The feasibility of removable prefab diaphragm walls

Abstract

A diaphragm wall is a cast in-situ reinforced concrete retaining wall applied in, among others, quay walls. The main advantages of this type of retaining wall are that it can be made in almost every preferred length and that it can resist high structural loads. However, there are several disadvantages: sufficient concrete cover on the reinforcement cannot be guaranteed and the wall has a low sustainability score because it requires a large quantity of building materials, which cannot be reused, and is difficult to remove. This study is done to improve the diaphragm wall design by applying prefabricated concrete elements that are connected by vertical prestressing. Research is done on the element dimensions and detailing, constructability, costs and the carbon footprint of the design option. The concept has been developed as an alternative to the quay wall in a reference project, namely the Euromax Terminal in the Port of Rotterdam. An optimized prefab element configuration is developed. The construction costs of the design option appear to be higher than those of the quay wall in the reference project, but the difference in costs reduces considerably when maintenance and removal costs are included in the analysis. The carbon footprints of the prefabricated wall and of the cast in-situ reference wall are almost equal. However, where there is a certain probability that a quay wall will be removed before it reaches the end of its technical lifetime, a prefabricated wall has a considerably better score than a cast in-situ wall; the prefab wall can be removed and its elements can be reused. The design option then has a better score on both costs and carbon footprint.