Armor Units Research Articles

DROP TEST OF PROTOTYPE CUBE AND CUBIPOD ARMOR UNITS

The structural strength of concrete armor units (CAUs) is a key factor in the design and construction of armor layers for large mound breakwaters. This paper describes the prototype drop tests carried out to assess the structural strength of conventional cube and Cubipod CAUs. Low intensity overturning tests, high intensity free fall tests and extreme intense free fall tests were conducted to measure the structural integrity under impact loads of the Cubipod CAU
 compared to the conventional cubic block. The casting systems and pressure clamps were specifically designed to manufacture and handle the 15-tonne conventional cube and 16-tonne Cubipod prototypes used for the drop tests.
 Two reinforced-concrete platforms were used for overturning and free fall tests. The 16-tonne Cubipod prototypes withstand drops more than 50% higher than 15-tonne conventional cube prototypes of similar concrete strength. Two extreme free fall tests verified the robustness of Cubipod prototypes in accidental falls during construction. Both Cubipod and conventional cube CAUs have similar stacking and handling procedures as well as manufacturing cycle
 time.

INFLUENCE OF ARMOR UNIT PLACEMENT ON ARMOR POROSITY AND HYDRAULIC STABILITY

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%

STABILITY OF WIDE TOE BERM BREAKWATER WITH VARYING SEABED SLOPE

ABSTRACT Stability of rubblemound breakwater as a whole depends primarily upon the stability of the individual armour units against the wave attack. The manner in which waves interact with the structure is governed not only by the form of the structure, but also by the seabed slope. In order to study the effect of seabed slope on the stability, hydraulic model tests were conducted on a breakwater section in a wave flume with different seabed slopes of 1: 120 and 1: 50. The tests were conducted with breaking and non-breaking waves with two different water levels and two wave periods. Model studies indicated that the stability of armour units decreases with steeper bed slopes. The results are useful for optimising the design of breakwaters. Simulation of seabed slope in the hydraulic model is crucial in finalising the design of rubblemound breakwater section.

CONCRETE CUBES AS ARMOUR UNIT—AN EXPERIMENTAL STUDY FOR BERM BREAKWATER

ABSTRACT Berm breakwater consists of a wide berm at or around the water level and has an armour layer, whose shape changes in response to wave action yielding a stable profile. In the present study the influence of wave height, wave period and berm width on the stability of the breakwater as well as on the wave runup and wave rundown are studied. Experiments were conducted on berm breakwater model of 1:30 scale using concrete cubes as armour units. For the given experimental conditions the stability number was found to vary from 2.21 to 3.63. Further the model in 0.37m water depth was more stable than the one in 0.40 and 0.43m. The runup values were within the range of 0.52 to 1.08. While, the rundown values had the variation from 0.45 to 0.88.

Experimental Study on Stability of Armor Units of Rubble Mound Breakwater against Tsunamis

Stability of armor units of rubble mound breakwater against tsunamis was investigated using armor units of which mass ranges from 14g to 500g. Water depth and velocity were measured on the rubble mound breakwater to discuss the applicability of an experimental formula. The water depth and velocity were also estimated applying 2D numerical simulation for complementing velocities which were not obtained by the experiments. Soliton fissions generated in short period tsunamis were also simulated. The present work has revealed that the mass of armor units is underestimated if the Isbash's formula is used for the rubble mound breakwater.

PHYSICAL MODEL STUDIES ON STABILITY OF CONCRETE ARMOURED BREAKWATERS

ABSTRACT As the breakwater construction started moving in to deeper waters, the wave load on its armour increased resulting in usage of heavier armour units inviting environmental and logistical problems. With the advancement in the technology, concrete armour units have been extensively replacing the natural stones with benefits such as saving in the material and cost while reducing loads on the seabed and helping in construction of environment etc. Tandem breakwater and berm breakwater could be the alternative solutions for the above said case. This paper presents the two cases of physical model studies on the stability of concrete armoured structures, one with tandem breakwater and another on berm breakwater. Both the models are subjected to monochromatic waves with varying characteristics. From the study it was observed that in case of tandem breakwater the crest width of submerged reef and the distance between breakwater and reef are the defining parameter while in case of berm breakwater the height of the berm and its width are the characteristic factors in reducing the breakwater damage.

