Application of XblocPlus on Breakwater Roundheads

Abstract

Twenty years after the introduction of Xbloc, DMC, which is a member of Royal BAM Group, introduced a uniformly placed and interlocking concrete armour unit named XblocPlus, which is suitable for straight to mildly curved breakwater sections, whereas Xbloc is currently applied on roundheads. Therefore, this study investigates modifications to the design or placement configuration of XblocPlus to enable its application on roundheads. Two concepts were tested on a H/V=4/3 roundhead slope for hydraulic stability in DMC’s wave flume. The first configuration consisted of regular XblocPlus combined with XP-Curve, a variant adjusted for narrowing radii, and XP-Base, a legged XblocPlus originally devised for bottom row applications. Tests with normative 0.02 wave steepness yielded a stability number (Hs/ΔDn) ranging from 2.72 to 3.09 due to uplift-related damage. The second configuration, featuring solely XP-Base and XP-Curve, resulted in a hydraulic stability number of 1.96 due to significantly less interlocking. No improvements were observed with respect to hydraulic stability compared to previous research. However, these designs notably reduced rotation-induced failure and enhanced applicability by enabling transition to the trunk and increasing maximum construction height. Additionally, this thesis investigated the validity of testing a three-dimensional structure in a 2D configuration, a method employed to maintain consistency with previous research. Wave heights in front of the structure were measured using parallel gauge sets, allowing the determination of the average disparity. This disparity was found to be within the acceptable margins for the principal test configuration. However, further research is needed to assess test conservativeness. In conclusion, this thesis provides recommendations aimed at improving the applicability and stability of XblocPlus on breakwater roundheads.