water stored in existing lakes). The case study of Lake Aguascocha catchment reveals a mean sediment yield of 0.64 to 1.63∙106 m3∙km−2 during the past 10.7 ± 0.3 ka, that is, a mean annual sediment yield of 58.5 to 156.4 m3∙km−2∙yr−1. Furthermore, 65 locations where preserved geomorphic evidence indicates possible outburst floods in the past are identified. These areas are particularly important for understanding patterns of lake outburst occurrence on longer timescales than traditionally considered in lake outburst flood hazard studies. The dataset presented in this study is intended to serve as a basis for identifying sites suitable for further site-specific paleo-geographical, sedimentological, geochronological as well as broader mountain landscape evolution studies.

Elimination mechanism of coal and gas outburst based on geo-dynamic system with stress–damage–seepage interactions

Coal and gas outburst is a complex dynamic disaster during coal underground mining. Revealing the disaster mechanism is of great significance for accurate prediction and prevention of coal and gas outburst. The geo-dynamic system of coal and gas outburst is proposed. The framework of geo-dynamic system is composed of gassy coal mass, geological dynamic environment and mining disturbance. Equations of stress–damage–seepage interaction for gassy coal mass is constructed to resolve the outburst elimination process by gas extraction with boreholes through layer in floor roadway. The results show the occurrence of outburst is divided into the evolution process of gestation, formation, development and termination of geo-dynamic system. The scale range of outburst occurrence is determined, which provides a spatial basis for the prevention and control of outburst. The formation criterion and instability criterion of coal and gas outburst are established. The formation criterion F1 is defined as the scale of the geo-dynamic system, and the instability criterion F2 is defined as the scale of the outburst geo-body. According to the geo-dynamic system, the elimination mechanism of coal and gas outburst—‘unloading + depressurization’ is established, and the gas extraction by boreholes through layer in floor roadway for outburst elimination is given. For the research case, when the gas extraction is 120 days, the gas pressure of the coal seam is reduced to below 0.4 MPa, and the outburst danger is eliminated effectively.

Evolution from gas outburst to coal outburst: An analysis from the perspective of asynchronous transfer difference of gas mass and coal deformation

Considering that coal and gas outburst is a highly complex nonlinear process, the synchronous energy criterion based on the gas expansion energy and the coal deformation potential energy is often adopted to evaluate the hazard. However, the synchronous energy criterion without considering the transfer difference of gas mass and coal deformation has defects in describing the evolution characteristics of coal-rock gas dynamic disasters. Hence, it is necessary to investigate the asynchronous characteristics of the gas expansion energy and the coal deformation potential energy. In this study, the deformation characteristics of coal injected with He and CH4 were measured respectively with the aid of a self-developed device for observing the asynchronous characteristics of effective stress and adsorption-induced deformation. Besides, the differentiated propagation characteristics of gas pressure and adsorption-induced deformation were obtained, and the asynchronous propagation starting point and propagation rate difference between them were analyzed and determined. Furthermore, based on the calculation formula of gas expansion energy and coal deformation potential energy, the values and propagation differences of the two types of energy at different times were revealed. Finally, the typical outburst phenomena were explained using the energy asynchronous theory. The following research findings were yielded. The adsorption-induced expansion process lasts longer than the gas pressure reduction process, which is the reason for asynchronous propagation of gas expansion energy and coal deformation potential energy. The coal deformation potential energy can be further divided into mechanical compression strain energy and desorption shrinkage strain energy. In the initial stage of outburst, the main sources of energy are free gas expansion energy and mechanical compression strain energy. As time progresses, the effect of desorption gas expansion energy and desorption shrinkage strain energy gradually strengthens. From the perspective of energy asynchrony, outburst occurrence at a low gas concentration in deep regions and delayed outburst in cross-cut coal uncovering can be explained as the result of dynamic load instability in surrounding stopes brought about by lagging superimposed deformation disturbances after gas desorption, or the result of self-induced lagging shrinkage deformation formed under special boundary conditions. The findings of this study are helpful to guide the design and connection of the prevention and control methods of deep coal-rock gas dynamic disasters.