212 EFFECT OF CONSECUTIVE SUPERSTIMULATORY TREATMENT-INDUCED FOLLICULAR WAVE SYNCHRONIZATION TO OPTIMIZE OOCYTE RETRIEVAL AND EMBRYO PRODUCTION BY OVUM PICKUP AND IN VITRO FERTILIZATION IN COWS

We previously reported that superstimulatory (SS) treatment-induced follicular wave synchronization after ovum pickup (OPU) was effective in enhancing the quality of obtained oocytes and blastocysts derived from in vitro maturation (IVM) and fertilization (IVF; Imai et al. 2010 Reprod. Fertil. Dev. 22, 296). The present study was designed to examine the efficiency of embryo production by 4 sessions of OPU-IVF using a series of the SS treatment-induced follicular wave synchronizations. For the SS protocols, 3 consecutive SS (3CSS) and 2 separated SS (2SSS) were used. In the 3CSS group, the first OPU was performed on random days of the oestrous cycle (Day 0) and all follicles larger than 2 mm in diameter were aspirated. On Day 5, follicles larger than 8 mm in diameter were aspirated and a CIDR (InterAg, Hamilton, New Zealand) was inserted. The cows then received 20 armour units of FSH (Kawasaki-Seiyaku, Kawasaki, Japan) in twice-daily decreasing doses by IM injection from Day 7 to 10. Cloprostenol (PGF; 0.75 mg, Fujita-Pharm, Tokyo, Japan) was administered on the morning of Day 9. The second OPU was performed 48 h after PGF administration on Day 11; the CIDR was removed from the cows just before OPU. After the second OPU, donors were treated consecutively with the SS protocol mentioned above for the third and fourth OPU sessions. In the 2SSS group, donors received 2 sets of the SS treatment mentioned above, with an interval of 11 days between the second and the third OPU session. Four OPU sessions were performed every 11 days on all cows. In this study, 8 Japanese Black cows were divided into the 3CSS and 2SSS groups, and the treatment for each group was reversed after a 65-day interval as crossover trials. After OPU, Grade 1 and 2 oocytes were used for IVM and IVF, and putative zygotes were cultured as described by (Imai et al. 2006 J. Reprod. Dev. 52, S19–S29 suppl.). A part of the zygotes were cultured in a micro-well system. Data were analysed by Student’s t-test and chi-square test. There were differences (P < 0.05) in the mean (±SD) number of follicles, collected oocytes, and cultured oocytes in the 3CSS (35.0 ± 8.6 and 24.4 ± 11.2, respectively) and 2SSS (30.8 ± 10.5 and 20.2 ± 9.0, respectively) groups. There were no differences in mean percentage of blastocyst formation and Grade 1 blastocyst rates between the 3CSS (38.5 and 55.8%, respectively) and 2SSS (34.8 and 54.8%, respectively) groups. However, the mean number of blastocysts produced per OPU session was significantly (P < 0.05) higher in the 3CSS group (8.1 ± 6.3) compared with the 2SSS group (5.8 ± 4.4). These results indicate that a series of 3 consecutive SS treatments had greater efficiency in producing OPU-IVF embryos. This work was supported in part by the Research and Development Program for New Bio-industry Initiatives.

