Abstract

Recently, ground structures have reached saturation, and underground construction using underground structures such as tunnels has been in the spotlight as a way to solve increasing traffic difficulties and environmental problems. However, due to the increasing number of underground structures, close construction is inevitable for continuousunderground development. When a new underground structure is constructed closely, stability may become weak due to the influence on the existing tunnel, which may cause collapse. Therefore, analyzing the stability of existing tunnels due to new structures is an essential consideration. In this study, the effect of excavating new tunnels under parallel tunnels on existing parallel tunnels was analyzed using numerical analysis. Using the Displacement Control Model (DCM), the volume loss generated during construction was simulated into three case (0.5%, 1.0%, and 1.5%). Based on the center of the pillar, the distance where the new tunnel is located was set to 5 m, 6 m, 7 m, 8 m, 9 m, and the space for each distance were set to 5 (0D1, 0.37D1, 0.75D1, 1.13D1, 1.5D1). In general, as the volume loss increased and the distance approached, the maximum displacement and angular displacement increased, and the strength/stress ratio toevaluate the stability of the pillar also decreased. As a result, when the distance between the new tunnel and the center of the pillar is 5 m, the space is 0D1, and the volume loss is 1.5%, the stability of the existing parallel tunnel is the weakest.