Positively and negatively charged additives tune MICP to strengthen Pb-contaminated loess. The optimized system enhances carbonate precipitation, improves Pb immobilization, and increases soil mechanical performance via controlled nucleation and crystal growth.

This study aims to evaluate the accuracy of different dynamic compaction (DC) load equivalent conversion methods in DC vibration calculations. It also investigates the effect of vibration isolation treatments on the vibration reduction performance of loess foundations, with the goal of optimizing vibration control during DC construction. Five classical methods were used to convert the DC loads into time-dependent surface loads, which were subsequently fed into Plaxis’s dynamic multiplier table for the numerical implementation of DC tests. By comparing the numerical simulation results with in situ monitoring data from a loess site, the accuracy of the five DC load equivalent conversion methods was evaluated. The momentum theorem method was identified as the most precise for both vibration velocity and settlement. Subsequently, the momentum theorem method was utilized to investigate the influence of depth and distance of vibration isolation trench, as well as the properties of vibration isolation materials on vibration reduction effect. It is indicated that the optimal depth for the vibration isolation trench of the loess site is 2 m, beyond which the improvement in vibration reduction effects is not notable. The excavation distance of the vibration isolation trench should be set as close as possible to the boundary of the construction site to achieve the best vibration reduction effect. As for the properties of vibration isolation materials, it is shown that the unit weight and damping ratio of the filling material have a significant effect on the vibration reduction effect, while the influence of the shear strength of the filling material is negligible. Besides the vibrating reduction influence of filling materials, utilizing spring dampers has a better vibration reduction effect. Increasing the stiffness of the spring dampers and reducing their spacing can significantly enhance the vibration reduction effect. In practical engineering applications, it is essential to consider both the effects and economic costs to select the optimal vibration reduction treatment and its parameters. This study provides a scientific basis for vibration control during DC construction, contributing to ensuring construction safety and efficiency while minimizing the impact on the surrounding environment.

Severe Cu and Pb enrichment in loess areas of northwestern China, mainly associated with mining and smelting activities, has increased the demand for efficient soil decontamination. Electrokinetic (EK) remediation is a promising in situ technology because it can drive ionic contaminants through low-permeability porous media with limited excavation and relatively low secondary disturbance. In this study, the effects of electric field strength, electrode type, and catholyte pH on Cu and Pb removal from contaminated loess were systematically evaluated using a large-scale EK reactor. The full name of EKG is electrokinetic geosynthetics. During treatment, pH, electrical conductivity, electric current, cumulative electroosmotic flow (EOF), and the spatial distributions of Cu and Pb were monitored. Increasing the electric field from 1.0 to 2.0 V cm⁻¹ increased current and EOF and accelerated anodic acid-front propagation, but it also strengthened cathodic alkalization and precipitation. Compared with graphite electrodes, electrokinetic geosynthetics (EKG) electrodes maintained higher current and EOF, generated stronger acidification, and increased Cu and Pb removal by approximately 25% and 5%, respectively. Among the tested catholyte conditions, pH 7.0 provided the best balance between electromigration and electroosmosis, achieving overall soil-phase removal efficiencies of approximately 19.0% for Cu and 8.0% for Pb. These results show that coordinated regulation of the electric field, electrode architecture, and electrolyte chemistry can mitigate the focusing effect in loess, although further enhancement is still required for field-scale decontamination.

Freeze–thaw cycling can strongly disturb the pore-water environment, soil fabric, and contaminant mobility of heavy-metal-contaminated loess, thereby threatening the long-term effectiveness of stabilization treatments in seasonally frozen regions. This study investigated the coupled hydro-environmental and geotechnical performance of Pb-contaminated loess (untreated control group, CK) treated with microbially induced calcium carbonate precipitation (MICP), graphene (GR)-assisted MICP, and graphene oxide (GO)-assisted MICP under controlled freeze–thaw cycles. One-dimensional consolidation tests, toxicity characteristic leaching procedure (TCLP) tests, zeta-potential measurements, X-ray fluorescence (XRF), and scanning electron microscopy (SEM) were conducted to evaluate compressibility evolution, Pb leaching behavior, interfacial electrochemical characteristics, mineralogical changes, and microstructural mechanisms. After 9 days of mineralization, MICP reduced the Pb leaching concentration from 38.05 to 23.00 mg L⁻¹, achieving a 39.55% reduction compared with untreated Pb-contaminated loess. Freeze–thaw cycling increased the susceptibility of treated loess to structural degradation and pore collapse, especially under medium to high vertical stresses. Nevertheless, the void ratio generally followed the order of CK > MICP > MICP + GR > MICP + GO under comparable loading and freeze–thaw conditions, indicating progressively enhanced resistance to compressive deformation. GR-assisted MICP showed an optimum dosage of approximately 1.0%, beyond which Pb leaching increased because of sheet restacking, agglomeration, and non-uniform biomineralization. In contrast, under up to 13 freeze–thaw cycles, GO-assisted MICP maintained the lowest void ratio and the most stable Pb immobilization performance among all treatments, demonstrating improved resistance against freeze–thaw-induced structural degradation. The results suggest that GO-assisted MICP can simultaneously improve Pb leaching control and soil-fabric stability, providing a promising low-carbon strategy for remediating heavy-metal-contaminated loess exposed to water-mediated freeze–thaw disturbance.

With the continued advancement of industrialization and urbanization in northwestern China, heavy metal contamination of loess sites has become an increasingly serious environmental issue. Heavy metals such as copper (Cu) and lead (Pb) are toxic, persistent, and readily retained by the mineral-pore framework of loess, which makes remediation difficult and threatens regional ecological security and human health. This study investigated electrokinetic (EK) remediation of artificially prepared loess co-contaminated with Cu and Pb using tartaric acid (TA), citric acid (CA), and disodium ethylenediaminetetraacetate (EDTA) as catholytes. Cu was generally removed more effectively than Pb because Pb was less adsorbed and immobilized more strongly. All three chelators enhanced metal desorption and migration through complexation, particularly in the cathode-side section. EDTA produced the greatest enhancement because it formed stable, negatively charged complexes with Cu and Pb over a broad pH range. Relative to the deionized-water control, EDTA increased the overall removal efficiencies of Cu and Pb to 55.4% and 27.2%, respectively, and promoted their transfer from the soil to the anolyte. These findings demonstrate that chelator-assisted EK treatment, particularly with EDTA, can effectively improve Cu and Pb removal from loess, while field application requires control of energy use, residual chelator, and post-treatment metal mobility.