Armor Units Research Articles

Development of an articulated concrete armor unit against high waves and uneven slopes

In this study, a new articulated concrete armor unit named Couple-Lock, which can be enlarged in size to cope with high waves, is easy to secure binding force between units, and can be applied to various field conditions, was developed. The Couple-Lock consists of two symmetrical blocks. One symmetrical block has four legs installed in all directions on one end of the body. Since two left-right symmetrical blocks are connected with a wire rope and behave, a pair of blocks can be treated as a single block and enabling large size to cope with high waves. Also, the Couple-Lock responds flexibly to topographical changes. In order to examine the hydraulic performance and stability of the developed armor unit, a hydraulic model experiment was conducted. As a result, the average reflection coefficients of ordinary wave and storm wave conditions were calculated as 0.433 and 0.533, respectively. The average transmission coefficients under ordinary wave and storm wave conditions were calculated as 0.046 and 0.147, respectively. Among the 62 storm wave conditions, wave overtopping occurred in 50 storm waves. The stability factor of the Couple-Lock was calculated to be about 18, which is twice of the stability factor of the tetrapod.

Evaluation of the Factors Affecting the Hydraulic Stability of Tblock™ Coastal Protection Armour Unit

Evaluation of the Factors Affecting the Hydraulic Stability of Tblock™ Coastal Protection Armour Unit

Hydrodynamic Assessment of A New Nature-Based Armour Unit on Rubble Mound Breakwater for Coastal Protection

Hydrodynamic Assessment of A New Nature-Based Armour Unit on Rubble Mound Breakwater for Coastal Protection

Storm damage assessment of a port in the Southwestern Black Sea

This paper presents a comprehensive investigation of the storm damage at a commercial port located in the Southwestern Black Sea Region that occurred on January 18–19, 2018. One week after the event, a field survey was conducted at the port focusing on significantly damaged mound breakwaters and protection structures that failed at several sections. A numerical wave modeling study is carried out to estimate the wave characteristics at deep sea, nearshore, and inside the port to assess the observed damage during the field survey. Widely used numerical models WAVEWATCH III, SWAN, and SWASH are utilized using nested computational domains and calibrated based on satellite measurements. As a result, the significant wave height of the storm is estimated as 7.8 m with a peak period of 12.4 s near the port area, approaching mainly from the northwest direction. The damage mechanisms of the mound structures are discussed based on the field observations and the wave modeling studies. The insufficient seaside armor unit sizes and the orientation of the breakwaters are found to be the main reasons for the damage.

2D And 3D Physical Model Testing For The Rehabilitation On The Frioul Port Breakwater (France)

A white archipelago anchored in the Mediterranean Sea 2 km off the coast of Marseille (France), the port of Frioul is made up of the Pomègues islands (to the south) and Ratonneau (to the north). It is protected on the west side by the Berry breakwater (renovated in 1984), and on the east side by the Condorcet breakwater (figure 1.a). The port was built in the early 1820s (Berry breakwater) to take care of the quarantine of ships coming from areas infected by yellow fever, then developed in the 1850s (Condorcet breakwater in the East) to make it a military port. The current findings highlight that the eastern breakwater is seriously damaged and must be rehabilitated (figure 1.b). Accordingly, the rehabilitation solution, which consists to replace the actual rock armour unit, was physically modelled, and tested for its hydraulic stability and the overtopping performance as well as the forces and pressures acting on the crown wall. The process includes recreation of breakwater cross sections in a 2D wave flume at a scale of 1:35 (figure 2.a), and a optimized breakwater configuration proposed in a 3D wave basin at a scale of 1:50 (figure 2.b). These two campaigns made it possible to compare and optimize the design, first with the state of the art (Van Gent, M., et van der Werf, I., 2019) (Mares-Nasarre and van Gent, M., 2020), then with the observations and measurements collected from the modeling.

