Analytische und numerische Standsicherheitsanalyse der Schlitzwandherstellung in einem weichen marinen Ton in Oslo, Norwegen

The stability of a slurry trench for the construction of a diaphragm wall in soft marine clays is investigated for a site in Oslo, Norway. Firstly, a conventional limit state analysis is performed on the basis of a collapse mechanism proposed by the Norwegian Geotechnical Institute. Since the system does not meet the safety factor required by DIN 4126-100, the excavation of the trench is modelled as a three-dimensional, time-dependent boundary-value problem using the FE-Method. Based on the numerical prediction, measurements on a test slurry wall section are planned, executed and used to verify the numerical results. It is concluded that by combining numerical simulations with monitoring data of the trench excavation, the trench stability may be guaranteed in such ductile soils, even if the safety margins provided by conventional limit state analysis do not meet the requirements of standards. For critical processes such as diaphragm wall construction in sensitive soils, constitutive laws, that model realistically the state-, history- and rate-dependent behaviour of the soft soil, are necessary for stability analyses.