Shear strength recovery of sand with self-healing polymeric capsules

© 2024 The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Self-healing approaches are increasingly being explored in various fields as a potential method to recover damaged material properties. By self-recovering without external intervention, self-healing techniques emerge as a potential solution to arrest or prevent the development of large strains problems in soils (e.g., landslides) and other ground effects that influence the serviceability of structures (e.g., differential settlement). In this study, a microcapsule-based self-healing sand was developed, and its performance during mixing and compaction, shearing, and recovery of shear strength was demonstrated. The cargo used for sand improvement, a hardening oil, tung oil, was encapsulated in calcium alginate capsules by the ionic gelation method. The surface properties, internal structure, thermal stability and molecular structure of the capsules were evaluated by advanced material characterization techniques. The survivability of capsules during mixing and compaction was assessed by measuring the content of tung oil released into the sand, while their influence on sand shear strength and its recovery was assessed with shear box tests. The results showed that the capsules could rupture due to movement of the sand particles, releasing the tung oil cargo, leading to its hardening and minimizing its strain-softening response and enhancing up to 76% of the sand shear strength (at a normal stress of 10 kPa and capsules content of 4%). This study demonstrates the potential of a capsules-based self-healing system to provide ‘smart’ autonomous soil strength recovery and thus with potential to actively control the large strain behavior of soils.Peer reviewe

Wettability decay in an oil-contaminated waste-mineral mixture with dry-wet cycles

The dependency of soil particle wettability on soil water content implies that soils subjected to drying-wetting cycles become wettable with wetting and water repellent with drying. While this has been demonstrated widely, the results are contradictory when water repellent soils are subjected to a sequence of cycles. Added to this, past wettability measurements were seldom done in batches of samples collected from the field at natural or dry water contents, with little appreciation that slight particle size variations, different drying-wetting histories and fabric (as required by different wettability measurement methods) may alter the results. This note presents soil particle wettability—soil water content relations by means of an index test following staged drying and wetting paths over a period of 8 months for an untreated, oil-contaminated anthropogenic soil (a mixture of slag, coal particles, fly ash and mineral particles) from Barry Docks (UK), a site formally used for oil storage, which is to be remediated and redeveloped for housing. The results revealed a decrease in the water repellency and increasing mineralization and bacterial activity with the wetting and drying cycles.postprin

DNM1 encephalopathy: A new disease of vesicle fission.

ObjectiveTo evaluate the phenotypic spectrum caused by mutations in dynamin 1 (DNM1), encoding the presynaptic protein DNM1, and to investigate possible genotype-phenotype correlations and predicted functional consequences based on structural modeling.MethodsWe reviewed phenotypic data of 21 patients (7 previously published) with DNM1 mutations. We compared mutation data to known functional data and undertook biomolecular modeling to assess the effect of the mutations on protein function.ResultsWe identified 19 patients with de novo mutations in DNM1 and a sibling pair who had an inherited mutation from a mosaic parent. Seven patients (33.3%) carried the recurrent p.Arg237Trp mutation. A common phenotype emerged that included severe to profound intellectual disability and muscular hypotonia in all patients and an epilepsy characterized by infantile spasms in 16 of 21 patients, frequently evolving into Lennox-Gastaut syndrome. Two patients had profound global developmental delay without seizures. In addition, we describe a single patient with normal development before the onset of a catastrophic epilepsy, consistent with febrile infection-related epilepsy syndrome at 4 years. All mutations cluster within the GTPase or middle domains, and structural modeling and existing functional data suggest a dominant-negative effect on DMN1 function.ConclusionsThe phenotypic spectrum of DNM1-related encephalopathy is relatively homogeneous, in contrast to many other genetic epilepsies. Up to one-third of patients carry the recurrent p.Arg237Trp variant, which is now one of the most common recurrent variants in epileptic encephalopathies identified to date. Given the predicted dominant-negative mechanism of this mutation, this variant presents a prime target for therapeutic intervention

Modelling of water droplet dynamics on hydrophobic soils: a review

The hydrophobicity of soils (or soil water repellency) can be naturally promoted by wildfires or synthetically induced by hydrophobic compounds (polydimethylsiloxane, tong oil, etc.). Soil phenomena can be related to hydrophobicity, such as soil erosion (splash erosion and rill erosion) and post-wildfire debris flows. The hydrophobicity of soils is characterized by the contact angle, and the interactions between water droplet and solid particles including spreading, oscillation, and infiltration. Early studies on soil water repellency mainly focus on the experimental aspects, while with the development of advanced numerical tools, numerical methods have been widely applied to study the hydraulic properties of hydrophobic granular materials in recent years. This paper comprehensively investigates the different numerical methods for modelling the interaction between water droplets and hydrophobic soils, i.e., smoothed particle hydrodynamics (SPH), lattice Boltzmann method (LBM), material point method (MPM), and volume of fluid (VOF). The features of different method are summarized, and the future work are discussed

Testing and monitoring of Earth structures

Monitoring structural behavior of earth structures during construction and in service is a common practice done for safety reasons, consolidation control and maintenance needs. Several are the techniques available for measuring displacements, water pressures and total stresses, not only in these geotechnical structures but also at their foundations. Materials testing has been used for calibrating models for structural design and behavior prediction, and these models can be validated with instrumentation data as well. Relatively recent investigation on the behavior of these materials considering their degree of saturation focuses on monitoring the evolution of water content or suction as function of soil-atmosphere interaction, necessary to predict cyclic and/or accumulated displacements, and has huge potential to predict the impact of climate changes on the performance of existing geotechnical structures. This new need justifies the investment on developing sensors able to be used for in situ monitoring of water in the soils, such as those presented here. Testing and monitoring becomes even more important nowadays when, for sustainability purposes, traditional construction materials are replaced by other geo-materials with unknown behavior and long-term performance (mainly accumulated displacements). Existing experimental protocols and monitoring equipment are used for such cases, however new techniques must be developed to deal with particular behaviors. Three case studies are presented and discussion is made on monitoring equipment used and how monitored data helped understanding the behaviors observed.Postprint (author's final draft

Synthetic water repellent soils for slope stabilization

Water repellent soils, or non-wettable soils, are described as having delayed wetting of the soil surface and water infiltration, and have been studied by soil scientists and agriculturists for decades. Soil water repellency induced by wildfire is believed to be a major trigger of post-fire debris flows, by changing the hydrological characteristics of the slopes, the rainfall infiltration is delayed, leading to the increased surface runoff and eventual soil mass movement. On the other hand, the potential applications of water repellent soils in the field of slope engineering have also been recognized recently. Due to their ability to inhibit water infiltration while remaining gas permeable, water repellent soils are considered to be promising fill materials and impermeable barriers. Soil water repellency is widely observed to occur in nature because of wildfire and organic matter, while in the laboratory, it can be induced by coating the soil particles with low surface energy substances such as silane compounds. An advantage of synthetic water repellent soils is that the level of water repellency is adjustable (from very wettable to extremely water repellent), and therefore the rate of infiltration can be controlled in various scenarios. Since intense rainfall and subsequent infiltration significantly contribute to fill and natural slope failures, water repellent soils have proved to be effective in hindering the infiltration and generation of excess pore pressure and therefore could increase the overall factor of safety during rainstorms. Landfill cover is another potential application of water repellent soils