Defence Structures Research Articles

Предвратные сооружения на плато Эски-Кермен: реальность и домыслы

Introduction. The architectural complex around the main (southern) gates of the city on the Eski-Kermen plateau in the mountainous Crimea was formed from the end of the 6th century to the end of the 13th century. It included structures that were different in architecture and purpose. Studying the remains of these structures, determining their role and chronology are important tasks in the study and reconstruction of the history of the city. Methods. The area around the gate was explored by N.I. Repnikov in 1929. Brief descriptions of the open remains of the structures are reflected in publications and archival documents. Based on the analysis of these descriptions and the study of the preserved rock foundations, first time in the historiography the article revises the widespread hypothesis about existence of the gate church in the medieval city on the plateau of Eski-Kermen in the mountainous Crimea. Analysis. Some researchers see an apse of this church in a rounded carved pit located in front of the main gate, east of the corridor carved into the rock leading to the city. Features of the architectural space at the city gates and the location of this clearing are likely to have its presence at the gate church. This felling arose simultaneously with the defensive structures near the gates in the end of the 6th c. As is known, gate churches as a type of church architecture appeared in the Eastern Christian world no earlier than the 10th or 11th centuries. Results. There is no reason to talk about the gate church on the plateau of Eski-Kermen. Directly at the entrance to the city (to the west of the passage) there was only one church-chapel of the 9th – 10th centuries, destroyed by an earthquake even before the onset of the city, burned at the end of the 13th century.

Seasonal benthic species composition linked to coastal defense structures (CDS) in Kuala Nerus, Terengganu, Malaysia.

The natural hydrodynamic process of Kuala Nerus, Terengganu, has changed since the extension of Sultan Mahmud Airport runway in 2008. Consequently, severe coastal erosion has occurred in the area, particularly during the northeast monsoon season (NEM). Numerous types of coastal defense structures (CDS) have been constructed to protect the coastline. Despite the loss of esthetic values, the effect of CDS construction on marine organisms in the area remains unknown. Hence, this study aims to assess the ecological aspects of macrobenthic compositions at the CDS area of Kuala Nerus, Terengganu, based on the differences between the southwest (SWM) and northeast (NEM) monsoon seasons. Macrobenthos were collected from the sediment in July (SWM) and December 2021 (NEM) using the Ponar grab at 12 substations from five sampling stations. The density of macrobenthos was higher in SWM (48,190.82 ind./m2) than in NEM (24,504.83 ind./m2), with phylum Mollusca recording the highest species composition (60-99.3%). The macrobenthos species had a low to moderate level of diversity (H' = 1.4-3.1) with the species were almost evenly distributed (J' = 0.2-0.8). Windward substations exhibited coarser grain sizes (38.56%-86.84%), whereas landward substations exhibited very fine grain sizes (44.26%-86.70%). The SWM season recorded a higher organic matter content (1.6%-6.33%) than the NEM season (0.4%-3.1%). However, metal concentrations in the surface sediment were within the safe range and permissible limits for both seasons, inferring that the macrobenthos composition was unaffected. This study demonstrated that the CDS associated with the monsoon system has controlled the hydrodynamics and nearshore sedimentary processes in the Kuala Nerus coastal zone, thereby affecting the macrobenthos population, in terms of richness and density. The ecological and energetic effects of the coastal structures in different seasons have resulted in a more significant result, with the SWM exhibiting a higher macrobenthos composition than the NEM.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

Several benefits can be gained by using additive Manufacturing (AM) or 3D printing, including design flexibility, mass customization, waste minimization, quickly producing complex structures, and rapid prototyping. The standard methods and materials used in 3D printing, along with their development and use, have been examined. The various applications of AM were discussed, especially in biology, aircraft, building, and defensive structures. Many materials and their stages of evolution, including concrete, ceramics, polymer composites, and metal alloys, were analyzed. We discussed several fundamental processing challenges that arise, including but not limited to void generation, anisotropic behaviors, computer design restrictions, and a layered appearance. This article thoroughly assesses 3D printing, including a survey of its pros and shortcomings, to establish a baseline for future research and development.

