The unified effective stress equation based on suction stress, a widely accepted method for calculating effective stress in unsaturated soils, provides a closed-form solution that enables the characterization of soils in both saturated and unsaturated states. The effect of desaturation on the water content of natural and treated soils was studied with respect to unconfined compressive strength (UCS) and indirect tensile strength (ITS). The soil's moisture-dependent behavior was characterized by the van Genuchten (Soil Sci Soc Am J 44:892-898, 1980. https://doi.org/10.2136/sssaj1980.03615995004400050002x) and Lu et al. (Water Resour Res, 2010. https://doi.org/10.1029/2009wr008646) models and implemented using the equation. Suction tests were conducted using the dew point and filter paper methods, alongside UCS and ITS tests, on silty clay soil and microsilica-treated soil with microsilica contents of 5%, 10%, and 15%. The equation was validated by comparing mean total stress (p) and mean effective stress (p ') to deviatoric stress (q) and analyzing the friction angle at different suction levels. It proved applicable to both natural and treated soils, with valid moisture content ranges of 4-17.5% and 6-20%, respectively. This study experimentally confirms the equation's effectiveness in characterizing the hydro-mechanical behavior of soils under varying moisture conditions.

Natural paper-based materials are desirable candidate materials for disposable hygiene products due to their environmental sustainability, cost-effectiveness, and biodegradability. However, their practical application is often hindered by poor water stability and limited functional properties. In this study, we developed a wet-laid web formation and hot-pressing technique to produce porous, layered paper-based materials with high porosity, flexibility, water stability, and antibacterial properties. These materials were created using naturally derived components, including kapok fiber, carboxymethyl cellulose (CMC), and cationic starch (CS). The synergistic interaction between CMC and CS significantly enhances the mechanical properties and water stability, achieving a 146.09 % improvement compared to materials without CMC/CS. The resulting paper-based materials also exhibit water stability for up to 30 days. Kapok fibers contribute excellent antimicrobial properties, with >95 % inhibition of both Escherichia coli and Staphylococcus aureus. Furthermore, the materials are biodegradable in soil, completely degrading after 60 days. This study provides novel insights into the valorization of kapok fiber and presents a sustainable approach to producing high-performance paper-based materials for disposable hygiene products applications.

This direction paper explores the evolving landscape of physics-informed machine learning (PIML) methodologies in the field of geotechnical engineering, aiming to provide a comprehensive overview of current advancements and propose future research directions. Recognising the intrinsic connection between geophysical phenomena and geotechnical processes, we delve into the inter of physics-based models and machine learning techniques. The paper begins by elucidating the significance of incorporating physics-informed approaches, emphasising their potential to enhance the interpretability, accuracy and reliability of predictive models in geotechnical applications. We review recent applications of PIML in soil mechanics, hydrology, geotechnical site investigation, slope stability analysis and foundation engineering, showcasing successes and challenges. Furthermore, we identify promising avenues for future research in geotechnical engineering, including the integration of domain knowledge, model explainability, multiphysics and multiscale problems, complex constitutive models, as well as digital twins and large AI models within PIML frameworks. As geotechnical engineering embraces the paradigm shift towards data-driven methodologies, this direction paper offers valuable insights for researchers and practitioners, guiding the trajectory of PIML for sustainable and resilient infrastructure development.

In a world increasingly focused on environmental sustainability and the imperative of efficient waste management, innovative approaches in material science are becoming crucial. This research is centered on the synthesis of cellulose nanocrystals (CNCs) from post-use exam waste paper and the development of a chitosan-CNC (CS-CNCs) composite. CNCs were successfully isolated from waste paper by alkali treatment, bleaching, and sulfuric acid hydrolysis with FTIR and XRD analyses confirming successful extraction and a crystallinity index of 66.3%. TEM imaging revealed CNCs with a unique spherical morphology and diameters of 6-7 nm, significantly smaller than those reported in existing literature. Chitosan (CS), derived from shrimp shell waste, was integrated into the CNCs to form a composite thin film. This film, as revealed by SEM, had a homogeneous and consistent structure. The CS-CNCs composite demonstrated superior mechanical properties, with tensile strength increasing from 17.74 megapascal (MPa) in pure CS film to 22.08 MPa in composite, indicating its potential for robust and sustainable packaging materials. Soil degradation tests over 25 days showed a 24.7% degradation for CS-CNCs films, compared to 9.09% for CS films, underscoring their enhanced biodegradability. The composite exhibited notable antibacterial activity against Escherichia coli, suggesting its suitability for medical and hygiene applications. The measured contact angle of 80.4 degrees indicates the film's hydrophilicity, making it an excellent candidate for self-cleaning surfaces, such as textiles and windows. Remarkably, the CS-CNCs composite demonstrated exceptional photocatalytic degradation of Alizarin Red S dye, achieving 99.7% efficiency in 45 min, far surpassing the 87% efficiency of standalone CS films. The study showcases the green-synthesized CS-CNCs composite from waste paper offering an effective, eco-friendly, and economical approach for wastewater treatment due to its dual capabilities in dye degradation and antibacterial properties, while also opening avenues for its prospective application in self-cleaning surfaces, environmental remediation, and packaging thereby presenting a sustainable and economical solution for environmental cleanup and material innovation.

