Advanced Materials Research Vol. 402

Abstract: The stability of mine ventilation system has a significant impact on coalmine safety production. It is not only an important index of ventilation system quality, but also an important safety index of coalmine. The author made an analysis of ventilation system stability on the basis of test on Yaoqiao coalmine ventilation system resistance and indicated that the ventilation system of this coalmine existed some problems, which had an important meaning for enhancing the management of mine ventilation system and directing the normal, safe production.

Abstract: The failure of coal rock under gas pressure and in-situ stress is an inevitable stage of coal and gas outburst. The propagation mechanism of coal rock fracture under gas pressure is studied in this paper using fracture mechanics. The expression of normal stress and shear stress is given first with the simplification that the fracture is elliptical. Then the relationship among critical gas pressure, fracture direction and side pressure coefficient is studied in two branches as tension-shear failure and compression-shear failure. For tension-shear fracture, the fracture will be easy to propagate while the fracture has the same direction as maximum principal stress. For compression-shear fracture, the propagation direction is determined by the difference of compression-shear parameter and friction coefficients.

Abstract: It is well known that mining method is the core of an underground mine. In order to select mining methods scientifically and reasonably, after summarizing the underground mining methods, an underground mining methods selecting system based on fuzzy theory is established, which includes primary selecting based on fuzzy clustering and final selecting based on multi-objective decision-making and fuzzy comprehensive evaluation. And the application shows that the mining method selected by the system is the same as the method used in practice, which proves that the selecting system is feasible and reliable.

Abstract: Morphology and micro-structure of the pyrite whiskers synthesized by hydrothermal process were systematically observed by using transmission electron microscope. The results indicated that whiskers revealed various morphologies, including smooth, rough and branched. Combined with the hydrothermal reaction conditions, the causes of whiskers morphology diversity is: straight smooth whiskers grow in the condition of stable concentration, temperature, and interface state; whiskers with rough surface and complex morphology grow in the condition of unstable concentration, temperature, and interface state; the same level branching structure rotation was the result of hydrothermal disturbance; nano-crystalline grains formed after the main growth of the whiskers.

Abstract: The paper introduces the application of surface pre-grouting in the construction of the main coalmine and the auxiliary coalmine of Xuandong No.2 coalmine.The engineering has achieved remarkable results for the grouting into more than 700 meters deep. To the characteristics of shaft deep and aquifer centralized, the practical for sealing and grouting scheme has been introduced in this paper. According to the high water pressure in the special aquifer, the special measure of increasing grouting pressure and increasing grouting quantity has been taken and which ensured the grouting effect. The paper also introduces the engineering practice of using new material, new technology in vertical shaft for reducing water yield into the shaft. So the water plugging up rate of the main and the auxiliary shaft is more than 99%. The engineering has achieved the target of high quality.

Abstract: The test on mine ventilation system resistance is an important task of coalmine safety production and ventilation safety management, and the size of the air resistance will affect ventilation directly. In view of the current situation of Baishan ventilation system, we selected 11 main test lines combined with practical application, to test on the ventilation system via adopting precision barometer of point test, by which we got a comprehensive result on the distribution condition of coalmine ventilation system. By analysizing results show as follows: the distribution of Baishan ventilation system resistance is basically reasonable, air quantity is able to meet actual production of the mine and the resistance centers in return airways. Finally, the author puts forward some rational suggestion for the stability of Baishan ventilation system.

Abstract: This paper has created a rapid optimum method to design the gas lift parameters. Optimal Containment Genetic Algorithm (OMSGA) is applied in this method to optimize the parameters such as mass flow rate(Q), volume of gas injection(Qin), injection pressure(Pin), tubing header pressure(Pt), tubing inside diameter(Dt). According to practical situation of gas lift production, the gas lift efficiency (η) is selected as the objective function, the suitable fitness function and value of operators of OMSGA are given, and reasonable convergence delay-independent conditions is set. Based on the intelligence and global quick search of GA and the convergence of OMSGA, the design parameters of gas lift can be globally optimized quickly and accurately. An example is taken to prove that the application of GA in the field of gas lift production is successful. This new optimization method based on GA can provide guide for field design.

Abstract: Failures caused by heavy duty conditions, as well as the changes of technological requirements, are basic reasons for the redesign of specific substructures of the bucket wheel excavators (BWE). The efficient redesign should be based on subtle external load identification and sufficient accuracy of stress – strain states determination. This paper gives solutions of reconstruction and comparative stress analyses for original and redesigned representative and vital BWE subsystems - slewing platform, undercarriage and two wheel bogie. The efficiency of these reconstructions is unquestionably confirmed by failureless service of mentioned subsystems.

Abstract: The main oil fields in China have gone gradually into the high or extra-high water cut production period, and conventional profile control technologies already cannot meet oilfields’ production requirements. The research and application of new fluid diverting technologies has got many new progresses, but their validity term is relatively short in the aspect of improving the high water cut oil reservoir. Based on the capillary bundle model, a comprehensive performance evaluation method of fluid diverting agents has been proposed, through systematical analysis of the fluid diverting agents evaluation methods at home and abroad and their existing problems, and all-sided understanding of the present reservoir situation. The experimental results showed that this method could effectively and comprehensively evaluate the fluid diverting agents’ diverting effect, shear resistance performance, temperature resistance performance and salt resistance performance, and could optimize injection process parameters. It has the important and practical significance to improve the duty validity of the fluid diverting agents.

Abstract: The exploitation of mining area is usually accompanied with surface subsistence, which may threaten the structure belonging to this area. So it is indispensable to evaluate the consequence and predict a relatively precise sedimentation value before the excavation. In this paper, theoretical calculation and numerical simulation are used to estimate the subsistence of Zhaofeng gob area, Jilin province in China. Comparing with the conclusions of two methods, the maximum sedimentation value and its position are given, which will contribute to the establishment of the restoration schemes in this area.