Sentyivskyi Shantse as a component of the defensive structures of New Serbia: Historical and archaeological aspects

The relevance of the research topic is manifested in the context of the unique geopolitical position of Potyasmynia and the broader region of the “Zadniprovian lands” of the Hetmanate and New Serbia in the mid- to late 18th century. This period was characterised by acute political and military transformations, which led to intensive construction of fortifications, including the Sentyi Shantse. Considering the importance of understanding the historical context and significance of defensive structures in this region, the study of the Sentyi Shantse becomes an essential element in unravelling historical events and processes. The aim of the study is a comprehensive elucidation of the historical significance of the Sentyi Shantse, the stages of its historical existence and fate, relying on the use of historiography, cartography, and archaeology data. In addition to general scientific methods, the authors employed special-historical methods, namely: chronological, historical-typological, and cartographic methods, which allowed for balanced and well-founded research results. The research included a historiographic analysis of scientific works, identifying the specificity and differences in the vectors of shantse research in scientific sources from the second half of the 18th century to the beginning of the 20th century and contemporary history. The predominance of the goals of historical anthropology was established. The specificity of the two main periods of studying the Sentyi Shantse in the system of defensive structures of Potyasmynia in the mid- to late 18th century was determined and characterised. Six chronological stages in the history of the shantse were identified and characterised. The results of its archaeological research were introduced into scientific circulation and analysed. The practical value of the work lies in the possibility of applying the research results in the study and writing of works on local history topics, in the preparation of lectures on regional and Ukrainian history, as well as in their use in highlighting the history of the region in museum activities

Damage assessment and restoration proposal following the 2023 Türkiye earthquakes: UNESCO World Heritage Site Diyarbakır City Walls, Türkiye

Diyarbakır City Walls, one of the longest defensive structures in the world, following the Great Wall of China, the walls of Antakya, and the walls of Istanbul, is a UNESCO World Heritage site since 2015. With a history of approximately 5000 years, the Diyarbakır City Walls have been affected by consecutive earthquakes centered in Kahramanmaraş in 2023, resulting in damages to various sections. Urgent restoration and repair interventions are needed for these sections of the Diyarbakır City Walls due to earthquake-induced damages. Although there are limited studies presenting stone analysis of the Diyarbakır City Walls in the literature, no studies focusing on mortar analysis have been found. The objectives of this study are as follows: (I) to identify the mechanisms and factors of earthquake damages in the Diyarbakır City Walls, (II) to conduct necessary analyses for the selection of mortar materials for post-earthquake repairs, and (III) to provide restoration and strengthening recommendations to ensure the sustainability of the original structure. Observational, petrographic, chemical, and SEM analysis techniques were used, and the findings were interpreted comparatively. The results demonstrate that the most severe damages after the earthquake in the Diyarbakır City Walls were caused by the inadequate adhesion of missing mortar joints and different types of materials used between double-walled structures. Additionally, the presence of clay minerals identified in the mineralogy of the mortar through experimental analysis was defined as an internal issue causing the loss of mortar due to osmotic pressure created by water absorption. Another factor causing the loss of mortar is the presence of chloride-type salts, which were found to be present in a significant amount in all samples and were attributed to the use of Portland cement in previous faulty repairs. It was also determined that recent faulty repointing works contributed to the loss of mortar. Finally, this article presents original restoration and strengthening recommendations to repair the earthquake-induced damages and prevent their reoccurrence in the future.

Traits coordination at leaf and branch level in response to the urban environment

The response of urban trees to the environment is the key content to explain the functional toughness of urban green space. However, how urban greening trees adapt to the dry and hot environment of the city remains unclear due to the single index and the limitations of the research area. We selected four representative cities in northern China with different regional dryness and measured 18 economic, hydraulic and anatomical traits of the common greening tree species (Fraxinus chinensis Roxb). The results show that there was generally a significant divergence in plant functional traits across urban dryness, and the traits have strong plasticity. As urban dryness increases, the number of leaf veins closed loops increases, forming a more complete network system of veins. While a significant decrease in the vessel vulnerability index further indicates the increased drought tolerance of urban trees to resist dry and hot environments. The increase of dryness leads to the decrease of vessel hydraulic diameter and area. The reduction in the vessel vulnerability index indicates an increase in the drought resistance of the twigs, which may be related to the input and distribution of resources in the branches and leaves. There was a strong correlation between plant economic-anatomical-hydrological traits. Under the stress of a dry urban environment, plants prefer to invest resources in the water sparing capacity of the stem, as well as in the construction of defence structures and nutrient storage capacity of the leaves.

