Layered Grouting for Offshore Wind Pile Stability
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Solution Overview
Problem
Offshore wind power foundations with single pile rock-socketed foundations in weakly weathered bed rock face issues with fatigue rupture and local buckling failure due to rigid connection with rock and soil layers, and existing grouting methods fail to provide adequate bearing capacity and stability.
Innovation Solution
A high strength grouting method involving a layered construction process with different strength grouting materials in five layers, where ultra-high strength, high strength, and common high strength cement-based grouting materials are used in specific layers to stabilize the connection between the steel pipe pile and the rock and soil layers, avoiding complete rigid connection and reducing stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If grouting material is used to fill the gap between steel pipe pile and pile hole to provide bearing capacity and stability, then the bearing capacity and stability of the single pile are improved, but complete rigid connection between single pile and rock layer is formed leading to fatigue rupture and local buckling failure
Solution Approach 1:
The grouting area is divided into five distinct layers with different grouting materials and strength characteristics. The first layer (bottom) uses ultra-high strength grouting material for rock stratum connection, while subsequent layers use progressively weaker materials for overburden layer connection. This segmentation allows the foundation to achieve adequate bearing capacity through the strong first layer while avoiding complete rigid connection throughout, thereby reducing fatigue rupture risk.
Solution Approach 2:
Different regions of the grouting area are assigned different grouting material strengths based on local requirements. The rock stratum interface (first layer) requires ultra-high strength material for maximum bearing capacity, while the overburden layer interfaces (second through fifth layers) use progressively weaker materials to provide flexibility and reduce stress concentration. This local differentiation resolves the contradiction between strength and fatigue resistance.
2Strength
If single high strength grouting material is used to fill the gap between steel pipe pile and pile hole, then the bearing capacity is improved, but stress concentration occurs leading to local buckling failure
Solution Approach 1:
The grouting system is segmented into five layers with progressively varying material strengths. The ultra-high strength first layer provides necessary bearing capacity at the rock interface, while subsequent layers with reducing strength levels distribute and reduce stress concentration throughout the grouting zone, preventing local buckling failure.
Solution Approach 2:
The grouting material strength parameter is systematically changed across the five layers, transitioning from ultra-high strength at the bottom to progressively weaker materials toward the top. This parameter gradient allows the system to achieve high bearing capacity where needed while reducing stress concentration effects in upper layers, eliminating the harmful stress concentration problem.
Data Source
AI summary
The present invention is a grouting method for single pile rock-socketed foundation for offshore wind power, comprising: driving a steel casing into an overburden layer to dig the overburden layer and a rock stratum so as to dig a pile hole; hoisting a steel pipe pile into the steel casing and positioning the steel pipe pile in the pile hole, wherein an annular cavity is formed between the inner walls of the steel pipe pile and the pile hole and the bottom of the steel casing; grouting a first grouting layer to the bottom of a pipe hole of the steel pipe pile; grouting a plurality of grouting layers into the upper end of the first grouting layer in the annular cavity; and pulling out the steel casing, wherein after a grouting solution is aged, the steel pipe pile is stably connected to the overburden layer and the rock stratum.