2D Dynamic Numerical Modelling of a Tunnel – Soil – Building System Subjected to Seismic Loading

Abstract

It is important to determine dynamic tunnel behaviour under cyclic loading for the seismic underground structural design. The dynamic response of tunnels is further complicated when considering the interaction with surface buildings. This paper investigates a series of 2D plane-strain numerical models to study the dynamic response of a shallow cut-and-cover rectangular tunnel in loose, cohesionless soil. Both dry and saturated conditions are considered. Input motion includes sinusoidal waves with 10 cycles of shaking. A raft foundation with a 50 kPa structural surcharge is adopted to simulate the effect of the surface building. Soil displacements, wave propagation, earth pressures and tunnel lining structural response are determined. These results show that the soil liquefaction introduced by accumulated excess pore pressures causes the attenuation of soil horizontal acceleration, reduction of soil effective stresses and promotes tunnel flotation. The existence of a building not only reduces the liquefaction ratio of sub-surface soil right below the foundation but also effects the earth pressure distribution on the adjacent tunnel sidewall. In addition, the presence of the tunnel may affect adversely the rotation of the foundation especially in saturated soils.