Standortgefährdung infolge seismisch induzierter Bodenverflüssigung und Nachweise in DIN EN 1998-5

Seismic hazard assessment of liquefaction potential following DIN EN 1998-5

The subsoil liquefaction stands for a group of phenomena which might cause a global building damage due to the induced drift and settlement processes. In general, these effects occur if a sedimentary soft soil site is shaken by strong cyclic loading. Examples from recent earthquakes demonstrate that liquefaction can contribute to whole damage situation, essentially; it might be concluded that the presence of codes alone is not sufficient to avoid these form of hazard if the planning is not adequately evaluated the critical liquefaction potential of the site.
Observed failure cases are indicating that the existing tool and models are not appropriate to derive realistic prognosis for the complex nonlinear response, i. e. engineering approaches have to be based on experience and the observed effects.
The paper starts with an overview of the different liquefaction describing hazard or failure types as well as the recommended methods of instrumental site investigation and derived compliance criteria.
The studies are concentrated on Eurocode 8, part 5 (DIN EN 1998-5:2010-12) and the implemented simplified decision criteria as well is the adopted original database. The background information is revaluated from the basic studies. Reference curves and magnitude scaling Factors (MSF) from different studies are compared. They enable the decision concerning a critical liquefaction potential.
For a simple example site and as a reconstruction of observed failure effects during the April, 13, 1992 Roermond-Earthquake (as the strongest event in the Lower Rhine Embayment over last six decades) it can be shown that the recommended evaluation criteria will lead to different results in dependence on the applied reference curves. With respect to the rather limited database, further studies are required to come-up with realistic site liquefaction evaluation approaches.