Application of the third theory of quantification in coal and gas outburst forecast

The essential principles of the third theory of quantification are discussed, the concept and calculated method of reaction degree are put forward which extend the applying range and scientificalness of the primary reaction. Taking the Zhongmacun Mine as example, on the base of analyzing the rules of gas geology synthetically and traversing the geological factors infecting coal and gas outburst, the paper adopts the method of combining carving up statistical units with the third theory of quantification, screens out 8 sensitive geological factors from 11 geological indexes and carries through the work of gas geology regionalism to the exploited area of Zhongmacun according to the researching result. The practice shows that it is feasible to apply the third theory of quantification to gas geology, which offers a new thought to screen the sensitive geological factors of gas outburst forecast.     

Sudden outburst of coal and gas — failure of natural coal as a solution of methane in a solid substance

Basic Conclusions  1. The methane dissolved in natural coal may participate directly in the dynamic failure of the coal during sudden outbursts. 2. The following are factors determining the participation of dissolved methane in the failure of coal during outbursts: a high natural methane content, the fracture microstructure of the coal, and its low crack resistance. 3. It can be stated that it is precisely the dissolved methane that predetermines the formation of "mad flour." The author expresses gratitude to S. V. Kuznetsov, V. A. Bobin, I. V. Zverev, V. A. Trofimov, and M. O. Dolgov for their discussion of the study. Institute of Problems of the Complex Exploitation of Mineral Resources, Russian Academy of Sciences, Moscow. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 6, pp. 18–28, November–December, 1997. The study was performed with financial support from the Russian Fund for Fundamental Research (Project No. 96-05-65884).     

Nappe structure＇s kinetic features and mechanisms of action to coal and gas outburst

逆冲推覆和重力滑覆的共性特征是存在一个以相对低的强度和高的剪切应变为特征的滑脱面或拆离层,分隔着其上下力学性质和应变特征不同的两盘。推覆构造对煤与瓦斯突出的作用机制主要表现为2个方面：①推覆构造形成过程中低角度滑动对煤体产生广泛的压剪作用,使得煤层作为相对软弱层面结构发生广泛的层域破坏和面域破坏,构造煤非常发育;②推覆构造的挤压应力环境以及地层增厚效应为瓦斯赋存提供了有利条件,低角度的主滑断裂面（大多为逆断层或逆掩断层）往往构成较好的瓦斯封闭系统,对瓦斯的赋存起一定的控制作用;推覆构造派生的具有压性特征的结构面形成了对煤层瓦斯系统的封闭作用。总体上推覆构造对煤与瓦斯突出的作用机制体现在其为煤与瓦斯突出创造了物质基础——高含量的瓦斯和低强度的煤体。     

The study of acoustic emission （AE） forecasting coal and rock disaster technique

Introduced the coal and rock AE propagation rule, wave guide fixing technics on AE sensors, and AE forecasting coal and rock disaster on the scene and so on. The coal and rock AE propagation rule that follows the exponent attenuation function on different AE frequencies, different quality factors and different propagation distances were analyzed and deduced by theory, numerical simulation, and by actual experiment. Consequently, it was deduced that the coal and rock AE propagation rule follows the exponent attenuation function. Based on the correlative theory of wave dynamics and AE sensor, the AE wave guide propagation mechanical model on the sensor fixing manner is found, and the relations of displacement and speed and acceleration between the AE signal source and the AE signal receiving terminal are presented. The effect of the AE sensor fixing manners on coal and rock surfaces, coal and rock bottoms and wave guides were studied by actual experiment. For the results, the effect of the AE sensor fixing manner on wave guides is better than on coal and rock surfaces, and was equivalent to the fixing manner on coal and rock bottoms. Based on the above study results, actual coal and rock dynamistic disasters were successfully forecasted. Supported by the Project of National Basic Research Program of China (973 Program) (2005CB221505); the Significant Project of National Natural Science Fund (50534080/E041503); the Project of Coal Mine Gas and Fire Hazard Prevention Major Lab in Henan Province (HKLGF200508)     

Welding technique and quality of large diameter X70 line pipe for gas transmission of China

1IntroductionWest-East Gas Transmission Pipeline Project was a great and key project of China in2001to2003.The total length of the pipeline is about4000km.The initial gas transmission is12×109m3/a and finaltransmission will be20×109m3/a.The design pressure is14MPa and operating pressure10MPa.About1·6×106t of line pipe were used for the project.It will transmit the natural gas from western of Chinawhere have rich energy to eastern where energyis very shortage,and so greatly promote ec…     

A probe into “mining technique in the condition of floor failure” for coal seam above longwall goafs

Targeting at the coal seam with useful value discarded above goafs, attempted to explore the feasibility of “mining technique in the condition of floor failure” from theoretical point of view, and predicted. It indicated that mining technique in the condition of floor failure used above Longwall Goafs in Baijiazhuang Mining is totally feasible. At law, the deformation of the floor in the mining technique by means of probability-integral method. And it is discovered that deformed basin can emerge in the footwall of No.6 coal seam and its maximum subsidence was possibly 1 633 mm or so and its maximum positive curvature is 61.74/10⁻³. At last, it therefore suggests appropriate ground pressure control measures as strengthening observation of ground pressure and adopting false slope for exploitation and strengthening support for reasonable push and slide based on the adverse ground pressure behaviors possibly occurring in the mining technique. This serves to gather data and lay sturdy foundation for further probe into the mining technique, and offers theoretical and technical grounds for concrete implementation of the mining technique. Supporteel by National Nature Science Foundation of China (50704024); Shanxi Youth Sci-Tech Research Foundation (2007021024); Taiyuan Innovation Program (special item for undergraduate innovation and starting business) (07010746)     

Study on the movement and fracture of ＂isolated island＂ working face overburden by numerical simulation

For circumstances of medium-embedding depth and medium-hard surroundings in Jining No.2 Colliery, Yanzhou Group, by using software RFPA2D to simulate the process of overburden fracture, studied the overburden separation which was caused by working face exploitation, its fracture characteristics and the isolated island coalface（IIC） formation systematically in comparison method. After the recovery of the IIC, the surrounding separation areas which lied above the working face and bilateral goaved respectively form a connected region, a region that is like a saddle with low middle （35 times） and high sides. The top boundary line of the separation area is an arc. Then the fracture rise rapidly to 28 times of working thickness; while it is smaller （only 8-17 times recovery height） when extracting bilaterally, though the fracture plane both are in shape of an unsymmetrical trapezium. As the recovery of IIC makes side recoveries change from insufficiency to sufficiency, the consequentially rapid change of characteristics of overburden separation and fracture would enhance the representation degree of mining pressure of IIC.     

The research progress and prospect for the technology of controlling surface subsidence by grouting separated layer in overburden at coal mines in China

The developed process and theoretical achievement for the technology of controlling surface subsidence by grouting separated layer in overburden is summarized in this paper. The research progress of the technology is discussed synthetically on the basis of practice and research results obtained at coal mine of China in recent years. According to the development tendency of mining under buildings, water bodies and railroads and the properties of the technology, the future research direction is proposed.