Numerical modelling of concrete tunnels exposed to rock fall

Abstract

Tunnel entrances are among the most likely places for rock fall events. For this reason, concrete tubes are constructed before tunnel entrances against rock falls. In this study, the normal stress and the deformation in both horizontal and vertical directions occurred by crashing rock on concrete tunnel tubes were investigated using finite element method in three dimensional conditions. Different velocities and masses of falling rock analyzed to demonstrate effect of velocity on normal stress and deformations. It was observed that deformations on the concrete tube increased as the impact energy increased due to increasing velocity and mass. The mass of crashed rock, M, is changes from 3 kN to 200 kN and peak deformations could reach approximately 150 cm when the mass of falling rock was M=200 kN and V = 30 m/s. When the velocity of rock V=10 m/s just before the impact, the ratios of deformations to rock mass of 3 kN, 25 kN, and 200 kN were approximately 0.00066 m/kN, 0.0014 m/kN and 0.00175 m/kN, respectively.