Comprehensive Evaluation And Numerical Simulation Anaysis Of The Surface Subsidence In Suancigou Coal Mine

With the rapid development of national economy, the growing demand of coal resources aggravates the mining strength of coal mines, which has caused a serious of geological problems. As one of these problems the surface subsidence has brought great negative effects for people's life and production as well as ecological environment. Previous researches mainly focused on the research of theory with less applicability. This paper made studies in the aspects of the law of goaf subsidence, influence factors, stability evaluation of surface subsidence and numerical simulation of subsidence conditions; analyzed the goaf stability of Suancigou coal mine. These researches have certain theoretical and realistic significance, and will apply scientific basis for the improvement as well as the later reasonable and safe mining of coal mines. The specific studies of this paper are list as following.Firstly, based on the analysis of previous researches and achievements, the variation and deformation characteristics of overburden stresses after coal mining were summarized in detail; the general laws of geotechnical movement, transformation and destroy were analyzed from the interior of overburden and the earth's surface. The geological and geomorphic features and engineering geological conditions of the goaf were evaluated combining with the current situation of surface subsidence in Suancigou coal mine, and the influence factors of surface subsidence were analyzed.Secondly, the physical and mechanical characteristics of rocks were analyzed by laboratory tests, which apply necessary physical and mechanical parameters for the stability evaluation and numerical simulation of goaf. At the same time, the tests show that the physical and mechanical characteristics of the same lithology increased with the increase of depth, while it is different of different lithology. These show that the physical and mechanical parameters of rock stratums are influenced by depth and lithology. Furthermore, on the basis of the introduction of stability evaluation methods of subsidence areas in coal mine, relevant data were obtained through site investigation and laboratory tests. The stability of goaf in Suancigou mine was evaluated by qualitative and quantitative methods. The qualitative evaluation was carried from these aspects as mining thickness ratio, structure, lithology, mining method and hydrogeologic condition, which obtained more stable conclusion. Quantitative evaluation contains formula method and fuzzy comprehensive evaluation method. The formula method worked out the development height of water flowing fractured zone by two formulas. While the fuzzy comprehensive evaluation method determined the given weights of indexes using analytic hierarchy process and set membership functions finally. And at last, these two methods determined the degree of subsidence of mining is "stable" at last.Finally, combining with the actual situation of Suancigou mine, a simulation model has been set using FLAC3D software, and a whole analysis and evaluation of goaf subsidence transformation in research area was made. The general law of surface settlement and horizontal tensile displacement were firstly calculated from different space positions. Then the range of goaf plastic failure was analyzed through the expansion of goaf plastic nephogram. Finally, the distribution law of stress filed and the causes of goaf caving zone were analyzed according to the primary stress nephogram. Meanwhile, compared with the stability evaluation of subsidence area in coal mines, and the results were basically identical with the former.