Armour Blocks Research Articles

Physics informed machine learning based applications for the stability analysis of breakwaters

ABSTRACT One of the key aspects in designing and stability analysis of breakwater structures is predicting the stability number of their armour blocks. This study presents a novel approach called physics informed deep neural network, for the stability analysis of rubble-mound breakwaters. The present work makes two main contributions. Firstly, it proposes a method for creating hybrid combinations of theoretical models or physical models and deep neural network architectures, leveraging the advantages of both physics and data. This framework incorporates the output of physics-based simulations and observational features into a hybrid modelling setup. Secondly, the framework employs physics-based loss functions in the learning objective of these deep neural networks, which not only demonstrate lower errors on the training set but also adhere to the established physical relations. The proposed study may have the potential to address the existing limitations in this field and provide better accuracy in estimating the stability number.

Application of SPH Method to Simulation of the Deformation of Tsunami and Storm Boulders, and Armour Blocks

Application of SPH Method to Simulation of the Deformation of Tsunami and Storm Boulders, and Armour Blocks

Experimental study on time-varying failure evolution of armour blocks on sloping breakwaters

The time-varying failure evolution is significant for revealing failure mechanism of breakwaters. Physical experiments were conducted to investigate the time-varying failure evolution of armour blocks on sloping breakwaters, and the effects of the block placement density, wave height, wave period, wave impact time, and block type on the stability of armour blocks are discussed. The results showed that the time-varying failure evolution of armour blocks was not uniform with an increase in wave impact time. However, a large-scale rapid damage maybe occur in a certain period of time, which was enhanced with a decrease in block placement density and an increase in the incident wave height and wave period. With the same block placement density, the instability rate with uniform reduction per row was generally lower than that with centralised and decentralised reduction. Furthermore, when the design wave height was increased by less than 30%, the protection effect of the accropode was superior to that of the dolosse. However, the protection effect of the two was opposite when the design wave height was increased by over 30%. The results reveal the time-varying failure law of breakwaters, which will contribute to further study the risk assessment and early warning of breakwater failure.

Ceramic Armour for Armoured Vehicles Against Large-Calibre Bullets

Modelling the armour-piercing bullets B-32 calibre 12.7 mm penetration into the double-layer ceramic-composite armour has been performed for the armour blocks of two designs. The first one is a layer of ceramic square tiles supported by the glass or polyamide fabric. Modelling and subsequent ballistic tests have shown that the conical Hertz crack localized in the ceramic tile is formed. The tile is destroyed from the spread of radial cracks, and the entire armour unit becomes unable to sustain the repeated hit of the bullet. In the second case, the armour block consists of the discrete epoxy-filled cylindrical ceramic elements with spherical ends. The advantage of this "discrete" armour is localization of the damage zone and thus an ability to sustain the multiple bullet hits. The ballistic tests of the compared armour units have shown that both provide effective additional protection of light-armoured vehicles against the normal impact of the calibre 12.7 mm bullet.

Numerical investigation of the stability of armour units in low-crested breakwaters using combined SPH–Polyhedral DEM method

Low-crested breakwaters have become more attractive because they do not hinder the beautiful coastal landscape and are more environmentally friendly comparing to traditional breakwaters. The available formulae for design of these types of structures mainly focus on wave transmission, reflection and dissipation aspects. However, stability of the armour blocks are not directly taken into account in the design process. In this study the Lagrangian meshfree method of SPH along with a discrete element method i.e. Polyhedral DEM are used to simulate the interaction between the sea water waves with different characteristics and low-crested breakwaters constructed using cubic armour blocks. SPH is used for computing the wave forces and moments applied to each armour unit subjected to sea wave action under various conditions. The fluid velocity and pressure time series near the armour units are calculated and based on those, the applied forces and moments are determined. Stability analysis for armour units are conducted by employing DEM which can determine whether the armour units can be displaced by wave action, a phenomenon that causes failure of the whole breakwater over time. Based on the results of a large number of numerical simulations, a practical non-dimensional relationship is proposed for calculating the required dimension of the cubic armour units that can be used for preliminary design of low-crested breakwaters. The newly proposed relationship can fill the gap that currently exists in the literature regarding using cubic armour units for this type of marine structures.