Impact of Soil on the Penetration of Prefabricated Spherical Fragments and Its Protective Effect

As a natural environmental medium, soil has a wide range of sources and is often used as a material for building houses. It can also be used to construct simple protective structures in actual battlefield environments. In order to study the protective effect of sand on prefabricated fragments in practical situations, the authors conducted experiments on spherical tungsten alloy prefabricated fragments penetrating into sand using sand as the target medium. Natural sand (naturally generated rock particles with a particle size less than 4.75 mm) was selected as the sand, and the initial velocities of the fragments were 689 m/s~1761 m/s (fragment diameter 6 mm) and 596 m/s~1325 m/s (fragment diameter 11 mm), respectively. Based on the residual velocity of fragments and experimental phenomena in experimental data, the authors used LS-DYNA software to numerically simulate and compare the residual velocity of fragments and obtained a numerical model for sandy soil media and a calculation formula for the residual velocity of spherical fragments. Based on modeling equivalence in practical environments, the authors studied the impact of different attack angles on fragment trajectory deviation and found that fragments have the highest deviation values at 20° and 70° attack angles. They also analyzed the soil boundary effect within a small scale range, and the effect was significant when the vertical distance was less than 40 mm. The penetration resistance of different thicknesses of soil was calculated, and the maximum soil thickness under prefabricated fragment penetration at different speeds was obtained. The effective protective size of the soil under actual conditions was about 550 mm. This experiment provides a reference for the construction parameters of simple soil defense structures in actual environments.

HIGHLIGHTING OF FOCAL LANDSCAPES ON THE EXAMPLE OF VALLEY-RIVER LANDSCAPE-TECHNICAL SYSTEMS

River valleys are important in the structure of natural landscapes. They are the places of population concentration, ecological gutters and the landscape "framework" around which all other geocomplexes function. If the framework landscapes have been analyzed in detail by scientists, the focal landscapes are inflated beyond the attention of scientists.
 The purpose of the article is to analyze the structure of focal landscapes on the basis of the improved classification of anthropogenic landscapes by significance on the example of landscape-technical systems (LTchS) in the river valleys of the model region - the flat part of Right Bank Ukraine.
 Within the valley-river landscapes, the focal group includes road, mining, agricultural, and beligerative LTchS. Most modern road landscape technical systems belong to the category of "landscape technogenic systems". The destruction of man-made cover is associated with the excessive load on the road surface of motor vehicles, the weight of which often does not meet the established standards. As a result of mining and processing of minerals in river valleys, mining LTchS are formed. Active mining LTchS are formed by quarries, waste rock dumps and beneficiation or crushing and sorting plants and factories. The river valleys of the Right Bank of Ukraine are characterized by new anthropogenic types of areas that were formed after the extraction of minerals: areas of pit-peat wastelands and "rocky badlands". Valley-river agricultural LTchS are represented by water regulation and irrigation systems and vineyards. The lack of modernization and the use of outdated equipment and facilities do not allow the LTchS to fully function and produce the appropriate amount of crops. Beligerative landscape and man-made systems include complexes of defensive nodal structures "lines of defense" of the 20th century. Some critical remarks were made regarding the analysis of the structure of focal landscapes after the beginning of the full-scale invasion of the Russian Federation on the territory of Right Bank Ukraine. It was concluded that in the context of the study of modern anthropogenic landscapes of Ukraine, the study of focal valley-river landscape-technical systems will contribute to a better understanding of their structure and the development of ways of optimization.

The Restoration and Refunctionalisation of Medieval Fortified Manor Houses by the Portuguese Dictatorial Regime (1926–1974)


 
 
 In the Modern Age, most fortified manor houses in Portugal fell into ruin, due to the lack of dignified living conditions, the obsolescence of defensive structures, and the decline decay of aristocratic families. However, between 1933 and 1974, many ruined fortified manor houses were restored by the Portuguese dictatorial regime. The nationalist dictatorship of Estado Novo used heritage as an ideological instrument of propaganda. This proposal aims to analyse the context of the ideological restoration of medieval fortified manor houses by the dictatorial regime, addressing symbolisms, restoration actions, and the contextualisation of fortified manor houses in Portugal by focusing on particular case studies.
 
 

WAVE OVERTOPPING OVER A DIKE FOR VARIABLE WATER LEVEL

The still water level (SWL) during a storm is always dynamic (storm surge). The variability of the water level can be schematized as a time-varying hydrograph of a certain duration. The average wave overtopping discharge q is a function of the ratio between the freeboard Rc (the structure crest elevation above SWL) and the significant wave height Hm0. Since the variation during a storm of the SWL changes the freeboard Rc, the wave overtopping discharge is variable. Typically, in the laboratory the wave overtopping on coastal defense structures is investigated for a constant water level (CWL) and a pre‐determined structural exposure time frame. This exposure time frame is often representative for the storm surge peak or for a statistically representative number of individual waves (e.g. 1000 waves), not considering any variable water level (VWL). For the case of wave overtopping in VWL conditions, no validated prediction formulae exist (Kerpen et al. 2020) and the prediction is rather based on safe assumptions and engineering judgement. This research investigated the influence of a VWL on the prediction of the average wave overtopping discharge q.