The application of flexible and porous concrete structures in training works and scour protection

Concrete armour units such as Xbloc have been applied as armour layer for breakwaters and bank protections for years. These smartly shaped blocks were invented to offer efficient protection at more exposed locations by applying blocks that work together with neighbouring units to withstand high wave loads (Interlocking). Also material use was lowered since steeper slopes could be realized compared to conventional rock structures. Xstream and Xstone can be applied in a large range of applications that are traditionally built with loose rock, pitched rock or smooth block revetments such as: - Bed protection (e.g. offshore wind foundations) - River training works - Detached breakwaters - Quay wall protection in harbours - Revetment structures This abstract elaborates on why flexible and porous structures made of these small-scale [0.2 – 0.6m] concrete armour units are an interesting, low CO2 and eco-friendly alternative for bed protections and river training works.

LOW-CRESTED AND EMERGENT BREAKWATERS WITH ECO-FRIENDLY ARMOUR UNITS

Artificial coastal defense systems (such as concrete armour units) frequently host less diverse aquatic populations than natural environments and feature higher concentrations of invasive species (Dafforn et al., 2009). Therefore, coastal structures need to be designed or refitted to achieve sustainable goals through the application of ecological engineering solutions applied to coastal defence structures and for the ecosystem, marine habitat, and biodiversity improvement. Ecological engineering, which integrates ecosystems with engineering principles to construct coastal structures that benefit both humans and the ecosystem, is growing as a means of reducing the adverse ecological impacts of coastal infrastructure (Mitsch & Jorgensen, 2003). Thus, creating new eco-friendly breakwater design guidelines is critical and will benefit from the multidisciplinary involvement of marine biologists and ecologists. The purpose of this experimental modelling study was to provide data on the hydraulic performance and stability of low-crested and emergent rubble mound breakwaters (RMBW) constructed using ecologically friendly armour units under various wave conditions. The University of Ottawa, the National Research Council of Canada (NRC), and ECOncrete collaborated to develop and conduct the physical testing program. Several breakwater models were tested to evaluate their performance, as the idea of an eco-friendly breakwater is still a new area of research. Thus, this experimental program is essential to promote environmentally-friendly armour units in the design of new coastal structures (such as Baker et al., 2018), as well as ecological retrofitting of existing coastal structures. The physical tests were conducted between June 2023 and August 2023 in the Large Wave Flume of NRC’s Ocean, Coastal, and River Engineering Research Center in Ottawa, Canada. ECOncrete's Coastalock armour units were tested in various configurations at a 1/15 scale using two-dimensional low-crested and emergent RMBW models. The hydraulic performance and failure mechanisms of these environmentally-friendly breakwater models were tested under severe wave conditions.

Investigation Of Coastalock Performance On A Breakwater With Porous Core

Hard stabilization methods have traditionally been employed to mitigate coastal erosion. Concrete armour is widely used due to its high level of dependence, robustness, ease of production and cost effectiveness (Cooke et al., 2020; Pikey and Cooper, 2012). It is inevitable that coastline ‘armouring’ will continue to rise because of the growing human population and urbanization, desire for and value of coastal property, opposed to predicted climate change (Chapman and Underwood, 2011). The environmental impact of such 'armouring' on coastal systems can be detrimental, resulting in a degradation or destruction of habitats and the loss of ecologically trivial species (Gittman et al., 2015). The CoastalockTM, a single-layer armour unit, aims to blend coastal protection with marine habitat creation. This armour unit is designed to mimic inter- and sub-tidal habitats, with chemical composition of substrate and micro and macro features that provide niches for various species. The key feature of CoastalockTM is the cavity that is integrated into the design, that caters to diverse marine life needs depending on its orientation (ECOncrete Tech Ltd., 2019). CoastalockTM's hydraulic performance is under research. Preliminary tests conducted in the Hydraulic Engineering Laboratory (HEL) of the Technical University of Delft (TUD) on a 2V:3H impermeable slope in deep water conditions highlighted that with tight placement of the units significant pressure gradients across the top layer led to damage. The introduction of spacings between units for enhanced permeability improved stability significantly (Gutiérrez et al., 2023). A redesign of the unit was proposed incorporating protrusions to enforce the spacings between the blocks (Molenkamp, 2022). This research focuses on evaluating the influence of a porous core on the hydraulic performance of a CoastalockTM armour layer, specifically assessing its stability, overtopping, and reflection on a 2V:3H breakwater slope in deep water conditions—from the toe to just below the crest. A pivotal aspect of this research is the investigation of the impact of protrusions on the hydraulic performance. Furthermore, the study explores the influence of different toe configurations, aiming to comprehend the vulnerability of the armour layer to sliding. Toe scour falls outside the scope of this study.

