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Development and selection of fuzzy variable weight vector and its application on fuzzy comprehensive decision-making (FCDM) are studied in detail in this paper. Firstly, a parameter contained variable weight vector is developed based on the definition of variable weight vector, and then further extended to obtain the fuzzy variable weight vector. Its capability on weights changing can be adjusted by changing the parameter. In order to make the fuzzy variable weight vector for different changes of states to be selected and applied easily, the concept of fuzzy dispersion degree, which can be used to measure the balance of decision factors' states, is proposed; And then the concept of fuzzy average relative adjustment degree, which can be used to measure the capability of fuzzy variable weight vector on weight changing, is also proposed. Based on the concepts of fuzzy dispersion degree and fuzzy average relative adjustment degree, relationship between the weight changing capability of the developed fuzzy variable weight vector and the parameters it contains is analyzed. With consideration of keeping balance among states, steps on selecting fuzzy variable weight vector with its corresponding capability on weight changing are presented. Based on the fuzzy combined weighting method, a FCDM model with fuzzy variable weight is developed. The fuzzy structured element is used to express fuzzy numbers and fuzzy operations in the model. An analytical algorithm of the FCDM model based on the fuzzy structured element is presented. The developed model was then applied on evaluating and predicting for coal and gas outburst of coal mining panels. The research finding provides an alternative way for fuzzy operations and determination of weights in other fuzzy analysis models. [ABSTRACT FROM AUTHOR]

Gas disaster is a major safety hazard in coal mine production, it studies the regularity of gas occurrence and analyzes the geological control factors of regional gas distribution, which plays a guiding role in the safe production of mines. Gas is a complex geological body that is stored in coal seams and its surrounding rocks. The occurrence and distribution of gas in coal reservoirs are controlled by geological conditions, and there is obvious gas geological regularity. Gas geology has developed into an independent discipline. In this paper, the following conclusions are obtained: (1) The geological control factors of gas storage, the gas occurrence regularity is obtained by analyzing the control methods of gas by various geological factors; (2) The gas geology is analyzed based on the research status of gas geological regularity at home and abroad for the development trend of gas learning. [ABSTRACT FROM AUTHOR]

Abstract: Gas hydrate-bearing porous media are natural or artificial porous deposits (soil sediments or coal) that contain gas hydrate in their pores. The mechanical properties of gas hydrate-bearing porous media are very necessary for researches on gas production and hydrate-based technology. This paper summarized the advances of the research on the mechanical properties of the gas hydrate deposit, from the experimental and numerical aspects. Also, this paper points out that research on the mechanical properties of synthesized gas hydrate porous media (coalbed seam) is necessary for coal and gas outburst prevention and mitigation. First, the theories about strength and deformation are introduced; second, a simple constitutive model for gas hydrate-bearing sediments is referred; third, the experimental and numerical researches are discussed; finally, this paper provides some suggestions for future study on mechanical properties of gas hydrate – bearing porous media. [Copyright &y& Elsevier]

In order to identify the causal factors of 88 coal and gas outburst accidents and their relationships, this paper proposed a cause classification framework based on the accident causation “2-4” model (24Model). The correlations between the high level and low level causes were analyzed by the Chi-square test for independence. Results showed that root causes, indirect causes and unsafe acts were prevalent in all cases. The main direct causes were violation operation and violation action; the main indirect causes were lack of safety knowledge and low safety awareness; the main radical cause was safety management procedures; the main root causes was safety depending on safety awareness. And there were ten groups of causes with significant correlation between the high level and low level causes. The work paths of different causes in coal and gas outburst accidents were identified by using the proposed cause classification framework. [ABSTRACT FROM AUTHOR]

This paper addresses airflow stabilization in airways induced by outburst gas flows after the disappearance of the outburst shockwave. Based on fluid dynamics theory, a mathematical model of an unsteady airflow in an airway was established. The formation conditions of additional force and gas ventilation pressure with their dynamic influences on airflow in an airway were investigated. The results of this study indicate that an additional force is created by the variation of the airflow rate after outbursts, and this force hinders changes to the airflow and maintains the airflow in its original state of motion. The gas ventilation pressure can be observed as an increase in the potential energy after coal and gas outbursts. For upward ventilation, the direction of gas ventilation pressure is positive and assists the ventilation. However, for downward ventilation, the direction of gas ventilation pressure is negative and hinders the ventilation. This hindrance may lead to an airflow reversal in the main airway. [ABSTRACT FROM AUTHOR]

Abstract: According to interrelated theory and influence factors for coal and gas outburst, the present paper sets up an evaluation index system and also applies fuzzy synthetic access method to show the result quantificational. With an actual simple, calculation process of index value and application of fuzzy synthetic appraisal method is particularly analyzed and the results show consistent quality to the fact situation preferably. Those researches can provide some theoretic references for prevention and management of coal and gas outburst. [Copyright &y& Elsevier]

Abstract: The paper proposed the principle and approach of comprehensive early warning of coal and gas outburst. Objectively existing outburst risk of working face, defects of outburst prevention measures and management are the main source of danger of coal and gas outburst. Based on the opinion, the integrated index system of outburst early warning is established. According to relevant regulations, standards, and actual mine condition, the rule base models of comprehensive early warning of outburst were established, and the warning degree system is divided into two major categories: the state and the trend. Implementation method of the warning system was studied, and the software, hardware architecture and computer systems were built. The onsite trials and applications indicate that the comprehensive early warning system of coal and gas outburst can realize the intelligent advance warning of hazards, improve the mine management level of outburst prevention, and secure the mine production safety. [Copyright &y& Elsevier]

