Scour Protection Slabs with Gapped Edges for Quay Walls
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Solution Overview
Problem
Existing scour protection methods for underwater bottoms alongside quay walls, such as granular protection and concrete mattresses, are inadequate in providing reliable and efficient protection against erosion caused by increasing vessel sizes and propulsion powers, often requiring large, heavy rocks that may not be readily available and leading to arbitrary thickness and density variations.
Innovation Solution
A scour protection system comprising a foundation/leveling layer of rocks with a specific size distribution (100 < D n50 < 225 mm) and prefabricated reinforced concrete slabs positioned with gaps between edges, which provides reliable support and stability, allowing for precise control of thickness and density, and facilitating easy replacement and installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If large and heavy rocks (1-5 tons) are used for scour protection, then the protection strength is sufficient to withstand vessel thrust forces, but the rocks may not be readily available and require thick layers that reduce maximum available water depth
Solution Approach 1:
The scour protection is divided into multiple layers with different rock size characteristics. The foundation layer uses rocks with Dn50 between 100-225mm, while the protection layer uses smaller rocks with Dn50 between 50-150mm. This segmentation allows achieving sufficient protection strength without requiring excessively thick single-layer configurations, thereby preserving water depth.
Solution Approach 2:
Different rock size distributions are applied at different locations and layers. The foundation layer receives coarser rocks (Dn50 100-225mm) for structural stability, while the protection layer uses finer rocks (Dn50 50-150mm) for erosion resistance. This local differentiation optimizes both strength and water depth requirements.
2Reliability
If granular protection is applied, then scour protection is provided, but accurate installation and leveling are required and thickness/density vary arbitrarily depending on crane driver experience
Solution Approach 1:
A foundation layer with specifically controlled rock size distribution (Dn50 100-225mm) is placed first to create a stable, level base. This preliminary action ensures that subsequent protection layer placement occurs on a uniform surface, reducing variability in final thickness and density regardless of installation operator experience.
Solution Approach 2:
The invention specifies precise rock size distribution parameters (Dn50 values) for both foundation and protection layers. By controlling the granulometric parameters of the rock materials, the system achieves consistent thickness and density characteristics that are not dependent on installer skill level.
3Strength
If mattresses of concrete blocks or rock are used, then sufficient strength is provided, but these materials may not always provide adequate protection or may not be available at the site
Solution Approach 1:
Instead of using pre-fabricated mattresses with fixed properties, the invention uses rock materials with controlled size distribution parameters (Dn50 100-225mm for foundation, Dn50 50-150mm for protection). This allows adaptation to locally available rock materials while maintaining consistent protective performance through parameter control rather than requiring specific manufactured products.
4Reliability
If thick layers of rocks are used for scour protection, then adequate protection is achieved, but the maximum available water depth alongside the quay wall is reduced
Solution Approach 1:
The protection system is segmented into a foundation layer (Dn50 100-225mm) and a protection layer (Dn50 50-150mm). This segmentation allows achieving adequate scour protection with optimized total thickness, as each layer performs its specific function efficiently, reducing the need for excessive overall thickness that would reduce water depth.
Solution Approach 2:
The system uses a composite structure combining two different rock size distributions. The coarser foundation layer provides structural stability while the finer protection layer provides erosion resistance. This composite approach achieves reliable protection with optimized material usage and reduced total thickness requirements.
Data Source
Figure 1
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Figure 3A~3B
AI summary
A scour protection for an underwater bottom alongside a quay wall is disclosed. The scour protection comprises a foundation/leveling layer of rocks with a size distribution conforming to 100 < Dn50 < 225 mm, and a plurality of prefabricated reinforced concrete slabs, adjacently positioned on top of the foundation/levelling layer and leaving a gap between edges of the slabs. A method for providing the scour protection is also described.