Structural Integrity of the Xbloc® breakwater armour units prototype and numerical droptests

Abstract

The structural integrity of the single layer armour unit Xbloc® has been investigated by means of an extensive program comprising dynamic prototype tests and dynamic and static numerical tests. The prototype test series comprised overturning and free fall tests with in total over 150 individual drops. The numerical test series comprised 9 cases. Comparing the prototype and numerical results of Xbloc® with Accropode and Core-Loc® it can be concluded that the Xbloc® has a better structural performance than the Core-Loc® and that Xbloc® has a strength that is comparable to Accropode.

Introduction

The armour unit has a simple, bulky shape and is made of unreinforced concrete. Due to its good interlocking quality it is randomly placed in a single layer, which makes the unit comparable to other single layer armour units such as the Accropode and Core-Loc®. The Xbloc® development comprised review of existing breakwater armour concepts, consulting marine contractors and designers, hydraulic model tests, structural tests, fabrication and placement studies and economic studies.There are several examples of breakwater failure that were attributed by breakage of armour units, e.g. Sines, Arzew, San Cyprian, Tripoli. It was therefore considered essential to investigate the structural integrity of Xbloc®. The dynamic and static structural response of Xbloc® has been investigated by means of prototype and numerical overturning and (quasi-) free fall tests. The purpose of these studies was to optimise the Xbloc® shape by simulating loads that may be generated during manufacturing, handling and placement and loads in-service due to rocking of the units. The paper describes these tests and compares the results with the performance Accropode and Core-loc®.

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Xbloc-structural-integrity-paper-ICCE-2004-Lisbon.pdf