Tunneling-Induced Settlement Evaluation for New Tunnel Underneath Existing Tunnel

Abstract

The relationship between subsurface settlement and ground volume loss caused by the excavation of a new tunnel underneath the existing tunnel was analyzed and identified based on Mair's theory. Subsurface settlements were determined by equations and a 3-D finite element numerical modeling. The settlement and ground volume loss control measurements for the tunneling-induced settlements in the existing tunnel were proposed and demonstrated by using 3-D finite element analysis. The large pipe-shed (LPS)ground stabilization was utilized to perform ground stabilization prior to the new tunnel excavation. The effects of using LPS ground stabilization on ground volume loss control were evaluated by comparing with non-LPS tunneling situations. The results indicate that the LPS ground stabilization can significantly reduce the settlement of an existing tunnel caused by the excavation of a new tunnel, and the ground volume loss method has proven to be an effective approach to estimate the effects of LPS ground stabilization.