Offshore Stone Foundation for Monopile Stability
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Solution Overview
Problem
Monopile constructions for offshore energy systems are not economically viable for water depths greater than 30 meters due to instability and high installation costs, and they are unsuitable for stony seabeds.
Innovation Solution
An offshore foundation composed of a conical heap of unbound broken stones, ranging from 1 mm to 200 mm in size, is applied to the seabed, compacting naturally to form a stable truncated cone shape that allows for reduced monopile penetration depth and enhanced scour protection, enabling monopile use in deeper waters without complex profiling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If monopile constructions are used in deeper waters (greater than 30 meters), then the use of monopile structures can be extended to deeper water depths, but stability cannot be guaranteed and installation becomes economically unviable
Solution Approach 1:
A stone foundation is constructed on the seabed before the monopile is installed. This preliminary foundation provides immediate stability support, allowing the monopile to be installed in deeper waters without requiring excessive penetration depth into the seabed, thus maintaining both adaptability to deeper waters and structural stability
Solution Approach 2:
The foundation system combines the monopile structure with a stone foundation base, creating a composite system that leverages the strengths of both materials. The stone foundation provides broad base stability while the monopile provides structural support, enabling stable installation in deeper waters
2Reliability
If monopile diameter is increased to 6-7 meters to ensure stability in deeper waters, then stability improves, but installation costs increase significantly
Solution Approach 1:
The stone foundation is constructed in advance before monopile installation, providing the necessary stability support beforehand. This allows the use of smaller diameter monopiles (reducing manufacturing and installation costs) while still achieving the required stability through the combined foundation system
Solution Approach 2:
The stone foundation acts as an intermediary element between the seabed and the monopile. It distributes and transfers loads from the monopile to the seabed, providing stability without requiring the monopile itself to be of excessive diameter, thus reducing manufacturing and installation costs
3Reliability
If monopile is driven deeper into the seabed to ensure stability, then stability improves, but the required penetration depth becomes excessively large
Solution Approach 1:
The stone foundation is constructed on the seabed before the monopile is installed. This preliminary foundation provides the necessary stability support, allowing the monopile to achieve sufficient stability with reduced penetration depth into the seabed, thus avoiding excessively large penetration depths while maintaining reliability
4Reliability
If complex profiling work is performed on the seabed to prepare for monopile installation, then installation stability improves, but the process becomes more complex and time-consuming
Solution Approach 1:
Instead of performing complex seabed profiling work, the invention constructs a stone foundation on the existing seabed surface. This preliminary action provides the necessary stability without requiring complex seabed modification, thus maintaining installation stability while avoiding complex profiling operations
Solution Approach 2:
The invention converts the challenge of unstable or unsuitable seabed conditions into an opportunity by constructing a stone foundation that adapts to various seabed types. This approach provides stability without requiring complex profiling work, regardless of the original seabed conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides cost-effective stability and scour protection, allowing monopile use in deeper waters, reduces material needs for monopile production, and is environmentally friendly with easy dismantling and material reuse.
Implementation Method 1
the stones in the composite are arranged in a conical, at least truncated cone-shaped, heaped sedimented manner, the stones are applied at specific points on the seabed at the later location of the monopile and are compacted, or at least sedimented, exclusively by their own weight
Implementation Method 2
the unbound broken stones interlock or connect with each other particularly well due to the introduction and self-compacting after being placed on the seabed, so that even strong movements and forces are very well integrated into the foundation and the seabed can be introduced
Data Source
Figure 1
AI summary
The invention relates to an offshore foundation (4) for a monopile (1) of an offshore power plant, in particular wind power plant or hydroelectric power plant, for securing the monopile in and on the sea bed (2) using stone, wherein the offshore foundation (4) consists exclusively of loose, broken stones (41) which are piled up on the sea bed (2), and are in the form of a widely graded mix with stone sizes ranging from 1 mm to 200 mm, and the piled‑up stones (41) sediment conically, at least frustoconically, together, wherein the stones (41) are arranged on the sea bed (2) at a certain point, where the monopile (1) will later be located, and are compacted, at least sedimented, exclusively under their own weight. The invention also relates to a production method for an offshore foundation (4) for and with a monopile (1) of an offshore power plant, at least one wind, solar or hydroelectric power plant, for securing the monopile (1) in and on the sea bed (2), the method having the following steps: - a stone mix made up of loose and broken stones (41) in the form of a widely graded mix with stone sizes ranging from 1 mm to 200 mm is piled up, up to the height M, at a certain point of the sea bed (2); - the piled‑up stones (41) self‑sediment to form a truncated cone, at least one cone; - the monopile (1) is introduced directly into, and through, the offshore foundation (4) by ramming, drilling and/or vibration, the monopile ultimately being introduced (h3) into the sea bed (2).