Abstract: Fuzzy mathematics is introduced in fuzzy cluster, and the fuzzy relation between samples is quantified in fuzzy cluster, so fuzzy cluster is more objective and accurate. Fuzzy clustering is applied in coal and gas outburst prediction in the paper. The drilling cuttings desorption index K1, maximum drilling cuttings quantity S, electromagnetic radiation intensity maximum etc index of different place are considered in the classification, and different categories is classified according to different levels of intercept. According to analogy, coal seam can be judged if it is outburst coal seal. The study can provide reference for coal and gas outburst prediction. [Copyright &y& Elsevier]

Abstract: The influence factors for the coal and gas outburst can be divided into two categories. They are external factors and internal factors, respectively. The external factors include in-seam gas pressure, geological structure and so on, while the internal factors are mainly the coal characteristics themselves. Currently, researchers have already agreed that the in-seam gas pressure and the geological structure are two very important factors to induce the propensity of the coal and gas outburst. Generally, the higher in-seam gas pressure and the more complicated geological structures are, the greater risk of the coal and gas outburst is. However, it is still unknown that the relationships between coal characteristics and the potential risk outburst, especially the microstructure of coal. In this paper, the mercury intrusion method and the Langmuir isotherm adsorption method are used to study the coal fractal characteristics. By comparing the relationships between the fractal dimension and outburst feature parameters based on various coal samples, the experimental results show that the fractal dimension D1 has a negative correlation with the coal strength while the fractal dimension D2 has also a negative correlation with the gas releasing speed. Based on the results, a new index“δ”, which is the mathematical difference of the driving force and resistance of the outburst, is proposed to predict the coal and gas outburst propensity. It also could be served as a new tool in managing the coal mine safety. [Copyright &y& Elsevier]

Abstract: The acoustic emission technique is used to research the deformation and the failure process, investigate the deformation and injury regularity, discuss the physical process of acoustic emission of the coal and gas outburst and reveal the evolution process and disaster mechanism of the coal rock dynamic disaster. In this paper, the relationship between the damage and the acoustic emission is researched to get the coal cock damage expression which is expressed by the acoustic emission cumulative value. Meanwhile, the quasi-static is used to analyze the evolution process of the coal rock''s inner damage and describe the coal rock''s single axis damage character. On the base of the coal rock unit damage model, the constitutive relationship of acoustic emission coal rock is studied, which is the theory analysis for the coal and gas outburst. It is very significant for the research of the coal and gas outburst mechanism and prediction. [Copyright &y& Elsevier]

Abstract: Hazard forecast of coal and gas outburst was an important step of comprehensive outburst-prevention measures. Aiming at the manifestation of disaster threatens such as the gas outburst to mine safety, this paper explained the forecasting principles of electromagnetic radiation to coal and gas outburst, by the electromagnetic radiation theory of coal rock damage; it studied the characteristics and rules of electromagnetic radiation during the deformation and fracture process of loaded coal rocks, and confirmed forecast sensitive indexes of electromagnetic radiation as well as its critical values by signals of electromagnetic radiation. By applying EMR monitoring technology in the field, outburst prediction and forecast tests to the characteristics of electromagnetic radiation during the driving process was taken, and figured out the hazard prediction values by using forecast methods of static and dynamic trend. [Copyright &y& Elsevier]

Abstract: A new outburst prevention method based on injecting and freezing, considering of the important role of gas pressure and the mechanical characteristics of coal in the sprout and occurrence in the coal and gas outburst, was put forward in this paper. The curves of stress and strain with different freezing temperatures were drawn, and the effects of the water content, compaction force as well as freezing temperature on mechanical properties was discussed, through the experiment on the outburst-prone coal seam injected frozen water. It was found that the uniaxial compression strengths of coal obviously rise, its Young''s modulus show a rise tendency,, and the effective stresses of gas-filled coal obviously rise and its strengths is further improved after the gas pressure falls with the freezing temperature decreasing. [Copyright &y& Elsevier]

Hydraulic fracturing can increase coal seam fractures and reduce gas outburst risks, but the main challenge of its implementation in coal mines is to achieve uniform fracturing and gas reduction. In this paper, we studied the mechanism of water-driven gas release through two aspects: the H 2 O molecule is more easily adsorbed by coal than CH 4 , and water can decrease the gas adsorption capacity of coal. Comparative experiments of conventional hydraulic fracturing and blasting-fracturing technologies were carried out in #8 coal mine in Pingdingshan, China. We found that fractures and water contents around the blasting-based fracturing hole were more uniform than the conventional fracturing hole. After hydraulic fracturing, low water content coal usually has high gas content, which confirmed that gas in wet areas was displaced by water and driven to dry areas. To improve the uniformity of hydraulic fracturing, we proposed the uniform fracturing technology by combining blasting-fracturing holes and control holes. Blasting before hydraulic fracturing will increase the uniformity of fracturing and water distribution, and the control holes are used to monitor and release gas driven by water injection. The effective wetting range of conventional hydraulic fracturing was from −6 to 6 m along the strike direction and from −3 to 9 m along the dip direction with 94.71 m3 water injected. While the effective wetting range using uniform fracturing was increased to from −21 to 18 m along the strike direction and from −12 to 18 m along the dip direction with78.13 m3 water injected. Furthermore, number of boreholes to be drilled was largely reduced from 1300 to 132 when using the uniform fracturing technology to replace the dense hole technology in a 300 m long roadway. This research has suggested that uniform fracturing can effectively reduce gas outburst risk in gassy mines in China. • Analyzed water-driven gas release mechanism for coal and gas outburst control. • Developed uniform hydraulic fracturing by blasting and water-driven gas release. • Demonstrated uniform fracturing in field trails with less borehole required and less outburst risk. [ABSTRACT FROM AUTHOR]