Geotechnical Evaluation of Quarry-to-Lake Conversion Using Numerical Modelling

Abstract

The conversion of exhausted sand and gravel quarries into artificial lakes represents an increasingly adopted post-mining land-use strategy, particularly in alluvial environments where excavations intersect shallow groundwater systems. However, the long-term stability of quarry slopes under changing hydrogeological conditions remains a critical geotechnical challenge. This study presents a numerical investigation of slope stability for the planned quarry-to-lake conversion of the Simeria Veche-2 perimeter (Hunedoara County, Romania), located within the Strei River floodplain. The site is characterised by thick gravel–sand alluvial deposits overlying compact marly clay, with excavation extending below the natural groundwater table. Slope stability analyses were performed using both limit-equilibrium (SLIDE2) and finite-element (RS2) modelling approaches under multiple hydrogeological scenarios, including dry conditions, a natural groundwater regime, partial filling, and full-lake development, using a drained analysis. The results indicate that groundwater conditions represent the dominant controlling factor affecting long-term slope stability. While the proposed 45° slopes remain stable under dry conditions, safety margins decrease significantly when pore-water pressure is considered. The study highlights the importance of integrating hydrogeological processes into post-mining geotechnical design and proposes practical measures, including slope optimisation, staged filling strategies and groundwater monitoring. The proposed methodology provides a useful framework for the safe rehabilitation and long-term management of quarry lakes developed in highly permeable alluvial deposits [1], [2], [3].