The interface between geotextile and geomaterials plays a crucial role in the performance of various geotechnical structures. Soil-geotextile interfaces often suffer reduced performance under environmental stressors such as rainfall and cyclic loading, limiting the reliability of geotechnical structures. This study examines the influence of gravel content (Gc), compaction degree (Cd), and rainfall duration (Rd) on the mobilized shear strength at the silty clay-gravel mixture (SCGM)- geotextile interface through a comprehensive series of direct shear tests under both static and cyclic loadings. A novel approach using Polyurethane Foam Adhesive (PFA) injection is introduced to enhance the interface behavior. The results reveal that increasing Gc from 0 % to 70 % leads to a 35-70 % improvement in mobilized shear strength and friction angle, while cohesion decreases by 15 %-60 %, depending on Cd. A higher Cd further boosts shear strength by 6 %- 70 %, influenced by Gc and normal stress levels. Under cyclic loading, increasing displacement amplitude reduces shear stiffness (K), while having minimal impact on the damping ratio (D); K and D appear unaffected by the number of cycles in non-injected samples. Rainfall reduces mobilized shear strength by 8 %-25 %, depending on the normal stress, with a 47 % drop in friction angle and a 24 % increase in cohesion after 120 minutes of rainfall exposure. In contrast, PFA-injected samples exhibit a marked increase in mobilized shear strength under both dry and wet conditions, primarily attributed to enhanced cohesion. Notably, PFA treatment proves particularly effective in maintaining higher shear strength and stiffness in rainfall-affected interfaces, demonstrating its potential in improving geotextile-soil interaction under challenging environmental conditions.

Foamed lightweight soil with red mud (FLS-RM), a new type of subgrade material commonly used in projects such as bridge backfill. In engineering applications, FLS-RM tends to crack after pouring to weaken its properties, which limits its further application, and this situation can be improved by adding fiber into FLS-RM. Thus, this study developed a new type of FLS-RM reinforced by polypropylene fibers, polyester fibers, and kenaf fibers to investigate the changes in the mechanical properties of FLS-RM and its deterioration mechanism. The experimental results showed that the mechanical properties of FLS-RM could be enhanced by the fibers, and the compressive and flexural strengths of FLS-RM specimens reinforced by polypropylene fiber reached 0.87 MPa and 0.85 MPa, respectively, when the fiber length was 12 mm and the content was 0.75 wt% and 1.00 wt%. Design Expert was used to analyze the experimental data to obtain the pattern of the effect of different fiber conditions on the strength of FLS-RM and optimal fiber conditions, and to establish the strength equation. The EDS results revealed that the red mud can be excited to generate an aluminosilicate gel filling in the skeleton under alkaline conditions. The results of the microscopic analysis indicated that the close bonding between the fibers and the matrix increased the friction and mechanical bite between the independent blocks and enhanced the strength of the specimens.

As an emerging environmentally friendly solid waste-based composite foam lightweight soil, saponified slag fly ash (SS-FA) foam lightweight soil has a wide range of application prospects in road engineering. In this paper, the dynamic characteristics of SS-FA foam light soil material were investigated. Dynamic triaxial tests under different cyclic loading conditions were designed to analyze the variation rules of dynamic elastic modulus and damping ratio. The results showed that the stress-strain curve of SS-FA foam lightweight soil can be divided into three stages: elastic stage, plateau stage, and stress yielding stage. Under cyclic dynamic load, with the increase of dynamic stress amplitude, the dynamic elastic modulus of 400-700 kg/m3 samples gradually increased to the maximum, reaching 235.24 MPa, 324.54 MPa, 356.45 MPa, 379.67 MPa, respectively. The damping ratio, on the other hand, shows a tendency to first decrease and then slowly increase to stabilize. The dynamic elastic modulus is positively correlated with density grade, confining pressure and loading frequency. The damping ratio decreases with the increase of density grade and loading frequency, and increases with the increase of confining pressure. The electron microscope test was designed and image processing and data statistics were carried out. Through the grey correlation analysis, the correlation degree between the microstructure parameters of SS-FA foamed lightweight soil and the macroscopic mechanical properties is basically above 0.6, indicating that the two have a significant correlation. A normalized prediction formula model between the dynamic elastic modulus of materials and the conditional parameters was established. The R2 of the linear fitting of the predicted value is 0.964, indicating that the prediction model has a high degree of fitting and a good prediction effect. The research results revealed the dynamic mechanical properties of foamed lightweight soil, and provided a reference for the application of SS-FA foamed lightweight soil in subgrade engineering.

