Advanced Materials Research Vols. 734-737

Abstract: To release the shale gas potential in China, hydraulic fracturing technologies play an important role. However, the latent technique risk deserves special attention. For example, the site-nearby micro-seismicity may have some relationship with the hydraulic fracturing. Nonetheless, the good news is that carbon dioxide stimulation can be used to displace hydraulic fracturing and obviate the potential earthquake risk. But the carbon dioxide methods are not economical nowadays, and hydraulic fracturing will continue to dominate. Through acoustic emission monitor, the reservoir characteristics and induced micro-seismicity magnitude and frequency will be collected and evaluated. Based on pre-existing project experience and numerical simulation, difference assessment standards about the hydraulic fracturing parameters are proposed to evaluate the micro-seismicity risk. Combined with other characteristics of rock property and fault location, this risk management can be used to guide the subsequent drilling and mining in practice.

Abstract: Characteristics of gas emission in face 40108 were analyzed. The results show that the high-position tunnel system and the grouting system are the effective gas control systems, and 83% gas emission rates in face 40108 come from gob. When monitoring points away from coal face about 33-38m and 78-93m in strike direction, gob gas concentrations reach to 5% and 10%, respectively. The relative gas emission rates decrease with a negative exponential function when the daily outputs or daily advancing rates increase. With the increased air flow rate in face 40108, the absolute gas emission rates in return airway increase coinstantaneous, while it is almost remain unchanged in coal face.

Abstract: in view of research situations of the fully mechanized sublevel caving, the similar simulation test model for fully mechanized sublevel caving was presented. During the top-coal caving process, variation of top-coal subsidence and abutment pressure were measured. Consequently, the ground pressure behavior of fully mechanized sublevel caving was analyzed. The following conclusions can be reached: (1) top coal subsidence experiences the process of slow increase, trend to aggressive and sharp increase; (2) undulate change as well as decay after reaching the peak of abutment pressure is appeared with the advance of working face, strata behaviors of main roof displays smoothly; (3) on account of cushion above hydraulic support, influence of dynamic load during periodic weighting such as rock burst can be eased and abutment pressure peak moves forward, consequently, strata behaviors in the working face presents smoothly.

Abstract: Based on the geological condition of MaHuangliang coal in the Yushen mining area, the paper systematically studied the overburden's destructiverules of fully-mechanized top coal caving, and established hydro-geological model of research area by using GMS numerical simulation. Based on the model, the paper predicted the water inflow of different aquifer, analyzed the influence of aquifer to coal mining, and introduced the technical plans about fully-mechanized top coal caving mining under water body with shallow overburden and thin bedrock.

Abstract: Deep borehole controlling blasting is one of the most popular methods which used to improve permeability of low permeability and highly gassy coal seam. Proper interval between blasting hole is the critical factor. On this paper, the theory and insufficiency of each method are discussed by theoretical analysis and field investigation. The result shows that, because of the complexity of outburst coal seam, the measuring result got by different methods is relative and declinational. We need to make a right choice according to the actual demand. And the method of gas flow index is quickly, visual and reliable, which to be worth paying the utmost attention to.

Abstract: The critical slip field theory is applied to optimization design of the slope angle. An intelligent matching optimization of the slope angle design is carried out based on the strata distribution, mechanics parameters of rock mass and a given security reserve. That is the implementation of the maximum allowable slope angle of slope rock mass under the given conditions. Optimized by the final highwall of Buzhaoba Open-Pit Mine, the overall slope angle increased 3°compared to the original design. Which implement the optimum slope angle of final highwall, modified the shortcoming in the original design and ensure the maximization of mine safety and the resource exploitation.

Abstract: In this paper,in the case of upper protective layer mining of a mine for the engineering background, based on the model of semi-infinite plane body in elastic mechanics, the theoretical calculation model of verticalhorizontalshear stress of floor coal rock is established, and it is concluded that the stress expression of any point in the impact of distributed force. By introducing the rock strength index I and generalized Hooke's law, it is concluded that the discrimination criterion of guide gas fissure zone and pressure relief desorption belt of underlying coal rock with upper protective layer mining. The pressure relief scope of protection with the mining of upper protective layer is determined. Theoretical analysis shows that: the "pressure relief desorption zone" of the underlying protected coal seam that the vertical distance to the protective layer is 40m lags behind 22.2m.Through field test, the results show that the obtained pressure relief scope of protection is 26.98m,and the theoretical analysis results are basically similar.

Abstract: For guiding coal mining under highway scientifically and systematically, Regulations of coal mining under highway is necessary to be compiled in a few years in China.Base on the study of laws about highway and coal mining and existent regulations about coal mining under other constructions, this paper proposed the principal parts of the regulations according to the deformation and failure characteristics of highway caused by the effect of coal mining.The study provided the supports about theories and mining technologies for extracting unexploited coal under highway, increasing the coal production, optimizing mining design, prolonging the coal mine life and put forward some constructive suggestions for completing the regulations in the coal mining area in China.

Abstract: Aiming at the problems that local roof falls during the roadway driving, similar simulation experiment and numerical analysis experiment is designed to compare and analysis the deformation and failure characteristics in anchorage areas for different supporting forms. The results show that: if the A3 round steelanchoris used to support in the experiment, the rocks loaded 240kg began to appear local caving, the roof loaded 360kg appear fully caving, the ultimate bearing capacity of the roof support structure is achieved, the falling height is 2.4m above the roof. As the distance beyond the bolt anchorage range, the stability of the roof is hardly to maintain. When we choose deformed steel bar bolt, the bearing capacity of supporting structure reach to 624 kg, 73% is increased compared to A3 round steel anchor, and the capacity is greater than the actual load in the overburden; the deformed steel bar bolt make the roof form a complete anchorage structure, increase the bearing capacity of the roof structure.

Abstract: Through the structure instability theory analysis of the coal roadway roof ,the author concluded that mechanical properties of rock, location, thickness and thickness ratio is the main factor affecting the instability and failure of rock structure. Capitalize on the roof caving hidden danger detector developed by the China university of mining and technology to synchronize, continuous and intensive monitor the rotational speed, thrust for synchronization and thrust. Based on the record ,the author inferred the coal seam roof lithology and rock structures of the different drilling location. Engineering practice shows that the use of roof caving hidden danger detector to identify lithology of strata and structure is in good agreement with the core test values. Coincidence rate reached 95.14% and the recognition effect is quite good.