Reliability Analysis of Breakwater Armor Blocks: Case Study in Korea

In Korea, Tetrapods have been widely used to protect rubble mound breakwaters against erosion due to wave action. The deterministic design method has been used based on Hudson or van der Meer formula. In this study, we have performed reliability analyses for thus designed Tetrapod armors of 12 trade harbors and 8 coastal harbors in Korea. It is found that there is a linear relationship between the safety factor and the probability of failure; the larger the safety factor, the smaller the probability of failure. It is also found that the probability of failure during 50-year service lifetime is about 60% for the Tetrapod armors designed by the deterministic design method with the safety factor of 1.0. This finding seems to be natural since the encounter probability that a breakwater will experience storm waves greater than the design wave during its lifetime is 63% if the lifetime is set equal to the design return period. The results of this study could provide a guideline for determining the target probability of failure of Tetrapod armors in the future. A similar approach could be used for armor units other than Tetrapods.

Prototype Drop Tests of Cube and Cubipod Armor Units

In this paper, an experimental methodology is described to assess the structural strength of unreinforced concrete armor units (CAUs). The methodology is applied to measure the structural integrity under impact loads of the new Cubipod CAU compared with the conventional cube CAU. The casting systems and clamps are described for manufacturing and handling the 15-t conventional cubic block and 16-t Cubipod prototypes used for the drop tests. Two separate reinforced concrete platforms were used for overturning and for free-fall tests, respectively. Compared with conventional cubes of similar size and concrete strength, Cubipods withstand drops that are more than 50% higher. Two extreme free-fall tests confirmed the structural robustness of Cubipod armor units. Manufacturing cycle time, as well as storage and handling procedures, are similar for both Cubipods and conventional cubic blocks.

Quantitative microstructural studies of the armor of the marine threespine stickleback (Gasterosteus aculeatus)

In this study, a quantitative investigation of the microstructure and composition of field-caught marine Gasterosteus aculeatus (threespine stickleback) armor is presented, which provides useful phylogenetic information and insights into biomechanical function. Micro-computed tomography (microCT) was employed to create full three-dimensional images of the dorsal spines and basal plate, lateral plates, pelvic girdle and spines and to assess structural and compositional properties such as the spatial distribution of thickness (approximately 100-300 microm), the heterogeneous cross-sectional geometry (centrally thickened), plate-to-plate juncture and overlap (approximately 50% of the plate width), and bone mineral density (634-748 HA/cm(3)). The convolution of plate geometry in conjunction with plate-to-plate overlap allows a relatively constant armor thickness to be maintained throughout the assembly, promoting spatially homogeneous protection and thereby avoiding weakness at the armor unit interconnections. Plate-to-plate junctures act to register and join the plates while permitting compliance in sliding and rotation in selected directions. Mercury porosimetry was used to determine the pore size distribution and volume percent porosity of the lateral plates (20-35 vol.%) and spines (10-15 vol.%). SEM and microCT revealed a porous, sandwich-like cross-section beneficial for bending stiffness and strength at minimum weight. Back-scattered electron microscopy and energy dispersive X-ray analysis were utilized to quantify the weight percent mineral content (58-68%). Scanning electron microscopy and surface profilometry were used to characterize the interior and exterior surface topography (tubercles) of the lateral plates. The results obtained in this study are discussed in the context of mechanical function, performance, fitness, and survivability.

Ovarian stimulation with follicle-stimulating hormone under increasing or minimal concentration of progesterone in dairy cows

