Modified Spudcan Skirt Tip Geometry for Jackup Fixity
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Solution Overview
Problem
Traditional spudcans face limitations in fixity on dense sand and hard soils due to conical bottoms, and long skirts cause issues on soft or hard seabeds, leading to increased friction, stress, and potential damage during jackup operations.
Innovation Solution
A modified spudcan with a peripheral skirt where the skirt tip is higher than the central tip, allowing for adjustable height and slope to optimize contact and resistance, ensuring the central tip bears most reaction forces and minimizing horizontal resistance and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional spudcan with conical bottom is used, then penetration into soft soil is facilitated, but fixity in dense sand or hard soil is insufficient
Solution Approach 1:
The spudcan is segmented into distinct functional zones: a conical bottom portion for initial penetration and a skirt portion extending downward for providing fixity. The skirt is further divided into an upper portion and a lower portion with different slopes, allowing each segment to perform its specific function optimally without interfering with others.
Solution Approach 2:
Different portions of the spudcan are given different geometric qualities suited to their specific functions. The conical bottom has a steeper slope for cutting through soil, while the skirt portions have gentler slopes for providing lateral support and fixity. The upper and lower skirt portions have different slopes to optimize performance at different depths.
2Reliability
If a long peripheral skirt is added to increase fixity in dense sand, then bearing capacity is improved, but friction and stress increase leading to potential damage on soft or hard seabeds
Solution Approach 1:
The spudcan design incorporates dynamic adaptability through its geometric configuration. The varying slopes of the skirt portions allow the structure to adapt to different soil conditions during penetration and loading, optimizing performance while minimizing harmful friction and stress concentrations.
Solution Approach 2:
The skirt slope parameters are specifically optimized to balance fixity provision with friction reduction. The upper skirt portion has a different slope angle than the lower portion, creating a gradient that reduces stress concentration and friction compared to a uniform long skirt, while still providing adequate fixity in dense sand.
3Reliability
If the skirt tip is lower than the central tip, then embedment effect is maximized, but horizontal resistance increases during installation
Solution Approach 1:
The skirt provides partial embedment effect rather than maximizing it, with the skirt tip positioned at or slightly above the central tip level. This partial action approach provides sufficient fixity for the intended application while avoiding the excessive horizontal resistance that would result from a longer skirt extending below the central tip.
4Ease of operation
If a conical bottom is used for penetration, then anchoring in soft rock or hard soil is achieved, but full diameter utilization is limited resulting in lower fixity
Solution Approach 1:
The spudcan is divided into a conical bottom portion for penetration and a skirt portion for fixity provision. This segmentation allows the conical bottom to perform its penetration function while the skirt provides the additional fixity that the conical bottom alone cannot achieve, utilizing the full diameter of the spudcan structure.
Data Source
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Figure 3(a)~3(b)
AI summary
A modified spudcan with optimal peripheral skirt for enhanced performance of jackup operations comprises a spudcan top part, a spudcan bottom part, wherein the spudcan bottom has a central tip protruding from the central part of the spudcan bottom; wherein the top and bottom parts are coupled at their peripherals or through a spudcan side wall to form a hull structure, and a peripheral skirt having an upper end being coupled to the spudcan bottom part and a lower end extending downwardly, wherein the tip of the lower end of the peripheral skirt is higher than the distal end of the central tip.