Study on Shape Characteristics of Plastic Zone in Heterogeneous Roadway-Surrounding Rock

Aiming at the surrounding rock failure of heterogeneous and unequal pressure circular roadways, the approximate analytical algorithm of the plastic zone is proposed. Through the comparison of analytical calculations and numerical simulation, the shape characteristics and evolution law of the surrounding rock’s plastic zone are studied, and the relative error of the two calculation methods is analyzed. The results show the following: (1) With an increase or decrease in the lateral pressure coefficient, the shape of the plastic zone of the roadway-surrounding rock presents a circular-ellipse-butterfly shape change law, and the outer edge of the plastic zone presents a scattered shape, without a continuous boundary. (2) In the butterfly-shaped plastic zone, the butterfly leaf always lies between the maximum confining pressure and the minimum confining pressure and rotates with the pressure. (3) There is a certain amount of error between the maximum value of the plastic zone solved by an analytical algorithm and numerical simulation, and the relative error is positively related to the burial depth and lateral pressure coefficient of the roadway and negatively related to the strength of the surrounding rock. (4) In addition, the relative error of the plastic zone calculation of the multi-layer heterogeneous combination roadway is larger than that of the single heterogeneous roadway.