Modelling the transverse behaviour of circular tunnels in structured clayey soils during earthquakes

Abstract

The paper presents novel results from advanced numerical simulations of the transverse behaviour of shallow circular tunnels in natural clays accounting for soil structure degradation induced by earthquake loading. It combines the calibration of a kinematic hardening model against real laboratory data with outputs from a parametric study with different degradation rates of soil structure to demonstrate the good performance of the model and draw conclusions of significance to both researchers and designers. The sensitivity analysis indicates an increase in the maximum and minimum values of the lining forces attained during the earthquake motions and in the lining hoop force and bending moment increments in response to the seismic events when higher rates of destructuration are accounted for. Hence, the paper highlights for the first time the importance of the initial structure and its degradation in controlling the magnitude of the tunnel lining forces and, consequently, the overall seismic tunnel design.