The objective of this study was to investigate the effect of the presence or absence of Corpus luteum (CL) on the follicular population during superstimulation in dairy cows (Holstein-Friesian cattle). Animals were divided into two groups as follows: (1) Growing CL group (G1): Cows (n = 7) received a total dose of 28 Armour units (AU) follicle-stimulating hormone (FSH) through the first 4 d (twice daily) after spontaneous ovulation (Day 0). (2) CL Absence group (G2): Cows (n = 10) received prostaglandin F 2α (PGF 2α) at 9 or 10 d after ovulation. After 36 h, all the follicles (larger than 5 mm) were aspirated (Day 0). The FSH treatment started 24 h after aspiration and continued for 4 d. The number of small (3 to <5 mm), medium (5 to <8 mm), and large (≥8 mm) follicles was examined on Days 1, 3, and 5 in all groups. Blood samples were collected daily for 5 d, and progesterone (P 4), estradiol (E 2), insulin-like growth factor-1 (IGF-1), and growth hormone (GH) in plasma were measured by enzyme immunoassays. The results showed that in G1, the P 4 level increased gradually from 0.5 ng/mL at Day 1 to 2 ng/mL at Day 5, whereas in G2, the P 4 level was completely below 0.5 ng/mL. All cows of the G2 group showed an increase of E 2 at Day 3 or Day 4 followed by an increase of IGF-1 within 24 h, while GH increased concomitantly with the E 2 increase in 8 of 10 trials. On the other hand, cows of the G1 group showed neither E 2 nor IGF-1 increase. Moreover, at the end of the treatment, the number of follicles in the G2 group was significantly increased compared with that of the G1 group (22.8 ± 2.0 vs. 11.6 ± 2.0). In conclusion, low P 4 level during FSH treatment enhanced multiple follicular growth and E 2 secretion, which was followed by increase of IGF-1 and GH. Therefore, the absence of the CL may play a critical role in the superovulation response by controlling the number of growing follicles.

Steel and Blood: South Vietnamese Armor and the War for Southeast Asia (review)

Reviewed by: Steel and Blood: South Vietnamese Armor and the War for Southeast Asia Jay Veith Steel and Blood: South Vietnamese Armor and the War for Southeast Asia. By Ha Mai Viet. Annapolis, Md.: Naval Institute Press, 2008. ISBN 978-1-59114-919-4. Maps. Photographs. Appendixes. Notes. Selected bibliography. Index. Pp. xi, 458. $40.00. Of the several thousand tomes published about the Vietnam War, only a few English-language viewpoints written by our Vietnamese allies grace the bookshelves. The South Vietnamese perspective, constrained by cultural and linguistic [End Page 1020] barriers, is unfortunately marginalized in the war's literature for Americans. Due to these barriers, U.S. historians, even if interested in South Vietnamese motivations and actions, are left with little except military adviser reports, obscure embassy cables, or shallow news articles. Thus reduced to bit players, the South Vietnamese have become caricatures; either cowardly incompetents or corrupt warlords, with an occasional brave soul or hard-fighting unit briefly mentioned. A more balanced and deeper picture of America's wartime partner has long been needed. Former armor Colonel Ha Mai Viet has offered precisely that, a penetrating insight into the battlefield contributions of the South Vietnamese tank officers who fought alongside their American friends. His book details the contributions of a small but influential element of the ARVN, its armor/cavalry forces. Unknown to most, by war's end the armor branch had grown considerably from its French roots. In 1975, Brigadier General Tran Quang Khoi's 3rd Armored Cavalry Brigade, the III Corps organic tank unit, was undoubtedly the most powerful brigade-size element in the ARVN. Reflecting a rare combined arms outlook, Khoi built a formidable combat out-fit from previously independent armor, artillery, engineer, and ranger units. His merged brigade was still defending outside of Saigon when the final surrender came. Viet spent ten years traveling the globe, tracking down and interviewing many of his former comrades-in-arms. He portrays the heroic deeds of his fellow soldiers while unflinchingly condemning South Vietnamese leadership errors. Covering two main topics, Combat and Military History, Viet outlines twenty-three separate battles from the ARVN side. The bulk of the Combat section covers the Tet Offensive, Lam Son 719, the Easter Offensive, and the bloody retreat in 1975 from the Central Highlands. He also provides rich details on unknown battles such as the terrible clash at Dambe in Cambodia in 1971. The Military History part provides unique facts on the formation and growth of the ARVN armor/cavalry branch from 1954 to 1975, including unit commanders, weapons, and organizational structure. Brilliantly translated, no future work on Vietnam battles will be complete without reviewing this publication. Colonel Viet has provided a tremendous amount of fresh information, almost all of it oral history. That is the strength and weakness of the book. Like all interviews, the ones in this book only provide the participant's side. For example, the account by Colonel Nguyen Van Dong concerning the Central Highlands retreat, while new and highly informative, perpetuates the myth that Brigadier General Pham Duy Tat, the II Corps Ranger Commander, was responsible for the convoy on Route 7B. Tat, when presented with Dong's remarks, categorically denied the accusations, a point of view absent from Viet's book. This is not to cast fault, as Viet was only interested in the stories of his armor colleagues. Yet without access to That's perspective, the unsuspecting historian would perpetuate the story. Unfortunately, as General Cao Van Vien once told the reviewer, the war remains much like the movie "Rashomon": the truth is subjective to the individual. Colonel Viet nevertheless deserves enormous credit for his industrious research and fine account. His is a major and much needed addition to the history of the Vietnam War. [End Page 1021] Jay Veith Bear, Delaware Copyright © 2009 Society for Military History