An integrated SPH-polyhedral DEM algorithm to investigate hydraulic stability of rock and concrete blocks: Application to cubic armours in breakwaters

In this paper, a combination of the Lagrangian meshfree method of SPH and Polyhedral DEM is presented to simulate the interaction between the free surface of water and solid objects possessing sharp edges and flat surfaces, such as armour units of breakwaters. Both SPH and DEM schemes are validated successfully against experimental data. The numerical scheme is utilized to inspect the stability of concrete cubic armours in rubble-mound breakwaters through systematic analyses with various geometrical parameters and environmental conditions. The numerical results regarding the required dimensions of the cubic blocks for providing stability of the armour units under the wave attack are compared with the existing empirical formulae. It is shown that armour units located at the still water level are more exposed to damage due to wave attack. The proposed numerical technique proved to be accurate and therefore it can be used for designing the armour blocks of the sloping breakwaters and also for inspecting the possible level of damage to the system of armour units.

Numerical Modelling of Wave Run-up with Interaction Between Wave and Dolosse Breakwater

ABSTRACT Liang, B.; Ma, S.; Pan, X., and Lee, D.Y., 2017. Numerical modelling of wave run-up with interaction between wave and dolosse breakwater. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 294–298. Coconut Creek (Florida), ISSN 0749-0208. Breakwaters play an important role in coastal disaster prevention and mitigation. In this study, a numerical modelling of the wave run-up on dolosse breakwater is set up by integrating the CAD software SolidWorks and the CFD software FLOW-3D. The breakwater is built with the lower porous media and the upper armour blocks (dolosse), which is different from the current approach that treats the whole rubble mound breakwater as porous media. The numerical wave flume has been validated by analytic solutions of Stokes wave theory. The computational results are in good agreement with the empirical formulas under different wave conditions. The model...

Erodibility assessment of Armour Blocks causing Damage to Breakwaters

ABSTRACT Yoo, D.H. and Lim, H.S., 2016. Erodibility assessement of Armour Blocks causing Damage to Breakwaters. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1272 - 1276. Coconut Creek (Florida), ISSN 0749-0208. Empirical equations such as the Hudson, van der Meer-de Jong, and Yoo equations were compared for estimating the armour block weight of the breakwater by introducing an incremental factor based on the Hudson equation. The equation for deriving the critical wave height of erosion at the structure toe was developed for additional consideration of the armour-blocked breakwater stability. All empirical equations were reformed according to the Hudson equation, which has been widely employed in engineering design, and an incremental factor was added to each reformed empirical equation. This factor reflects the characteristics of each empirical...

Simulating three dimensional wave run-up over breakwaters covered by antifer units

The paper presents the numerical analysis of wave run-up over rubble-mound breakwaters covered by antifer units using a technique integrating Computer-Aided Design (CAD) and Computational Fluid Dynamics (CFD) software. Direct application of Navier-Stokes equations within armour blocks, is used to provide a more reliable approach to simulate wave run-up over breakwaters. A well-tested Reynolds-averaged Navier-Stokes (RANS) Volume of Fluid (VOF) code (Flow-3D) was adopted for CFD computations. The computed results were compared with experimental data to check the validity of the model. Numerical results showed that the direct three dimensional (3D) simulation method can deliver accurate results for wave run-up over rubble mound breakwaters. The results showed that the placement pattern of antifer units had a great impact on values of wave run-up so that by changing the placement pattern from regular to double pyramid can reduce the wave run-up by approximately 30%. Analysis was done to investigate the influences of surface roughness, energy dissipation in the pores of the armour layer and reduced wave run-up due to inflow into the armour and stone layer.

