77 / 2023-03-31 23:55:59

厚黄土层下开采覆岩及地表移动变形特征研究

厚黄土层下；垮落法开采；承载拱模型；覆岩结构演化；地表沉陷特征

        Many mining areas in western China have a large amount of coal resources under the thick loess layer. Most of this area is the transitional zone between the Loess Plateau and the Eastern Plain, with obvious characteristics of loess coverage. The thickness of the loess layer accounts for about 30% to 70% of the entire overlying rock and soil layer, with characteristics such as uneven soil quality and non cementation of particle structure, which will produce significant additional deformation during mining.This paper takes mining under thick loess layer in a mine in Shanxi Province as the research object, and studies the characteristics of overlying rock and surface subsidence during caving mining under thick loess layer conditions through theoretical analysis, similar material simulation, and numerical simulation.

       Based on the effective stress theory and the shear strength of soil, combined with the maximum principal stress and the minimum principal stress, this paper obtains the vertical stress, horizontal stress, shear stress, and failure criteria of thick loess layer soil. Based on the bearing arch model and the limit equilibrium theory, the values of vertical stress, horizontal stress, and shear force of sinking loess are obtained.Based on similar material simulation, it is found that the basic roof completely collapses and lags behind the coal wall of the working face, with a roof fracture angle of about 59 °. The collapse laws and periodic weighting steps of the direct roof and the basic roof are obtained as the working face advances. The analysis shows that the height of the water conducting crack increases with the advancing distance, and the soil body bends and sinks to form an arch structure. As the mining progresses, the bearing arch damage and subsidence develop to the surface, resulting in stepped subsidence.Through UDEC numerical simulation, the forms of surface and bedrock subsidence and destruction are obtained. Through analysis, the manifestation of the inhibition effect of soil layers on horizontal movement is obtained, as well as the mechanism of the action of coal seam mining thickness and the development height of the three zones on bench subsidence.

       In this paper, the characteristics of overlying rock and surface movement and deformation during mining under thick loess layers are studied. Combining the loess layer bearing arch model and the loess layer stress failure criterion, the ultimate stress situation of the soil mass damaged by thick loess layers is given. Combining similar material simulation and numerical simulation methods, the dynamic process of rock structure evolution and the analysis of surface subsidence and deformation are beneficial supplements to the theory of rock layer movement, It also provides a basis for studying the surface subsidence under the condition of thick loess layer.