Coupled FEMDEM/Fluids for coastal engineers with special reference to armour stability and breakage

Sea-level rise and increased storminess present huge challenges to coastal engineers worldwide. The seaward slope of many breakwaters and shoreline defence structures consists of thousands of interlocking units of concrete or rock making up a massive granular defence against wave attack. The units are placed freely to form an armour layer which is intended to both dissipate wave energy and remain structurally stable. Design guidance on the mass and shape of these units is based on empirical equations derived from Froude scale physical model tests. The two main failure modes for concrete armour layers are displacement (hydraulic instability) and breakage (structural instability) which are strongly coupled. Breakage mechanisms cannot all be faithfully reproduced under scaled physical models. Fundamental understanding of the forces governing such wave-structure interaction remains poor and unit breakages continue to baffle the designers of concrete armour units. This paper illustrates a range of DEM and FEMDEM methods being developed to model the granular solid skeleton of freely packed brittle units. Such discrete element methods are increasingly being used by engineers for solids modelling. They are especially powerful when coupled with a CFD model which can resolve ocean wave dynamics. The aim is to describe a framework for coupled modelling technologies applicable to coastal engineering problems. Preliminary simulation test cases, still at proof of concept stage, but based on a wealth of validation studies are presented. Thus, we report a snap-shot of progress towards a future where designers combine multi-physics numerical technology with knowledge from scaled physical models for a better understanding of wave energy turbulence, block movement, and internal stresses within armour units.

Sediment budget analysis in light of high-resolution echo sounding of seabed topography

Coastal erosion is a long-standing serious issue in Japan and extensive lengths of coast lines have been protected with seawalls, armour units and detached breakwaters. Extreme cases of coastal protection can render sandy beaches totally isolated from otherwise available sediment-supplying systems. The authors took up Ogata Beach on the Joetsu coast as such and applied a high-resolution side scan imaging with bathymetry to it, revealing marked morphological changes underwater. What is most noteworthy is that the areas of significant erosion extended offshore beyond the so-called closure depth.

Damage Mechanism of Armor Units at the Breakwater Head Using the 3D Numerical Wave Tank

The rubble mound of composite breakwaters is usually covered with armor stones or armor concrete blocks. However the damage of armor units is almost appeared at the breakwater head. The minimum weights of the armor units at the breakwater head is 1.5 times the value of the breakwater trunk. This paper aims to elucidate the damage mechanism of armor units at the breakwater head of a composite breakwater by numerical simulation with a 2 or 3-dimensional numerical wave tank `CADMAS-SURF' under regular wave action. Numerical results are compared with experimental data. At the last, the numerical wave tank is applied to real disaster of the armor units of the composite breakwater.

