Experimental and numerical study of the behaviour of shallow rectangular tunnels

Abstract

The behavior of an underground structure under dynamic loading is affected by many factors such as shape, depth and stiffness of the structure as well as the frequency content of the input motion. Scarcity of experimental/field investigations precludes proper understanding of these parameters’ effects on the seismic behavior of aforementioned structures. In this study, the effects of input motion along with structural stiffness properties on seismic behavior of rectangular tunnels are investigated. Three reduced-scale 1 g shaking table models were constructed in 1/48 scale. Tests were carried out in the shaking table facility at the University of Tabriz on model tunnels of the rectangular section of the shallow Tabriz subway tunnel, using input motions of different amplitudes and frequencies. In addition, a numerical study was done using the coupled scaled boundary finite element-finite element (SBFE-FE) method. A good agreement between the numerical model and the results of the experimental test was achieved. Using the shaking table test, the accelerations and bending moments of the tunnel lining were measured. The results show that tunnel lining stiffness affects the acceleration response of the ground. A parametric study by the numerical approach was presented and effects of the variation of elastic modulus and mass density of the soil were evaluated.