Underwater Concrete Column Support for Seabed Soft Ground Subsidence
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Solution Overview
Problem
Existing underwater concrete structures installed on seabed soft ground face subsidence issues due to the difficulty in creating a suitable foundation, especially in deep water and thick soft ground conditions, leading to structural instability and high construction costs.
Innovation Solution
A construction method involving the installation of a main concrete structure with vertical penetration holes, followed by forming a ground perforated part and inserting a concrete column formation part comprising a reinforcing member, waterproof membrane, and fresh concrete to create a concrete column with distinct parts supporting the main structure, thereby preventing subsidence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soft ground improvement methods (replacement riprap, deep mixing) are used to create a suitable foundation, then structural stability is improved, but construction complexity and cost increase significantly
Solution Approach 1:
The concrete column is divided into multiple segments with different diameters: an upper portion with diameter D1 and a lower portion with diameter D2 (where D2 > D1). The lower portion with larger diameter provides enhanced bearing capacity and prevents subsidence in soft ground, while the upper portion maintains structural integrity. This segmentation allows the single column to simultaneously address both stability requirements without complex construction procedures.
2Reliability
If soft ground improvement equipment is extended to reach bedrock in deep water (60-100m length required), then foundation suitability is improved, but construction cost and difficulty increase
Solution Approach 1:
Instead of extending soft ground improvement equipment upward from the seabed to reach bedrock (conventional approach), the invention inverts the approach by pouring concrete columns downward through penetration holes from the upper structure. The concrete is poured under its own weight through the penetration holes, automatically forming columns that extend into the soft ground and reach bedrock without requiring long improvement equipment.
Solution Approach 2:
The concrete column formation process utilizes the concrete's own weight to drive the material downward through the penetration holes and into the soft ground. The concrete self-forms the columns without requiring external vibration, compaction, or long equipment extensions, thereby simplifying construction and reducing costs while still achieving bedrock contact.
3Ease of manufacture
If a uniform concrete column diameter is used throughout, then construction simplicity is maintained, but subsidence prevention capability is insufficient in soft ground
Solution Approach 1:
The concrete column employs different diameters for different locations: the lower portion embedded in soft ground has a larger diameter D2 to provide maximum bearing capacity and prevent subsidence, while the upper portion has a smaller diameter D1 to maintain structural integrity and reduce material usage. This local differentiation of geometric properties optimizes both subsidence prevention and construction efficiency.
Data Source
AI summary
An underwater concrete structure for preventing subsidence at seabed soft ground, includes: a main concrete structure installed on an upper part of seabed soft ground on a top of seabed rock, wherein the main concrete structure is spaced apart upward from the seabed rock and has a plurality of vertical penetration holes extending vertically; and a plurality of concrete columns formed continuously along the vertical penetration holes and the seabed soft ground and the seabed rock located under the vertical penetration holes.