Rising world trade and the following consolidation of material flows cause a growing need for bigger bulk carriers. Therefore, the quay walls of the harbours need to be adjusted to realize the depth of the channels. Combined sheet pile walls are used to build quay walls. They consist out of up to 45 m long H-shaped beams and Z-shaped intermediate piles. As a result of the loads, which cause normal forces and bending moments, the stability of the slender profiles is endangered, whereby the deflection of the profile head and the embedding in the soil plays an important role. With the introduction of the standards of DIN EN 1993-5:2010-12 [1] in connection with DIN EN 1993-1-1:2010-12 [2] the proofing of combined walls needs to be done under combination of the resistance against flexural buckling and lateral-torsional buckling. For that reason the rotational resistance of the soil must be considered in order to ensure an economical design. The rotational bedding in cohesive soil is different from that in noncohesive soil and was investigated by laboratory tests as well as by numerical simulations. The results of a FOSTA / aif project with the goal of optimizing the stability procedure of combined walls are be presented.