Stability Of Concrete Armor Unit (Tetrapod) On Rear Side Of The Rubble Mound Structures With Rectangular Super Structure

The coastal structures allow the wave overtopping within a certain quantity. However the extreme wave overtopping could cause the damage of coastal structures. The most of the previous researches for the stability of armor unit were performed about the armor units placed on sea side of coastal structures. A rubble-mound structure is normally composed of a bedding layer and a core of quarry-run stone covered by one or more layers of larger stone and an exterior layer or layers of large quarry stone or concrete armor units. Coastal Engineering Manual (USACE, 2006) suggested the design figures without super structures and showed the ratio of the armor weight for each location of rubble mound structures and it could be known that the same weight ratio was needed to the sea side and harbor side slope of rubble mound structures. In this design figure, the filter rule is applied to the design figures of CEM, that is, the weight ratio for under layer is W/10 for the main armor weight ratio (W) to prevent smaller rocks in the under layer from being pulled through an over layer by wave action

Rocking Of Single Layer Armour Units Measured By Embedded Sensors

Single layer randomly placed armour units are used in many rubble mound breakwaters around the world. For these armour layers, breakage of armour units due to rocking could be a major damage mechanism, but no good methods exist to evaluate and quantify rocking. The aim of the study is to quantify the rocking impact velocities for irregularly placed single layer armour units. This study utilizes embedded Rocking Sensors to obtain the first measurements of rocking impact velocities of single layer armour units. More generally, the paper (Hofland et al. 2023) shows how novel measurement techniques can be used for the investigating the stability of single layer armour layers.

Concrete Armour Unit Breakwater Physical Model Monitoring With 3D Modeling Tools

SEABIM® is a patented scan to BIM process that can generate a reliable and complete 3D model of a rubble-mound breakwater precast protective layer (Xbloc®, Accropode™, Core-loc™ etc.). Using computer vision techniques, the known 3D shape of the Concrete Armour Units (CAU) is detected in a high-resolution point cloud, which allows to obtain the position and orientation of each unit relative to the cloud. By superimposing 3D models produced from different scans at different dates, the movement of each block can then be quantified and represented as a vector. For natural riprap armours, a point cloud segmentation algorithm is applied. Each rock is identified, and then geometric characteristics of the armour can be computed (apparent rock diameters, placement density), and the movement between each scan can be monitored. This tool has been applied to numerous real-scale projects since 2019, both in the monitoring of newly built infrastructures and in the asset management phase (Aberdeen South Harbour, Calais port 2015, Nouvelle Route du Littoral etc...). Breakwater physical models in laboratories, in wave flumes or basins, also require monitoring of the movement of reduced-scale blocks between each wave series. With SEABIM® this movement can be computed with accuracy for each CAU, allowing for a consistent evaluation of the armour layer response to wave loads. The automatic block detection process can be launched on the point cloud from a survey of the initial physical model, obtained either by photogrammetry or LiDAR. Then a new survey is done after each wave series in order to create a sequence of 3D models. Those models can be compared by computing the displacement vectors of the centers of gravity of the units. The vectors can be visualized using color graded arrows within the 3D model. All the information can then be exported to a spreadsheet for further analysis. Using this technique, settlement, rocking and sliding effects can be identified. In this paper we will discuss in detail the adaptation of the survey techniques from real scale to laboratory projects (difference in scanning technique, scale effect on point cloud density etc.). Then we will explain the 3D modeling process and the applications of the 3D models for engineering analysis purposes.

