Earthquake analysis of quay walls

Abstract

In this thesis the impact of an earthquake on quay walls located at the Euromax terminal of the Port of Rotterdam is analyzed. A quay wall is a soil retaining structure where ships can moore and transfer goods. Seismic behaviour of two different types of quay walls are investigated and compared by performing a seismic analysis on the Euromax terminal. The first quay wall is the existing quay wall of the Euromax terminal which is a diaphragm quay wall with relieving structure and the second quay wall is a caisson quay wall. The seismic analysis is based on three steps which will include assessment of the regional seismicity, the geologic hazards and soil-structure interaction analysis. The first step is to define the earthquake motion and its magnitude for the Euromax terminal. This is done by making a seismic hazard analysis which is based on geologic, tectonic and historical seismicity data available for the Netherlands. The probability of occurrence of a high earthquake magnitude at the Euromax terminal is very low due to the fact that no major faults are located near the terminal. The second step is to define the dynamic soil response of the Euromax terminal. This is accomplished by making a liquefaction analysis to determine the liquefaction resistance of the near surface soils and the associated potential for ground failure. Loose soils are much more susceptible to liquefaction than dense soils. The soil deposit at the eastern side of the terminal consists of several layers of loose sand which made this the most sensitive section to liquefaction. Liquefaction at this location occurs at earthquake magnitude of ML = 6,2 which corresponds with a horizontal peak ground acceleration of aH = 3 m/s2 and a return period of 751000 years. The final step is to make a seismic analysis of the quay wall structure including seismic forces acting on the two different quay walls. A literature study shows that once an earthquake hits the Euromax terminal causing the ground to shake may result in three major disadvantageous consequences for a quay wall structure. First the driving forces acting on the quay wall will increase. Secondly, shear resistance may decrease due to excess pore water generation resulting in softening of the soil and resonance may develop when the earthquake frequency reaches the fundamental frequency of the structure. The three consequences may result in strength, stability and displacement failure of a quay wall structure. Over all it can be concluded that the probability of occurrence of high magnitude earthquakes are very low. When an earthquake does strike the Euromax terminal the diaphragm quay walls and a caisson quay walls fail in a different way. It appeared that the critical failure mechanism of the diaphragm quay wall is caused by the insufficient bending capacity of the diaphragm wall resulting in breaking of the diaphragm wall. For the caisson quay wall the critical situation relates to large deformations of the landside crane track causing the cranes not to function properly. Nevertheless, both failure mechanisms occur at the same order of earthquake magnitude ML ? 5,1 which corresponds to a return period of approximate 2500 years. This indicates that both quay walls have the same order of resistance against earthquake. However, the consequences of the diaphragm quay wall failure and probably also for the combined walls will be much higher compared to that of the caisson. For this reason, the caisson quay wall is a better solution against earthquakes compared to the diaphragm wall.