Researh On Characteristics Of Overling Strata Movement And Mining-induced Stress And Fracture In Close Multiple-seam Minings In Assending Order

The utilization of coal resources must be enhanced not only due to its non renewable nature and the need of coal resources to develop society but also because of the contradiction between environment and itself coal resources. With the increasing of mining depth, a series of problems have become increasingly prominent such as rock burst, coal and gas outburst, stability control of roadway and etc. It is the most effective way to realize mine power disaster prevention and strata stability control in ascending order mining. In this paper, it is the criterion and control countermeasures of ascending mining in theory that is determined by analyzing10natural factors and4mining factors influencing ascending mining and the impact of various factors on the upper coal seam mining, not only consulting relevant literature and data but also summarizing ascending mining theory and being applied to the feasibility, and then analyzing importantly the mining height, spacing of layers as the key factors affecting the feasibility of ascending mining. According to the occurrence of coal measures and geological characteristics in close multiple-seam mining (3,4-1,5-2,6-1,7-1,8-lcoal seam),physical and numerical simulation models were constructed to obtain the law of surrounding rock displacement, deformation,failure and the evolutionary characteristics of overlying movement and mining-induced which reveal the mechanism of effect on the overlapping of mining displacement, fracture and stress field evolution in ascending order multiple-seam mining. By overlapping effect of the pressure arch on the upper and lower coal seam, there is a characteristic that the degree of stress concentration is higher in the edge region of pressure arch than in the single coal seam.In order to clarifying multiple-mining effect on the stress distribution of overlying strata detailedly, the coupling effect of the multi-field evolutionary law among deformation and breaking law of stope wall rock, the stress distribution of surrounding rock and the migration characteristics of overlying strata is comprehensively analyzed based on the overlying and homogenous effect in multiple-seam mining that is obtained by contrasting and studying the evolutionary law of stress and the evolutionary characteristic of high mine-induced stress in different order mining. Although there is a similar stress evolutionary law between multiple-seam ascending and descending mining that is the overlying effect of stress after initial mining and the homogenous effect of stress far away from influencing area of mining along the longitude and the evolutionary process of local slow accumulation to overall mutation to periodic variation to ultimate stability in both stress and fracture field, it is stronger to accumulate and mutate in ascending mining than in descending mining and there is also a higher degree of overlying strata deformation and failure.It is able to provide a prediction, evaluation and basis for safety and efficient multiple-seam mining in ascending order to study on ascending mining technology. It is also favorable to increase coal output, prolong the service life, achieve the remarkable social and economic benefits, and enrich the basic theory of ascending mining which has important theoretical research value and realistic significance.