Uplift Prevention Analysis of a Water Retaining System Subjected to a Large and Rapid Drawdown

Abstract

This research addresses the complex challenge of mitigating uplift within a water-retaining system, specifically focusing on the Valmeer Energy Storage Lake (ESL), an integral part of the DELTA21 project. The need for rapid emptying of the ESL during storm surges, often within a tight 12-hour window, has raised concerns about potential seabed uplift and associated volume loss. The central objective of this research is to ensure the stability and integrity of the ESL under these drawdown conditions, particularly by investigating how the soil at the lake’s bottom can achieve equilibrium.
This study explores the Delta21 plan and the energy storage lake concept. Subsequently, it investigates the geological characterisation of the ESL site, providing data for subsequent analyses. Furthermore, a possible solution for using anchor piles is proposed; for that, a review of the Eurocode is done to understand the mechanisms of anchor piles and anchor pile groups. This research study employs Finite Element Method (FEM) calculations to assess bottom stability, both with and without incorporating anchor piles.

Throughout the research, a combination of hand calculations and Finite Element Method (FEM) analysis was employed to understand the subject matter comprehensively. The optimal centre-to-centre distance of 1.2m emerged as the key to effectively preventing uplift. The study also explores the interchangeability of volume elements and embedded piles within the FEM analysis, highlighting their comparable functionality.
Furthermore, an investigation into complete collapse scenarios suggests that tension piles ́ contribution to soil stability might be closely related to their weight rather than their spacing. Nevertheless, the spacing implementation presents challenges, emphasising the necessity for innovative solutions.
Additional soil investigations are recommended to understand the impermeable layer's exact location further. With its potential for uplift due to backpressure, this impermeable layer adds complexity to the interaction between soil layers. Recognising the constraints of the research scope, it is evident that further field investigations and research endeavours are indispensable for a comprehensive understanding of the site conditions and the impermeable layer’s behaviour.
In the final stages, the research concludes with a discussion and recommendations for the DELTA 21 plan specifically and presents the results obtained during this research.