Rubble Structures Research Articles

A Multidisciplinary Approach for the Mapping, Automatic Detection and Morphometric Analysis of Ancient Submerged Coastal Installations: The Case Study of the Ancient Aegina Harbour Complex

The documentation of underwater cultural heritage (UCH) is the basis for sustainable maritime development including its protection, preservation, and incorporation in coastal zone management plans. In this study, we present a multidisciplinary, non-intrusive downscale approach for the documentation of UCH implemented on the coastal area of Aegina Island, Greece, where a unique submerged harbour complex is preserved. This approach succeeded in obtaining information that serves both geomorphological and archaeological purposes in a time- and cost-effective way, while obtaining information of centimeters to millimeters scale. The geomorphology of the area was mapped in detail through marine geophysical means while ancient submerged conical rubble structures and breakwaters were documented using automatic seafloor segmentation techniques, revealing previously unknown sites of archaeological interest. The structures’ parameters were extracted from the acoustic data to analyze their morphometry, while photogrammetry was realized using a Remotely Operated Vehicle to expose their micro-structure. The spatial distribution of the structures revealed the construction of a well-planned harbour complex with multiple passages and different possible functionalities. Finally, through the structures’ morphometric analysis (geometry and terrain statistical parameters) their preservation status was revealed, demonstrating the anthropogenic impact on the submerged ancient structures due to the modern harbor activity.

Metagenome of Acropora palmata coral rubble: Potential metabolic pathways and diversity in the reef ecosystem

Over the past 30 years, the stony coral Acropora palmata has experienced an excessive loss of individuals showing few signs of recovery throughout the Mexican Caribbean, resulting in long stretches of coral rubble structures. When the coral dies, the skeleton begins to be colonized by algae, sponges, virus, bacteria and other microorganisms, forming a new community. Here we analyze, using a metagenomic approach, the diversity and biogeochemical cycles associated to coral rubble in La Bocana (Puerto Morelos, QRoo, Mexico). This study provides the first broad characterization of coral rubble associated communities and their role in biogeochemical cycling, suggesting a potential view of a world where coral reefs are no longer dominated by corals.

COMPARISON OF SILL AND REVETMENT IN REDUCING SHORE EROSION AND WAVE OVERTOPPING

Sills (low–crested rubble mounds) are constructed to protect eroding bluffs and planted marshes in living shoreline projects (http://mycopri.org). Revetments are conventionally used to protect eroding shores and reduce wave overtopping and damage to backshore areas. However, revetment construction may result in loss of buffering wetlands. On the other hand, no established method exists to design the sill geometry (crest height, width and side slopes) and its distance from the eroding shore. This study compares the efficacies of the two different rubble structures with the same number of stones in order to clarify their similarity and difference for the purpose in reducing shore erosion and wave overtopping.

New discoveries in the Piraeus

Numerous archaeological finds have come to light in the Piraeus in the last 15 years. These finds enrich our knowledge of the deme's city planning, domestic architecture, water system, quarries, ports and walls in the Classical, Hellenistic and Roman periods.Since Klaus-Valtin von Eickstedt's (1991) seminal study on the Hippodamian development of the Piraeus, which was based on excavation data for houses and roads, more evidence has become available. Numerous new domestic complexes have been excavated on the Akte (ID1718, ID4907, ID4908, ID4909, ID4935, ID4981, ID4982, ID4983, ID4984, ID4985; ADelt 56-59 [2001-2004] B1: 441-42) and on the rest of the peninsula (ID4877, ID4910, ID4914, ID4915, ID4932). New roads and sections of roads already included in Höpfner and Schwandner 1994 (fig. 14) have been revealed in several areas (ID1718, ID2438, ID4907, ID4908, ID4909, ID4921, ID4935, ID4937; ADelt 56-59 [2001-2004] B1: 442). Amongst these is the road that ran between the Long Stoa and the walls of the Piraeus (ID4937). Additionally, a horos stone, marking the limits of the Emporion and its adjacent road, was found in Akte Miaouli. The inscription had been built into the wall of a small rubble structure; the date of the structure has not been identified, but it is thought to postdate the Classical period (ID4935).

Wave forces and dynamic pressures on slotted vertical wave barriers with an impermeable wall in random wave fields

The use of vertical slotted barriers can be a cost effective solution for wave energy dissipation when sloped rubble structures are not desirable. For a cost-effective design of such barriers, an accurate estimation of dynamic pressures and wave forces is needed. A well-planned physical model study is carried out for this purpose on single and twin wave barriers of various porosities under a wide range of random wave conditions. This study provides explicit data for the vertical variation of the dynamic pressures from the seabed to the still water surface and for the resulting forces, both seaward and shoreward. The experimental results indicate that the porosity affects the dynamic pressures significantly, especially near the free surface, but less so closer to the seabed. Further, the resultant seaward horizontal wave forces are 20% to 25% less than the shoreward forces. Forces on the front panel in the twin wave barrier cases are 20% to 25% greater than those on a single porous wall, whereas the forces on the rear or second barrier are always 20% to 25% less than those on the single wave barrier under identical test conditions. These and other results presented in the study can be used for designing wave dissipaters, especially for inner harbors and vertical sea walls.

