Advanced Materials Research Vols. 361-363

Abstract: In background of the geological engineering and the mining technical conditions of ZhangJi coal mine 17258 fully-mechanized face and rail roadway of 1724 (1) fully-mechanized face,by the field observation and computer numerical simulation studying the stress distribution law of roadway surrounding rock heading advancing coal face.Obtain the influence scope of the dynamic pressure along coal seam trend and tendency, the stress peaks position, perturbation boundary angle of dynamic pressure,and the surrounding rock stress distribution law of roadway excavating in the zone of the stress concentration and stress reduced area. Provides the theoretical foundation for roadway layout under similar conditions.

Abstract: In present，a series of uniaxial compressive experiments on sandstone samples have been conducted in the laboratory by using jointed devices of triaxial loading equipment and medical SOMTOM-plus CT scanner. Based on CT value, expression of density damage variables and density damage increments (DDI) of brittle rock and the method to determine the rock initial damage variables have been worked out. From real-time CT observations of sandstone sample under uniaxial compression condition and the analysis on CT digital images and the relation curve between sandstone density damage increment (DDI)and stress, the evolution process of fracturing in brittle rock sample can be divided into five stages, i.e. initial densification stage, crack occurrence-propagation, crack merging-bifurcation, crack rebifurcation-propagation, and crack cut-through-massive failure stage. Crack occurrence-propagation is a local phenomenon and the whole rock is still in the densification stage. Therefore, the rock failure process under compression is mainly including three stages, namely initial damage densification, local dilatation-bulk dilatation, and massive failure. The use of CT images and relation curve between density damage increment and stress in analyzing the meso-damage evolution processes of brittle rock sample is an important and effective method. As an important mechanics index in rock meso-mechanics, the density damage increment can be used to analyze the quantitative fracturing process in brittle rock under compressive condition, as well as being an important factor in a rock fracturing process model to be constructed.

Abstract: In the case of gas radial flowing in layer-though boring, use the method of draining water gathering gas measured the Gas flow of borehole that there is water flow out from drilling Sometimes,the coal seam gas permeability coefficient is calculated using"Radial Flow Method"and"Optimizing Method,found out the range of 5-3 original coal seam Hongmiao coal mine permeability coefficient is0.007~0.008 m²/(MPa²·d).

Abstract: Heidaigou Surface Coal Mine (HSCM) is a large surfaces coal mine that first uses the throwing blasting - dragline stripping technology. Lots of new demanding prompt solution issues appears in HSCM without any successful experience in China, such as the stability of dragline stripping bench, the design and implementation of throwing blasting parameters, and the optimization of dragline stripping technology parameters. Rigid Body Limit Equilibrium Method (RBLEM) was used to study the safety and stability of dragline solid high bench and dragline stripping loosen bench under different workface parameters and influence factors. The safe operation parameters of dragline stripping bench are proposed. The dozer lowered height of the stripping bench, the width of extended bench and dragline operation parameters are optimized using the Optimization System of Dragline Stripping Technology (OSDST). The results can provide the decision support for HSCM.

Abstract: Given the particularity and the first time for shallow thinner seam mining in Shendong mining area, the overlying strata movement law during shallow thinner coal seam mining has been studied in this paper based on the fully mechanized thinner coal face of NO.71301 in Shi Getai coal mine, resorting to observation on spot, numerical simulation and other methods. Through research, the important laws and features had been obtained, such as, initial pressure step, periodical pressure step, the obvious partition of periodical weighting, the unitary elasticity distribution of front abutment pressure, and the stress shell morphology over the mining rock, which provides important characteristic for roof control and foundation for the powered support selection.

Abstract: The gob-side entry retaining technology can be used to not only solve the problem of intensity in successive mining but also reduce the 10,000 tons' drivage rate and improve the coal recovery. Based on the established roof cutting mechanical model, the method of numerical simulation is used to determine the technical parameters of gob-side entry retaining in one coal mine. The reduction in cross-section of the roadway is 10.8% according to the field observation, which shows that the gob-side entry retaining has obtained preferable results and fulfilled the demand of safe production in the face.

Abstract: The size of the fully mechanized caving face is optimized by theoretical analysis and the dip length of the face is determined as 260m. With the method of numerical simulation, the reasonable cutting height of the face is determined as 3.5m and the caving method is determined as one round caving in order. The physical simulation is used to analyze the caving effects under different drawing intervals and the reasonable drawing interval is determined as 0.8m. The coal recovery is improved by 3.43% after the parameters are applied in field and the goal of high production and high efficiency of the mine has been achieved.

Abstract: Under the basis of the “arch” failure of thick sand layer in preliminary period in shallow seam through field experiment, arch math model is set up. The conclusion establish the basis to study the coupling problem between key stratum (key block) and the sand layer.

Abstract: This paper takes gas as a geological-mass to study, using gas geology theory, by analysising the geological conditions of Yongju mine in ShanXi, combining with the coal seam gas content data which measured underground to study the relationship between geological conditions and gas occurrence, reveal the gas occurrence factors: geological structure, roof and floor lithologic of coal seam, buried depth of coal seam and thickness of coal seam. Finally, using the measured data of gas content and gush, regression analysis, the gas gush is forecasted, playing a guiding role in the gas control and production safety .

Abstract: In China, the coal gas formation is characterized as low permeability, low pressure and low water saturation. The coal bed methane (CBM) has strong adsorption and is difficult to develop. Hydraulic fracture is currently the main measure to improve its permeability, drain the liquid and lower the pressure, which promotes desorption of CBM. But it is not efficient. Based on the principle of high energy gas fracturing (HEGF) and the study of new methods, we proposed the test application of the multi-pulse loading fracturing technology for development of shallow CBM. The mechanism of the technology is that it generates high-temperature and high-pressure gas in the target coal bed to produce a long multi-fracture system with effects of multi-pulse loading. It can also produce strong impulse oscillation acting on formation matrix to loose formation pressure, improve the pore connectivity and permeability of coal bed, which promotes pressure drawdown and desorption of CBM. Thus, the goal of increasing the yield of CBM wells is achieved. This paper focuses on the research ideas, mechanism, process design and feasibility. We carried out analysis combined with field test applications. The study provides a new direction to explore new technologies for China’s CBM development.