The long-term disposal of high-level radioactive waste (HLW) in deep geological repositories requires the reliable performance of engineered barrier systems (EBS). Compacted bentonite, widely used for its high swelling capacity, low permeability, and self-sealing properties, plays a critical role in these barriers. However, understanding the complex coupled thermo-hydro-mechanical (THM) behavior governing water infiltration dynamics remains a significant challenge, especially when gap spaces (or technological voids) are present. This study investigates water infiltration dynamics in bentonite-based EBS using a novel laboratory-scale experimental setup. Time-lapse photography was employed to monitor the evolution of hydration and swelling under thermal gradients and varying gap sizes, simulating repository conditions. The experimental program was designed to compare the effects of two gap sizes on infiltration rates, swelling behavior, and desiccation cracking. Results demonstrated that larger void spaces accommodated greater swelling, leading to lower dry density and higher permeability, while smaller gaps restricted desiccation cracking due to mechanical constraints. The correlation between pixel intensity and water content allowed the derivation of a linear calibration model, enabling real-time, non-destructive estimation of moisture distribution in bentonite. Findings in this study highlight the interplay between gap size, water infiltration, and thermal effects, emphasizing the need for optimized EBS designs to balance mechanical integrity and hydraulic performance. It is anticipated that the insights provided by this study contribute to the refinement of predictive models and advancing the safe and effective containment of HLW over geological timescales.

The disposal of excess milk can pose significant challenges for dairy farms during supply chain disruptions, extreme weather events, or plant closures. Improper disposal methods risk causing environmental damage, public health issues, and regulatory violations. This study evaluates three on-farm milk disposal methods, lagoon discharge, composting, and land application, to guide the effective management of large-scale milk disposal events. Laboratory experiments assessed the impact of milk disposal on lagoon water quality, highlighting that lagoon discharge was feasible for large-scale operations but increased total solids and chemical oxygen demand (COD), potentially overloading the system's treatment capacity. Similarly, experiments on composting showed that adding milk enhanced compost quality but required careful monitoring to prevent moisture imbalance and odors. For land application, experiments demonstrated improvements in soil health and plant growth but also revealed risks of nutrient imbalance and gas emissions, particularly at higher application rates. Dividing milk into smaller, multiple applications consistently reduced adverse impacts across all methods. Each method's suitability depends on farm size, infrastructure, and disposal volume. Lagoon discharge is better suited for large farms with sufficient capacity to manage treatment risks. Composting works well for smaller volumes, while land application benefits soil health when carefully managed. The findings have practical applications in helping dairy farms select appropriate disposal strategies, minimizing environmental harm, and complying with regulations during large-scale milk disposal events. Additionally, this study serves as a foundation for creating more comprehensive guidelines and strategies to address milk disposal challenges, fostering sustainable practices across diverse agricultural settings.

Per- and polyfluoroalkyl substances (PFAS) are commonly used in proton exchange membrane fuel cells due to their high stability and resistance. These ionomers act as binding agents and their hydrophobic effect helps to remove excess water from the gas diffusion layer. Their proton conductivity and hydrophobicity, gained by incorporation of functional side chains, are essential features for their application as membranes.. However, the harsh conditions in fuel cells can lead to degradation of PFAS compounds, which are released into the environment. Due to their persistence, there are growing concerns about the enrichment of PFAS in groundwater and soil. As these substances accumulate in the environment, they are incorporated by living organisms through drinking water and plants. Some of these substances are associated with causing health disorders, such as cancer, brain and liver damage, and negative impacts on embryo development. This review highlights the sources of PFAS during fuel cell production, operation and recycling and currently available alternatives used in proton exchange membrane fuel cells. The degradation of fuel cells during operation has the potential to result in the emission of PFAS. Membrane degradation mechanisms have been investigated and results can serve as a foundation to reduce PFAS emissions by identifying critical operating conditions.