This paper presents an experimental investigation into the interaction mechanism between aqueous foam and unsaturated granite residual soil during conditioning. Contact filter paper tests and undrained shear tests were used to analyze foam's effects on soil water retention and shear behavior, while surface tension tests, capillary rise tests, and microscopic observations examined the role of soil particles in foam stability. The findings demonstrate that foam-conditioned granite residual soils exhibit three distinct saturation- dependent phases (soil-only, transition, and soil-foam mixture) governed by foam's gas-liquid biphasic nature, with foam injection effectively reducing matric suction in unsaturated conditions. Increasing foam injection ratio reduces shear stress while enhancing pore water pressure, with vertical displacement transitioning from contractive to expansive behavior at low shearing rate. Effective cohesion stress varies with gravimetric water content via a rational function, while other effective cohesion stress and friction angles with respect to foam injection ratio, shearing rate, and gravimetric water content obey exponential relationships. The probability distribution function, cumulative distribution function, and decay pattern of bubbles in foam-only systems and soil-foam mixtures all exhibit exponential relationships with elapsed time. Furthermore, a new water-meniscus interaction model was established to characterize rupture and stabilization mechanisms of foam in unsaturated granite residual soils, with particular emphasis on capillary-dominated behavior. Saturation-dependent particle contact modes were identified for foam-conditioned unsaturated granite residual soils, offering valuable guidance for enhancing soil conditioning protocols in earth pressure balance shield tunneling operations.

Phenolic foam (PF) produces much PF waste during processing because of its friability and tendency to pulverize. Currently, commonly used disposal methods like incineration and landfill cause air and soil pollution. Moreover, protective polyurethane foam (PUF) requires both excellent acoustic insulation and mechanical strength in scenarios, such as factories and roads, to enhance environmental comfort and safety. In this study, PF waste was recycled via a mechanical method, and compounding the recycled PF powder as a functional filler with PUF significantly improved its mechanical and acoustic properties. The sample (PUFB-2.5) with 2.5 g PF powder added achieved a compressive strength of 372.19 kPa, 99.03% higher than the standard foam sample (PUFB-0). Additionally, the sample (PUFB-10) with 10.0 g PF powder added achieved an optimal average sound absorption coefficient (alpha) of 0.59, 63.89% higher than PUFB-0. In the 400-2400 Hz frequency range, sample PUFB-2.5 displayed superior sound absorption properties, with alpha reaching 0.78. This study not only achieves the recyclable and circular utilization of PF waste but also enhances the mechanical and acoustic properties of PUF and offers new paths for the convergence of material science and environmental engineering industries.

Foamed lightweight soil (FLS) is frequently used for roadbed backfilling; however, excessive cement use contributes to higher costs and energy consumption. Desulfurized gypsum (DG), a by-product of industrial processing with a chemical composition similar to natural gypsum, presents a viable alternative to cement. This study evaluates the potential of DG to replace cement in FLS, creating a new material, desulfurized gypsum foamed lightweight soil (DG-FLS). This article is conducted on DG-FLS with varying DG content (0-30%) to assess its flowability, water absorption, unconfined compressive strength (UCS), durability, and morphological characteristics, with a focus on its suitability for roadbed backfilling, though its performance over the long term in engineering applications was not evaluated. Results show that as DG content increased, flowability, water absorption, and UCS decreased, with values falling within the range of 175-183 mm, 8.24-12.49%, and 0.75-2.75 MPa, respectively, all of which meet embankment requirements. The inclusion of DG enhanced the material's plasticity, improving failure modes and broadening its applicability. Durability tests under wet-dry and freeze-thaw cycles showed comparable performance to traditional FLS, with UCS exceeding 0.3 MPa. Additionally, the incorporation of SO42- in DG-FLS reduced sulfate diffusion, decreased C-S-H content, and increased calcium sulfate content, improving sulfate resistance. After 120 days of exposure to sulfates, the durability coefficient of DG-FLS surpassed 100%, with a 25% improvement over traditional FLS. A sustainability analysis revealed that DG-FLS not only meets engineering strength requirements but also offers economic and environmental benefits. Notably, DG-12 showed a 20% reduction in environmental impact compared to conventional FLS, underscoring its potential for more sustainable construction.

Foamed lightweight soil is widely used in subgrade engineering as a lightweight, high fluidity material. However, due to the use of cement as the main raw material, its cost is relatively high. Therefore, the preparation of foamed lightweight soil by mixing muck excavated at the project site with iron ore tailings (IOT) is not only helpful to reduce costs, but also can promote the efficient and comprehensive utilization of inactive solid waste. In this paper, the fluidity, wet density, compressive strength and specific strength of muck-IOT foamed lightweight soil with different content were tested, and the optimal mixing ratio was selected according to the engineering specifications. Then, through uniaxial and triaxial compression tests, the strength and deformation characteristics of muck-IOT foamed lightweight soil under different dosage, wet density and confining pressure conditions were studied. Finally, the influence mechanism of muck and IOT on the strength and structure of foamed lightweight soil was revealed through Scanning Electron Microscope (SEM) analysis. The research results show that the wet density of foamed lightweight soil prepared by the optimal mixing amount (20% muck and 10% IOT) is 894 kg/m3, and the uniaxial compressive strength is 4.6 MPa. While meeting the requirements of fluidity, the mixing amount of solid waste is higher, with the specific strength increased by 28.12%. In the triaxial compression test, for every 100 kg/m3 increase in wet density, the peak strength and residual strength increase by 1.30 MPa and 1.00 MPa, respectively; For every 200 kPa increase in confining pressure, the peak strength and residual strength increase by 0.27 MPa and 0.32 MPa, respectively. In addition, the shear strength levels of muck-IOT foamed lightweight soil under different normal stress conditions under different wet densities were determined by establishing the linear equations of c and phi related to the wet density. From the microstructure, it can be seen that the pores in the muck-IOT foamed lightweight soil are evenly distributed, resulting in a denser structure and reduced stress concentration, which significantly enhances the material's compressive strength.

