Jie Hu

Field tests were conducted at a heterogeneous industrial site using one circulation well and six monitoring wells. Groundwater circulation well (GCW) extraction–injection (30 d), multi-component tracing (6 h), and circulation–oxidation (20 h) tests were performed to investigate the flow-field characteristics and their influence on multi-component solute transport. The results suggested that the extraction–injection circulation mode increased the flow rate of the single well from 0.5 m³/h to 3.5 m³/h, establishing a composite flow field with near-field circulation and far-field outward expansion. Short-term circulation achieved limited concentration attenuation primarily near the well with rebound. Long-term circulation elevated the average concentration attenuation rates of benzene from 13% in the short-term test to 61%, and chemical oxygen demand (COD) from 16% to 47%, expanding the remediation scope of the circulation well. Bromide tracer tests and an advection–dispersion equation characterized the heterogeneous flow field with preferential flow channels and slow migration zones. Furthermore, sulfate tracer transport was governed by adsorptive retardation and advective delivery. Circulation–oxidation tests showed that benzene and COD showed higher concentration attenuation than naphthalene. After cessation, benzene and COD concentration attenuation rates increased by 39% and 29% compared to the short-term test without oxidation. Electrical resistivity tomography (ERT) revealed the downward diffusion of the oxidant, suggesting that the circulation well system enhances oxidant transport and expands the oxidant-affected zone. This research provides field-scale diagnostic evidence and in situ diagnostic methodologies for GCW remediation at complex contaminated sites.

Trommel screens are widely used for screening of landfilled municipal solid waste (MSW). Due to the heterogeneous composition of MSW, the particle-size-based screening efficiency of different waste fractions under limited screening time requires further investigation. This paper presents an experimental study on the trommel screening performance of MSW samples obtained by large diameter drilling at a landfill. After sieving tests, screening products were manually grouped according to density and particle size differences to explore the effects of moisture content ( ω w ), fine particle content ( ω f ) and rotational speed ( n ) on the size-based separation efficiency of the light and heavy materials. Screening efficiencies of heavy material ( η H ), light material ( η L ) and content of light material in the undersized product ( ω L , U ) are proposed to evaluate the screening performance based on the quality and yield of undersized products. The results revealed that light materials generally exhibited lower screening percentage than heavy materials. When ω w was 20%, higher ω f improved η H but reduced η L and ω L , U . When ω w was 60%, with increasing ω f , η H decreased slightly while ω L , U decreased first and then increased. As ω w increased from 20% to 60%, the optimal n at which η H reached its maximum rose from 15 to 25 r/min. At this point, ω L , U corresponding to the maximum η H reached its peak. When n was higher, screening efficiency of MSW could be improved by appropriately increasing the screen length. High η H and low ω L , U cannot usually be realized simultaneously, the optimal parameters should be set according to specific requirements.

Accurately describing slurry diffusion in fracture remains challenging due to the complexity of fracture roughness and the non‐linear rheological properties of slurry. This study presents an analytical solution for the single‐hole grouting in rough fractures considering the time‐dependent viscosity of Bingham fluid. Fracture roughness is described by introducing two parameters, the fractal dimension D and the characteristic scale parameter G . The accuracy of the analytical solution is validated by comparing the slurry flow and diffusion radius from experimental results with predicted results. The corresponding slurry flow Q calculated from the analytical solution is used to delineate different areas. Variations in D and G shift the slurry flow resistance from rough ( Q < 0.1 L) to transitional (0.1–0.8 L) and smooth ( Q > 0.8 L) areas under constant other parameter conditions. Variations in yield stress and viscosity shift the slurry flow areas among low, medium, and high sensitivity areas. Additionally, numerical analysis of two‐hole grouting in rough fractures is performed to determine optimal grouting hole spacing based on the percentage of the area covered by the slurry relative to the total fracture area. During two‐hole grouting, mutual squeezing effect between slurry alternately promotes and impedes flow. The optimal grouting hole spacing of Bingham fluids with varying water‐to‐cement ratios decreases with fracture roughness and increases with grouting pressure. Bingham fluids with water‐to‐cement ratios of 1.0–2.0 exhibit greater sensitivity to grouting pressure in wide fractures due to complex flow characteristics, providing a reference for simplifying grouting process across varying geological conditions.

The microscale solid and pore structures of waste is crucial for the bio-hydro-mechanical behaviors of landfilled municipal solid waste (MSW). The quantitative analysis of the structural characteristics of MSW is still limited. In this study, borehole MSW samples at different depths (i.e., 0 m, 2.5 m, 5 m, 7.5 m, 10 m, and 12.5 m) were drilled from a landfill. The waste composition and basic physical properties of these samples were tested in laboratory. Solid and pore structural characteristics were studied through computed tomography (CT) analysis. The results indicate that the ratio of cellulose content to lignin content (i.e., C/L) decreased from 0.85 to 0.47 with increasing depth. For solid particles, two-dimensional (2D) particles constituted the greatest fraction (60.22~72.16%), which showed a decrease with increasing depth. The deeper sample tended to have more fine particles. For pores, the void ratio decreased from 1.68 to 1.10 with increasing depth, with more small pore channels. Meanwhile, the average pore diameter coefficient (λ) decreased from 0.209 to 0.190, the pore angle (θ_e) decreased from 29.6° to 17.8°, the tortuosity (τ) increased from 1.129 to 1.184, and the connectivity (c_e) decreased from 12.0 to 4.1. These quantitative findings can further the understanding of fluid flow behaviors in landfilled waste.