This study presents a method for remediating soils contaminated by organic pollutants through the selective blocking of pores. This technique is based on the use of yield stress fluids, specifically concentrated biopolymer solutions, which, due to their distinctive rheological properties, preferentially flow through high-conductance flow paths. Following the injection of yield stress fluid, its presence redirects subsequent water flow towards the pores that are typically unswept during standard waterflooding. Laboratory experiments at the pore scale were conducted to validate this method and confirm previous findings from core-flooding experiments. Aqueous xanthan gum solutions were used as microscopic blocking agents in well-characterized micromodels exhibiting microscopic heterogeneities in pore size. The impact of polymer concentration, soil wettability and operating conditions (injection pressure and flow rate) on the residual pollutant saturation following treatment was analyzed, enabling the optimization of the remediation strategy. The use of xanthan gum as a blocking agent led to a significant improvement in pollutant removal compared to conventional waterflooding, delivering consistently better results across all cases studied. The method demonstrated strong performance in water-wet medium, with the average polymer concentration yielding the highest efficiency in pollutant removal.

Understanding the rheological properties of clayey soils is significant for construction and geotechnical engineering, as these properties influence the stability and performance of building materials and structures. This study offers a new prospective for the rheological behavior of soils with water content near the liquid limit. Steady-state and dynamic rheological tests were conducted on kaolin, montmorillonite, and other three mixed clays of them at different water contents. In addition, microstructural analysis was performed to explain the microscopic mechanisms influencing the rheological responses of clays. The results show that for all the clays, the yield stress decreases with increasing water content. With the increase of shear rate, the viscosity first decreases rapidly and then decreases slowly. Clay mixtures exhibit greater microstructural stability than pure kaolin and montmorillonite, resulting in higher yield stress. Furthermore, dynamic shear testing provided insights into energy storage and loss modulus of clays near the solid-liquid transition phase. The proposed dynamic yield stress model effectively describes yield stress variation with the liquid limit under dynamic loading, relevant for assessing soil liquefaction potential and seismic resilience of structures. These findings offer valuable guidance for optimizing soil behavior in construction and enhancing structural performance in clay-rich regions.

Foam concrete boasts widespread applications in backfill engineering, energy -efficient insulation components, and road infrastructure. However, the foam concrete with lower density tends to possess the lower stability. The unstable characteristics of foam concrete restricts its application. In this study, the feasibility of employing biochars to increase stability of foamed concrete is investigated. The rheological properties of base mix are carried out to analyze the foam concrete stability. The analysis of water state, interparticle distance and ion concentration are tested to analyze the stabilization mechanisms. Our findings demonstrate that the introduction of corn husk biochar (CHBC) within the base mix expedites flocculation formation, reducing interparticle distance and subsequently elevating the yield stress. Conversely, the inclusion of rice husk biochar (RHBC) diminishes ion concentration, heightening repulsion forces between particles and thereby reducing yield stress of base mix. Higher yield stress exert the higher constraining force and frictional force to the bubbles, thereby decreasing bubble size in fresh foamed concrete, bettering pore structure, compressive strength and foam stability of foamed concrete. Additionally, the increase in CHBC content enhances pore sphericity, potentially attributed to decreased bubble deformation parameters Ca eta.