Numerical simulation of the stress wave propagation and collapsing process of the tunnel surrounding rock

WANG Xuebin; MA Bing; PAN Yishan; GUO Xiang

Abstract：The stress wave propagation in the surrounding rock of a circular tunnel during progressive unloading,and the deformation-cracking-collapsing processes of the surrounding rock of a circular tunnel and a rectangular tunnel under compressive displacement-controlled loading were modeled by use of the proposed continuum-discontinuum method.The continuous part of the proposed method was verified through a comparison of the present results with the previous numerical and analytical results of the radial and circumferential stresses in the surrounding rock of the circular tunnel during progressive unloading.The effects of unloading time and local nonviscous damping coefficient were studied.The stress wave propagation and the deformation-cracking-collapsing processes of the tunnel surrounding rock were presented.The following conclusions were found.With a decrease of unloading time,the dynamic response of the surrounding rock is obvious and the excavated model difficultly reaches its equilibrium state.As the local nonviscous damping coefficient increases,the energy consumption in the surrounding rock increases,which is beneficial to the fast balance of the surrounding rock,but not for the stress wave propagation in the surrounding rock.When the displacement loaded reaches a certain value,the cracking of the surrounding rock occurs,and a few elements depart from the tunnel surface,so that the roof caving and the floor heave can be observed;as deformation proceeds,many elements have been squeezed or have fallen into the tunnel,leading to the collapsing of the surrounding rock.