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Fractal Forecast Theory and Its Application of Coal and Gas Outburst

Author: WangHanBin
Tutor: ChenHongZhang
School: Taiyuan University of Technology
Course: Mining engineering
Keywords: Coal and gas outburst System atical engineering theory and method Influence factors of coal and gas outburst Fractal theory Fractal box dimension Forecast technique and technology Fractal forecast theory
CLC: TD713
Type: PhD thesis
Year: 2009
Downloads: 715
Quote: 5
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Abstract


The coal and gas outburst is one kind of gas power imagination which is extremely complex in coal mines. It is one of serious disasters in coal mine. China is one of the most serious countries in the world where the coal and gas outburst often happens, furthermore, there are some common features related to many outburst wells during these outbursts in China, such as widely distribution, outnumbered outburst, high frequency, shallow penetration outburst depth, completely outburst type, huge outburst strength, amount outburst gas. However, the coal and gas outburst mechanism still hasn’t been fully understood right now. No country can absolutely prevent the occurrence of outburst. So seeking a better contactless prediction measure is quite necessary.In the thesis for the Doctorate, according to the achievement of coal and gas outburst forecast method and gas outburst mechanism research, through deeply field-work, widely collecting information and referencing to the systematic engineering theory and method, this article analyzes potential factors which would cause coal and gas outburst, four kinds of factors which influence coal and gas outburst, geologic agent, coal body structure, gas and underground pressure (geostatic pressure). These four factors can be further divided into eight sub-factors, which in total of 35 influencing factors can be summarized, therefore establish an indicator system of influential factors of coal and gas outburst. Due to different mines have different factors influencing coal and gas outburst, some factors may not apply, analyzing every factors to each mine will increase the degree of complexity, thus intensifying the computation work and waste effort. It is a scientific approach to seek for the primary factor influencing coal and gas outburst, which is easy to gain the data and reflect the overall outburst forecast. By using gas outburst data collected from Wangjia Zhai, Dashu village, Handan, Hongwei mine, Fengcheng, Sanhui Yi, Pingding Shan, Huainan, Nantong and Shangshu Ping with overall level analytic method and calculation, the result indicated that gas factor occupies proportion is the biggest in outburst influence, it is about 56.639%. In order to further inquire and confirm this conclusion’s reliability, this article carried on the principal components analytic method computation with the identical material, the calculation result is that the gas diffuses index, the gas discharge speed and the gas concentration contribute to 94.78% in the first principal component. Obviously, the gas concentration is the primary factor of causing coal and gas outburst which conforms to the coal and gas outburst related mechanism. The gas diffuses index, the gas discharge speed and the gas concentration is determination target, some needs to be measured and calculated in laboratory, one time calculation takes too long in time and takes massive excavation space, obviously, it is unable to achieve in real-time, continuously, quickly and the non-contact, and inconvenient for coal and gas outburst forecast. Therefore by analyzing the relationship between these three targets and the gas discharge quantity, using systematic method to determine that the coal and gas outburst forecast target is the gas discharge quantity target. The gas discharge quantity target concludes all factors’overall target, this data’s gain is fulfilled by the gas monitoring meter observation system, not only convenient, quick, continual, real-time, but also it has realize the non-contact gain data truly, non-contact predict and needn’t any extra investment.In order to establish coal and gas outburst fractal prediction theory, this article has pick up gas outburst data randomly, and calculated Poincare mapping, Hurst index and power spectrum index; determined gas discharge’s fractal characteristic and established rationale and practice basis for the fractal theory forecast coal and gas outburst. Based on this, it proposed the coal and gas outburst fractal theory forecast method.The coal and gas outburst fractal theory forecast method which is based on the gas discharge time series of coal and gas outburst accident in B mine coal lane tunneling working surface to analyze and calculate, and took the evidence by the C mine data, as well as entire process gas discharge time series data of outburst conclusion until restores the normal, drawing gas discharge line chart uses each time computation sample time series length td, using data quantity in this time d, data migration step pitch tl of each time forecast computation, and every time calculated once moves data integer l, using this chart calculates fractal box dimension of gas gushes out normally and the coal and gas outburst time, and then makes tables and figures and seeks for change rule from not outburst to outburst fractal box dimension.It also has proposed in this essay a concept that coal and gas outburst“the fractal box dimension marginal value”. The marginal value refers to a certain condition spot that a physical quality needs to satisfy when an object transforms from one physical state to another. As to mine well B, when there is no outburst, its fractal box dimension is D=1.4-1.753, otherwise, its fractal box dimension is DO=1.8106, outburst Marginal value is Dc=1.7533. Here is a proved example that as to the normal gas discharge quantity, it is larger in mine pit C rather than B, however, the calculated result in mine pit C in normal condition with no outburst, D=1.4-1.7617, and when outburst Do=1.8177, Marginal value Dc=1.7617,it is almost the same with what happens in mine B. At the same time, through calculating the branch dimension rate of mine B and C, in disorder, this article confirmed that the fractal dimension is the only symbol in order to judge whether there is outburst or not. As a corroboration of“the fractal box dimension marginal value”proposed in this research, C mine is far away from B, and they are in different coal fields.In this essay, it also has started an issue regarding the coal and gas outburst warning in early time. Reference to data of gas outburst happened three times both in mine pit B and C, it indicated that between the time that gas density fractal box dimension achieves the marginal value of the working surface and the time of gas outburst, there is an interval time, called the coal and gas outburst early warning time. Because of various working surfaces’ geological condition and the difference of the technological process and the technical management aspects, the coal and gas outburst early warning times are various. For example, the early warning time of the mine B is 19 hours, and it is respectively 38 and 15 hours in the outbursts of mine C two times. Thus the significance of proposing the early warning time concept is, firstly, the early warning time is used for people to work and prevent outburst, and to create condition to reduce or eliminate outburst accidents; secondly, the outburst time means to predict outburst accident. And as to a mine pit where accidents happened once, the time when outburst reaches the marginal value can be used as the early warning time. As to a mine pit where outburst accident has not happened, we can comparatively analyze in order to determine the marginal value and the early warning time both according to fractal box dimension of the similar geological-condition mine pit where outburst once happened and the fractal box dimension of this mine.It announced that the fractal box dimension assumed V curve in early warning time. Related research indicated that the fractal box dimension in the early warning time has experienced a process during which from the marginal value, the fractal box dimension reduced gradually, then suddenly advanced and reached to outburst when it is closed to outburst. And it is quite different that as people habitually believe the fractal box dimension progressively ascends f before outburst. By applying this rule, it reduces or even eliminates the gas outburst disaster in practical.Based on the fractal theory and predictive technique, it is in this paper further discussed how to perform the fractal prediction theory. In order to realize the coal and gas outburst real-time forecast, this paper also stated a web service based information system model for predictive coal and the gas outburst, which helped real-time data acquisition, box dimension computation and box dimension curve plan, and it provided a way for the real-time forecast

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CLC: > Industrial Technology > Mining Engineering > Mine safety and labor protection > Mine atmosphere > Coal (rock) and gas outburst prevention and treatment
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