Damage characteristics and seismic capacity of buildings during Nepal M s 8.1 earthquake

The extensive damage to buildings caused by the Nepal Ms 8.1 earthquake has attracted much attention by the international community. After the preliminary scientific investigations on the different affected areas in Nepal, the construction and damage characteristics of five different types of buildings commonly existing in Nepal were discussed and the reasons of their disaster performance were analyzed. Types of buildings investigated include reinforced concrete (RC) frame structures, rubble structures, brick-wood structures, raw soil structures, and brick-wood structures of historic buildings. In addition, the weak links of the seismic design were pointed out, which was very important for the post-earthquake reconstruction and recovery, and gave a preliminary explanations for the damage experienced.

Characterization of a subtropical hawksbill sea turtle (Eretmocheyles imbricata) assemblage utilizing shallow water natural and artificial habitats in the Florida Keys.

In order to provide information to better inform management decisions and direct further research, vessel-based visual transects, snorkel transects, and in-water capture techniques were used to characterize hawksbill sea turtles in the shallow marine habitats of a Marine Protected Area (MPA), the Key West National Wildlife Refuge in the Florida Keys. Hawksbills were found in hardbottom and seagrass dominated habitats throughout the Refuge, and on man-made rubble structures in the Northwest Channel near Cottrell Key. Hawksbills captured (N = 82) were exclusively juveniles and subadults with a straight standard carapace length (SSCL) ranging from 21.4 to 69.0cm with a mean of 44.1 cm (SD = 10.8). Somatic growth rates were calculated from 15 recaptured turtles with periods at large ranging from 51 to 1188 days. Mean SSCL growth rate was 7.7 cm/year (SD = 4.6). Juvenile hawksbills (<50 cm SSCL) showed a significantly higher growth rate (9.2 cm/year, SD = 4.5, N = 11) than subadult hawksbills (50–70 cm SSCL, 3.6 cm/year, SD = 0.9, N = 4). Analysis of 740 base pair mitochondrial control region sequences from 50 sampled turtles yielded 12 haplotypes. Haplotype frequencies were significantly different compared to four other Caribbean juvenile foraging aggregations, including one off the Atlantic coast of Florida. Many-to-one mixed stock analysis indicated Mexico as the primary source of juveniles in the region and also suggested that the Refuge may serve as important developmental habitat for the Cuban nesting aggregation. Serum testosterone radioimmunoassay results from 33 individuals indicated a female biased sex ratio of 3.3 females: 1 male for hawksbills in the Refuge. This assemblage of hawksbills is near the northern limit of the species range, and is one of only two such assemblages described in the waters of the continental United States. Since this assemblage resides in an MPA with intensive human use, basic information on the assemblage is vital to resource managers charged with conservation and species protection in the MPA.

Human-Target Detection and Surrounding Structure Estimation Under a Simulated Rubble via UWB Radar

The presence of a human target and the surrounding rubble structure are both important information in postdisaster rescue. In this letter, we study the signal-processing algorithm for detecting a human target in radar echo data. Furthermore, a solution is proposed to estimate the surrounding structure-the distance between the human target and the top wall of the cavity where the human target is trapped. In the latter procedure, the human position estimated before is used as a prior knowledge. In order to verify the feasibility of the proposed method, experiments are carried out with a human subject lying under the simulated rubble structure. The results show prospects of the proposed method.

Stone Armor Damage Initiation and Progression Based on the Maximum Wave Momentum Flux

Abstract The armor layer on the sea side of a rubble structure must be designed to protect against incident waves during storms. Formulas for armor stability and damage progression have been developed and are widely used for practical applications. However, none of the formulas accounts for the water depth at the toe of the structure explicitly. An alternative approach based on the maximum wave momentum flux at the toe of the structure is proposed in this article. Equations for sizing stable armor stone for constant incident waves and water level are proposed and calibrated using available data. Equations are also developed for determining damage progression in a life-cycle analysis involving varying wave and water level characteristics. The developed equations are calibrated using the damage progression tests conducted previously by the authors and verified using an additional 10 tests conducted for this article.

