The effect of pore water pressure on structural performance of CERN concrete-lined tunnel

Abstract

The European Centre for Nuclear research (CERN) operates the most powerful circular particle accelerator in a large-scale underground tunnel network of over 70 km. Even over four decades after construction, substantial cracks, water infiltration and structural deformation have still been developing with time based upon field observation and measurements. In particular, recent blockage of tunnel drainage system alters the hydraulic boundary condition and results in the development of pore-water pressure around the tunnel circumference, which in turn accelerates the tunnel deterioration and leakage. In this study, the development of pore water pressure and its effect on tunnel lining are investigated using 3D hydro-mechanical coupled finite element modelling. In the numerical simulation, particular emphasis is placed on the change of lining permeability and the drainage system with time. Results show that the pore water pressure on tunnel lining is significantly affected by the change of hydraulic condition, and consequently exacerbates the tunnel structural performance in the long term.