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The clogging of a stream bed has a significant impact on the exchange of water between a river and groundwater, known as hyporheic exchange. Clogging issues in orifices influenced by fluid flow have long been a concern, particularly in understanding clogging mechanisms and particle dynamics. This study focuses on investigating the behavior of poly-dispersed particle systems in the Shanghai soft soil using a coupled lattice Boltzmann method and a discrete element method (LBM-DEM). A particle-orifice model was developed based on LBM-DEM to study the clogging problem. Three different orifice diameters with the same particle size distribution were set at a microscopic scale. The simulation results indicate that the primary form of clogging is the formation of particle domes, exhibiting distinct characteristics depending on orifice size. As the orifice size increases, clogging becomes more challenging. Interestingly, the flow rate of fluid passing through clogged orifices is quite complex, as it does not decrease significantly. The formation process of the particle structure shows significant randomness, posing challenges for quantitative analysis and experimental validation. This study provides insights into the initial stages of clogging formation, leading to a better understanding of hyporheic exchange phenomena in stream bed ecosystems. [ABSTRACT FROM AUTHOR]

Soil in situ remediation, such as washing, always produces much sludge that has the characteristics of a high fine particle proportion, high moisture content, and high metal content. Problems such as high transportation costs, large land area, and the influence on landfill capacity often occur in the process of reclamation or landfill disposal. To solve the above problems, the vacuum preloading method was used to treat the sludge. The effect of this method on reducing the water content and volume of the sludge was investigated. Initial vacuum preloading (IVP) and step vacuum preloading (SVP) laboratory experiments were carried out on the sludge from the washing waste at a heavy metal soil remediation site in Shanghai. The drainage rate and settlement rate of the sludge during the experiment were recorded, and the moisture content and unconfined compressive strength (UCS) of the sludge samples after the experiment were tested and analyzed. Finally, the mechanism of uneven water content and shear strength of sludge treated by IVP and SVP were analyzed based on the grain size distribution. The results showed that the moisture content of the sludge near the prefabricated vertical drains (PVDs) decreased to 48.55%, and its volume decreased to 41.6% of the initial volume. The UCS of the sludge near the PVDs under SVP was 20.32% higher than that under IVP. The sludge treated by the vacuum preloading method can be disposed of in a landfill or other resource utilization. [ABSTRACT FROM AUTHOR]

In view of the deep dewatering of landfill sludge (LS) that had been buried for more than ten years in Shanghai, Fenton's reagent combined with a vacuum preloading method was proposed. First, a vacuum filtration test was carried out to study the optimal amount of Fenton's reagent for LS. Then, four filter membranes with different pore sizes were used for a vacuum preloading model box test to study the influence of pore size on the consolidation behaviour of LS. Through particle analysis, SEM and MIP testing, the consolidation behaviour of sludge under different pore sizes was studied from the microscopic perspective. The results show the following: the optimal amount of Fenton's reagent for conditioning LS is Fe2+ 4%, H 2 O 2 12%; the water content of LS with different pore sizes is reduced from 73% to 56%–63%; the unconfined compressive strength is increased from 10 kPa to above 80 kPa; and the volume reduction ratio is approximately 50%, among which the filter pore size of 180-μm has the best performance. The micro-test results show that the pore size of the filter membrane has an important influence on LS's consolidation. The research results can provide significant references for the in-situ treatment of LS. • Fenton's reagent combined with vacuum preloading was used to treat landfill sludge(LS). • Four different filter pore sizes are adjusted to solve the clogging problem of LS. • The consolidation behaviour of LS was analysed from the micro-mechanism. • The LS has the best consolidation effect when the pore size is 180-μm. [ABSTRACT FROM AUTHOR]

Taking the waste high-moisture slurry produced at a construction site in Shanghai as the research object, the pressure filtration effect of the slurry under the condition of agent conditioning was studied. First of all, the geotechnical characteristics of the waste slurry under agent conditioning were studied through laboratory experiments, and the selection and addition amount of the agent were preliminarily determined. Then, the influence of agent addition, stirring time, and pressure filtration time on the pressure filtration efficiency was studied through field experiments. Finally, a method to guide the field filtration time by the indoor model test was put forward. [ABSTRACT FROM AUTHOR]