Гігієна планування та забудови населених місць як безпекова детермінанта громадського здоров’я в умовах воєнного стану

Introduction: Martial law continues to operate in Ukraine, in which the primary task of the state is to preserve the health and life of the population. The priority in this regard is the prevention of the harmful influence of martial law conditions on the formation of children's bodies and the creation of conditions for their upbringing and education. Proceeding from the above, the solution to the issues regarding collective civil protection should be carried out through the construction/reconstruction of civil protection facilities, taking into account the specific conditions for both the adult population and the children's contingent. Objective: there is the development of sanitary and hygienic requirements for civil defense structures of public and residential buildings during the period of martial law and their use in the post-war state - as dual-purpose structures, taking into account the experience of warring countries. Research methods: research methods are used in the work: bibliosemantic, analytical, hygienic and sanitary-epidemiological examination of construction projects. The materials of the research were the sanitary, urban planning and educational legislations of Ukraine and other countries in the field of designing civil defense structures of residential and public buildings, construction projects of public and residential buildings. Results: the article highlights the activities of the Laboratory, which is aimed at studying the hygienic urban planning problems of the comprehensive restoration of settlements (territories) that suffered as a result of hostilities, terrorist acts, and the development of hygienic criteria for their reconstruction in order to create safe living conditions of the population, in particular ensuring the conditions of collective civil protection in civil protection facilities of public and residential buildings. Conclusion: The activities of urban planning specialists in the direction of hygienic assessment of urban planning documentation of settlements affected by hostilities and the development of requirements for safe living of the population should be aimed at strengthening the safety determinant of public health by creating optimal conditions for collective civil protection of the population in civil protection structures of public and residential buildings - for the period of martial law and construction - the use of these structures in a dual location.

MONITORING OF A DYNAMIC REVETMENT DURING A SPRING TIDAL CYCLE IN NORTH COVE, WASHINGTON STATE, USA

A dynamic revetment is a cobble-gravel berm constructed around the high tide wave runup limit. These structures mimic composite beaches, which consist of a lower foreshore of sand and a backshore berm constructed of gravel or cobbles, which stabilizes the upper beach and provides overtopping protection to the hinterland. Dynamic revetments contrast with static coastal defense structures as they are “dynamic” and are expected to reshape under wave attack. The idea of a dynamic structure made of smaller material than a classic riprap type of revetment is not new, and previous laboratory and field research has investigated the use of dynamic revetments for coastal protection (Allan et al., 2016). However, applications of such a structure remain sporadic and often differ to each other in terms of their design and aim. Furthermore, few existing dynamic revetments have been monitored to evaluate their function, and therefore, the way they behave at the particle and global scale remains poorly understood. In this study, 2D Lidar, GPS topography, particle tracking, and sub-surface particle composition data were collected on the dynamic revetment at North Cove, Washington State, USA, during a spring tidal cycle. Together they enabled investigation of the revetment dynamics and evolution in response to waves and water levels. In addition, this monitoring is proposed as a suitable protocol for short and long-term monitoring of dynamic revetments.

NATURE-BASED FLOOD RISK REDUCTION VIA MULTIPLE LINES OF DEFENSE

Sea level rise, land subsidence and population growth lead to steadily increasing flood risks in low-lying coastal areas. Hard flood defense structures such as dikes and dams should be regularly heightened and strengthened to sustain their protective function. Further, such hard structures can induce negative effects on the surrounding ecosystem. Therefore, nature-based approaches to flood risk reduction are increasingly promoted. Vegetated foreshores (such as salt marshes and mangrove forests) reduce wave loads on coastal dikes (Vuik et al., 2016). Furthermore, they are able to keep pace with sea level rise due to natural sediment accretion. However, foreshores cannot always exist in front of flood defenses, for example because of shipping lanes, protected habitats or harsh waves and currents. Even in such situations, coastal safety can be enhanced by creating salt marshes in between multiple lines of defense (double dikes). In this study, we investigate the effectiveness, costs and coastal protection benefits of nature-based flood risk reduction via multiple lines of defense.

