Comparative Study on the Plastic Zone of Circular Hole Surrounding Rock in Anisotropic In Situ Stress Conditions

Anisotropic in situ ground stress is an objective stress state of rock mass that should be taken into account when calculating the plastic zone of the circular hole surrounding rock. The point stress method and approximate plastic condition method for calculating plastic zone are derived, and the finite element numerical calculation is carried out. Different analytical and finite element approaches are employed for calculation based on the representative parameters. The outcomes of the calculations are thoroughly examined. There are four shapes of plastic zone, among which the butterfly plastic zone can be obtained only by approximate plastic condition method and finite element method. The distribution of plastic zone calculated by using the point stress method and the Ruppneyt formula is identical, with only small deviations. The modified Fenner formula should not be used to calculate the plastic zone under in situ stress anisotropy since it would result in an underestimation of the maximum plastic radius. The detailed calculation and results comparison of this paper can provide a reference for more comprehensive and reasonable evaluation of the surrounding rock plastic zone.