The mechanical behaviour of filtered iron ore tailings is governed by stress paths and fabric anisotropy induced during placement and compaction in “dry”-stacked facilities. Although cementation is widely used to enhance strength and stiffness, most studies remain limited to axisymmetric conditions, providing limited insight into multiaxial stress states and the role of intermediate principal stress. This study evaluates the multiaxial behaviour of cemented iron ore tailings under different stress paths, focusing on stress-path dependency and anisotropy. Initial characterization comprised unconfined compression tests on mixtures prepared with varying dry unit weights and cement contents. Selected mixtures were then tested in a true triaxial apparatus under constant mean effective stress, considering compression, plane stress, and extension loading paths. Results show that cementation increases stiffness and strength while reducing sensitivity to loading direction and stress path. Compaction-induced anisotropy observed in untreated tailings is mitigated after cement addition, particularly under compression and plane stress conditions. Cemented specimens also exhibit lower volumetric strains, indicating improved resistance to contractive behaviour. Overall, cementation promotes a more isotropic multiaxial response in iron ore tailings under stress conditions representative of “dry”-stacked facilities, highlighting the importance of incorporating stress-path effects in stability assessments.
This paper presents a field-based assessment of near-surface hydraulic conductivity in a compacted filtered iron ore tailings stack using mini-infiltrometer tests. A total of 115 in situ measurements were performed on the compacted surface, providing a dataset for evaluating the variability of near-surface field measurements under controlled suction conditions. The mini-infiltrometer results are interpreted as hydraulic conductivity values associated with the pressure head applied at the porous disk–tailings interface, not necessarily as fully saturated hydraulic conductivity. The measured values ranged from 1.14 × 10−7 m/s to 4.59 × 10−6 m/s, with an arithmetic mean of 1.31 × 10−6 m/s, a median of 1.20 × 10−6 m/s, and a geometric mean of 1.12 × 10−6 m/s. Although the results were concentrated around 10−6 m/s, the coefficient of variation was approximately 56.9%, indicating relevant relative variability. Most values were located between 5.0 × 10−7 m/s and 3.0 × 10−6 m/s, supporting the use of the geometric mean as a representative central estimate for engineering analyses. The influence of imposed suction (h0 ) was also examined; however, no systematic dependence on the applied values was identified. Comparison with published data shows that the results fall within the range reported for compacted and filtered tailings, while reinforcing that hydraulic conductivity cannot be inferred from void ratio alone. The study highlights the importance of direct field measurements for supporting seepage analyses, transient flow modelling, water balance assessments, and hydraulic characterization of filtered tailings stacks.
Fault-induced permanent ground deformation poses a serious threat to foundations located near active reverse faults. This study numerically investigates the coupled response of a shallow foundation and a single pile subjected to reverse fault rupture using a two dimensional finite element model. The numerical framework is developed based on centrifuge test configurations and validated against experimental observations in terms of rupture trajectory, foundation deformation, and pile response. The results demonstrate a strong coupled interaction between the shallow foundation and the pile. The presence of the pile significantly increases the rotation and lateral displacement of the shallow foundation, while the shallow foundation alters the surrounding soil stress field and leads to higher bending moments along the pile. Parametric analyses conducted for different normalized fault offsets (h/H) demonstrate that increasing fault displacement intensifies stress concentration and expands the plastic zone in the vicinity of the pile–foundation system. The findings emphasize that shallow and deep foundation elements should not be designed independently in fault-affected regions, and that coupled soil–foundation interaction should be considered to improve seismic resilience under reverse fault rupture.
The geotechnical behavior of non-plastic tailings is governed by a unique critical state line (CSL) that, unlike those of many natural soils, may exhibit pronounced non linearity associated with state transitions from strain-softening at low mean effective stresses to strain-hardening at higher stress levels. This study investigates the material properties and state variables controlling this behavior, with particular emphasis on their correlation with index properties and their role in defining inflection points associated with transitions from flow instability and liquefaction to stable soil response. A data driven meta-analysis is performed using a global database of laboratory test results on iron tailings. The methodology integrates statistical characterization of physical attributes, followed by exploratory analysis using Spearman correlation matrices to identify the variables governing the shape and position of the CSL. Results demonstrate that CSL parameters are primarily controlled by minimum and maximum void ratios and specific gravity, while fines content and mineralogy exert secondary influences. The established correlations enable prediction of the CSL geometry, providing a practical screening framework for preliminary assessment of the geomechanical behavior of iron tailings and their susceptibility to liquefaction.
Recent tailings dam failure in Brazil resulted in significant social, environmental and economic impact. Following the failures, Brazilian regulation changed and demanded tailings dam breach analysis to consider Non-Newtonian fluid behavior, where applicable. However, in addition to rheology, other variables such as failure mode, breach hydrograph and Manning coefficient also influence tailings runout. The objective of the present study is to evaluate the influence of rheological and breach parameters (including failure mode) on tailings runout and, especially, on self-rescue zone (ZAS) definition. The study evaluated tailings breach runout for four iron ore tailings dams located in Brazil. Runout simulations considered different peak flow hydrographs for overtopping and piping, through Monte Carlo analysis. For liquefaction a single hydrograph was considered. Different combinations of hydrographs and rheology were evaluated, as well as Newtonian behavior (water parameters). Rheological parameters were taken specifically for one dam and from a database of 1162 vane rheometer tests in iron ore tailings and sediments for other three dams. Manning coefficient variation was also evaluated. Results were evaluated for four hydraulic variables along downstream path: frontal wave arrival time, time to peak, maximum wave velocity and height. Comparison of results through Kruskall-Walis test indicated that for most of the cases rheological parameters and Manning coefficient variation produced similar results. Peak flow hydrographs influenced results significantly. Self-rescue zone downstream extent was only influenced by liquefaction failure mode. Lateral extent of self-rescue zone was only slightly influenced by rheology variation but was influenced by peak flow hydrographs.