On Gas Desorption-Diffusion Regularity of Bituminous Coal with Different Particle Sizes and Its Influence on Outburst-Coal Breaking

Coal and gas outburst is an urgent and constantly perplexing problem with coal resource extraction, threatening coal mine safe and sustainable production severely. Its mechanism and the participation of gas in coal breaking are still unclear. To explore this problem, in this paper, gas desorption-diffusion regularity of bituminous coal with different particle sizes and its influence on outburst-coal breaking were investigated through mercury intrusion porosimetry (MIP) tests, isothermal adsorption tests, and desorption-diffusion tests for coal particles with different sizes. The results indicated that the cumulative diffusion amount (Qt) and rate (Qt/Q∞), the effective diffusion coefficient (D′), and the kinetic diffusion parameter (υ) decreased as particle size increased. That meant gas was easier to desorb and diffuse from the smaller coal blocks, consequently making coal break into more tiny particles and accelerating gas desorption. As a result, a positive feedback effect that coal breaks continuously and gas releases rapidly and abundantly was formed in a short time when outbursts started, which caused gas release in quantities and promoted the occurrence of outbursts. The findings of this study enhance our understanding of the mechanism of gas participating in coal fragmentation during outbursts, which are significantly conducive to the prevention and control of coal mine disasters and sustainable production of coal resources.

Occurrence and development criteria of coal and gas outbursts based on energy conversion

Coal and gas outbursts are sudden disasters in coal mines, they are major dynamic hazard during coal mining and have to be controlled for mining safety. To further understand the outburst process of coal and gas outbursts, an energy conversion model of coal and gas outbursts are established from the perspective of outburst energy conversion, and the criteria of outburst occurrence and development are determined. The energy conversion relationship and criteria of outburst occurrence and development are analyzed by physical simulation experiments. The results show that the critical threshold of the two groups of experiments is 2600 J. When the outburst potential energy exceeds the critical threshold, the outburst phenomenon occurs. Some of the outburst potential energy is converted into effective outburst potential energy to participate in the outburst work with the outburst process. The effective potential energy conversion rate of the two groups is 52 %-55 %. In the outburst of each experiment with outburst phenomenon, the development criterion values are 1.16–1.20 for experimental group 1, and the values are 3.06–3.75 for experimental group 2. The result indicates that the necessary condition for outburst development is that the outburst effective potential energy is sufficient to overcome the outburst energy consumption. This study will be of great scientific significance for exploring the outburst mechanism.

Numerical modelling of coal and gas outburst initiation using energy balance principles

Coal and gas outburst is a common mining hazard as it cannot be readily predicted due to complex processes controlling its occurrence. Understanding these complex processes such as gas flow, mechanical properties and behaviour, stress regimes, and geological structures, is required to enable mitigating the outbursts. The most current thresholds proposed for outburst prediction are empirically based thus ignoring the physical processes involved. While numerical modelling is a powerful tool to simulate the involved physical mechanism in coal and gas outbursts, the use of thresholds for outburst initiation in numerical models has not attracted enough attention to date. In this study, the law of conservation of energy is used to determine the moment of the outburst occurrence; the energy of which is obtained through numerical simulation. Different sources of energy including elastic energy and, free and desorbed gas energies linked to the complex physical processes are modelled and discussed. Different mechanical properties of coal are assigned to discuss the distinction of energy values between normal coal and coal affected by geological structures (known as deformed coal). A 30 m long roadway excavation that penetrates through both normal and deformed coals is simulated to assess the effect of induced stress on outburst initiation during roadway development. In addition, the effects of initial gas pressure and damaged area on the propensity of outburst events are analysed. The numerical model can successfully simulate gas outbursts caused by deformed coal, which poses a higher outburst risk. In addition, the modelling results demonstrate that by increasing the gas pressure in the coal seam, outburst happens in the earlier stages of the roadway development, and more intense outburst can be expected.

