Experimental Analysis of Water-Injection Uplift Recovery for Fixed Foundations in Offshore Wind Power

As early offshore wind turbines approach their design life, the efficient decommissioning of their foundations has become a critical technical challenge. Current methods often suffer from low recovery efficiency and poor operational stability. This study addresses these problems by systematically investigating the mechanical characteristics of the water-injection uplift recovery technology using laboratory-scale model tests. We analyze the influence of key operational parameters—specifically water injection rate, embedment conditions, and pile dimensions—on the full-process uplift mechanics. The research results indicate that while a faster injection rate improves recovery velocity, it also induces detrimental “jump-like behavior” and eccentric uplift, significantly increasing the risk of pile toppling. We identify that employing a combined “fast-to-slow” injection sequence is an optimal strategy, as it effectively balances recovery efficiency with process stability while reducing the risk of seepage failure. This study reveals the critical coupling relationship between injection pressure distribution and the pile–soil seepage state, providing an experimental basis and theoretical reference for optimizing the water-injection process to ensure safe and stable foundation recovery.