Mechanical response of highly gap-graded mixtures of waste rock and tailings. Part I: monotonic shear response

The idea of mixing mine tailings and waste rock to form 'paste rock' prior to disposal is now receiving significant attention from the point of view of sustainable mine waste management practices. This approach has been viewed as a favourable alternative to traditional methods of mine waste disposal because paste rock has the potential to overcome deficiencies (e.g., acid rock drainage and liquefaction-induced failures) associated with traditional methods. To advance the current limited knowledge, a laboratory research program was undertaken to study the mechanical response of paste rock. Testing was undertaken on paste rock specimens prepared so that the tailings would 'just fill' the void spaces within the waste rock particle skeleton. The findings suggest that the material is unlikely to experience flow deformation under monotonic shear loading conditions, at least up to the tested initial effective confining stress conditions of 400 kPa. The monotonic shear response of paste rock was found to be similar to that of rock-only material; this finding is in agreement with previous observations from one-dimensional consolidation testing where it had been shown that the rock particle skeleton would carry almost 90% of the externally applied stress on a given paste rock mass. Key words: mine tailings, mine waste rock, triaxial testing, monotonic shear loading. Le concept de << pate residus-steriles >> (PRS), c'est-a-dire le melange de rejets de concentrateur et de roches steriles avant leur deposition, recjoit maintenant beaucoup d'attention d'un point de vue de gestion durable des residus miniers. Cette approche est consideree comme une alternative favorable aux methodes traditionnelles de gestion des residus miniers puisque la pate residus-steriles peut potentiellement pallier a certaines preoccupations (ex. drainage minier acide et ruptures induites par liquefaction) associees aux methodes traditionnelles. Afin d'ameeliorer les connaissances actuelles, un programme de recherche en laboratoire a ete elabore pour etudier le comportement meecanique de la PRS. Les essais ont ete effectuees sur des echantillons de PRS prepares de facon ace que les rejets remplissent << tout juste >> les vides entre les particules des roches steeriles. Les resultats suggerent que le mateeriau a de faibles chances de subir des deformations sous des conditions de chargement en cisaillement monotonique, du moins jusqu'aux conditions testees de contraintes effectives de confinement initiales de 400 kPa. Le comportement en cisaillement monotonique de la PRS est similaire a celui de la roche sterile seule. Ce resultat concorde avec des observations precedentes obtenues lors d'essais en consolidation unidimensionnelle avec lesquels il avait ete; deemontre que le squelette des particules rocheuses pouvait supporter pres de 90% des contraintes externes appliqueees sur une masse de PRS. Mots-cles: rejets de concentrateur, roches steriles, essais triaxiaux, chargement en cisaillement monotonique. [Traduit par la Redaction]
Introduction The disposal of mine waste mainly involves management of the following two main waste types: relatively fine-grained tailings and coarse-grained waste rock. Fine-grained tailings are typically discharged in slurry [...]