Lactic acid impregnated ground film paper was prepared using the method of lactic acid impregnation of raw paper. The physical properties, chemical composition, crystallinity, thermal stability, surface morphology of the paper, barrier properties, and light transmittance of the lactic acid paper were investigated using FT-IR, XRD, TGA, SEM, water vapor blocking, oxygen blocking, mechanical properties testing, and optical property testing. Results showed that at room temperature (20 degrees C), when lactic acid concentration was 100 %, reaction time was 48 h, and 100 degrees C high temperature drying prepared lactic acid paper, it exhibited superior performance: dry strength of 2.83 IkN/m, wet strength of 0.36 kN/m, Cobb value of 4.50 g/m2, tear of 359.42 mN, water vapor barrier of 693.46 g m-2 24 h-1, and oxygen barrier of 933.43 cm3 m-2 24 h-1. Degradation rate reached 22.94 % after two weeks of soil landfill.

An understanding of the mechanical properties and macroscopic behavior of unsaturated soil can be improved through an in-depth microscopic insight of the variables controlling the soil-water characteristic curve (SWCC). In this study, the effects of the initial conditions on the pore structure and SWCC of silty soil was examined. Their relationships to the soil behavior during water loss was addressed from both macroscopic and microscopic perspectives. In this study, patterns different from those of previous studies were revealed; this especially pertained to the effect of the initial water content on the SWCC. The SWCC was obtained using repeated centrifugation and filter paper tests. Mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were performed to collect the microstructure information. The results showed that soils compacted using the optimal dry side conditions had double S-shaped SWCC for their bimodal pore size distributions, and these pores were classified as intra-aggregate and inter-aggregate pores. Thus, these soils underwent two distinct stages of water loss during drying, and water loss occurred more easily in the first stage because of the presence of many large macropores or inter-aggregate pores. However, soils compacted at the optimum water content produced a single S-shaped SWCC for the multimodal pore structure. Water drained from these soils at a relatively constant rate from a more homogeneous and uniform pore system. This study has provided a comprehensive set of macroscopic and microscopic experimental data and well-established relationships among the PSD, SWCC and initial state of the silty soil.

Stabilizing and improving weak and poorly graded soils in road construction projects is a widely used and highly interesting technology. This research study utilizes paper sludge ash (PSA) residues as a geopolymer waste material to stabilize loose and poorly graded sands (SP), improve mechanical properties, and support sustainable pavement development. Geotechnical tests using the unconfined compressive strength test (UCS), Young's modulus (Es), California bearing ratio (CBR), and a direct shear test (DST) assessed the performance and strength development of geopolymer-stabilized soil. The stabilized soil's microstructure and chemical mineralogy were also examined using SEM and XRD. Additionally, a laboratory testing apparatus was designed and developed to assess the permanent strain behavior of subgrade soil and geopolymer-stabilized soil layers under cyclic loading. The research analysed variables including curing duration (1, 3, and 7 days), PSA concentration (5, 10, and 15%), and the type and concentration of alkaline activators (NaOH or Na2SiO3). Soil samples treated with PSA and Na2SiO3 geopolymers showed higher UCS, Es, and CBR values, leading to improved strength from increased N-A-S-H and C-A-S-H gel formation among sand soil particles. On the contrary, the NaOH solution enhanced the strength parameter of geopolymer-stabilized soil samples. The results showed that geopolymer-stabilized soil significantly improved its resistance to permanent deformation after applying loads. The mineralogical examination also shows a high concentration of lime and cubic aluminate, which may be active cementitious pozzolanic material. This research reflects that PSA has promising potential to stabilize sandy soil and improve the design and maintenance of roads and infrastructure in areas with weak soils.

