Abstract:The mechanical behaviors of rock mass in deep tunnel are different from those in shallow tunnel. The surrounding rock in shallow tunnel is classified into loose zone,plastic zone and elastic zone;while the surrounding rock in deep tunnel is classified into fractured zone and non-fractured zone,which occur alternatively. The mechanism of the alternative occurrence of fractured zone and non-fractured zone in deep tunnel is studied. It is assumed that the outer boundary of the deep tunnel is subjected to an in-situ far-field stress field,whose inner surface is subjected to an internal pressure which changes during tunnel excavation. As a result,the tunnel excavation process is related to dynamic problem. The motion equation expressed by displacement potential function is established,which determines the release of pre-existing stress upon excavation of the opening. The general solution of motion equations is obtained by using Laplace transform. Based on the elastic theory and boundary condition,the near-field stress redistribution and displacement field around circular opening induced by excavation are determined. If the elastic stress fields satisfy the failure condition of rock mass,failure of rock mass occurs. It results in the discontinuous displacement,and the fractured zone is formed,and the deformation localization occurs. On the basis of the deformation localization theory,the support reaction acted on the elastic zone is defined. Then,the fracture mechanics theory is applied to analyzing residual strength of the rock mass and the time of onset of fractured zone. Width and quantity of fractured zone and non-fractured zone are given. It is found from numerical results that the width and quantity of fractured zone and non-fractured zone depend on the strength of rock mass and the velocity of tunnel excavation. The quantity of the fractured zone increases with increase of tunnel excavation velocity. The width of the fractured zone decreases with increase of tunnel excavation velocity. The quantity and width of the fractured zone increase with decrease of the rock mass strength.