50 Years Of Hanbar Concrete Units In Australia And New-Zealand: Lessons Learned From Physical Modelling Studies And Recently Built Structures

During the last 50 years, numerous breakwaters along the eastern coast of Australia, and more recently in New Zealand, have undergone construction, repairs, or upgrades using Hanbar concrete armour units. These units are distinct to Australasia, and there is limited information about their properties in standard coastal engineering literature. This paper first provides a survey and timeline of all known projects using Hanbars. An overview of the Hanbar concrete unit features and manufacturing method is then provided. The paper presents a summary of results of previous modelling studies of Hanbar applications to specific breakwaters, as well as recent research programs completed at WRL, and provides placement density guidelines as well as recommended damage coefficient (Hudson Kd) for design. The paper concludes with a brief overview of two recent case studies which have successfully capitalized on the economical, robustness and manufacturing simplicity of the Hanbar concrete units. The first case study is on the Opotiki Harbour Development (“OHD”) in New Zealand. The OHD scheme comprises twin 400 m long training wall breakwaters to train a dynamic river mouth. A multi-stage approach to physical modelling was adopted by conducting 2D modelling of key sections of the training wall trunks, quasi-3D modelling of the breakwater head, and full 3D modelling of complete structures. The second case study presents the results of a field trial investigating the potential for high-density geopolymer concrete (GPC) coastal armour units. This resulted in the casting and placing of thirteen 16 t GPC Hanbar units (SG 2.6) on the Port Kembla northern breakwater in NSW. The trial proved the viability of production of geopolymer armour units, and allowed long-term monitoring of the integrity of the concrete in the aggressive marine environment.

Sustainable And Bioengineered Concrete For Armor Units Of Low-Crested Structures

In the last two decades, Eco-engineering has emerged to mitigate and compensate the environmental impacts of man-made structures while integrates benefits to society, being concrete the most widely alternative material used to natural rocks for construction of artificial coastal structures. Over the past three decades, an extensive literature has documented different supplementary cementitious materials (SCMs) to reduce CO2 emissions from Portland cement, with common SCMs used in marine and coastal structures such as fly ashes, ground granulated blast furnace slags, pozzolanas and limestones. However, there is a need to further investigate the suitability of SCMs for the construction of Low-Crested Structures (LCS) to decrease carbon footprint from concrete production and improve the bioreceptivity of concrete armor units during the breakwater lifetime. A literature review conducted in this study shows several advantages of slag cements compared to other SCMs to reduce carbon emissions and enhance biological colonization and durability of concrete submerged in seawater, identifying surface roughness as the most effective factor in design of bioreceptive concrete. This study also highlights the importance of the type and quantity of cement used in concrete mixes to reduce carbon footprint of the manufacture of concrete armor units of LCS and the implementation of long-term monitoring plans to fully understand the functioning of local communities that develop on concrete surfaces of artificial structures, and thus, to improve the integration of environmental parameters in the field of coastal engineering.

Hydraulic Stability Of The New Cubilok™ Armour Unit On A 3:4 Slope

The Cubilok™ (or Cubilok) is a new trademarked armour unit that has been developed in South Africa by PRDW Consulting Ports and Coastal Engineers to accommodate a wide range of breakwater designs. The Cubilok is still in its early stages of development and therefore it has not yet been applied or tested in prototype conditions. 2D Physical model tests were conducted as part of a master’s research project to investigate the stability and behaviour of the Cubilok on a 3V:4H slope. From this study, it was observed that the wave steepness has a significant influence on the performance of the Cubilok, where superior stabilities were recorded during conditions with shorter wave periods. When placed on a 3V:4H slope and with a packing density of ɸ = 0.63, the stability of the Cubilok is comparable to that of other concrete armour units, however, it is susceptible to severe settlement. Some results also showed that the settlement of the armour layer can probably be significantly reduced when the armour layer is constructed on a milder 1V:2H slope or when the packing density is increased to ɸ = 0.65.

Digital Profiler Based On A Low-Cost 3D-Scanner To Evaluate The Hydraulic Performance Of Homogeneous Low-Crested Structures

