Integration of New Eco-Friendly Armour Units into Coastal Structures

Abstract

Growing demands for resilient and sustainable shoreline protection have led to the development of a new generation of armour systems that combine hydraulic efficiency with ecological performance. This thesis addresses this need by providing an empirical-based framework for the Coastalock armour unit, an eco-engineered alternative to traditional single-layer armour units. Through large-scale experiments, numerical modelling, and design guidelines, the study defines hydraulic performance and bio-enhancing design parameters that facilitate reliable, environmentally enhanced coastal defence solutions. The large-scale experiments examined the hydraulic performance of Coastalock armour units on low-crested and emergent rubble mound breakwaters under irregular wave conditions, quantifying wave transmission, overtopping, and breakwater stability. Numerical modelling was conducted using the IH2VOF CFD tool to reproduce some of the experimental conditions and investigate detailed hydrodynamic processes for the tested configurations. Sensitivity analyses of grid resolution, boundary conditions, and varying wave and structural configurations assisted the model’s accuracy and guided optimal parameter selection for Coastalock units in future simulations. The model simulated wave–structure interaction by providing free-surface elevations, wave transmission coefficients, and overtopping rates observed in laboratory tests, demonstrating its capability to capture complex wave–structure interactions. The final stage of the research consolidated 417 test runs from four multi-institutional experimental testing campaigns to develop the first comprehensive design recommendations for the Coastalock armour unit. Statistical and deterministic analyses were performed to quantify the effects of Coastalock-specific design parameters on armour stability. Armour unit spacing and underlayer size ratio emerged as the critical parameters for hydraulic stability. Design stability constants of Ns ≈ 2.8 and KD ≈ 15, determined for a 1V:1.5H slope, demonstrating that Coastalock performs comparably to well-established single-layer armour units. The design framework integrates biological performance by correlating ecological outcomes from ECOncrete’s monitoring of Coastalock installations with structural configuration variables, including unit orientation and spacing. Integrating these outcomes into the design process allows engineers to consider ecological functionality as a design objective alongside traditional hydraulic design. The research, therefore, establishes a data-driven foundation for designing dual-purpose coastal structures that satisfy both engineering and environmental targets, offering a practical pathway toward sustainable and resilient coastal infrastructure.