Laboratory and Numerical Studies of Hydrodynamics Near Jetties

Numerical and physical modeling studies were performed by the Coastal Inlets Research Program (CIRP) of the U.S. Army Corps of Engineers to investigate the spatial and temporal behavior of waves and wave-induced currents near jetties of an idealized coastal inlet. Hydrodynamics were examined in the vicinity of two extreme types of jetty structure: a highly absorbing jetty (resembling fairly porous rock rubble structure) and a fully reflective jetty (resembling a vertical sheet pile or caisson type breakwater). Laboratory experiments in a Froude scale of 1:50 were conducted with regular and irregular shore-normal (0°) and obliquely incident (20°) unidirectional waves. Current and wave measurements were made on the up-wave side and inside the inlet as well as in the bay, along a number of cross-shore and along-shore transects. Wave directions were measured by a remote-sensing video-camera system and Acoustic Doppler Velocimeters (ADV). Numerical modeling was performed with the Coastal Modeling System (CMS) consisting of a two-dimensional circulation model coupled to a spectral wave model. Calculated current and wave fields from CMS in the area around and between absorbing or reflected jetties were compared to measurements. The highly reflecting jetty created a circulation cell on the up-wave side of the inlet, whereas the absorbing jetty did not.

Response of concrete armor units to wave-induced hydrodynamic loads

Concrete armor units are commonly employed for the protection of shorelines and rubble structures. Their design is based primarily on hydraulic stability, but their structural response to wave loading is poorly understood. In this first of two companion papers, a robust wave force model is presented that predicts hydrodynamic loads on A-Jacks concrete armor units. A comprehensive finite element method analysis indicates that the A-Jacks retain their structural integrity at hydraulically stable wave conditions. Nomographs to facilitate the structural design of A-Jacks are presented.

Static stresses in dolos concrete armor units

Concrete armor units are commonly employed for the protection of shorelines and rubble structures. A three-dimensional finite element model is used to determine the states of static stress in dolosse with varying dimensions and concrete properties. An analytical procedure is developed which accurately predicts the tensile stress in the shank and horizontal fluke of a simply supported dolos subject to self-weight loading. Several numerical examples are presented which illustrate the application of prediction and iso-stress equations.

Dynamic response of dolos armor units to drop test impact loads

Dolos concrete units have been used extensively throughout the world for the protection of shorelines and rubble structures. A three-dimensional finite element model is used to determine the states of dynamic stress in dolosse with varying dimensions and concrete properties. An analytical procedure is developed which accurately predicts the tensile stress in the shank and horizontal fluke of dolosse subject to drop test loading conditions Numerical examples are presented which illustrate the application of prediction and iso-stress equations.

Dynamic response of pre-stressed concrete armor units to pulsating loads

Concrete armor units are commonly employed for the protection of shorelines and rubble structures. Their design is based primarily on hydrodynamic stability. However, several recent breakwater failures indicate that unreinforced concrete armor units are susceptible to structural failure for hydraulically stable wave conditions. The structural stability of 42-ton dolos armor units, both unreinforced and pre-stressed and subject to wave-induced pulsating loads, are examined in this paper.

Dynamic response of dolos armor units

Concrete armor units are commonly employed for the protection of shorelines and rubble structures. Their design is primarily based on hydrodynamic stability, but their structural response to wave loading is poorly understood. In this study a wave force model is presented, which includes drag, inertia, kinetic and buoyant force components, to estimate hydrodynamic loads on the concrete armor unit, dolos. These loads are employed in a three-dimensional FEM analysis to determine the dynamic states of stress in a 42-ton dolos.

Nonlinear dynamic analysis of concrete armor units

Concrete armor units are commonly employed for the protection of shorelines and rubble structures. Their design is primarily based on hydrodynamic stability, but their structural response to wave loading is poorly understood. In this study, a simple model is presented to estimate impact loads due to wave slamming on the concrete armor unit, dolos. A nonlinear dynamic analysis indicates that the units will experience a structural failure at hydrodynamically stable wave conditions.

Parameters Affecting Stability of Rubble Mounds

The paper examines the hydraulic reasons for failure of rubble structures suggesting improvements in design methods. The importance of forces by uprush and downrush, and forces depending upon friction and permeability is analyzed. The most dangerous combinations of these forces and of resonance between uprush/downrush period and wave period is evaluated. The conclusion is that armor units should be “placed.” Impermeable sheets should be put in the upper as well as in the lower part of the slope. Furthermore the commonly used trapezoidal linear slope profile should be substituted by better reasoned design to obtain a greater degree of compatability between the wave action, slope geometry structure, and armor unit geometry. A “self-adjusted” profile may be divided into three zones with different slope angle and block-characteristics and combined to achieve maximum stability.