EPB tunnelling in hard rock conditions and transition zones
Various TBM projects around the world are digging in predominantly hard rock conditions – facing difficulties when weathered rock or even soft ground zones penetrate the tunnel profile. To tunnel through these „weak zones”, like in Oslo centre, is a risk to the environment and causes high costs for treating the soil or additional measures if not handled properly. So far, only one TBM project has used an Earth Pressure Balance (EPB) TBM to ensure a safe face pressure in the transition zones from hard rock to soft ground and vice versa. The use of special admixtures and other additional measures enabled safe and controlled tunnelling through these difficult zones, maintaining perpetual earth pressure and thus avoiding settlements.