Recognising soft-sediment deformation structures as evidence of static liquefaction in historical tailings from Central Mexico

Abstract

This paper presents a case study of soft-sediment deformation structures (SSDSs) in mining tailings from Central Mexico’s Guanajuato Mining District (GMD). We analyse SSDSs formed in anthropogenic historical environments (tailings) and under static (non-seismic) conditions in three inactive tailings deposits. Physical characterisation tests and sedimentological analyses were conducted at each site for SSDSs and their associations. We found that rapid sedimentation resulted in excess pore pressure, which caused overloading. This overloading was enough to trigger liquefaction and the formation of various SSDS types like flame structures, convolutes, folds, load casts, detached pseudo-nodules, and clastic dykes. The SSDSs and mechanisms described show that the tailings were momentarily liquefied and locally fluidised. However, no flow failure has been reported in the tailing deposits studied. SSDS studies based on known contexts are needed to improve and document the diagnostic features of liquefaction and fluidisation studies of non-seismic origin. Also, it is important to exercise caution when undertaking mining activities near tailing storage areas to prevent catastrophic consequences.