Shapes and formation mechanism of the plastic zone surrounding circular roadway under partial confining stress in deep mining

Abstract

To reveal the failure mechanism of roadway surrounding rock under the partial confining stress in deep mining, by means of theoretical analysis and numerical simulation, this paper studied the distribution laws of the principal stress field around the circular hole and compared the shapes of the plastic zone surrounding rock under the same conditions. The results show that: under hydrostatic stress (λ=1), the circumferential principal stress around the hole is the same everywhere, and the shape of plastic zone is circular; under low partial confining stress (1<λ<2), the rock element at the abscissa axis is most likely to be destroyed, while it is the least likely to be destroyed at the ordinate axis, resulting in the formation of an elliptical plastic zone; under high partial confining stress (λG2), the rock elements near the middle axis are easier to be destroyed, while the destructive force decreases gradually when it approaches the two axes, resulting in the formation of a butterfly plastic zone. The lateral stress coefficient is the main factor causing the butterfly failure of the roadway surrounding rock. And the depth is the main factor causing the large-scale failure of the roadway surrounding rock. Under the condition of deep and high partial confining stress, the roadway surrounding rock will appear large-scale and butterfly failure zone.