Geotechnical and structural analysis in the remediation of sinkholes: A case study in Alcalá de Ebro (Zaragoza, Spain)

Abstract Karst-related subsidence constitutes a major geotechnical hazard in areas underlain by evaporitic formations. The municipality of Alcalá de Ebro (NE Spain) has experienced recurrent sinkhole activity associated with gypsum dissolution, causing damage to roads, buildings and public infrastructure. Previous remediation measures, including aggregate backfilling and resin injections, achieved only partial success and did not prevent further subsidence. This study evaluates the effectiveness of a ground-improvement system based on low-mobility mortar columns combined with geogrid reinforcement. A numerical model was developed using the finite element method in SAP2000. The model incorporated the stratigraphic profile obtained from geotechnical investigations and reproduced the mechanical behaviour of the untreated ground and the reinforced configuration. Attention was given to the assessment of vertical displacements and settlement reduction under service and ultimate loading conditions. The results indicate that the proposed solution substantially improves the mechanical response of the ground. Maximum calculated settlements were reduced by approximately 96% compared with untreated conditions. The mortar columns increase ground stiffness and load-bearing capacity, while the geogrid contributes to load redistribution and improved deformation control. The proposed technique therefore represents an effective solution for mitigating sinkhole-related ground deformation in evaporite-karst environments.