Expansive soil, a commonly distributed clay, is unsuitable for direct engineering applications. This study proposes a method to produce foam lightweight soil from expansive soil, effectively mitigating its expansive properties. The physical and mechanical properties of expansive soil-based lightweight soil (E-LS) were systematically investigated under varying water-solid ratios, wet densities, and expansive soil contents, using tests for flow value test, drying shrinkage test, pH test, and compressive strength test. An orthogonal experiment was conducted to quantify the influence of these factors on unconfined compressive strength (q(u)), leading to the development of a strength determination method. The results show that the preparation of E-LS modifies the expansive soil structure, completely eliminating its expansiveness. Compressive strength of E-LS increases with both wet density and curing age. For expansive soil contents ranging from 30% to 60%, the unconfined compressive strength at 28 days (q(u-28 d)) varied from 0.21 MPa to 1.58 MPa. Specifically, for E-LS with 50% expansive soil content, a water-to-solid ratio of 0.8, and a wet density of 900 kg/m(3), the q(u-28 d) reached 0.92 MPa, meeting the requirements for embankment construction. The factors affecting compressive strength are ranked as expansive soil content wet density water-solid ratio, and a predictive model for E-LS strength was developed. E-LS exhibits the capability to fulfill diverse embankment filling requirements in engineering applications, while demonstrating distinct advantages including expansive property mitigation, compaction-free implementation, and construction efficiency, thereby presenting significant potential for practical engineering deployment.

This study explores the influence of the water-cement ratio and fiber content in engineered cementitious composite (ECC) on the mechanical characteristics of foamed lightweight soil (FLS) through experimental analysis. Two types of cementitious materials-ECC and ordinary Portland cement (OPC)-were utilized to create FLS specimens under identical parameters to examine their mechanical performance. Results indicate that ECC-FLS exhibits superior toughness, plasticity, and ductility compared to OPC-FLS, validating the potential of ECC as a high-performance material for FLS. To assess the influence of the ECC water-cement ratio, specimens were constructed with varying ratios at 0.2, 0.25, and 0.3, while maintaining other parameters as constant. The experimental results indicate that as the water-cement ratio of ECC increases, the flexural strength, compressive strength, flexural toughness, and compressive elastic modulus of the lightweight ECC-FLS gradually increase, exhibiting a better mechanical performance. Moreover, this study investigates the effect of basalt fiber content in ECC on the mechanical properties of FLS. While keeping other parameters constant, the volume content of basalt fibers varied at 0.1%, 0.3%, and 0.5%, respectively. The experimental results demonstrate that within the range of 0 to 0.5%, the mechanical properties of FLS improved with increasing fiber content. The fibers in ECC effectively enhanced the strength of FLS. In conclusion, the adoption of ECC and appropriate fiber content can significantly optimize the mechanical performance of FLS, endowing it with broader application prospects in engineering practices. ECC-FLS, characterized by excellent ductility and crack resistance, demonstrates versatile engineering applications. It is particularly suitable for soft soil foundations or regions prone to frequent geological activities, where it enhances the seismic resilience of subgrade structures. This material also serves as an ideal construction solution for underground utility tunnels, as well as for the repair and reconstruction of pavement and bridge decks. Notably, ECC-FLS enables the resource utilization of industrial solid wastes such as fly ash and slag, thereby contributing to carbon emission reduction and the realization of a circular economy. These attributes collectively position HDFLS as a sustainable and high-performance construction material with significant potential for promoting environmentally friendly infrastructure development.

Protein-based foams are potential sustainable alternatives to petroleum-based polymer foams in e.g. single-use products. In this work, the biodegradation, bioassimilation, and recycling properties of glycerol-plasticized wheat gluten foams (using a foaming agent and gallic acid, citric acid, or genipin) were determined. The degradation was investigated at different pH levels in soil and high humidity. The fastest degradation occurred in an aqueous alkaline condition with complete degradation within 5 weeks. The foams exhibited excellent bioassimilation, comparable to or better than industrial fertilizers, particularly in promoting coriander plant growth. The additives provided specific effects: gallic acid offered antifungal properties, citric acid provided the fastest degradation at high pH, and genipin contributed with cross-linking. All three additives also contributed to antioxidant properties. Dense beta-sheet protein structures degraded more slowly than disordered/alpha-helix structures. WG foams showed only a small global warming potential and lower fossil carbon emissions than synthetic foams on a mass basis, as illustrated with a nitrile-butadiene rubber (NBR) foam. Unlike NBR, the protein foams could be recycled into films, offering an alternative to immediate composting.