Reverse fault rupture propagation through dense sand and interaction with a shallow RC tunnel

Abstract

Past major seismic events have demonstrated the vulnerability of almost any type of structure to large tectonic deformations. The present work focuses on a particularly important challenge for countries of high seismicity, related to the design of shallow tunnels against seismic faulting. A shallow reinforced concrete (RC) tunnel with continuous lining is analysed, embedded in dense sand, subjected to a propagating reverse fault rupture. A detailed 2D finite element (FE) model of the soil-tunnel system is developed in ABAQUS. Two advanced soil constitutive models (Hypoplastic and Mohr-Coulomb Hardening-Softening) are employed, carefully calibrated against triaxial compression tests at various consolidation pressures. The RC tunnel lining is modelled with the Concrete Damaged Plasticity (CDP) model, which can realistically reproduce tensile and compressive damage. Before imposing the tectonic deformation, the initial stress state of the soil is simulated in a first step, followed by modelling the tunnel construction sequence in a simplified manner. The reverse tectonic dislocation is introduced in a third step, modelling fault rupture propagation through dense sand and its interaction with the RC tunnel. The focus is primarily on tunnel deformation and damage in function of the applied fault dislocation and the location of the tunnel relative to the outcropping fault rupture.