INFLUENCE OF ARMOR UNIT PLACEMENT ON ARMOR POROSITY AND HYDRAULIC STABILITY

Josep R. Medina, M. Esther Gómez-Martín, Antonio Corredor

Abstract


The handling procedure and placement grid of concrete armor units (CAUs) are the key construction factors of armor layers. This paper analyzes conventional cube and Cubipod CAUs which are handled by pressure clamps and placed randomly. Two methodologies for small-scale blind construction of armor layers in laboratories are compared using a Cartesian system and crawler cranes. Model construction by hand in laboratories is usually done in excellent conditions contrary to actual construction at prototype scale which is blind underwater and is influenced by wind, waves and equipment constraints. For randomly placed CAUs, the layer coefficient is an unnecessary and subjective concept which should be disregarded to prevent misunderstandings when considering armor porosity. For a given CAU, the placement grid affects armor porosity which is directly related to armor hydraulic stability. Crawler cranes can only place CAUs in a narrow armor porosity band; therefore, porosity of small scale armor models constructed by hand must be selected within that viable porosity band to avoid uncontrolled model effects. Armor layers of conventional cubes placed randomly by hand are not realistic if porosity is p%<35% and have more hydraulic stability than the higher porosity armors which can actually be constructed with crawler cranes.

Keywords


rubble-mound breakwater; armor porosity; armor unit placement; Cubipod armor unit; cube armor unit; placement test; placement grid; crawler crane

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