296 EFFECT OF GnRH AND ESTRADIOL BENZOATE INJECTION ON SUPEROVULATORY RESPONSE IN EARLY POSTPARTUM SUCKLING JAPANESE BLACK COWS

The objective of this study was to investigate the effect of GnRH and EB injection on the SOV response in early postpartum suckling Japanese Black cows. Forty-eight cows were included in this study. All cows received a controlled internal-drug-releasing device containing 1.9 g progesterone (CIDR; Easi-Breed; InterAg, Hamilton, New Zealand) at 40 days postpartum, and were subsequently superstimulated with a total dose of 20 armour units FSH (Antrin 40; Kawasaki-Mitaka, Kanagawa, Japan) twice daily, with gradually decreasing doses from day 45 till day 47. CIDR was withdrawn with 0.75 mg of cloprostenol (Estrumate; Nagase Medicals, Itami, Japan) injection at day 47. After FSH treatment, the cows were assigned to 3 groups: (1) 100 μg GnRH (Conceral; Nagase Medicals) injection at day 49 (GnRH, n = 19), (2) 2 mg EB (Kawasaki-Mitaka) injection at day 48 (EB, n = 15), and (3) control (n = 14). AI was carried out twice based on the estrous behavior of the cows, which was examined several times daily. Embryos were nonsurgically collected 7 to 8 days after estrus. The ovaries were examined by ultrasonography, and the number of CL and unovulated follicles (UF) were counted. After uterine flushing, the cows were re-employed for reproductive purposes. The intervals to first estrus after flushing and days open were examined. Blood samples were collected temporally, and concentrations of progesterone (P4) and estradiol (E2) were measured. The ovaries were examined by ultrasonography and the number of CL, small follicles (&lt;5 mm in diameter), medium follicles (between 5 and 10 mm in diameter), and large follicles (&gt;10 mm in diameter) were counted temporally. Data were analyzed by GLM and Dunnett’s T3 test. There were no significant differences between both treatment groups and the control group in the number of CL (15.2 ± 6.8, 18.9 ± 9.4, and 14.9 ± 8.9 in the GnRH, EB, and control groups, respectively; mean ± SD), UF (5.3 ± 3.2, 4.7 ± 3.2, and 7.2 ± 9.5, respectively), recovered ova or embryos (11.4 ± 8.1, 11.1 ± 8.9, and 11.1 ± 9.1, respectively), transferable embryos (6.8 ± 5.3, 7.5 ± 7.6, 7.2 ± 6.7, respectively), and freezable embryos (6.3 ± 5.6, 6.6 ± 7.9, and 5.7 ± 6.1, respectively). Furthermore, there were no significant differences in the intervals to first estrus after flushing and days open (12.7 ± 13.6 and 90.0 ± 23.1 in the GnRH, 8.6 ± 5.3 and 79.1 ± 20.1 in the EB, and 9.4 ± 6.0 and 88.5 ± 33.8 in the control groups, respectively). Changes in the P4 level were similar among the 3 groups. The E2 level of the EB group at 15 h after EB injection was significantly higher (P &lt; 0.05) than that in the other groups (19.0 ± 15.7, 49.4 ± 22.8, and 8.0 ± 5.7 pg mL–1 in the GnRH, EB, and control groups, respectively). The number of small follicles in the control group (17.0 ± 12.2) was significantly greater (P &lt; 0.05) than that in the GnRH group (7.4 ± 7.2) at the first AI. These results suggest that EB and GnRH injection after SOV treatment in early postpartum Japanese Black cows does not affect the SOV response or embryo quality.

Modelling of massive particulates for breakwater engineering using coupled FEMDEM and CFD

The seaward slope of many breakwaters consists of thousands of interlocking units of rock or concrete comprising a massive granular system of large elements each weighing tens of tonnes. The dumped quarry materials in the core are protected by progressively coarser particulates. The outer armour layer of freely placed units is intended to both dissipate wave energy and remain structurally stable as strong flows are drawn in and out of the particulate core. Design guidance on the mass and shape of these units is based on empirical equations derived from scaled physical model tests. The main failure mode for armour layers exposed to severe storms is hydraulic instability where the armour units of concrete or rock are subjected to uplift and drag forces which can in turn lead to rocking, displacement and collisions sufficient to cause breakage of units. Recently invented armour unit designs making up such granular layered system owe much of their success to the desirable emergent properties of interlock and porosity and how these combine with individual unit structural strength and inertial mass. Fundamental understanding of the forces governing such wave–structure interaction remains poor. We use discrete element and combined finite-discrete element methods to model the granular solid skeleton of randomly packed units coupled to a CFD code which resolves the wave dynamics through an interface tracking technique. The CFD code exploits several methods including a compressive advection scheme, node movement, and general mesh optimization. We provide the engineering context and report progress towards the numerical modelling of instability in these massive granular systems.

