Analysis of Twin Circular Tunnels Subjected to Impact Loads

Tunnels are important underground structures which require due attention at all stages of their construction process. This task involves huge expenditure and time. Hence, other factors which may affect the functioning of the tunnel in the long run must also be incorporated in the studies. With the growing demand of space for developing various facilities, the best possible way to economize the underground space is being looked after. The purpose of this paper is to study the tunnel behaviour addressing both issues of space and impact loading, i.e. twin circular tunnels running parallel to each other are analyzed under impact loading. Synthetic rock material is prepared in the laboratory and its engineering properties are determined. These properties are used to develop FEM model of the twin tunnel using ABAQUS to study stress and displacements induced in the rock model due to incidence of impact load. The point of load application has a major effect on the deformations in the tunnels. This effect is studied by considering two cases of point of load application on the top surface: (i) at the midpoint between the tunnels, and (ii) at the centre of one of the tunnels. Extent of damage suffered by the tunnels due to combined effect of rock strength, magnitude and application of impact load and overburden depth is quantified.