Abstract:Deep coal occurrence conditions are complicated,and the roadway pressure is more radical.A considerable number of roadways are distributed in crumbly and severely deformed rock mass,coal mass or semi-coal rock body.To tackle the deep roadway failure problem,two prominent difficulties in deep roadway surrounding rock control namely floor heave and creep deformation were elaborated.Related control methods were put forward.The results show that according to the "two point and three-zone" deformation characteristics of floor heave,the depth of floor bolt and grouting hole should be below "zero displacement point" of the floor strata.Together with the rib corner reinforcement,the floor heave can be effectively controlled.Reasonable first and secondary support can be adopted to ensure that the radial stress provided by the anchoring end is greater than that required for roadway creep deformation,which can keep the roadway creep deformation rate within 0.02 mm per day and achieve longterm stability of roadway surrounding rock.The application effect is good in combination with engineering project,which is of great significance to ensure the safe exploitation of deep coal resources.

Abstract:Coal reservoirs are ternary structure system containing macrofratures, microfractures and pores. Based on statistics of macrofratures and microfractures measured continuously, and data of the special hole volume measured in sections of different diameters by mercury porosimeter, pores and fractures of coal reservoirs were systematically researched through fractal analysis. The results show that the pore and fracture-structure with different origination correspond to different invariable ranges of scale. To denote quantitatively the characteristics of pore and fracture-structure in coal reservoirs, a few fractal dimensions are necessary. Fractal dimensions can reflect status of pores and fractures of coal reservoirs and their distribution rules, and so are significant in the research of adsorption and permeability of coalbed methane.

Abstract:Based on the occurrence characteristics of coal resources and challenges in China,the concept of green coal resources and green coal resources index were put forward.Under the restriction of the four effects of coal mine safety,technology,economy and environment,the evaluation system of green coal resources was established,which consists 4 aspects,such as resource security degree,resource occurrence degree,ecological restoration degree,market competition degree,and 16 secondary indexes.The distribution of green coal resources were systematically analyzed in the five regions of China.The green coal resources in 2020,2030 and 2050 were calculated by the scenario analysis method.The results show that the future stock of green coal resources is not rich.The reasonable planning and development of green coal resources is inevitable trend in the coal industry.Finally,several strategic suggestions were put forward for education,scientific research,equipment manufacture,and government policy.

Abstract:It is shown that the empirical formula widely used by technical staff to calculate the height of the water flowing fracture zone in underground mines is unreasonable and has limited application. An analysis of the background of this empirical formula shows only mining thick- ness is taken into account. A new theoretical formula appropriate to deep mining conditions where roof rock movement is important was developed. It incorporates mining thickness, depth, face span, the rock mechanical properties and other characteristics, and aquifer water pressure. Using the Baodian coal mine number 1303 face as an example the applicability of the formula is demonstrated.