Domestic laundry wastewater is a major contributor to microfiber emissions in the aquatic environment. Among several mitigation measures, the use of external filters to capture microfibers from wastewater is one of the most efficient and commercially viable methods. This study attempted to develop an eco-friendly filtration medium to filter microfibers in laundry wastewater using luffa cylindrica fibers. Sourced luffa fibers were made into tight rolls and stacked in a filtration column to filter the effluent. The analysis showed that the alkali-treated luffa fiber rolls were more effective in filtering the microfibers than untreated luffa fibers. Hence, the alkali treatment process was optimized for better performance; an alkali concentration of 5.8%, treatment time of 5 h, and 37 degrees C temperature provide better performance. The characterization of alkali-treated luffa fibers showed significant changes in the morphology and removal of lignin and hemicellulose components, enhancing the physical adsorption of microfibers on the surface. The experimental filtration results showed that the developed filter can effectively remove up to 93% of microfibers from laundry effluent, and the efficiency remained superior for up to 15 filtrations. Furthermore, an increase in filtration leads to the accumulation of detergents in the luffa net-like vascular structure and reduced effectiveness. The use of the developed product in a real-time washing machine outlet was found to be effective with an efficiency of 98%. The developed product is a versatile and cost-effective solution, suitable for use in domestic washing machines. Its simplicity and ease of integration make it an effective and eco-friendly alternative for filtering microfibers from laundry effluent. The future direction of the study also suggests a sustainable disposal method for luffa fibers using it as a matrix material in red soil-based thermal or sound insulation panels and restricting the reach of microfibers into the environment.

This work is devoted to numerical analysis of thermo-hydromechanical problem and cracking process in saturated porous media in the context of deep geological disposal of radioactive waste. The fundamental background of thermo-poro-elastoplasticity theory is first summarized. The emphasis is put on the effect of pore fluid pressure on plastic deformation. A micromechanics-based elastoplastic model is then presented for a class of clayey rocks considered as host rock. Based on linear and nonlinear homogenization techniques, the proposed model is able to systematically account for the influences of porosity and mineral composition on macroscopic elastic properties and plastic yield strength. The initial anisotropy and time-dependent deformation are also taken into account. The induced cracking process is described by using a non-local damage model. A specific hybrid formulation is proposed, able to conveniently capture tensile, shear and mixed cracks. In particular, the influences of pore pressure and confining stress on the shear cracking mechanism are taken into account. The proposed model is applied to investigating thermo-hydromechanical responses and induced damage evolution in laboratory tests at the sample scale. In the last part, an in situ heating experiment is analyzed by using the proposed model. Numerical results are compared with experimental data and field measurements in terms of temperature variation, pore fluid pressure change and induced damaged zone. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The deep geological repository for radioactive waste in Switzerland will be embedded in an approximately 100 m thick layer of Opalinus Clay. The emplacement drifts for high-level waste (approximately 3.5 m diameter) are planned to be excavated with a shielded tunnel boring machine (TBM) and supported by a segmental lining. At the repository depth of 900 m in the designated siting region Nordlich Lagern, squeezing conditions may be encountered due to the rock strength and the high hydrostatic pressure (90 bar). This paper presents a detailed assessment of the shield jamming and lining overstressing hazards, considering a stiff lining (resistance principle) and a deformable lining (yielding principle), and proposes conceptual design solutions. The assessment is based on three-dimensional transient hydromechanical simulations, which additionally consider the effects of ground anisotropy and the desaturation that may occur under negative pore pressures generated during the drift excavation. By addressing these design issues, the paper takes the opportunity to analyse some more fundamental aspects related to the influences of anisotropy and desaturation on the development of rock convergences and pressures over time, and their markedly different effects on the two lining systems. The results demonstrate that, regardless of these effects, shield jamming can be avoided with a moderate TBM overcut, however overstressing of a stiff lining may be critical depending on whether the ground desaturates. This uncertainty is eliminated using a deformable system with reasonable dimensions of yielding elements, which can also accommodate thermal strains generated due to the high temperature of the disposal canisters. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Strongly alkaline dispersive soils pose a significant global challenge to both engineering applications and agricultural production, particularly in arid and semi-arid regions. Conventional soil modifiers used to address this issue not only present environmental and economic concerns but also fail to effectively improve soil alkalinity. This study investigates the potential application of acidic desulfurization gypsum (DG) as a soil modifier for dispersive soils, aiming to achieve high-value utilization of industrial solid waste. The dispersibility of soil under hydrostatic and dynamic conditions are studied using the mud ball test and pinhole test. The engineering properties and modification mechanism of DG consolidated soils were revealed by combining the unconfined compressive strength (UCS), Brazilian split tensile strength (BTS), microstructure, and mineral evolution. Results show that 3% DG significantly reduces soil dispersibility and improves disintegration and erosion resistance, with UCS and BTS increases of 210% and 94%, respectively. The mechanism involves DG releasing hydrogen ions to reduce soil alkalinity, which in turn activates cation activity of DG, replacing sodium ions on the soil surface and forming a binding hydrate within 7 days. Tests on natural dispersive soil from check dams confirmed effectiveness of DG. Advanced machine learning techniques quantitatively analyzed the impact of DG on soil dispersibility, highlighting the relationship between soil dispersibility and chemical/mechanical properties. This study establishes a novel link between hydraulic erosion parameters, mechanical parameters, and soil stressstrain relationships, providing valuable insights for future soil stabilization. The results show potential of waste acidic DG in practical engineering applications and contribute to the sustainable advancement of dispersive soil stabilization technology. Alkaline dispersive soils also aid in regulating the acidity and alkalinity of DG and controlling toxic emissions.

