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The use of rock bag type filter units for scour protection on revetments and in berth pockets are becoming more common around Australia. This is primarily driven by their ease of installation and ability to efficiently replace larger rock armour units, especially where there is limited supply. However, to date primarily only scale model testing of rock bag performance against propeller wash has been completed. Project Material Pty Ltd organised the use of Pacific Tug's Cape Mac tug located at their Brisbane Pacific Marine Base to conduct full-scale trials on the performance of the 2 t, 4 t and 8 t AquaRockBags®. The aim of the trial was to determine the water velocity at which the rock bags fail, or are dislodged from the constructed revetment and base. The trials were conducted on the 7th of October 2022, with the Cape Mac utilising both engines to thrust water towards the rock bags. The water velocities were measured near the revetment using an acoustic doppler velocimeter (ADV). After each condition, a hydrographic survey was conducted to measure the movement of the rock bags and surrounding riverbed. The bathymetric scans showed minimal movement of the 4 t and 8 t AquaRockBags® in all three configurations, as well as the surrounding 2 t AquaRockBags®. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study, which concerns about scour around the pilesupported wharf under progressive waves and pressure variations on the pile around the scour hole. In this context, rigid bed and actual scour bed experiments were conducted. The cylinder was flush mounted to the flume wall and flume base, water seepage was prevented in these regions. Pressure measurements were obtained by five pressure transducers, which were flush mounted on the surface of the cylinder above the flume bottom. The pressure measurements were made also for actual scour bed at the same low Keulegan-Carpenter number (KC ≌ 1). In order to determine the scour and deposition regions around the cylinder, the sediment pit located on the flume bottom was scanned with a laser scanner before and after the experiments and the final bed topography was visualized and contour maps were sketched. The results are indicated scour hole near the cylinder is more than 4 times than the wall free pile cases. [ABSTRACT FROM AUTHOR]

The collapse mechanism of breakwater and countermeasures under the continuous tsunami overflow were investigated using a drum centrifuge. A 1/70-scaled model, representing a 10 m high prototype breakwater, was set in the waterway in the drum centrifuge to 1) reproduce the caisson collapse mechanism and 2) investigate the effect of countermeasure by placing the embankment over the breakwater foundation mound using rubble materials and filter units. The study found that the caisson failure was due to the scouring of rubble mound and the seepage flow. Moreover, placing the embankment over the mound by using rubble materials or filter units was confirmed effective against breakwater instability. [ABSTRACT FROM AUTHOR]

A number of coastal dykes were damaged by the 2011 off the Pacific coast of Tohoku Earthquake. The main cause of the failures is assumed as the local scour at the landward toe. Furthermore, liquefaction damage caused by the earthquake has been reported. When tsunami strikes and overtops a coastal dyke, there is a possibility that liquefaction occurs by earthquakes and promotes scour at the landward toe. Liquefaction is caused by a decrease in effective stress. Therefore, it is important to evaluate the influence of the effective stress on the scour due to overtopping. In the present study, flume experiments were conducted. The effective stress was controlled by upward seepage to reproduce liquefied ground. As a result, it is found that scour profile is influenced by the effective stress, and backfilling of the scour hole due to slope failure is observed at low effective stress. [ABSTRACT FROM AUTHOR]

A numerical scour model is developed based upon OpenFOAM for the simulation of local scour below a pipeline. It is found that the maximum height of the wake sand dune may be under-predicted in previous studies due to: (1) an inadequacy of the mesh resolution in the streamwise direction, and (2) a bed morphology scheme which may cause mass loss. By adopting an improved bed morphology scheme, the predicted bed profiles appear to agree better with the experimental results. It is also found that care should be taken when considering the suspended load together with the wall function at the seabed boundary. [ABSTRACT FROM AUTHOR]

The article discusses research which analyzed the scour behavior characteristics of pipelines on mobile seabeds in terms of scout hole mechanisms, prevalence, length, depth and spacing. Topics discussed include an overview of the MOBILEspan Joint Industry Project launched in November 2013, seabed characterization and freespan length and frequency.

This article discusses research which investigated the breakwater foundation instability during tsunami in a drum centrifuge. Topics discussed include the centrifuge tsunami tests performed in a drum centrifuge under a centrifugal acceleration of 70 gravities, seepage-induced instability of rubble foundation and developments of scout and erosion under prolonged tsunami overflow.

The article discusses research which examined the local scour of pipeline under combined wave and current conditions. Topics discussed include the numerical model descriptions and setting which used the computational fluid dynamics (CFD) code and enhancement of the pipeline stability through hydrodynamic shielding and the increase of lateral soil resistance.

The article discusses research which examined the local scour in wave basin under the oblique waves. Topics discussed include the depth and width of scour, relationship between gap ratio and scour propagation, analysis of the influence of pipeline burial depth on scour and bed evolution and change of buried pipeline bed form under different wave conditions.