In order to evaluate the hydraulic performance of breakwaters, mechanical profilers were first used in wave flumes. Vertical bars and rolling wheels have been used to track the breakwater shape. Once surveyed, useful hydraulic parameters were able to be measured (e.g., envelope shape and eroded area). Nevertheless, the methodologies based on mechanical profilers have some limitations: they are intrusive, require specific equipment and are time-consuming. On the other hand, non-intrusive laser scanners can also be used; recent studies proved the feasibility of non-intrusive fast methods of surveying with 3D-scanning, (see Musumeci et al., 2018). These instruments are fast and reliable at capturing the shape of the breakwater in real-time. However, this method did not consider the distortion caused by light refraction. Laser scanners usually require to measure models in dry conditions, which is not efficient in time and resources. Regardless of the drawbacks when using non-intrusive laser scanners as digital profilers, the distortion can be corrected. The data suits for the usage of Neural Networks (NN) that can be trained to correct distortion. This study is focused on Homogeneous Low-Crested Structures (HLCS) which is a new typology of Low-Crested Structures (LCS), made out large quarry stones or concrete armor units that are suitable to reduce shoreline erosion on degraded coastlines and natural environments. HLCS can be classified as reef-type breakwaters and are considered an environmentally-friendly solution that fulfils two purposes: to protect beaches nearby and to enhance coral regeneration and marine colonization, (see Medina et at., 2020). For the correct design of HLCS or conventional LCS, it is required to evaluate both the hydraulic stability and wave transmission (see van der Meer and Daemen, 1994). HLCS are structures without core which may erode under intense wave attack. Breakwater damage and crest freeboard must be estimated depending on incident wave conditions. The breakwater envelope evolves and finds an equilibrium state related to the incident wave conditions in which the crest freeboard and the transmitted wave energy levels may change. The goal of this study is to provide a low-cost non-intrusive methodology based on 3D-scanning to study the hydraulic performance of mound breakwaters, specifically for Cubipod HLCS. This surveying procedure allows to obtain the real-magnitude shape of the envelope of the HLCS, even with a certain water level. The methodology mimics previous surveying techniques and provides relevant hydraulic and structural parameters (crest freeboard, damage, envelope shape, etc.) that can be then used to study the hydraulic performance of breakwaters.

PentaPod: A new type of concrete armor for coastal protection

This paper explores PentaPod, an invention in concrete armor units developed to protect coastal areas from damage caused by waves and currents. Until now, there hasn't been an armor unit intentionally designed to enhance its stability through connections with neighboring units. PentaPod provides a novel perspective, suggesting that the stability of armor units can be significantly improved not only by having substantial weight and effective interlocking but also by securely connecting them to each other. With this in mind, PentaPod concrete armor can be installed in a random or regular manner without the need for fasteners. Alternatively, it can also be installed regularly in layers with fasteners. Compared to conventional concrete armor installations, the overall stability of structures is significantly improved with interconnected PentaPod, either partially or entirely. In this paper, the results of testing the Stability Coefficient (Kd) for two variations of armor, namely PentaCone and PentaOcta, tested in a Wave Tank are also presented. The objective of this testing is to ascertain the stability coefficient for both variations of armor when installed randomly or regularly without any tying involved. The PentaPod arrangement allows for the implementation of both Grey Protection (using concrete armor) and Green Protection (conservation of mangrove areas) simultaneously, showcasing its versatility and integrated approach to coastal protection.

UAV close-range photogrammetry for breakwater damage assessment in a Tyrrhenian coastal site

ABSTRACT Assessing breakwater damage following intense storm events is crucial for preventing failures that can compromise safety and service quality. This study focuses on assessing the impact of a severe storm event that took place in November 2022, resulting in significant damage to the Amalfi breakwater in Campania, Italy. The breakwater damage and repair armor unit volumes have been evaluated with an integrated approach consisting of a combination of Differential Global Navigation Satellite System (DGNSS) surveys and Unmanned Aerial Vehicle (UAV) photogrammetry. The assessment of the added areas gained for the breakwater reconstruction has been performed using the UAV. The final goal was to estimate a damage parameter to give an assessment of the breakwater stability and to find a rapid and cost-effective method to evaluate the necessary rehabilitation works. The method, being relatively rapid, can also be applicable in the immediate aftermath of a storm surge or even as a systematic monitoring of the breakwater conditions. The findings of the study highlight the importance of monitoring coastal structures to prevent failure mechanisms from occurring in response to future, increasingly frequent and intense storm events.

