Analysis of plastic zones in surrounding rocks around a circular tunnel considering the effect of intermediate principal stress and heterogeneityShuxin Deng, Yonglai Zheng, Lipo Feng, Le Van Tuan, Cuizhou Yue and Zhuorui WuMATEC Web Conf., 275 (2019) 03007DOI: https://doi.org/10.1051/matecconf/201927503007