Simulation of Flow within Armour Blocks in a Breakwater

Dentale, F.; Donnarumma, G., and Pugliese Carratelli, E., 2014. Simulation of flow within armour blocks in a breakwater. This paper provides some results of a new procedure to analyze the hydrodynamic aspects of the interactions between maritime emerged breakwaters and waves by integrating computer-aided design and computational fluid dynamicsCFD. The structure is modeled in the numerical domain by overlapping individual three-dimensional elements (Xbloc®), very much like the real world or physical laboratory testing. A computational grid is fitted fine enough to provide enough computational nodes within the flow paths. Flow of the fluid within the interstices among concrete blocks is evaluated by integrating the Reynolds averaged Navier–Stokes equations inside the voids instead of using the “porous media” approach. The aim is to investigate the reliability of this approach as a design tool. Therefore, for the results' validation, the numerical run-up and reflection effects on virtual breakwater (armour in Xbloc, toe protection, and filter layer in stones) were compared with some empirical formulas and some similar laboratory tests. Obviously, the presented model can be supportive to the physical modeling, comparing multiple preliminary design solutions, and providing guidance on the optimal choice to be subjected to subsequent laboratory tests. Here are presented the results of a first simple validation procedure. The validation shows that, at present, this innovative approach can be used in the breakwater design phase for comparison between several design solutions with a significant minor cost.

防波堤の腹付け被覆ブロックの安定性

防波堤の腹付け被覆ブロックの安定性

Numerical modelling of armour block sea breakwater with smoothed particle hydrodynamics

The application of smoothed particle hydrodynamics (SPH) to model the three-dimensional fluid–structure interaction for waves approaching a rubble mound breakwater is presented. The main aim is to model the armoured structure and to validate its response under the action of periodic waves. The complex geometry is represented by grooved cubic blocks such that the surrounding gaps within the breakwater seaward layer require a large number of particles to obtain a sufficiently detailed description of the flow. Using novel computer architecture solutions such as graphics processing units (GPUs), the fluid-structure interaction is modelled with SPH particles between armour blocks that are representative of the real structure. The open-source GPU code, DualSPHysics, enables the simulation of millions of particles required for the accurate simulation of the run-up on an armoured structure. SPH has been proven to be a suitable method for practical applications in coastal engineering. In the present work the run-up heights are computed and compared with empirical solutions and experimental data. Reasonable agreement is obtained for the run-up due to regular waves over a range of surf similarity numbers from 3.0 to 5.5.

RUBBLE MOUND BREAKWATER OVERTOPPING: ESTIMATION OF THE RELIABILITY OF A 3D NUMERICAL SIMULATION

Until recently, physical models were the only way to investigate into the details of breakwaters behavior under wave attack. From the numerical point of view, the complexity of the fluid dynamic processes involved has so far hindered the direct application of Navier-Stokes equations within the armour blocks, due to the complex geometry and the presence of strongly non stationary flows, free boundaries and turbulence. In the present work the most recent CFD technology is used to provide a new and more reliable approach to the design analysis of breakwaters, especially in connection with run-up and overtopping. The solid structure is simulated within the numerical domain by overlapping individual virtual elements to form the empty spaces delimited by the blocks. Thus, by defining a fine computational grid, an adequate number of nodes is located within the interstices and a complete solution of the full hydrodynamic equations is carried out. In the work presented here the numerical simulations are carried out by integrating the three-dimensional Reynolds Average Navier-Stokes Equations coupled with the RNG turbulence model and a Volume of Fluid Method used to handle the dynamics of the free surface. The aim of the present work is to investigate the reliability of this approach as a design tool. Two different breakwaters are considered, both located in Southern Sicily: one a typical quarry stone breakwater, another a more complex design incorporating a spill basin and an armoured layer made up by Coreloc® blocks.

A Preventive Maintenance Problem of Armour Blocks with an In-Service Period

A Preventive Maintenance Problem of Armour Blocks with an In-Service Period

Development of Armour Block Removing Equipment (Grab Type)

Recently, enlargement of port facilities towards offshore zones or reconstruction of existing facilities has been requiring the removal or replacement of armour blocks used in breakwaters or quay walls. During the blocks removal, usually a diver slings a wire rope around each block and then crane lifts it. This task may be therefore inefficient and very dangerous for the diver. In this paper, the authors introduce an improved orange peel type grab bucket which makes the removal of armour blocks safe and efficient. The results obtained from tests performed with both a model of this equipment and its prototype are also presented.