A novel physical model of coal and gas outbursts mechanism: Insights into the process and initiation criterion of outbursts

Coal and gas outburst (outburst) is one of the most serious disasters in the underground mining industry. Understanding the mechanism of outbursts is essential to predict and prevent the outbursts. In this work, a key structural body model of outbursts was firstly proposed by considering the geological structure and environmental conditions of outbursts. Based on the key structural body model, the process of outbursts was illustrated and compared with previous insights in detail. The mechanical and energy initiation criterions of outbursts were further established through the theoretical analysis. The simulation experiment of outbursts and case of outbursts were applied to study the new model and verify the initiation criterions of outbursts. The results show that the initiation pressure of outbursts in our tests was 0.4 MPa, which is not related to gas type. Compared with CO2 and N2, the occurrence of outburst at 0.4 MPa for He indicates the initiation of outbursts is mainly determined by the free gas. At the same gas pressure, the mass of the ejected coal and the relative intensity of outbursts for CO2 were the largest, while the lowest for He. This phenomenon is because the CO2 has the strongest adsorption ability, which could provide enough energy for transporting the coal powders after the initiation of outbursts. Both the experimental results and case analysis proved the rationality of the mechanical and energy initiation criterions of outbursts. Therefore, the key structural body model could reveal the initiation mechanism of outbursts and provide the guidance for prediction and prevention of outbursts.

A Testing Apparatus for Gas-Driven Coal and Gas Outbursts and its Application

In this study, a multi-physics coal and gas outburst experimental apparatus is developed to allow investigating the gas-driven mechanism behind the disaster caused by coal and gas outbursts in tectonic regions. The apparatus can simulate the coal and gas outbursts under different initial geo-stresses, gas pressures and temperatures. By integrating acoustic emission sensors in the holes on axial platens, acoustic signals from coal samples during the whole test can be monitored. A series of testability experiments were conducted on the developed apparatus to verify its performance. The damage characteristics and outburst occurrence of raw coal under different gas pressures were experimentally studied and that provided a more complete theoretical basis for coal and gas outburst. The degree of fragmentation of coal samples and the mass proportion distributions of the outburst pulverized coal after outbursts under different gas pressures were analyzed, as a reference for exploring the evolutionary characteristics of coal and gas outburst with gas-driven action.

Simulation Test System for Coal and Gas Outburst Triggered by Tunneling under Gas-Filling Condition and Its Application

Abstract The physical simulation test is an important means for studying the conditions of outburst occurrence and understanding the evolutionary pattern of outburst. However, the existing physical simulation test device cannot realize the real simulation of coal and gas outburst. In this study, a simulation test system for coal and gas outburst triggered by tunneling under a gas-filling condition was developed. This system consists of five key units: a sealed counterforce unit, a stress-loading unit, a gas-filling unit, a tunneling unit, and an information-acquisition unit. Through the cooperation of these units, the technical difficulties, such as high-pressure gas filling and rapid-pressure replenishment, high-pressure gas sealing, servo tunneling and slag discharge, information acquisition, and inclined model preparation, were overcome. The test system can be used to simulate the outburst triggered by tunnel (Φ150 mm) excavation in a coal-rock model (dimensions: 1,300 mm × 730 mm × 730 mm) under stress loading (maximum of 5 MPa) and gas-filling (maximum of 3 MPa). The proposed test system was employed to simulate the “6.12” coal and gas outburst incident in Huainan, China. The simulated outburst was similar to the original outburst in the following ways: phenomenon and duration of outburst (4.36 s); the shape and location (above the tunneling face) of the outburst holes; the mass (24.5 kg) and ejection distance (16 m) of the coal rock; and the sorting behavior of the ejected coal and rock. Additionally, the information of several physical quantities, including stress, gas pressure, and temperature, was also obtained. The development of this test system is important for an in-depth investigation of the information and patterns of outburst precursors, and for understanding the mechanism of outburst occurrence.

