1,180 research outputs found
A Gas Monitoring and Control System in a Coal and Gas Outburst Laboratory
Coal and gas outburst is a phenomenon characterized by the ejection of gas and coal from the solid face of a mine. Physical minioutburst experiments are a very important tool for analyzing outbursts of coal and gas. However, few reports have focused on the safety problem produced by gas concentration or the role of gas spread during the physical experiments. In this study, we designed a simple monitoring and control system for the safety of staff during the minioutburst experiments. The results showed that, in the simulation of four dangerous situations, the system based on a sensors feedback loop can monitor the development of gas content in the temporal and spatial domains for the enhancement of accurate warnings. The system also automatically chooses the appropriate ventilation measures to lower the gas content considering different degrees of danger
Research on Establishing the Indexes System of Controlling the Coal and Gas Outburst Accident
AbstractCoal and gas outburst accident aggravates with the increasing depth of coal mining, which amplifies geostress on coal seam, gas pressure and gas capacity. Studying on coal and gas outburst accident, this paper sets up the indexes system of controlling on the coal and gas outburst accident with consideration on technology factor, including basic technological work, reliability of relative system, prevention technology and concept, technological innovation, technic equipments, and management factor, including investment, management, institution configuration on governing gas, as two main elements
An investigation into gas emission and outburst control in thick seam coal mining
Nowadays, coal mining is extending to deeper and deeper levels, facing ever increasing coal seam gas contents, much higher gas emissions and outburst risks. Capturing coal seam gas before it migrates into atmosphere has been seen as an effective approach to simultaneously improve mining safety, reduce greenhouse gas emissions, and produce clean energy.
Thick seams account for a considerable share of global coal reserve. The application of longwall top coal caving (LTCC) method to extract thick seams generally yields a much higher productivity and is more efficient in comparison to a mechanised single-slice longwall panel. However, the greater productivity achieved by LTCC may further exacerbate the gas emission problems often faced in longwall mining. Geomechanical response of the strata and associated gas emission patterns around thick seam layouts are significantly different from coal mining under thinner multi-seam mining conditions, which is not well understood.
This thesis focuses on establishing an understanding of the stresses, pressure regimes, and gas emission patterns around advancing LTCC faces. During the PhD research, gas pressure and gas concentration were measured in a large number of boreholes in and around an advancing LTCC face at a coal mine. These data are complemented with ventilation and seismic monitoring programmes at the same LTCC district. An integrated analysis of the monitoring data has been carried out and conceptual models for gas emission and drainage for LTCC faces have been developed. These were later used as the basis for numerical modelling research.
A two-way sequential coupling of a geomechanical simulator with a reservoir simulator has been achieved, whereby mining induced stresses and pressures are linked by two coupling parameters: permeability and pore pressure. By applying this approach, gas emission during coal extraction at a LTCC panel in the study coal mine has been successfully modelled and history matched with field data. Recognising that coal and gas outbursts are the most serious and violent gas emissions in both thick and thin seam mining, the application of the coupled modelling approach has been further extended to model two common types of outbursts experienced in an outburst-prone coalfield.
Gas drainage before mining is a standard gas emission control technique, however, its application is largely limited to high permeability coal seams and roof/floor source seams undermined/overmined by single level longwall mining. The feasibility of utilising mining induced permeability enhancement zones to drain gas at thick and tight seams mined by multi-level LTCC method was studied via field trials and numerical models. Building upon the gas emission model developed earlier, a parametric study was carried out to assess different borehole layouts in order to optimise gas drainage designs.
It is believed that the findings of this research and gas drainage methods developed for thick seam mining will create a safer underground environment for miners at high productivity LTCC panels.Open Acces
Experimental and numerical modelling investigations into coal mine rockbursts and gas outbursts
Rockbursts and gas outbursts are a longstanding hazard in underground coal mining due to their sudden occurrences and high consequences. These hazards are becoming prominent due to the increase in mining depth, difficult mining conditions, and adverse gas pressure conditions. Several researchers have proposed different theories, mechanisms, and indices to determine the rockbursts and gas outbursts liability but most of them focus on only some aspects of the complex engineering system for the ease to represent them using partial differential equations. They have often ignored the dynamics of changing mining environment, coal seam heterogeneity and stochastic variations in the rock properties. Most of the indices proposed were empirical and their suitability to different mining conditions is largely debated.
To overcome the limitations of previous theories, mechanisms and indices, a probabilistic risk assessment framework was developed in this research to mathematically represent the complex engineering phenomena of rockbursts and gas outbursts for a heterogeneous coal seam. An innovative object-based non-conditional simulation approach was used to distribute lithological heterogeneity occurring in the coal seam to respect their geological origin. The dynamically changing mining conditions during a longwall top coal caving mining (LTCC) was extracted from a coupled numerical model to provide statistically sufficient data for probabilistic analysis. The complex interdependencies among several parameters, their stochastic variations and uncertainty were realistically implemented in the GoldSim software, and 100,000 equally likely scenarios were simulated using the Monte Carlo method to determine the probability of rockbursts and gas outbursts.