Conventional and geosynthetic scour protections around the slender pile under the waves were experimentally studied in the laboratory flume. One layer dumped stones was used for conventional protection. As a geosynthetic supported protection, geogrid wrapped one layer stones and geomembrane applications under the stone layer were used for protection around the pile. Experiments show that stones behave individual and turn, slide and roll through scour at the edge of protection at conventional random stone dump. Geogrid wrapped stone layer shows elastic behavior against edge scour and supplies better protection then classical way and geomembrane solution. Geomembrane which spreads under the stone layer also give better protection regarding classical way against edge scour although stones move over geomembrane and edges of membrane moves with waves. [ABSTRACT FROM AUTHOR]

The article discusses a study on numerical and experimental models of scour progression for complex structures such as tripod or gravity base foundations for offshore wind turbines. Topics addressed include the general possibility for conducting numerical simulations, the extension of OpenFOAM software code by a scour model, and rigid-bed and scour investigations. Also mentioned are the use of a multi-phase fluid flow model and load situations such as wave and current load cases.

The article presents an assessment of the relative density of backfilled soil material around monopiles for offshore wind turbines through experimental testing in the Large Wave Channel (GWK) of the Coastal Research Centre (FZK) in Hannover, Germany. Three-dimensional numerical modeling of a monopile foundation at the offshore wind farm in Denmark was used to asses the dependency of the relative density of backfill on the maximum pile bending moment.

The scour at abutments and elliptical and straight guide banks with a stratified bed under steady and unsteady clear-water conditions was studied. Tests were performed with uniform sand, standard deviation, one or two layers of different grain diameters, and different sequence and thickness of the layers. New methods for computing the depth of scour development in time and elliptical guide banks under stratified bed conditions are presented. Method are confirmed by tests results. At a stratified river bed, the most critical conditions for structures occur when a fine-sand layer lies under a coarse-sand layer. According to the results obtained in tests and by the method presented, the depth of scour is always greater when a fine-sand layer is under a coarse-sand layer(s). Using the mean grain size on the top of the river bed for calculating the scour depth, neglecting stratification, can lead to wrong results and possible damages and losses. [ABSTRACT FROM AUTHOR]

The scour development with time during multiple floods, equilibrium stage and the assessment of flood damage risk for engineering structures have been investigated. A method for computing scour development with time at engineering structures during multiple floods was used. The test confirmation of the method allows as to perform computer modelling of scour processes and to estimate the influence of floods with different probability, duration, sequence and frequency on the depth of scour. It was found that the scour parameters increase with decrease in probability and with increasing duration and frequency of the floods. The sequence of floods can increase or reduce the scour development with time, depending on their probability. The successive floods of the same probability considerably increase the value of the scour depth. [ABSTRACT FROM AUTHOR]

This article discusses a study which evaluated the required embedded lengths of monopile foundations with respect to scour. The study used the guidelines and regulations that provide the design procedures for pile foundation of offshore wind turbines. It examined the suitability of adopting the design criteria for monopile foundations. It showed the impact of the portions of moments applied on the monopiles on the pile deformation responses.

The article presents a study which examined pipe-soil-fluid interactions in subsea pipelines under extreme metocean conditions. It is stated that there is a neglect of seabed instability in the calculation procedures which may not reflect the actual behaviour. To reduce physical scale, there is a need to undertake laboratory studies due to the perceived high power demands and enormous test facility.

The article explores improved prediction methods for tsunami back-flow induced coastal scour and erosion. It discusses the numerical method utilized by the authors on the study, which was aimed at testing the prediction method for erosion and scour caused by the tsunami. It focuses on the examination of a scour fronting a seawall with high height crown with the use of a two-dimensional numerical model, which did not fit the two-dimensional numerical model as crown height is much higher than the thickness of the back-flow.

The article highlights the scour effect in terms of the deformation response of offshore foundation elements like the monopile, tripod and jacket systems. The authors used a three-dimensional finite element model to assess the lateral deformation of a pile that has been subjected to monotonic and cyclic loading. They also applied the degradation stiffness model to account for cyclic loading that utilize the cyclic triaxial tests results. According to the authors, the scour significantly affected the lateral displacement and rotation of the monopile.

The article presents the conducted study to analyze the development and impact of scour on the foundation of the jacket type offshore wind turbine that is exposed to wave and current. In the study made in the Near-Shore Wave Basin (NSWB) at the Tainan Hydraulics Laboratory (THL) in Taiwan, two locations of the foundations are independently simulated. It cites the four-layer scour protection that is tested to be effective in scour prevention of jacket type foundation at water depth of 12 meters (m) and 16m.

The article discusses a study that analyzed the function of flexible spoilers in submarine pipeline protection. According to the article, the pressure difference between the downstream and upstream of the pipe will induce a seepage underneath it to cause scour if the pipeline is laid on a sediment bed. It proposed a method for scour prevention. Results of the study showed that pressure gradient is near zero and the bottom scours disappear when the flexible spoilers exceed or reach a certain length.

The accurate prediction of the depth of scour around hydraulic structure (trajectory spillways) has been based on the experimental studies and the equations developed are mainly empirical in nature. This paper evaluates the performance of the soft computing (intelligence) techiques, Adaptive Neuro-Fuzzy System (ANFIS) and Genetic expression Programming (GEP) approach, in prediction of scour below a flip bucket spillway. The results are very promising, which support the use of these intelligent techniques in prediction of highly non-linear scour parameters. [ABSTRACT FROM AUTHOR]

The article presents a study that investigated the flow characteristics of the submerged suspended flexible curtain (SFC) for sediment harvest. The physical properties of the foamed polystyrene used for the experiment are cited. Major advantages of SFC which include self-adjustment to the flow conditions and its behaviors are discussed. Diagrams showing dynamic pressure contours at the base of SFC are presented.