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According to the mine strata pressure bump accidents frequently occurred in shallow depth seam mining of Shenxin Mining Area, the mining activities could make the strain energy increment in the surrounding rock to induce the mine strata pressure bump occurred. An energy equation of the mine strata pressure bump was established. There were three types of the strain energy increment including the static load type, dynamic load type and superposition or mixing type. The site analysis held that there were four types of the mine strata pressure bump existed in Shenxin Mining Area, including the coal mining face with the suspended type hard roof, the strain superposition type gateway, 45° steep inclined seam with falling type roof and 87° almost vertical seam with lever type rock pillar. The paper analyzed the energy resources mode and the major disaster occurred factors of each type mine strata pressure bump. Based on the circumstances, from the mining layout, monitoring and measuring method, danger evaluation, damage releasing method, effect inspection and others, the paper pro- vided relevant countermeasures to prevent and control the mine strata pressure bump. [ABSTRACT FROM AUTHOR]

After analyzing series monitoring data of micro-seismic and powered support pressure in Xinjiang,rock-burst mechanism was obtained. Thick and hard roof is main pressure source of rock-burst. Bad and delayed supporting make roof pressure transferred on coal-wall ahead of mining face. Thus, elastic energy and stress concentration formed, and fast mining speed aggravates energy and stress concentration degree. In this instance, rock-burst is inevitable because of strong burst liability of coal-seam. Based on this, rock-burst prevention principle was established that avoiding transferring hard and thick roof pressure to coal-wall. The prevention methods included broken blasting of hard roof, pressure-relief blasting of coal-body and increasing setting load of powered supports. The practice shows that prevention methods are effective. [ABSTRACT FROM AUTHOR]

Pointed out that the mining of region-wide has a close relation with the form of concentrated static load, needed by locally rock burst to occur. An regional preparedness idea of rock burst was brought forward, which based on the concept of dredging method of wide concentrated static load. Analysed the feasibility of adjust and effect law of high concentration stress of rock burst coal bed, by theoretical analysis and numerical simulation. It is indicated that the system of regional preparedness of rock burst, which based on the burst seam identification, stress testing, mining method selection, roadway location identification, protection layer mining and the orderly mining of the same coal bed, can avoid or reduce the high stress concentration. The study results give a guidance for design stage of the new mine, new mining area or new level design phase of producing coal mining to prevent rock burst. [ABSTRACT FROM AUTHOR]

Through field survey and laboratory analysis, we examined the composition and fractal features of soil micro-aggregates in different types of treefall gaps and microsites (pit bottom and mound top) in broad-leaved Korean pine forest and spruce-fir-Korean pine forest. Results showed that the contents of soil microaggregates under the classes of 0.25-2 mm and 0.05-0.25 mm were higher in both forest types, ranging from 25.7% to 50.7% and from 27.0% to 42.8%, respectively, and that of <0.002 mm was the lowest, ranging from 4.4% to 8.9%. In the pit bottom and mound top of gaps, soil bulk density was higher in both forest types. Soil nutrient content in mound top was higher than that in pit bottom and was higher in broad-leaved Korean pine forest than spruce-fir-Korean pine forest. Soil microaggregates of <0.002 mm had no correlation with soil physical and chemical properties, whereas that of 0.25-2 mm and 0.002-0.02 mm had significantly positive and negative correlation with soil non-capillary porosity, total porosity, aeration porosity, organic matter, total phosphorus, total nitrogen and organic carbon, respectively. On the whole, soil fractal dimension (D) and the proportion of characteristic soil micro-aggregates (PCM) in broad-leaved Korean pine forest were larger than those in spruce-fir-Korean pine forest, and the ratio of soil microaggregates diameter (RMD) in mound top and pit bottom was increased in two forest types. Soil D and PCM had no significant correlation with soil physical and chemical properties, while RMD was negatively correlated with capillary porosity, total porosity, soil bulk density and aeration porosity. In two forest types, the formation of mound and pit microsites could decrease the larger size micro-aggregates and the stability of soil micro-aggregate, increase soil D and PCM, and signifi-cantly increase RMD. RMD could be used as a quantitative index of soil physical and chemical properties in pit and mound microsites of forest.