Featured Application The findings of this study establish the behavior of sanitary landfill cover materials, such as compacted clay and compacted polyurethane-clay, in unsaturated conditions under several wet-dry cycles, which would aid in predicting the performance of the material under varying environmental conditions. By predicting the unsaturated hydraulic conductivity and understanding the effects of environmental stresses, the findings can aid in the design and implementation of more durable and efficient landfill liners and covers.Abstract Sanitary landfill covers are exposed to varying environmental conditions; hence, the state of the clay layer also changes from saturated to unsaturated. The study aimed to predict the unsaturated hydraulic conductivity of the locally available compacted clay and clay with polyurethane to determine their behavior as they change from wet to dry using matric suction and empirical models proposed through other studies. The specimens underwent three wet-dry cycles wherein the matric suction was determined for several moisture content levels as the specimen dried using the filter paper method or ASTM D5298. The results showed that the factors affecting the soil structure, such as grain size difference between clay and polyurethane-clay, varying initial void ratios, and degradation of the soil structure due to the wet-dry cycles, did not affect the matric suction at the higher suction range; however, these factors had an effect at the lower suction range. The matric suction obtained was then used to establish the best fit water retention curve (WRC) or the relationship between the matric suction and moisture content. The WRC was used to predict the unsaturated hydraulic conductivity and observe the soil-water interaction. The study also observed that the predicted unsaturated hydraulic conductivity decreases as the compacted specimen moves to a drier state.

Chemical stabilization is among the methods utilized to improve the shear strength properties and volumetric changes of problematic soils. This research assesses the possibility of using sludge ash from a wood and paper mill (SAWP) as an industrial sludge to improve the fat clay engineering characteristics. Thus, unconsolidated-undrained triaxial, direct shear, one-dimensional swelling, and consolidation tests were conducted. Results showed that shear strength parameters (both in short and long-term) increase with increasing SAWP contents and curing period due to the production of sufficient cementitious components and the formation of strong bonds between the particles. Investigating the direct shear test results indicated that the failure envelope in stabilized samples with high SAWP contents was slightly curved. Stabilized samples with high amounts of SAWP at low vertical stresses show brittle failure, while the type of failure observed for these samples at high vertical stresses is more ductile. Moreover, the magnitude of free swell gradually decreased with increasing SAWP contents. The replacement of clay particles with SAWP and flocculation and/or agglomeration of clay particles were the main reasons for this issue. Finally, the compression index, swell index, and coefficient of volume compressibility decrease with increasing SAWP content for the applied load increment, indicating the effect of stabilization in reducing the consolidation settlement of the layers. The test results revealed that the sludge ash used in this study can be used to enhance the engineering properties of fat clay.

In recent years, the growing demand for sustainable packaging has significantly fueled the quest to explore novel approaches that enhance the applicability of renewable alternatives. This study leverages the unique properties of silica aerogel (SA) to address the limitations of traditional molded pulp products. By integrating SA into recycled paper pulp (RP), we aimed to improve water resistance, thermal stability, and mechanical properties. Composites were prepared with varying SA concentrations (1-10 %). Contact angle measurements showed enhanced hydrophobicity, with RP/SA3 % achieving a contact angle of 152.09 degrees, compared to 122.39 degrees for neat RP. The tensile index (TI) of RP/SA composites with 3 % SA increased by 21.09 % compared to neat RP, indicating better mechanical strength. Thermal conductivity significantly decreased, with RP/SA10 % reducing from 0.155 W m- 1 center dot K- 1 in neat RP to 0.088 W m- 1 center dot K- 1, a 43.2 % improvement in thermal insulation. Additionally, composites with 1 % and 3 % SA maintained high biodegradability, showing over 50 % degradation after six weeks in soil. These results suggest that incorporating SA into RP composites enhances their functionality without compromising biodegradability, offering a promising solution for sustainable packaging. As regulatory bodies emphasize resource management and waste reduction, the potential of these innovative and environmentally friendly packaging solutions becomes increasingly significant.