Beach maintenance refers to artificially replenishing the beach when the natural supply of sand on the beach is relatively insufficient, that is, placing a certain particle gradation of sand and gravel on certain eroded beaches by means of hydraulic or mechanical transportation. At the same time, depending on the characteristics of the coastal environment, it should be supplemented by guide embankments to promote siltation or external breakwaters (or submerged embankments) to protect against storm surges.
The engineering concept of beach maintenance is to create a sand-replenishing environment for the coast lacking sediment, instead of resisting natural forces to prevent sediment loss. This method can not only be used for emergency treatment of eroded shore sections but also for long-term prevention and control. coastal erosion.
Beach maintenance usually includes three stages of the investigation, reconstruction, and repair, and the project scale can range from several thousand cubic meters to several million cubic meters. According to the different positions of sediment accumulation on the coastal section, it can generally be divided into the following four forms:
(1) Sand dune replenishment: All the replenishment sediment is accumulated above the average tide level, without directly increasing the width of the dry beach, which can block the storm wave period
The sediment in between can migrate across the top, with little loss and low sand-throwing technology.
(2) Beach shoulder replenishment (dry beach replenishment): The replenishment sediment is mainly accumulated above the average tidal level, and the width of the dry beach is increased, and the effect is remarkable.
The sand-throwing technology is medium, and the loss is relatively large. It is the most frequently used sand-throwing scheme at present.
(3) Section sand replenishment: fill the replenishment sediment on the entire beach section, and throw sand directly according to the balanced shape of the section during construction.
The effect is remarkable, the sand-throwing technology is high and it is easily damaged by storm surges.
(4) Inshore sand replenishment (submerged sand dam replenishment): Dispose of the replenishment sediment below the average low tide level near the shore to form a
Several underwater artificial sand dams rely on the action of natural waves to transport sediment to the shore and beach
On those beaches with big waves, little sand, and bare reefs, it is difficult to rebuild the beach by throwing sand and raising the beach alone.
The dam and the hard engineering combined with two are used to protect the sand from the waves to maintain the stability of the thrown sand.