Abstract: With the continuous development of the underground road construction in various cities in China, accidents including damage or even collapse of the surrounding structures can often happen due to the underground excavation. Therefore, it is very importannt to predict reasonably the ground settlement for the protection of ground buildings and structures. We combine the ground settlement velocity coefficiennt with the three-dimensional imaging method, and establish a new calculation method for the tunnel surface settlement considering the time effect. We take a subway tunnel in Shenzhen as an example, and demonstrate the rationality of the method by comparing it with the on-site monitorinng data. This method is then used to further analyze the variation of the ground lateral and longitudinal settlement with time during the tunnel shutdown, and the time dependencies of the ground settlement and the settlement velocity are studied through a parameter analysis. The results show that the ground settlement and the maximum slope of the longitudinal settlement increase gradually with the increase of shutdown time and eventually tend to be stable. The maximum ground settlement velocity increases following a logarithmic function with the increase of the excavation speed and the settlement velocity coefficient. In contrast, the final ground settlement is less affected by those two factors. The final ground settlement and the maximum ground settlement velocity both increase linearly with the increase of the ground loss. The time at which the ground settlement velocity reaches its maximum has nothing to do with the amount of the ground loss.

Key words: tunnel construction, ground surface settlement, time effect, virtual image technique, settlement velocity coefficient