Prediction of excavation damage zone of a deep tunnel with large size subjected to high in-situ stress

The analytical and numeral methods are used to predict the excavation damage zone of a deep tunnel with large size subjected to high in-situ stresses. Based on an empirical damage criterion and the classical solutions of stress distributions around a circular tunnel, the range of excavation damage zone in the horizontal and vertical directions can be analytically determined, which can serve as a first-order approximation to estimate the range of excavation damage zone. By integrating the empirical damage criterion with the finite element models, more accurate range of excavation damage zone can be determined. The results show that the excavation damage zone is dependent on the tunnel shapes and sizes: (1) When the diameter of circular tunnel increases, the range of EDZ is larger in the horizontal level than that in the vertical level; (2) The circular tunnel is more economical and reasonable than the other one in the same area; (3) When the width/height of rectangle tunnel increases, there is tensile stress generated in the vicinity of excavation,and the range of EDZ is also larger in the horizontal level.