"DOUBLE U BLOCK" AND "IBLOCK" - THE ARMOUR BLOCKS OF TWO NEW TYPES

A total of eleven new types of blocks are developed for this project. After performing a series of model tests for them and having a consideration of easy casting, two types of blocks are selected and presented here in this paper. They are named "Double U block" and "I block", respectively. The two have been compared with several existing types which have been widely used in Taiwan. It is shown that the Double U block is an excellent type of block with high stability and low reflection coefficient. The I block has an advantage of easy casting, although it is not outstanding in other characteristics.

THE RELATIONSHIP BETWEEN WAVE LENGTH AND WEIGHT OF ARMOUR BLOCKS

Every coastal engineer realizes that the weight of armour blocks decided by Hudson's formula is safe enough for short steep waves, however, suffering damage from long period swells, even though the incidental wave height is the same. Several corrections have been made and submitted to ICCE as well as in other occasion. The authors try to explain analytically the influence of wave length on the design weight of armour blocks and justify by much of experiments in order to offer new formula and graphs for practical application.

Controls of size and shape of natural armourstone

Summary The sizes and shapes of armourstone blocks for rubble breakwaters are primarily determined at the quarryface, and later modification then occurs in situ in the breakwater environment. The principal controlling parameters in the quarry include: rock type, rock joint frequency and orientation, size and type of blasting charge and the orientation of the blast's fractionating power. The majority of existing data on this subject has been obtained from detailed studies of quarries principally concerned with aggregate production in Britain, but extensive studies have recently been carried out on a variety of rock types in quarries that are currently producing primary armourstone for breakwater structures in the United Arab Emirates and the United Kingdom. These studies combine to permit the relative importance of the various controlling factors which operate during quarrying, transport, placement and subsequently in service to be evaluated and are reported here. The quarry-orientated study is supplemented by detailed studies of block modification and deterioration in the several different environmental zones of breakwater structures. The principal factors controlling this shape modification are micro-fracture pattern, mineralogy and fabric, grade of weathering of the original rock, grain interlock and intergranular cement type. Changes in shape will modify the stability factors of in situ armour blocks and alter void ratios and slope angles, which together are perhaps the most important factors controlling the dissipation of wave energies on rubble mound breakwaters. The importance of long-term abrasion effects should not be underestimated; to monitor these effects, damage assessments have been used to relate the shape modification to slope.

ON THE EFFECT OF ARMOUR BLOCK FACING ON THE QUANTITY OF WATTE OVERTOPPING

Japan, surrounded by sea, is constantly threatened by storm surges and beach erosions, for which protection works are being vigorously undertaken. As a measure for protection, facings of various armour blocks have come to be used for the seawalls and embankments. This is a skillful utilization of characteristic functions of armour blocks to dissipate and absorb wave energy effectively. However, systematic experiments and studies on this subject have been conducted only in very few cases. This paper treats of the effect of the facing of armour blocks on wave overtopping by comparison of the quantity of waves topped over the vertical seawal] with facing and that of without facing. Furthermore, this paper attempts to compare the results of the field observation and the experiments on the quantity of wave overtopping. Based on these data, the authors present a design criterion of the crown height of seawall with armour block facing.

THE ECONOMIC VALUE OP A NEW BREAKWATER ARMOUR UNIT 'DOLOS'

The Dolos, a new type of armour unit which closely resembles a normal ship's anchor, was developed and tried out under field conditions on the main breakwater of East London harbour. Since these full-scale Dolosse proved very successful, tests were made in a wave channel to compare the stability of Dolosse with other known types of armour blocks. The test results showed that the Dolos is outstandingly stable, and since manufacture and random placing of Dolosse offers no particular difficulties it is concluded that in many cases the use of Dolosse in armour layers may lead to more economical solutions for rubble mound breakwater and shore protection works.