Evaluation and improvement on analysis of plastic zone in roadway surrounding rock under unequal compression in two directions

Abstract

Based on the special lateral pressure coefficients of 1,the radius of surrounding rock plastic zone obtained by approximate implicit method has a large theoretical error contrasted with the corresponding analytical solution of the mature axisymmetric plane strain theory.In order to improve this shortcoming, from the existing estimation method for surrounding rock plastic zone radius on horizontal axis and based on the formulas of plastic zone under axisymmetric stress field and assumption of the constant total collection degree of line loads,the approximate analytical solution of the surrounding rock plastic zone of unequal stress field on vertical (or horizontal) axis was derived.Then combining with shape of plastic zone determined by approximate implicit method,the plastic zone of surrounding rock under unequal compression in two directions was relatively accurately determined.The proposed method not only eliminates the theoretical error of the approximate implicit method for the lateral pressure coefficient of 1,but also overcomes the theoretical defects of radial stress equal to zero in elastoplastic boundary of surrounding rock by using original estimation method with axisymmetric stress.So proposed method could be considered as a relatively reasonable and accurate estimation method for the plastic zone in roadway surrounding rock under unequal compression in two directions.

Keywords

• approximate implicit method
• unequal compression in two directions
• surrounding rock plastic zone
• estimation method