On-Site Stability Assessment of Rubble Mound Breakwaters Using Unmanned Aerial Vehicle-Based Photogrammetry and Random Sample Consensus

Traditional methods for assessing the stability of rubble mound breakwaters (RMBs) often rely on 2.5D data, which may fall short in capturing intricate changes in the armor units, such as tilting and lateral shifts. Achieving a detailed analysis of RMB geometry typically requires fully 3D methods, but these often hinge on expensive acquisition technologies like terrestrial laser scanning (TLS) or airborne light detection and ranging (LiDAR). This article introduces an innovative approach to evaluate the structural stability of RMBs by integrating UAV-based photogrammetry and the random sample consensus (RANSAC) algorithm. The RANSAC algorithm proves to be an efficient and scalable tool for extracting primitives from point clouds (PCs), effectively addressing challenges presented by outliers and data noise in photogrammetric PCs. Photogrammetric PCs of the RMB, generated using Structure-from-Motion and MultiView Stereo (SfM-MVS) from both pre- and post-storm flights, were subjected to the RANSAC algorithm for plane extraction and segmentation. Subsequently, a spatial proximity criterion was employed to match cuboids between the two time periods. The methodology was validated on the detached breakwater of Cabedelo do Douro in Porto, Portugal, with a specific focus on potential rotations or tilting of Antifer cubes within the protective layer. The results, assessing the effects of the Leslie storm in 2018, demonstrate the potential of our approach in identifying and quantifying structural changes in RMBs.

Seismic stability evaluation of rubble mound breakwater: Shake table tests and numerical analyses

Rubble mound (RM) breakwaters are coastal structures constructed to provide tranquil condition around the port areas. After past earthquakes such as the 2004 Indian Ocean earthquake and the 2011 Great East Japan earthquake, it was found that stability of breakwater not only depends on the wave action but seismic motions also play an important role for this. Very limited studies are available for the stability evaluation of RM Breakwater under earthquake motions by conducting physical model tests. To the end, an attempt has been made in the study to evaluate the stability of RM breakwater subjected to earthquake loadings. A series of shaking table tests conducted to evaluate the seismic behaviour of the RM breakwater. A prototype RM breakwater is modelled on two layers of seabed foundation soil. Different amplitudes of sinusoidal seismic motions (foreshocks and main shock) are provided at the base of the model. Later, the breakwater stability was evaluated for real earthquake motions. Various parameters such as settlement, horizontal displacement, acceleration-time histories and excess pore water pressure were measured during the tests. Deformation pattern was also studied by photos and videos captured during the tests. During the mainshock, the crown wall settled by 111 % more comparable to second foreshock; and the structure laterally displaced by more than 200 % comparable with first foreshock. The peak acceleration of input wave amplified while it was travelling from bottom to the crest of breakwater. The excess pore water pressure was maximum beneath the rubble mound, in loose sand and it was five times more during the mainshock compared to first foreshock. Due to loss in bearing capacity of foundation soil, the breakwater collapsed. Also, the effects like rolling down of armor units, densification and slumping of core material, shear deformation of breakwater body were observed during the main shock. Thus, the breakwater failed during the mainshock. Numerical analyses were also executed for both sinusoidal and real earthquake motions to make clear the mechanism of the breakwater behaviour subjected to the earthquake loadings.

Numerical construction tests to assess the feasibility of placement grids for Cubipod Homogeneous Low-Crested Structures

Placement grid design is a key phase when constructing armor layers in mound breakwaters. Homogeneous Low-Crested Structures (HLCS) are low-crested structures designed as artificial reefs for marine colonization, coral reef regeneration and beach protection. The placement grid affects the construction feasibility, hydraulic stability and wave transmission of HLCS. This study presents a numerical methodology to simulate a realistic placement procedure for armor units during the construction of HLCS. This numerical simulator is based on the open-source physics engine Bullet Physics Engine (BPE), which applies Newton's laws of motion to rigid bodies. From an initial theorical placement grid for Cubipod HLCS, a series of numerical realistic unit placement tests are carried out to emulate the placement process at prototype scale; placement velocity and spatial deviation of crawler cranes are given parameters associated with each specific project. Considering the placement velocity and spatial deviation during construction, the quality of each specific placement grid is associated with the measured placement errors and the corresponding initial construction deviation to HLCS. This numerical methodology is valuable to understand the influence and the uncertaintly of the construction procedure of armor layers in mound breakwaters.