The instability criticality and safety factor of coal-gas outburst induced by shear failure based on limit analysis

Coal is a kind of natural pore-fracture dual medium, which determines the diffusion and seepage characteristics of gas inside under the stress conditions. In turn, the gas migration has an effect on the mechanical damage properties of coal and is closely related to the occurrence of coal-gas outburst. The occurrence of outburst is inevitably accompanied by the instantaneous displacement mutation of gas-bearing coal, which is difficult to explained by conventional plastic zone analysis. And the process from plastic failure to instability is still vague, which makes the instability critical of outburst difficult to determine. Therefore, aiming at the outburst in the working face, we put forward a progressive failure and outburst hypothesis model based on the limit analysis method of strength reduction theory. Then, the limit instability criterion of gas-bearing coal is modified, and the coal-gas outburst in the strength reduction process is simulated by using the cyclic calculation method of COMSOL software. It describes the characteristics of fluid–structure coupling and progressive failure instability of gas-bearing coal. Finally, we use the limit safety factor to describe the outburst criticality and the outburst risk. We find that the initial uncovering coal area, stress and gas pressure play an important role in controlling outburst, especially the coal stability is extremely sensitive to gas pressure changes under high stress. And based on these, the outburst prevention and control measures are put forward. The method has potential application value for the risk assessment and prevention of outburst on site.

Energy-limiting factor for coal and gas outburst occurrence in intact coal seam

This research reviewed the mechanics and gas desorption properties of intact coal, and tested the crushing work ratios of different intact coals, and then, studied the stress conditions for the failure or crushing of intact coal and the gas demand for the pulverization of intact coal particles. When a real-life outburst case is examined, the required minimum stress for intact coal outburst is estimated. The study concludes that the crushing work ratios of three intact coal samples vary from 294.3732 to 945.8048 J/m2. For the real-life case, more than 2300 MJ of transport work is needed, and 10062.09, 7046.57 and 5895.47 m3 of gas is required when the gas pressure is 1, 2 and 3 MPa, respectively. The crushing work exceeds the transport work and even reaches 13.96 times of the transport work. How to provide such an enormous crushing work is an energy-limiting factor for the outburst in intact coal. The strain energy is needed for the crushing work, and the required minimum stress is over 54.35 MPa, even reaching 300.44 MPa. These minimum stresses far exceed the in-situ vertical and horizontal stresses that can be provided at the 300–700 m mining depth range.

Eruptive Behavior of Magnetically Layered Protoplanetary Disks in Low-metallicity Environments

Abstract A protoplanetary disk (PPD) typically forms a dead zone near its midplane at a distance of a few astronomical units from the central protostar. Accretion through such a magnetically layered disk can be intrinsically unstable and has been associated with episodic outbursts in young stellar objects. We present the first investigation into the effects of a low-metallicity environment on the structure of the dead zone, as well as the resulting outbursting behavior of the PPD. We conducted global numerical hydrodynamic simulations of PPD formation and evolution in the thin-disk limit. The consequences of metallicity were considered via its effects on the gas and dust opacity of the disk, the thickness of the magnetically active surface layer, and the temperature of the prestellar cloud core. We show that the metal-poor disks accumulate much more mass in the innermost regions as compared to the solar-metallicity counterparts. The duration of the outbursting phase also varies with metallicity; the low-metallicity disks showed more powerful luminosity eruptions with a shorter burst phase, which was confined mostly to the early, embedded stages of the disk evolution. The lowest-metallicity disks with the higher cloud core temperature showed the most significant differences. The occurrence of outbursts was relatively rare in the disks around low-mass stars, and this was especially true at the lowest metallicities. We conclude that the metal content of the disk environment can have profound effects on both the disk structure and evolution in terms of episodic accretion.

