Abstract
Bedding plane shear slip becomes more obvious in rock strata with quite different mechanical properties. A composite beam model considering the behaviors of the main roof and the immediate roof in the “three-soft” coal seam is established based on physical similarity simulation experiments and the slip theory in this paper. The movement and failure of the overlying strata and the mechanism of the bedding plane slip at the 2211 working face are studied by experimental and theoretical analysis. The results suggest that the front abutment stress distribution occurs 50 m ahead of the working face, the initial caving interval of the main roof is 55 m, and the peak stress appears at a distance 20 to 32 m ahead of the working face. The bedding plane slip areas can be divided into the obvious slip area and the slight slip area along the mining direction. The range of the obvious slip area becomes wider and the range of the slight slip area grows to be narrower as the working face advances. The bedding plane slip becomes steady after gradual increase and leads to the subsidence of the overlying strata in the “three-soft” coal seam. The observed initial caving interval of the main roof by field measurement is 51 m, which is consistent with the results of physical similarity simulation experiments and theoretical analysis. The results demonstrate that the beam slip model proposed in this paper is reasonable and able to describe the behaviors of overlying strata and bedding plane slip.
Highlights
Complex problems related to soft rocks are often encountered in engineering projects
As a worldwide issue from the 1960s, the soft rock problem has great influence on coal mine construction and mining safety [1], such as resulting in great mining difficulty, high technical cost, and low production efficiency. It is of great significance for sustainable development, and there are many “three-soft” coal seams in China. e “three-soft” coal seam (TSCS) in this paper refers to a coal seam with soft roof, soft coal, and soft floor in coal mining [2]. e roof of TSCS is extremely fragile, and the coal walls often break during the mining process; that is, roof fall, rib spalling, and constraint of support structures occur from time to time. is affects the mining safety and efficiency, but threatens the life safety of mine workers. us, it is necessary to study the overburden movement and failure during the TSCS mining
In the process of mining-induced bending deformation, the shear slip among rock layers is more obvious due to incompatible deformation. erefore, the slip effect is introduced in this work to study the overburden movement failure and bedding plane slip mechanism in the “three-soft” coal seams
Summary
Complex problems related to soft rocks are often encountered in engineering projects. Erefore, the slip effect is introduced in this work to study the overburden movement failure and bedding plane slip mechanism in the “three-soft” coal seams. The mining pressure behaviors in the fully mechanized top coal caving face of the “three-soft” coal seam can be summarized as follows: (1) the first and periodic weighting is not obvious; (2) the resultant pressure point of the top coal moves forward, causing unreasonable performance of the rear support; (3) the deformed roof is easy to fall and inflow gangue; damage of the coal walls may lead to serious rib spalling; and low strength of the floor can induce floor heave. The mining pressure behaviors in the fully mechanized top coal caving face of the “three-soft” coal seam can be summarized as follows: (1) the first and periodic weighting is not obvious; (2) the resultant pressure point of the top coal moves forward, causing unreasonable performance of the rear support; (3) the deformed roof is easy to fall and inflow gangue; damage of the coal walls may lead to serious rib spalling; and low strength of the floor can induce floor heave. ese features make the problem of roof fall more serious and result in more support work, which greatly increases mining and supporting difficulty, leading to heavy economic losses and casualties. erefore, deformation and bedding plane slip mechanism are studied in this paper based on experimental and theoretical analysis
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