To alleviate problems in urban living environments, an increasing number of shield tunnels have been built that go through rivers or underwater areas. Most of these tunnels experience leakage after a long period of operation, which can impact the safety of the tunnel and induce dangerous accidents, resulting in a loss of life and property. This paper reports the leakage characteristics during operation of a double-line ultralarge-diameter underwater shield tunnel that crosses the Yangtze River. After detailed geological surveys and field inspections of the prototype tunnel, the leakage characteristics and patterns of the tunnel were summarized based on long-term monitoring data. The distribution of leak-related defects was described in-depth with sketches and field photographs. Factors influencing the leakage of the prototype tunnel (i.e., the groundwater table, longitudinal settlement, and soil conditions) were interpreted based on field measurements. The mechanisms that triggered two typical leakage accidents that occurred during tunnel operation were systematically analyzed. The leakage mechanisms of the prototype tunnel were subsequently categorized into three patterns: joint leakage, bolt hole leakage and concrete crack leakage. Four countermeasures against leakage were proposed considering the leakage-associated damage to the prototype tunnel: backfill grouting, joint grouting, installation of a bolt hole sealing cover, and caulking gasket addition. The proposed mitigation measures were validated through laboratory tests and field applications. This unique tunnel prototype engineering case can provide a reference for water leakage prevention and control in the design, construction, and operation stages of similar underwater shield tunnel projects.

Deep geological disposal is the preferred solution for radioactive waste management in many countries, including Belgium, where the Boom Clay is one of the potential candidate host formations. Over the long term, corrosion mechanisms are expected to release large amounts of gas that will rise in pressure and activate different gas transport processes in the system and the surrounding geological formation. Assessing which transfer mode prevails under which range of pressure conditions in the sound rock layers remains a major issue. This paper presents a multi-scale Hydro-Mechanical (HM) model capturing the influence of the microstructure features on the macroscopic gas flow, and especially the emergence of preferential gas-filled pathways. A detailed constitutive model for partially saturated clay materials is developed from experimental data to perform the modelling of a Representative Element Volume (REV), and integrated into a multi-scale scheme using homogenisation and localisation techniques for the transitions to the macroscopic scale. Using this tool, numerical modelling of a gas injection test in the Boom Clay is performed with the aim of improving the mechanistic understanding of gas transport processes in natural clay barriers.

Steel slag (SS) is a byproduct that comes from the production of crude steel in alkaline oxidation furnaces. Resource utilization of steel slag, a calcium-silicon solid waste, is an urgent problem. This paper investigates a solid waste disposal method that applies different steel slag contents to modify dispersive soil. The engineering properties and modification mechanisms of dispersive soil specimens are studied and revealed by performing microstructure, mineral evolution, unconfined compressive strength (UCS), and tensile strength analysis. The pinhole test, mud ball crumb test (BCT), and mud cube crumb test (CCT) were carried out to determine the dispersivity of the soil specimens. Results show that when the steel slag content increases from 1% to 10%, the unconfined compressive strength and tensile strength increase by 176.05% and 75.40%, respectively. For soil specimens without curing time under 50 mm water head, the weight loss of the specimen with 10% steel slag content decreases by 72.03% compared to specimens with 1% steel slag content. Microstructural and mineralogical analyses indicate that the hydration reaction of steel slag changes the ionic composition of the soil and generates reaction products with effects such as filling and connection. To sum up, steel slag effectively improves water stability and mechanical properties of dispersive soil.