Skirted Gravity-Based Foundation with Gravel Drainage Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gravity-based offshore structures face instability due to pore pressure build-up and pumping effects caused by weak seabed soils and water pockets, with existing solutions like dredging and grouting being costly and environmentally disruptive, and current scour protection methods not addressing pore pressure issues.
Innovation Solution
A gravity-based structure featuring a skirted foundation with a pre-installed gravel layer acting as both a drainage layer and scour protection, with graded pore openings for effective water drainage and sediment prevention, reducing pore pressure and pumping effects while providing immediate erosion protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dredging operations are performed to remove weak seabed layers, then pore pressure build-up is reduced, but costs increase and marine environment is disturbed
Solution Approach 1:
A gravel drainage layer is introduced as an intermediary between the foundation and the weak seabed soil. This layer mediates the interaction by providing a controlled drainage path for pore water while protecting the foundation from direct contact with problematic soft soils, thereby reducing pore pressure without requiring extensive dredging that would disturb the marine environment
Solution Approach 2:
The foundation base is segmented into multiple drainage compartments or zones through the gravel layer configuration. This segmentation allows localized drainage control and reduces the need for large-scale dredging operations, thereby maintaining foundation stability while minimizing environmental impact
2Reliability
If a gravel layer is placed on the seabed to prevent water pockets, then pumping effect is reduced, but manufacturing precision requirements increase and differential settlement may occur
Solution Approach 1:
The gravel drainage layer is designed with specific local properties including controlled thickness, grain size distribution, and permeability characteristics. By optimizing these local qualities, the system achieves effective drainage without requiring strict overall placement tolerances, thereby maintaining stability while reducing manufacturing precision requirements
Solution Approach 2:
The grain size distribution and thickness of the gravel layer are optimized to create appropriate void spaces that allow water drainage while preventing differential settlement. By changing these physical parameters within specific ranges, the system achieves both drainage functionality and tolerance to placement variations
3Ease of manufacture
If the foundation has a generally even underside, then installation is simplified, but ability to resist sliding under side forces is limited
Solution Approach 1:
The foundation base incorporates curved or inclined surfaces rather than completely flat surfaces. These curved geometries increase the contact area and frictional resistance to sliding forces while maintaining relative simplicity in construction, thereby improving sliding resistance without significantly complicating the manufacturing process
4Reliability
If grout is injected into compartments to avoid water pockets, then pumping effect is reduced, but cost increases and drainage of seabed water is blocked
Solution Approach 1:
Instead of using grout to block water pockets (which would prevent drainage), the invention converts the water pockets into beneficial drainage reservoirs by surrounding them with highly permeable gravel material. The trapped water is then drained through the gravel layer, transforming the harmful pumping effect into a beneficial drainage mechanism that reduces pore pressure while maintaining simplicity
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
The solution significantly enhances the stability of offshore installations by effectively draining pore pressure and preventing erosion, allowing for a substantial amount of water pockets beneath the foundation without compromising load-bearing capacity, and can be installed with reduced environmental impact and cost.
Implementation Method 1
a plurality of openings for drainage of water... pre-installed on the seabed before the installation of the foundation... suitable for draining water entrapped beneath the basal portion to the openings
Implementation Method 2
a plurality of openings for drainage of water... pre-installed on the seabed before the installation of the foundation... filter material, with a gradation suitable for draining water
Data Source
AI summary
A gravity-based structure (1) for supporting offshore installations comprising a foundation (4). The foundation (4) has a basal portion (11). The basal portion (11) has a plurality of openings (10) for drainage of water. There is at least one first layer (7) of filter material, with a gradation suitable for draining water entrapped beneath the basal portion (11) to the openings (10). The layer (7) is installed on the seabed (8) beneath the foundation (4). The foundation has a downwardly extending skirt (5) that is adapted to penetrate into the seabed beneath the filter material layer (7).