Abstract
Based on the coal seam mining under the condition of thick soil layer, the mechanical mining subsidence process under the condition of thick soil layer was analyzed. Combined with the results of core drilling and laboratory test in the mining area, the mechanical analysis of the special transition strata of “hard soil-soft rock” at the bottom of the soil layer was carried out. Additionally, the characteristics of the shallow buried soil layer were compared and analyzed. Furthermore, the significance of this transitional font to the surface subsidence law was proposed. By using the numerical simulation software of FLAC3D and choosing the thickness of “hard soil-soft rock” transitional font as the influencing factor, a model was established and the surface subsidence characteristics of different stratum combinations were numerically simulated. The research results show that the transitional font is the special strata indicating that the hard soil is transiting to the soft rock, having a significant effect on the ground movement and deformation induced by coal mining. It cannot be designated into the loose strata. Also, it cannot be regarded as the bed rock to study the influence of it on the surface subsidence. The “hard soil-soft rock” transitional font has the support effect on the overlying strata during coal seam mining, which can restrict the surface subsidence. Furthermore, the larger the thickness of the transitional font is, the more obvious the restricting effect of it on the surface subsidence is. Meantime, this restricting effect will not be changed with the variation of the proportion between the loss bed and the bed rock thickness. Only the restricting extent is a little different.
Highlights
In East China, Central China, and North China, the overburden bedrock above coal seams in mining areas is usually thin, whereas the unconsolidated layers are thick [1]
The law of surface subsidence caused by mining under the ultrathick unconsolidated layer was studied in this paper, which was based on the analyses of field data from the 1304N working face of a coal mine in Shandong Province, China
The mechanism of mining subsidence caused by mining in the thick unconsolidated layer was studied in this paper
Summary
In East China, Central China, and North China, the overburden bedrock above coal seams in mining areas is usually thin, whereas the unconsolidated layers are thick [1]. The law of surface movement in the ultrathick unconsolidated layer under different mining and geological conditions has been studied by researchers both in China and abroad. Yang and Xia [2] used on-site measurement and artificial neural network prediction methods to study the deformation characteristics of settlement and motion caused by mining under thin bedrock and huge thick loose layer. The law of surface subsidence caused by mining under the ultrathick unconsolidated layer was studied in this paper, which was based on the analyses of field data from the 1304N working face of a coal mine in Shandong Province, China. The results are of great significance to the study of effective control of surface subsidence caused by mining under the ultrathick unconsolidated layer and protection of above-ground structures
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