ASSESSMENT OF THE FAILURE PROBABILITY OF UPGRADED RUBBLE-MOUND BREAKWATERS

Nowadays, the existence of a huge number of aging harbor defense structures and climate change-induced forcing variability highlight the need for a methodology able to deal with uncertainties which arise during the design of new and above all upgraded structures. In the present work, a probabilistic design methodology based on the Monte Carlo simulation technique for the assessment of the failure probability due to independent failure modes and on the factor of change method for the inclusion of the effects of climate change is described, together with its application to the emblematic case study of the Catania harbor breakwater (Italy). The performances of the rubble-mound breakwater under present and future climate scenarios are assessed considering the existing structure and different upgrading options, which include both the raising of the wave wall and the addition of extra armor blocks. Three novel indexes describing the acceptability level of the structure performances as well as the rate of growth and the coefficient of variation of the failure probability along lifetime are employed to quantitatively asses the performances of the existing and upgraded breakwater under present and future climate, considering the ultimate limit state due to the collapse of the outer armor layer and the serviceability limit state due to excessive mean wave overtopping discharge. The obtained results demonstrate that such indexes may give useful indication to designers and decision makers who deal with the upgrade of existing harbor defense structures under the effects of climate change.

FAILURE OF SEAWALLS DUE TO TSUNAMI-INDUCED SCOUR

The Indian Ocean tsunami in 2004 and the Tohoku tsunami in 2011 have shown that tsunami-induced scour is one of the primary reasons for the failure of coastal defence structures (Bricker et al., 2012; Jayaratne et al., 2016). In a coastal structure, scour can occur when the plunging jet impacts the landward toe of the structure, resulting in digging a hole around the foundation which eventually may destabilize the structure. This can be exacerbated by rapid drawdown induced liquefaction during the receding wave, and can lead to the failure of the structure. Therefore, accurate prediction of local and plunging scour is very vital in order to ensure the safety of the coastal structures under such conditions. Data we have at present are based on final or equilibrium scour depths, not the maximum scour depths. Survey teams measure scour profile once the extreme event is over. However, the trough or scour hole made can be partly filled by sediment transport from upstream (in the live bed case) or from sediment suspended within the scour hole that settles after the flow slows down. Thus, the scour depth survey teams measure are less than the actual maximum depths. Therefore, a novel experimental and numerical study is proposed to tackle this problem with the funding of the Royal Society, UK.

2DH modelling and mapping of surfbeat-driven flooding in the shadow of a jettied tidal inlet

Near estuaries and harbours, submerged shoals and defence structures impact the exposure to overtopping. These features may be accounted for in two-dimensional horizontal (2DH) numerical models, either based on phase-resolving or phase-average solvers for wave propagation. In between, surfbeat solvers, such as in XBeach, combine an affordable computational cost with the ability to generate and propagate the longer infragravity (IG). However, surfzone wave characteristics and the overtopping exposure modelled with XBeach are sensitive to settings such as the shape of the forcing wave spectra and the numerical scheme for wave propagation. The present paper explores this sensitivity and assesses the performance of different inundation models built with the 2DH surfbeat solver of XBeach. These models were forced with downscaled water levels and directional wave spectra and the results fuelled a discussion bounded by data collected downdrift of the entrance to the harbour of Figueira da Foz (Portugal). The original second-order upwind scheme, which propagates short-waves with a lower numerical diffusion improved the model performance in terms of long-wave height, and an unconventional breaking criterion better represented the cross-shore distribution of short-wave height near the shore. A calibrated model was validated through the hindcast of an overtopping event observed under moderate swell forcing, and was used to map the overtopping exposure during a hypothetical combination of an energetic swell with a water level having a return period of ∼70 years. Compared to the default wave spectra shape and model settings, using an appropriate representation of the short-wave directional spectrum at the open boundary was necessary to reproduce the observed overtopping extent. Refining the cross-shore resolution of the model helped to better represent the observed inundation extents, as also did the reduction of the friction coefficient. Additional phase-resolving simulations in 1DH overestimated IG wave energy and produced higher and more frequent overtopping discharges. However, differences with the calibrated 2DH surfbeat model increased with the proximity of the inlet and with short-wave height and angle of incidence. Overall, required calibration steps were provided. They aim at making 2DH XBeach surfbeat a credible tool for 1) predicting short and IG wave characteristics until the shoreline, as well as for 2) providing first estimates of exposure to overtopping in areas with shallow and alongshore-irregular morphologies.

