ABSTRACT
Construction of open excavation pits and tunnels below groundwater level in urban areas are continuous geotechnical challenges. Reducing the water ingress to excavations is vital, to limit drawdown of the groundwater head at bedrock level and consequent consolidation settlements in soft clays deposits, which potentially can cause damage to nearby buildings and infrastructure. In connection with the development of the E18 highway near the city of Oslo in Norway, a hydrogeological barrier consisting of sheet pile walls, rock mass pre-grouting and jet column grouting have been designed and executed for a deep excavation in soil and rock. This paper presents the design of the barrier and control of pre-grouting execution which was required to optimize the barrier construction with respect to local ground conditions.
