Groyne

About: Groyne is a research topic. Over the lifetime, 397 publications have been published within this topic receiving 4549 citations. The topic is also known as: groin & Breakwater.

Concrete groyne of consolidation structure

Abstract: PURPOSE: A prefabricated concrete groyne is provided to keep stability against strong water current, to prevent the disassembly of unequal subsidence, and to improve constructability by uniform products. CONSTITUTION: The prefabricated concrete groyne comprises the steps of forming a center assembly unit(5) in the center of a square wing-shaped body(2) to couple with a straight assembly bar(3), forming a coupling projection on an assembly bar(3) to make an assembly bar(3) support a main body(2) when coupling a main body(2) and an assembly bar(3), and forming a binding groove on the assembly bar(3), then fitting a steel bolt to prevent the separation of the main body(2) and the assembly bar(3) when overturning.

Variation in beach behaviour in relation to groyne spacing and groyne type for mixed sand and gravel beaches, Saltdean, UK

Abstract: Coastal protection schemes that combine beach recharge and the construction of hard structures are becoming increasingly common. Accurate prediction of the post-recharge behaviour of sand and gravel beach material in such schemes is vitally important to ensure that the vulnerable points of the structures, such as the toes of seawalls or the roots of groynes, do not become exposed through any longshore or cross shore movement of the material. Increasing the volume of material between groynes reduces the risk to the hard structures, but increases costs for both the recharge material and the structures designed to contain them. Monitoring of the behaviour of a mixed beach between groynes of different spacing and type at Saltdean on the southeast coast of England, over a period of 4.5 years, using detailed topographic surveys, has shown; i. that there is no natural cross shore exchange between the mixed beach and the subtidal zone; ii. that the pattern of sediment movement within the groyne bays is very similar, independent of groyne spacing and type, and iii. that the magnitude of change is dependent on groyne spacing. Rock groynes were permeable to gravel at average rates of between 0.5 to 1.1 m3 per day. Surveys also show that rotation of beach planform even under storm conditions is only 9 compared to a rotation of up to 74 that was predicted by numerical modelling in the design study for the scheme. This suggests that almost 50% of the recharge material, costing 1 million is in excess of that needed to ensure satisfactory protection and highlights the need for better prediction input to design.

Measurement of momentum transfer caused by a groyne in compound channel

Abstract: The present study investigates flow in an asymmetrical compound channel with a thin obstacle set on the floodplain, perpendicular to the main flow direction. Six flow configurations were investigated. Two flows were carried out under uniform flow conditions and four flows were carried out with a thin obstacle of variable length (d). Depending on the investigated relative depths (Hr) and aspect ratios d/Bfp (where Bfp = floodplain width), depth-averaged velocity and distribution of water depth across the channel were first examined. Streamwise profile of discharge distribution and mass exchanges were then deduced. Using a one dimensional momentum equation in each subsection, momentum balances were finally worked out. In addition to the classical turbulent exchange located at the vertical interface between the main channel and the floodplain, a significant momentum flux related to mass exchanges between subsections was observed when flow occurred near the groyne. In the floodplain, analysis emphasizes that the momentum transfer due to mass exchanges is (1) several orders of magnitude larger than momentum transfer due to turbulent exchange and (2) have the same magnitude order as friction on solid walls, whatever the groyne length and the relative depth are. In the main channel, solid wall friction is equivalent or larger than momentum transfers.