Managing rising residual flood risk: A national survey of Aotearoa‐New Zealand

AbstractFlooding is one of the most frequent and costliest natural hazards around the world. Traditionally, flood risk management has relied on building protective structures such as levees and dams to protect assets based on historical data (e.g., 1% AEP flood), which encourages development on floodplains, provides a potentially false sense of security to communities, particularly in the context of climate change, and increases residual flood risk (the risk remaining after implementing risk reduction measures). This article aims to contribute to the management of residual risk by drawing on empirical findings from a survey carried out with flood risk practitioners from the public and private sector in Aotearoa New Zealand. Findings indicate fundamental concerns relating to how to best manage residual flood risk, despite its long profile and integration in current policy and practice. Other issues revolve around the use of outdated information to guide decisions and the lack of regulatory power to restrict developments in flood‐prone areas protected by hard defense structures. Identified barriers to improving current practice include the lack of national guidance and support, financial resources, public awareness, and some technical constraints such as uncertainties in flood modeling, staff expertise, and data availability.

Sediment and bottom water eDNA metabarcoding to support coastal management

Ocean sprawl and climate change exacerbate coastal erosion and flooding, resulting in habitat loss and decreasing biodiversity. To counteract these threats, different coastal defence tools have been developed, with an increasing emphasis on nature-based solutions. However, tracking the impacts of these interventions on marine benthic organisms requires appropriate sampling designs and timely investigation methods due to the dynamic nature of coastal environments. Environmental DNA metabarcoding is a promising, non-invasive, and quick technique to monitor community changes. Here, environmental DNA COI-based metabarcoding data from sediment and bottom water samples were used to characterize benthic communities at three sites along the Emilia-Romagna coast differing in the topology of coastal defence actions (from no defences to groynes and low-crested barriers) and to evaluate the effectiveness of the two sampling matrices in detecting local biodiversity. The findings revealed significant differences in the structure of the benthic communities depending on site, sample type (i.e., sediment versus bottom water), and their interaction. The three sites differ in abiotic characteristic affecting the community composition. Lido di Dante and Riccione showed higher species diversity due to the new type of substrata provided by the hard defence structure, while Foce del Bevano showed the presence of species typical of low impacted areas. Bottom water, hosting more traces of pelagic and nektonic species, showed significantly different species composition compared to sediment samples, suggesting the need to consider both matrices in coastal monitoring.

Size, but not sex, predicts pinch force and exoskeleton mechanical properties in crayfish of the genus Faxonius

AbstractStudies of animal weaponry and defensive structures rarely take into consideration their underlying mechanical properties. We measured the compressive strength and thickness of the exoskeleton of the claw (chela) in two North American crayfish species, Faxonius virilis and F. limosus. We performed similar measures on the carapace, a body region not directly involved in agonistic contests. Males of both species generated significantly stronger maximum pinch forces than females. However, these differences can be attributed to differences in claw size between the sexes. The thickness (ultrastructure) of the claw exoskeleton was a significant predictor of its compressive strength and likely explained the difference in compressive strength we observed between the two species. Neither claw thickness nor claw compressive strength was correlated with maximum pinch force. Additionally, we found that crayfish body size was a strong predictor of carapace compressive strength and thickness, whereas sex was not. The claw had greater compressive strength and thickness than the corresponding values for the carapace. Our study shows that the mechanical properties of the crayfish exoskeleton are largely a function of size and highlights the need to integrate mechanical properties into studies of animal morphology and performance.

Effect of the buffer blocks in attenuating a tsunami-like flow

The construction of protective structures along the coast constitutes a crucial component of tsunami mitigation measures. Most commonly adopted tsunami mitigation measures are submerged structures, elevating the crest level of existing coastal defence structures, or soft measures. However, less considered measures to reduce the inundation level are a well-planned group of buffer blocks, which could not only act as a mitigation measure but also can serve as a facility along the shore to sit and relax during normal conditions. The buffer blocks can be constructed without affecting the scenic beauty. This paper presents the influence of the buffer block characteristics in attenuating the flow depth, and flow velocity. To carry out the study, the numerical model, OpenFOAM is adopted to simulate the dam break setup generating tsunami-like flow. The reduction in the flow velocity is governed by its the configuration. It was observed that a single-row configuration can reduce the momentum flux to an extent of 5–40%. Further, the results indicate that an increase in the number of rows in staggered configurations might enhance the percentage reduction in the flow characteristics. In addition, the forces on the buffer blocks for various configurations are computed and analysed from the existing literature.