Abstract
By analyzing and studying the deduced theory of the surrounding plastic zone in the circular mining roadway, it is found that the radius of the surrounding plastic zone in the roadway considering the influence of mining coefficient can be divided into two stages: In the first stage, when the mining coefficient is small, the radius of the plastic zone is less sensitive to the mining coefficient, and the process increases linearly with the gradual increase of the mining coefficient. In the second stage, when the mining coefficient increases to a certain extent, the sensitivity of the radius of the plastic zone to the mining coefficient increases rapidly, and the non-linearity increases rapidly with the increase of the mining coefficient. With the gradual increase of the mining coefficient, the geometrical distribution morphology of the surrounding plastic zone of the roadway varies from circular to ellipse to round rectangle to butterfly, and the larger the mining coefficient, the more easily the surrounding rock is butterfly plastic zone, and the developmental dimension and range of the butterfly-leaf are larger. The growth of the buried depth of the roadway and the decrease of the cohesion and internal friction angle of the surrounding rock will lead to an increase in the radius of the plastic zone. With the rise of the mining coefficient, the sensitivity of the plastic zone radius to the buried depth of the roadway, cohesion and internal friction angle gradually enhanced. The butterfly plastic zone of the mining roadway has directional, and the butterfly-leaf will rotate to different degrees with the change of the principal stress direction of the surrounding rock of the roadway, When the maximum depth of butterfly-leaf plastic zone is located directly above the roof of roadway, the roof stability is the worst, and roof caving is easy to occur, thus, the support should be strengthened.
Highlights
The coal mine roadways of 70 % to 80 % are affected by different degrees of mining, and the mining stress generated during the coal seam mining is generally 2 to 3 times higher than the primary rock stress [1]
Zareifard et al [12] deduced the analytical solution of displacement and stress in the elastic-brittle-plastic analysis of circular tunnels, found that the plastic zone under uniform stress state has a great influence on the stability of roadway surrounding rock
When the butterfly plastic zone of the surrounding rock is formed, with the increase of the mining coefficient, the expansion mode of the plastic zone is mainly based on the rapid expansion of the butterfly-leaf, supplemented by other parts
Summary
The coal mine roadways of 70 % to 80 % are affected by different degrees of mining, and the mining stress generated during the coal seam mining is generally 2 to 3 times higher than the primary rock stress [1]. Zha et al [11] investigated the influence of mining stress and lateral pressure coefficient on the plastic zone of surrounding rock in the semi-circular arched roadway with elastic-plastic theory, M-C criterion and modified “equivalent radius” based on measured in-situ stress. This paper is based on elastic-plastic theory and Mohr-Coulomb strength theory, the parameters of the mining coefficient are introduced, and the mechanical analysis model of the surrounding rock in a circular mining roadway is established, the implicit boundary equation of the surrounding rock plastic zone of the mining circular roadway is derived, and the geometric distribution morphology characteristics of the surrounding plastic zone of the mining roadway are studied, and the influence degree of mining coefficient, roadway depth, surrounding rock cohesion and internal friction angle on the plastic zone is analyzed. Theoretical analysis of the plastic zone of surrounding rock in mining roadway
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