Experimental Research on Coal and Gas Delay Outburst and AE Characteristics under Conditions of Geostress and Gas Pressure Disturbance

Adopting yellow mud as barrier layer materials, coal and gas delay outburst experiments under conditions of geostress and gas accumulation disturbance were carried out by using self‐developed simulation system, to find out roles of geostress and gas pressure played in the process of the delay outburst and ways to predict it, through analysis of variations of gas pressure, and AE characteristics during the process. The results show that after the geostress increased by 0.11 MPa from 1.80 MPa, an outburst occurs, while in gas accumulation situations, the gas pressure increase of 0.27 MPa from 0.67 MPa induces an outburst; hence, geostress is one of the dominant factors impacting an outburst occurrence. The lasting time of the outburst triggering under geostress disturbance is shorter than that under gas accumulation disturbance, while the duration of the outburst development under gas accumulation conditions is longer than that under geostress conditions. Coal seam breakage by geostress is the precondition for an outburst risk, and gas expansion energy is the dominant parameter influencing the duration of the outburst development. The AE signals show distinctive features in different stages of the outburst under geostress disturbance. At the preparation stage of the outburst, the AE signals increase sharply but have a low intensity and then drop to a lower balance level. At the triggering stage, the AE signals become active and increasing until up to the peak where the outburst occurs, and the intensity is highest.

Experimental Study of Coal–Gas Outburst: Insights from Coal–Rock Structure, Gas Pressure and Adsorptivity

Coal–gas outburst is a complex dynamic phenomenon in underground coal mines that has occurred frequently over the past 150 years. This phenomenon has seriously restricted the efficient development of coal resources and it poses a great threat to global energy security. Physical simulation experiments under different conditions that considered the coal–rock combination structure and gas adsorptivity were carried out by using a true triaxial coal–gas outburst experimental system, and the experiments controlled for the type of adsorbable gas, the presence (or absence) of a roof and the gas pressure. The influence of the coal–rock structure and gas adsorptivity on the disaster occurrence conditions and dynamic response characteristics was discussed, and the gas–solid-coupling disaster-inducing mechanisms of coal–gas outburst under unloading were obtained. The results show that outburst pulverized coal does not present an obvious sorting performance under the experimental conditions of this work. All the outburst holes are characterized by small openings and large cavities. Coal walls around the holes are damaged by spallation, and the strength of the outburst holes is low, but relatively stable. Stronger gas adsorptivity and greater gas pressure correspond to more intense outburst dynamic effects. Moreover, greater outburst intensity corresponds to more obvious coal spallation characteristics. Whether there is roof or not has no significant effect on the sweeping and handling of thrown pulverized coal. Compared with the condition without roof, the existence of a roof will promote an increase in the outburst intensity and more obvious spallation damage of the outburst coal. The coal–gas outburst process includes four stages: outburst occurrence, rapid development, deceleration development and outburst termination. The research results have certain guiding significance for studies on the mechanism of coal–gas outburst.

Analysis of the Occurrence Mechanism for Coal and Gas Outburst Based on Multiple Discriminant Indices

In order to reveal the occurrence mechanism of coal and gas outburst and optimize the measures to prevent the disaster, a coal mine in Henan Province was undertaken as the research background. Based on the geological and mining conditions of the coal mine, the gas geological analysis method is applied to determine the outburst occurrence and to classify the risk levels. A multifactor pattern recognition method is used to determine the risk probability of the dynamic disasters such as coal and gas outburst. The relationship between geological structure, rock mass stress, and mine dynamic hazards is determined using geo‐dynamic division method and FLAC3D numerical simulation. The occurrence and manifestation characteristics of the dynamic hazards are determined. COMSOL Multiphysics software is used to evaluate the original prevention measures and to optimize the measures. The research results determine the main influencing factors and regional distribution law of coal and gas outburst, which is of great significance to the risk prediction and prevention of dynamic disasters such as coal and gas outburst.

