Three-dimensional influence zone of new tunnel excavation crossing underneath existing tunnel

Abstract

Due to an increasing number of constructed tunnels in urban areas, excavation of a new tunnel may cause damage to adjacent existing tunnels. In order to assess damage on the existing tunnel, it is important to improve our understanding of the influence zone due to new tunnel excavation. The influence zone may include the location of significant tunnel settlement, tensile strain, shear stress or normal stress acting on an existing tunnel. To investigate the influence zone of new tunnel excavation crossing beneath an existing tunnel, a series of three-dimensional centrifuge tests in dry sand was carried out. To identify the zone of substantial stress transfer on an existing tunnel, three-dimensional numerical back-analysis was also conducted using an advanced hypoplasticity constitutive model with small strain stiffness considered. The influence zone of new tunnel excavation on the existing tunnel is presented and discussed.