Overtopping performance of different armour units for rubble mound breakwaters

This paper describes a major programme of small-scale physical model tests to establish better the influence of armour type and configuration on overtopping. Specifically, 179 tests determined the relative difference in overtopping behaviour for 13 types/configurations of armour. Roughness factors γ f were determined for rock (two layers), cubes (single layer and two layers), Tetrapod, Antifer, Haro, Accropode, Core-Loc™ and Xbloc™. These roughness influence factors have been included in the CLASH database and are for use in the neural network prediction of overtopping. Individual wave-by-wave overtopping volumes were analysed and found to compare well with current prediction methods. Measured reflection coefficients for the different units are also presented and compared with recent formulae.

Effects of new variables on the overtopping discharge at steep rubble mound breakwaters — The Zeebrugge case

This paper describes on the one hand parametric tests on wave overtopping for a steep rubble mound breakwater in Zeebrugge, Belgium. On the other hand the comparison between prototype measurements at the breakwater and their scale reproductions in two laboratories is dealt with. The objective is to gain information on possible scale and model effects for wave overtopping from this comparison. The prototype measurements are described together with the resulting dataset of 11 storms where wave overtopping occurred. Scale models and the laboratory measurements are described into detail mentioning similarities and differences to the prototype. Several model effects are identified and special attention is given to wind effects and to the placement pattern of the armour units, respectively. Monte Carlo simulations have been performed to get an idea about the influence of selected model uncertainties. Finally, scale effects are discussed and the influence of model and scale effects for the performed tests is quantified. Recommendations on how to treat these effects are presented.

The new wave overtopping database for coastal structures

Significant effort has been made to generate a homogeneous database on wave overtopping consisting of more than 10,000 irregular wave overtopping tests from more than 160 independent projects or test series, each described by means of 31 parameters. Many coastal structures, including dikes, rubble mound breakwaters, berm breakwaters, caisson structures and combinations have been considered and have been schematised for inclusion in the database. All these overtopping tests are represented by over 300,000 numbers in the database. Within the framework of the CLASH-project specific overtopping tests on missing parameters and structures (white spots) in the database have been performed, as well as prototype overtopping measurements and small scale overtopping simulations. The results of these tests have enlarged and homogenized the database. White spot tests concentrated on the roughness of all kind of armour units and on the influence of oblique wave attack. These tests were performed by the University of Edinburgh (UK) and Aalborg University (DK), respectively. Prototype measurements were performed at Ostia (IT), Samphire Hoe (UK) and Zeebrugge (BE). The small scale simulation tests were performed by most of the partners in CLASH. The database has been created in such a way that particular and confidential information on actual projects is not present. This creates the opportunity to finally release the database to all interested people. The database was created as a first step and as basis for the generic prediction method on wave overtopping. The latter has been described in Van Gent [Van Gent, M.R.A., Van den Boogaard, H.F.P., Pozueta, B., Medina, J.R., 2007. Neural network modelling of wave overtopping at coastal structures, Coastal Engineering, Vol. 54, Issue 8, pp. 586–593]. But the database can also be applied on its own. Furthermore, the minimum set of hydraulic and structural parameters to describe a test is very useful in creating other databases and could be considered as essential parameters to be described in each test report on physical model investigation of coastal structures. The paper describes: • the gathering of the data • the screening of the data • the development of parameters to describe each individual test • the parameters required for an artificial neural network prediction method • a parameter analysis of the total database • the application of the database for design purposes