Advanced Materials Research Vols. 616-618

Abstract: In order to solve the problems appeared in mining process of upper seam in Xiaohezui coal mine, a technical scheme of ascending mining was put forward. UDEC, a discrete element numerical simulation soft was used to study the characteristics of zoning of overburden strata and the rule of vertical stress distribution of the upper coal, the results show that the upper coal is on the top of the equilibrium belt without step dislocation, the structure of roof stratum and floor stratum stay complete with slight separations, so ascending mining is feasible; the range of the upper coal influenced by the stoping of below working face is -85m~65m, the vertical stress reaches a maximum 15m ahead the below working face, and reaches a minimum behind it 25m. It is applied in the engineering practice, the roadway deformation discipline of the upper coal is similar to the distribution rule of vertical stress, provides a theoretical basis for guiding and improving the roadway support of ascending mining.

Abstract: With the development of economic and the shortage of energy, repeated mining is an important measure. Based on the production characteristic of small coal in Tangshan, the situation and existing problems of small coal mining was Summarized; with years of practice in mine ventilation technology and teaching experience, a part of the mine gas level identification results were analyzed and discussed; the result is that the repeated mining of Tangshan was a low gas mine, but the carbon dioxide emission was too high; The results show that the reasons of high carbon dioxide emission, which were abandon coal spontaneous combustion and wooden support decayed and geological and mining technology. The measures of control high carbon dioxide are proposed. The study result is important to improve safety production in the repeated mining coal.

Abstract: Solid-gas coupling effect of coal containing gas is studied in order to understand the gas percolation mechanism in coal and rock. On the premise of that porosity and permeability of coal and rock are in dynamic changes and Klinkenberg effect, then seepage mechanics and elastic-plastic mechanics are considered together to established solid-gas coupling model of coal containing gas. With the given fixed solution conditions and parameters, the simulation results of mathematical model is found by the Comsol Multiphysic finite element software. Simulation results are consistent with the stress-strain law, deformation and failure modes of specimen in the experiment. Seepage law obtained in numerical simulation has same trends with experimental data. The elastoplastic solid-gas coupling model of coal containing gas can effectively describe the mechanical percolation characteristics of coal containing gas.

Abstract: Based on digital image processing, use Matlab mathematical software to write Flac3D modeling interface program, and suppress noise transported from CAD software, for establishing numerical simulation model rapidly. With the No.59 exploration line profile picture of Yunnan Phosphate Group Jinning mine as the object of study, which is transformed from the open pit to deep underground mining, to establish Flac3D model mined with the way of room and pillar method study, it shows that: (1) using the method of multi-threshold segmentation, build the appropriate mask to suppress image noise effectively; (2) with controlling the horizontal grid cell size, achieve uniform mesh of the model; mesh at the strata border with the triangular grid, for weakening the jagged edges; (3) as the stopes excavated gradually, the movement extent of roof and floor is increasing influenced by mining; the roof is relatively stable, while the stress concentration factor of room pillars is bigger, therefore some measures should be taken to prevent the mine wall caving. The numerical simulation results provide a reference for the design feasibility study of phosphate mining and have a guiding significance for parameter optimization as well.

Abstract: This paper analyses China's listed coal companies based on Tobit-DEA model. DEA model results show that these companies have low technical efficiency level, containing the high scale efficiency and low pure technical efficiency. Then dig the factors to the pure technical efficiency and scale efficiency with Tobit regression model, and the result shows the increasing of management fee rate and debt capital ratio of technical efficiency has some negative effects, and the increasing of sales rate, asset turnover and P/E ratio is beneficial to technical efficiency. Then analyzes the possible reasons for these results and gives suggestions.

Abstract: In order to anlysis the rock deformation characteristics in influence of mining disturbances, water pressure and crustal stress, a multi-physics coupling model is created by Comsol4.2a in this paper. By debugging mining steps and water pressure, the model simulated rock stress and deformation characteristics.the results showed that: (1)the water pressure is fixed conditions, the plastic damage scope in stress concentration zone where was formed by mining disturbanceis were greater than the mining floor,and with an extension of the scope of mining, the scope of plastic failure zone in the rock surrounding which including the vertical and horizontal was increased; (2) Stope width is fixed conditions,with the water pressure increases, resulting in the surrounding rock mechanical strength decrease, and increase the scope of the plastic collapse and plastic damage within thefault zone intensified.

Abstract: To alleviate the problems of casing collapse induced by the coupling effect of rock salt creep and casing wear, the effects of salt creep, attrition rate and casing abrasive position on the equivalent stress on casings in non-uniform in-situ stress field is analyzed by finite-difference model with worn casing, cement and salt formation. It indicates that, creep reduces the yield strength of worn casing to a certain extent; Equivalent stress on casings is bigger and more non-uniform when the abrasion is more serious; Wear position obviously changes the distribution of equivalent stress on casing, and when the wear located along the direction of the minimum in-situ stress, equivalent stress on casing could be the largest that leads to the casing being failed more easily. Equivalent stress on casings increases gradually with creep time increasing and will get to balance in one year or so; In addition, new conclusions are obtained which are different from before: the maximum equivalent stress on casings is in the direction of the minimum horizontal stress, only when the attrition rate of the casing is little; otherwise, it is not. This method could help to improve the wear prediction and design of casings.

Abstract: Aiming at the disadvantage of power plant sootblowing system presently, this paper takes 330MW unit boiler as research object, firstly calculates boiler optimal sootblowing frequency and cleaning coefficient when the heat net income of heat absorbing surface is maximum. And then based on neural network software, both boiler convection heat absorbing surface and radiate heat absorbing surface are implemented real-time monitoring by using DCS data. At the same time, it compares monitoring cleaning coefficient with critical cleaning coefficient real-time, and the optimized system will alarm and instructs the operator to take sootblowing command when it requirements. The reality application performence in power plant has proved that this system have great advantage and practicability in energy-saving.

Abstract: Collision between mechanical equipment during the process of hydropower station construction frequently happens, and always causes great damage. Consequently, a set of collision early alert system, which employs GPS positioning technology, wireless microwave communication technology and virtual instrument technology, was developed. Functions of this system include dynamic picture display of the field model, sound light anti-collision alert of the mechanical equipment, remote monitoring of the running equipment, and fault diagnosis of the GPS equipment. With this system, the collision possibility among the various equipment in the process of operation was reduced. The paper mainly introduces the system’s hardware design, software design, collision calculation and so on. Practicability, efficiency and reliability of this system have been proved through experiment and practice in LONGKAIKOU hydropower station.

Abstract: Coal bed Methane(CBM) is commonly known as “gas”，of which the main component is methane. It mainly exists in the coal seam in the adsorption state, not only different from petroleum which is also fluid but in the liquid state, but also different from the conventional natural gas which exists in the formation in the free state. In the present, the drilling technique of coal bed methane is mainly based on the drilling technique of petroleum. But as the coal bed methane is attached to the coal seam and different from the conventional hydrocarbon reservoir in the physical and mechanical properties and in the storage, it determines the particularity of the drilling techniques. This paper mainly discusses the drilling technique of coal-bed methane in order to provide some useful reference. Coal bed methane is an important type of non-conventional natural gas which has great potential for exploration.