Hydraulic structures play a crucial role in managing the dynamic forces of water bodies, especially along coastlines and riverbanks. One such essential structure is the groyne, designed to dissipate wave energy and prevent erosion by effectively trapping sediments. In this comprehensive article, we explore the classification of groynes based on various factors, shedding light on their construction materials, permeability characteristics, height, and functions.
Classification of Groynes
Types Based on Materials Used for Construction
1. Wood Groynes
Wooden groynes, constructed with timber piles, offer an economical solution for short-term purposes. While their durability is relatively low, they effectively meet specific requirements.
2. Sandbag Groynes
Utilizing sand or earth-filled bags, sandbag groynes serve temporary or short-term needs. A unique filter cloth prevents the bags from sinking into the ground, ensuring stability.
3. Rock Groynes
Constructed with large rocks, rock groynes provide exceptional durability and stability. They absorb significant wave energy, making them reliable in various conditions.
4. Concrete Groynes
Reinforced concrete or pre-fabricated concrete blocks form concrete groynes, known for their stability and durability. Proper foundation and soil conditions are crucial for their construction.
5. Sheet Pile Groynes
Using steel sheet piles, sheet pile groynes can be single or double walls. Double sheet pile walls enhance durability and stability, making them a robust choice.
6. Rubble-Mound Groynes
Widely employed along seashores, rubble-mound groynes utilize stones or specially made concrete units like tetrapods. The addition of sheet piling enhances their strength, ensuring high durability and stability.
Types Based on Permeability Characteristics
1. Permeable Groynes
Allowing water flow with reduced velocity, permeable groynes, constructed with materials like wood and sandbags, suit situations where a river carries suspended sediment.
2. Impermeable Groynes
Constructed with impermeable materials like rock and gabions, impermeable groynes prevent water flow. Adequate protection is essential to manage potential overflow during peak conditions.
Types Based on Height
1. Submerged Groynes
Constructed in deep river areas, submerged groynes, using permeable materials, reduce flow velocity, preventing erosion of the groyne’s top portion.
2. Non-Submerged Groynes
Built with a height exceeding the maximum flood level, non-submerged groynes utilize impermeable materials for construction.
Types Based on Functions
1. Attracting Groynes
Positioned with an angle of 45 to 60 degrees towards the downstream side, attracting groynes direct water flow toward the bank. While providing safety to one bank, they may impact adjacent banks and are not recommended due to limited silting possibilities.
2. Repelling Groynes
With an inclination of 60 to 80 degrees towards the upstream side, repelling groynes redirect water flow, creating a silt pocket. Widely used for river training and bank protection, they offer advantages over attracting groynes.
3. Deflecting Groynes
Built perpendicular to the bank, deflecting groynes redirect water flow without repelling, providing local protection to the banks.
4. Sediment Groynes
Constructed to manage sediment-laden river water, sediment groynes reduce stream velocity, facilitating sediment deposition. Permeable groynes are commonly used for this purpose.
In conclusion, understanding the diverse classifications of groynes is essential for effective hydraulic engineering and shoreline management. Each type serves a specific purpose, contributing to the overall stability and sustainability of water-related structures.