The results obtained from the probabilistic risk assessment analysis incorporate the variations occurring due to lithological heterogeneity and give a probability for the occurrence of rockbursts, coal and gas outbursts, and safe mining conditions. The framework realistically represents the complex mining environment, is resilient and results are reliable. The framework is generic and can be suitably modified to be used in different underground mining scenarios, overcoming the limitations of earlier empirical indices used.Open Acces
Response law and indicator selection of seismic wave velocity for coal seam outburst risk
The accurate detection of coal seam stress field effectively prevents coal and gas outbursts. This study uses wave velocity, wave velocity anomaly coefficient, and wave velocity gradient as indicators to identify stress anomalies in coal seam. The results show that these three indicators of wave velocity are all positively correlated with load, while changes in the wave velocity anomaly coefficient and wave velocity gradient are more gentle than those of wave velocity. The degree of damage of coal can be judged by the wave velocity anomaly coefficient, while the transition between high and low stress zones can be identified by the wave velocity gradient. In areas affected by geological structures such as valleys and mountain tops, the coal seam wave velocity and wave velocity anomaly coefficient may exhibit anomalies. The comparative analysis of wave velocity and its derived indicators can reveal the stress state and coal structure of coal seam with higher accuracy, identify the areas affected by geological structures such as valleys and mountain tops, and determine the boundary of the stress relief zone after hydraulic fracturing. Combined with the actual geological structure characteristics of coal seam, it can accurately identify the stress disturbance region of coal seam and achieve the purpose of predicting coal and gas outbursts.Document Type:Ā Original articleCited as: Qiu, L., Zhu, Y., Liu, Q., Guo, M., Song, D., Wang, A. Response law and indicator selection of seismic wave velocity for coal seam outburst risk. Advances in Geo-Energy Research, 2023, 9(3): 198-210. https://doi.org/10.46690/ager.2023.09.0
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Research progress on coal mine laser methane sensor
This paper discusses the research progress of low-power technology of laser methane sensors for coal mine. On the basis of environment of coal mines, such as ultra-long-distance transmission and high stability, a series of studies have been carried out. The preliminary results have been achieved in the research of low power consumption, temperature and pressure compensation and reliability design. The technology is applied to various products in coal mines, and achieves high stability and high reliability in products such as laser methane sensor, laser methane detection alarm device, wireless laser methane detection alarm device, and optic fiber multichannel laser methane sensor. Experimental testing and analysis of the characteristics of laser methane sensors, combined with the actual application
APPLICATION OF STATISTICAL PROCESS CONTROL THEORY IN COAL AND GAS OUTBURST PREVENTION
With Chinese coal exploitation extending to depth rapidly, a large number of coal and gas outburst accidents happened and resulted in thousands of casualties in the last decade. Coal and gas outburst prevention project has become the prerequisite of underground coal mining, but its process control ability is especially poor. By integrating statistical process control theory into the process of coal and gas outburst prevention, three urgent problems were solved. First at all, data structure of the process inspection parameters was designed asvectors, which only consisted of principle elements and formed data series as time went by. Secondly, based on sample data of the experimental area, statistical characteristic of inspection parameters was gained and their X-Rs control charts were drawn. Finally, performance of process running statuses that might be in control or beyond control were analyzed in detail. When the process was in control, curves should slightly fluctuate around their center lines and between upper control limits and lower control limits. Otherwise, the process was beyond control, in which X control charts were used to identify anomalies of data value fluctuation and Rs control charts were used to identify anomalies of data fluctuation amplitudes. By the experimental application in Hexi colliery of China, the interdisciplinary research was proved to be helpful to improve process control ability and then prevent coal and gas outburst accidents
The General Characteristics of Electromagnetic Radiation During Coal Fracture and Its Application in Outburst Prediction
Coal and methane outburst are catastrophic in coal mining, their prediction is difficult. In this paper, the electromagnetic radiation (EMR) generated during coal or rock deformation and fracturing is measured and analyzed. The results show that EMR truly exists during the fracture of coal or rock (with or without the presence of gas). It follows the Hurst statistical rule, and it basically exhibits gradually enhancing tendency during the process. The EMR strength and frequency are correlated to the coal or rock fracture process. Based on the experimental and theoretical studies, a new method for coal and methane outburst prediction is proposed -the EMR method. This new method significantly facilitates methane outburst prediction
Experimental investigations of stress-gas pressure evolution rules of coal and gas outburst: A case study in Dingji coal mine, China
Coal 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, coalālike materials and gas sources, and experimental design were discussed systematically in this paper. Experimentally, the study analyzed the geoāstress has significant influence on the outburst evolution. At the driving face, the stress concentration possibly caused gas outburst, under the influence of miningāinduced 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
Proceedings of the 2004 Coal Operators\u27 Conference
Proceedings of the 2004 Coal Operators\u27 Conference. All papers in these proceedings are peer reviewed in accordance with The AUSIMM publication standard
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