Understanding the water retention behavior of unsaturated granular materials is essential for interpreting water redistribution in porous media, particularly when changes in moisture content may affect drainage, saturation and flow-type responses. In iron ore logistics, this issue is relevant both during maritime transport, where internal moisture redistribution within bulk cargoes may generate locally saturated zones, and in stockpiles, where variations in water content influence drainage conditions and mechanical behavior. Although Transportable Moisture Limit (TML) procedures provide operational criteria for safe shipping, they do not explicitly describe the hydraulic state of the material or the transient redistribution processes that may occur after loading. This study investigates the soil water retention curve (SWRC) and the unsaturated hydraulic conductivity function, k(ψ), of a Brazilian iron ore fines material using the HYPROP system, a semi-automated evaporation apparatus based on Wind’s method. Tests were performed on the complete grain-size distribution at different void ratios, and additional tests were conducted on grain-size fractions associated with TML-related procedures, including the Flow Table Test. The results show that changes in packing state produce modest shifts in the SWRC but more pronounced differences in k(ψ), indicating the sensitivity of hydraulic conductivity to void ratio and pore connectivity. The comparison between the MPFT/PFD80 and Flow Table results suggests that the normative TML criteria can be interpreted within a hydraulic state framework defined by moisture content, degree of saturation, suction and hydraulic conductivity. The findings support the interpretation of TML not only as an empirical moisture threshold, but also as an initial hydraulic condition for time-dependent moisture redistribution under restricted drainage conditions.
Wicking geotextiles are specialized geosynthetics designed to regulate soil moisture through a combination of capillary-barrier and lateral-drainage mechanisms. Laboratory and field studies demonstrate their effectiveness in reducing volumetric water content, restricting capillary rise, and maintaining subgrade and base stability under rainfall, dry–wet cycles, freeze–thaw cycles, and traffic loading. Performance is influenced by soil type, fines content, installation depth, edge exposure, and environmental conditions. Field applications show benefits in pavements, expansive soils, pumping-prone sections, cold-region roadbeds, and permeable urban infrastructure. Multi-layer and composite geotextiles further enhance hydraulic and mechanical performance. Despite these advantages, gaps remain in standardized testing, long-term monitoring, design methods, and durability assessments under aggressive conditions. This review synthesizes recent experimental and field evidence, highlighting mechanisms, performance factors, and research needs to guide the optimal design and application of wicking geotextiles in geotechnical engineering.
Muhammad Shahbaz, Jun Guo, Jiajun Liao et al.· Applied Sciences· 0 citations
Tailings storage facility (TSF) reclamation commonly involves the construction of cover systems, requiring large volumes of materials with specific hydro-geotechnical properties. When suitable materials are not locally available, their extraction and transport can generate significant environmental and economic costs. On abandoned or inactive TSFs, where long-term acid mine drainage may occur, reclamation is highly sensitive to geochemical conditions, especially for weathered tailings affected by indirect oxidation and secondary mineral precipitation. Using these tailings as cover materials represents a promising alternative but would require improvement of their mechanical performance and limitation of metal leaching. This study investigated the effectiveness of general use limestone (GUL) and slag-based cements, a combination of GU and ground granulated blast furnace slag (GGBFS), for the solidification/stabilization of weathered tailings to create a hydraulic barrier. Cemented paste mixtures incorporating 5–7 wt% binder were evaluated through unconfined compressive strength (UCS), saturated hydraulic conductivity (ksat), and mineralogical analyses. The addition of binder significantly increased mechanical strength and reduced ksat, with UCS > 1000 kPa and ksat < 1 × 10−9 m/s, generally achieved after 28 days of curing with 7 wt% binder. Performance depended on tailings geochemistry: slag-based cement (20GU/80GGBFS) performed better in tailings with neutral paste pH, while GUL yielded higher UCS in acidic tailings. Very limited hydrate formation was observed: mainly ettringite in GUL-treated sulfate-rich tailings and C–S–H in slag-treated mixtures. These results demonstrated that cementitious treatment of TSFs could be an efficient, if binder type and dosage are adapted to site physical and geochemical variability of weathered tailings.
Audrey Jalce, Isabelle Demers, B. Plante et al.· Geotechnical and Geological...· 0 citations
Cementitious and glass waste forms are being evaluated for disposal in engineered facilities as a strategy for the long-term immobilization of radioactive and hazardous contaminants. Contaminant release is largely influenced by evolving hydrological and physical conditions within the disposal environment. This study investigates the hydrological behavior of cementitious and glass waste forms and surrounding backfill through field experiments and numerical modeling. Field lysimeter experiments containing waste forms are ongoing at the Hanford Site, WA, to measure water movement, water balance, and solute transport. The lysimeters are filled with representative backfill materials from the Integrated Disposal Facility site. Variably saturated flow (VSF) models were developed to simulate water movement within the lysimeters using site-specific soil water retention properties and showed generally good agreement with measured water content profiles. Particle-tracking analysis suggests that pan lysimeters installed below the waste forms capture a substantial fraction of percolating water that did not directly contact the waste forms. Water originating beyond the 0.3-m diffusion distance accounted for approximately 28% of collected percolation, although irrigation uniformity may influence this dilution and percolation chemistry. The lysimeter tests approximate predicted high-saturation perimeter areas of the disposal facility, providing an upper-bound assessment of water-waste interaction. These findings support lysimeter data interpretation, field-scale extrapolation, and boundary-condition development for contaminant transport modeling.