Practice of outburst prevention by pre-driving rock roadway unloading pressure of coal roadway strip in Fengcheng mining area

In view of the new characteristics of the coal and gas outburst disaster of single serious outburst dangerous coal seam in the deep mining area of Fengcheng mining area, the article puts forward regional outburst prevention measures of unloading pressure by pre driving rock roadway and constructing wear layer drilling to pump coal roadway strip gas, a complete set of technical system of regional outburst prevention in coal roadway strip by pre driving and unloading floor roadway in the Fengcheng mining area is obtained. The field practice shows that after entering the deep mining stage, under the conditions of high stress, high gas, high temperature and low permeability, the situation of outburst occurrence is more and more serious, and the mechanism is more complicated, although coal roadway of B4 coal seam has taken the measure of construction of drilling for pre pumping gas along B4 coal seam, but the damage of the high ground stress has not been completely eliminated, the proportion of in-situ stress dominated outburst is increased. Regional outburst prevention is carried through pre driving of floor roadway layout in the rang of 8∼12m which just below the coal roadway to carry on the pressure relief combined with crossing drilling drainage gas, it can greatly improve the permeability of coal seam and the effect of pressure relief, and ensure the safe and fast roadway driving.

Hazardous manifestation of gas-dynamic phenomena in the faces of coal mines

The statistics of coal and gas outbursts in the faces of the Russian coal mines is provided. The mining-geological and mining-engineering conditions for the occurrence of sudden outbursts during the coal mining are considered, and the distinctive features in the factors of their occurrence and behavior are discussed. The criteria for identifying the potentially hazardous zones with the help of geophysical measurements are given. It is shown that it is important to take into account the data on the actual occurrence of outburst hazard in overlying and underlying longwall faces and development workings, as well as the results of the current forecast when preparing the extraction area for mining, as it follows from the results of underground investigations. The features are noted and the concept of the mechanism causing sudden coal and gas outbursts of faces is formulated. According to this concept, the probability of a hazardous situation is minimal at the beginning of the face advancement before the primary roof collapse. After the primary caving, the outburst hazard increases with the face advancement from the place of caving due to increased stresses in the bearing pressure zone, strengthening of the restraint of the nearest roof support, and the formation of a low permeable bridge in the coal seam near the exposed surface of the coal massif, which increases the pressure and free gas volume behind this bridge. The maximum degree of outburst hazard in the cleaning face is reached at the time of secondary roof collapses.

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.

Experimental research into the relationship between initial gas release and coal-gas outbursts

Coal and gas outbursts are a rapid and powerful energy-releasing process. The damage to coal and the release of gas in the initial stage play key roles in the occurrence of outbursts. Existing studies have mainly focused on the gas desorption processes in coal under specific conditions such as particle size, specified mass and exposure time of pulverized coal. However, these studies have focused less on the gas release during the initial stage, and the quantitative relationship between the outburst risk level and the test results. Seven coal samples with different metamorphic degrees were chosen for use in outburst simulation experiments to investigate trends in gas release from pulverized coal in the presence of N2 and CO2. The results demonstrate a strong correlation between the gas release capacity during the first 10 s and natural desorption gas content of the onset of coal exposure during the first 120 min. In general, the higher the gas content, the larger the released gas volume, and thus the larger the limiting amount of desorptive gas. The gas release from an outburst coal sample is larger than that from a non-outburst coal sample within the first 10 s. There is a good linear relationship between the initial volume of released gas (in the first 10 s) and the initial expansion energy of released gas (IEERG), which can reflect the risk of coal outburst. Thus, according to the outburst critical value (42.98 mJ/g) of IEERG, the critical value of initial volume of released gas could be calculated to be 1.113 cm3/g. The results can provide a reference for further study of the effect of gas on outbursts and the investigation of coal and gas outbursts disasters.