Loess is widely distributed in Northwestern China and serves as the preferred engineering construction material for anti-fouling barriers. Heavy metal contamination in soil presents significant challenges to the engineering safety of vulnerable loess structures. Hence, there is an urgent need to investigate the impact of heavy metal ions on their percolation performance. In order to investigate the effectiveness of microbially induced carbonate precipitation (MICP) using Sporosarcina pasturii (CGMCC1.3687) bacteria in reducing internal seepage erosion, a saturated permeability test was conducted on reshaped loess under constant water head saturation conditions. The response of loess to deionized water (DW) and ZnCl₂ solution seepages was analyzed by monitoring changes in cation concentration over time, measuring Zeta potential, and using scanning electron microscopy (SEM). The results indicate that the hydrolysis of Zn²⁺ creates an acidic environment, leading to the dissolution of carbonate minerals in the loess, which enhances its permeability. The adsorption of Zn²⁺ ions and the resulting diffusion double-layer (DDL) effect reduce the thickness of the diffusion layer and increase the number of free water channels. Additionally, the permeability of loess exposed to ZnCl₂ solution seepage significantly increased by 554.5% compared to loess exposed to deionized water (DW) seepage. Following the seepage of ZnCl₂ solutions, changes in micropore area ratio were observed, decreasing by 48.80%, while mesopore areas increased by 23.9%. MICP treatment helps reduce erosion and volume shrinkage in contaminated loess. Carbonate precipitation enhances the erosion resistance of contaminated loess by absorbing or coating fine particles and creating bridging connections with coarse particles. These research results offer new perspectives on enhancing the seepage properties of saturated loess in the presence of heavy metal erosion and the geochemical mechanisms involved.

The repurposing of carbide slag (CS) coupled with the advancement of eco-friendly engineering methodologies promises a novel approach to addressing the technical challenges inherent in loess refinement. This inquiry delves into the feasibility of employing CS as an economically viable and ecologically sustainable remedy to amplify the engineering attributes of loess within the context of optimal preservation. In this investigation, assorted quantities of CS, spanning from 1% to 6%, were infused into the loess. The efficacy of CS as an additive was ascertained through a comprehensive array of tests administered across varied curing durations (0, 5, 10, 20, and 30 days), concentrating on its influence over the soil’s mechanical attributes. The study conducted various tests such as dual hydrometer, Attberg limit, specific gravity, compaction, unconfined compressive strength (UCS), consolidation, physico-chemical properties (pH, conductivity), and chemical analysis (sodium percentage and sodium adsorption rate). The study demonstrated that the incorporation of CS into loess resulted in an increase in hydraulic conductivity, UCS, and optimum water content while reducing maximum dry density, plasticity, and compressibility. Specifically, the application of 6% CS resulted in a significant 6.7-fold increase in UCS from 226.8 (kPa) to 1508.8 (kPa) over a 30-day curing period. It was also observed that the addition of CS and curing period resulted in a decrease in soil pH from 8.5 to 7.5 and an increase in electrical conductivity (EC) from 250 to 490 μs/cm. When the CS concentration was increased to 6%, the amount of Na⁺ ions, the total soluble salts, and the percentage of Na in the loess decreased. The phenomenon can be ascribed to the replacement of Ca²⁺ for Na⁺, leading to a more slender, diffuse double layer and heightened stability. The application of calcium silicate in loess subgrades enhances their stability and potency, concurrently providing an ecologically sound waste management resolution. Consequently, it emerges as a profoundly viable choice for ameliorating loess within the realm of the construction sector.

Prolonged exposure to landfill leachate can weaken the impermeability of liner systems, leading to leachate leakage and the contamination of surrounding soil and water. To improve loess impermeability to enable its use as a liner material, this study uses synthetic landfill leachate to investigate its effects on loess permeability via a series of laboratory tests. This study focused on the influence of varying dosages of calcium lignosulfonate (CLS) on loess permeability, along with its capacity to adsorb and immobilize heavy metal ions. Microscale characterization techniques, including Zeta potential analysis, X-ray fluorescence spectroscopy (XRF), and scanning electron microscopy (SEM), were employed to investigate the impermeability mechanisms of CLS-modified loess and its adsorption behavior toward heavy metals. The results indicate that the permeability coefficient of loess decreases significantly with increasing compaction, while higher leachate concentrations lead to a notable increase in permeability. At a compaction degree of 0.90, the permeability coefficient was reduced to 8 × 10⁻⁸ cm/s. In contrast, under conditions of maximum leachate concentration, the permeability coefficient rose markedly to 1.5 × 10⁻⁴ cm/s. Additionally, increasing the dosage of the compacted loess stabilizer (CLS) effectively reduced the permeability coefficient of the modified loess to 7.1 × 10⁻⁵ cm/s, indicating improved impermeability and enhanced resistance to contaminant migration. With the prolonged infiltration time of landfill leachate, the removal efficiency of Pb²⁺ gradually decreases and stabilizes, while the Pb²⁺ removal efficiency of the modified loess increased by approximately 40%. CLS-modified loess, through multiple mechanisms, reduces the fluid flow pathways and enhances its adsorption capacity for Pb²⁺, thereby improving the soil’s protection against heavy metal contamination. While these results demonstrate the potential of CLS-modified loess as a sustainable landfill liner material, the findings are based on controlled laboratory conditions with Pb²⁺ as the sole target contaminant. Future work should evaluate long-term performance under field conditions, including seasonal wetting–drying and freeze–thaw cycles, and investigate multi-metal systems to validate the broader applicability of this modification technique.

The shear behavior of basalt fiber-reinforced polymer (BFRP) bars is crucial for their applications in geotechnical reinforcement and composite structures. In this study, double-side direct shear tests were conducted to investigate the progressive failure mechanism of BFRP bars. The results reveal a three-stage process: initial matrix-dominated vertical shear, followed by fiber-bridging dominated oblique tension-shear, and finally formation of a “brush-like” fracture surface with significant residual strength. The average peak shear strength of the ten specimens was 204.04 MPa with a coefficient of variation of 7.25%, while the initial shear modulus averaged 3.37 GPa with a coefficient of variation of 11.82%. Based on statistical damage theory, a shear constitutive model incorporating fiber bridging and residual strength is established. Parameter analysis indicates that the shape parameter m governs the post-peak softening rate, while the residual strength τ_res essentially determines the height of the residual plateau. The model achieves a goodness-of-fit (R²) exceeding 0.98 for most specimens, accurately describing the mechanical behavior from linear elasticity, damage-induced hardening, peak softening, to the residual stage. This study provides theoretical and experimental support for the engineering application of BFRP bars under complex stress states.