Abstract
Excavation of shield tunnel was deemed as a combination problem of the ground condition and tunnel linings. A two-dimensional linear elastic FEM was used to incorporate lining-members in structuring an analytical model. The analysis separated the redistribution process of the loading due to excavation into two phases, viz. prior to the loading and after the loading to the linings. The rate of stress release prior to the loading is defined in the analysis as the stress release ratio.
It was shown that soil properties and construction factors determine the stress release ratio. The analysis was applied to four tunnels that run closely together. Verification was carried out by comparing the numerical analysis with monitored results on site with regard to such factors as the acting earth pressure and section stresses of a preceding tunnel itself and the variation of those factors in the course of the excavation of the succeeding tunnels.