Martha Maria Santos, Jiannan Chen, C. Gruber et al.· Canadian geotechnical journa...· 0 citations
The influence of soil water content and contaminant injection pressure on the migration behaviour of p-Xylene (one of the organic pollutants in Benzene Toluene Ethylbenzene & Xylene) is investigated in the unsaturated zone using the controlled laboratory sandbox experiments. The results show that, at equivalent migration distances, higher soil water content leads to longer migration durations and reduces transport velocities, whereas greater injection pressure promotes faster contaminant movement. These findings highlight the governing role of water saturation in the water–oil–gas three-phase system, in which increased water content decreases the relative permeability of the oil phase and retards capillary-driven BTEX transport. Unlike many previous studies in which contaminants commonly migrate downward toward the groundwater table, the BTEX in this study did not reach the water table and exhibited partial upward migration. Overall, the results provide experimental-scale insight into key mechanisms governing BTEX transport in unsaturated sandy media and serve as a reference for improving predictions of contaminant fate and migration pathways in field settings.
Yi Jiang, Yong Huang, Yue Su et al.· Water· 0 citations
Water uptake through plant transpiration is a critical hydraulic boundary condition in modelling geostructures under climatic loading. Transpiration occurs in two regimes: energy-limited, controlled by atmospheric evaporative demand; and water-limited, governed by soil hydraulic conductivity around roots. While energy-limited (potential) transpiration is generally modelled using a physically based approach, the water-limited regime is usually modelled macroscopically by way of an empirical transpiration reduction function. This paper first presents an experimental investigation into the influence of soil hydraulic behaviour and potential transpiration rate on water-limited transpiration. Two soil textures were tested – silty sand and clayey-silty sand – planted with Medicago sativa. The use of high-capacity tensiometers enabled the investigation of an unprecedented suction range in clayey soils. Results show that the water-limited branch of the reduction function is non-linear, and its decay is strongly influenced by unsaturated hydraulic conductivity. Furthermore, the suction marking the transition from energy- to water-limited regimes varied with potential transpiration rate and soil hydraulic behaviour. A novel physically based, closed-form reduction function is then formulated to advance water uptake modelling in the water-limited regime. This function is shown to compactly capture the combined effects of soil hydraulic conductivity, root system architecture expressed through root length density and potential transpiration rate on transpiration in the water-limited regime, consistent with observations from both this experimental campaign and the literature data.
Eve Roberts-Self, A. Tarantino· Geotechnique· 0 citations
The vadose zone (VZ) mediates contaminant migration to aquifers, yet its attenuation efficiency under transient conditions remains poorly understood. Most studies have employed batch experiments at a fixed saturation degree, which could not capture the coupled effects of water and oxygen content under transient conditions. This study evaluated nitrate behavior using unsaturated soil columns packed with sandy loam (SL) and loamy sand (LS) subjected to infiltration rates of 6.25-75 mm/h for simulating the VZ environment. Water and oxygen contents were continuously monitored, and pore-water samples were collected at multiple depths to characterize nitrate transport and fate. The presence and abundance of denitrifiers were analyzed to support apparent denitrification within the column. The modular 71.5-cm column packed with SL had a higher water content (∼0.3 v/v) and a capillary fringe of ∼22 cm, and retained 38.8-41.4% of introduced nitrate, predominantly at mid-depths (∼38.5 cm). Under a moderate infiltration rate (6.25 mm/h), 40.8% apparent denitrification occurred in SL. In contrast, coarser-textured LS with a shallower capillary fringe (∼10 cm) showed stronger vertical nitrate transport, with most nitrate remaining in the deeper ∼60.5 cm layer (25.5-47.7%). Although LS still showed 15.8% apparent denitrification at 6.25 mm/h, no apparent denitrification was detected under very heavy rainfall (75 mm/h) due to enhanced drainage, which inhibited stable microbial niche development. These results show that infiltration rate and soil texture control nitrate partitioning between apparent denitrification and leaching by regulating water residence time. Groundwater vulnerability to nitrate contamination may therefore vary with rainfall conditions.
Sungjik Oh, Jaeshik Chung, Man Jae Kwon et al.· Journal of Environmental Man...· 0 citations