Sustainable Reuse of Mine Tailings as Cemented Backfill for Urban Ground Stabilization: Geomechanical and Numerical Assessment in Zaruma, Ecuador

The sustainable reuse of mine tailings as engineered backfill offers a potential strategy for simultaneously addressing mining-waste management and underground instability in historical urban mining districts. This study evaluates the geomechanical response of shallow underground galleries beneath Zaruma, Ecuador, by integrating geological, geotechnical, hydrogeological, geophysical, underground-mapping, and laboratory data within a 3D geometry-informed, two-dimensional finite-element framework under pseudo-static loading. Cemented tailings properties were derived from experimental programs using locally generated mine residues. Unsupported galleries developed pronounced stress concentrations, with maximum principal stresses of approximately 86.5 MPa and localized numerical total displacements approaching 4 m. Under the modeled complete-filling and full-contact condition, maximum principal stresses decreased to approximately 10 MPa, accompanied by marked reductions in displacement concentration and yielding. These results demonstrate an improvement in the modeled underground geomechanical response but do not quantify field-scale subsidence or sinkhole probability. The fully contacted configuration represents a favorable upper-bound stabilization condition. Beyond the Zaruma case, the study provides a transferable framework for critically evaluating cemented mine-tailings backfill in shallow, irregular urban underground workings.