Buried pipes are subjected to static and dynamic loads depending on their areas of use. To mitigate the risk of damage caused by these effects, various materials and reinforcement methods are utilized. In this study, five buried uPVC pipes designed in accordance with ASTM D2321 standards were reinforced with three different ground improvement materials: Geocell, Geonet, and Geocomposite, and experimentally subjected to dynamic impact loading. Acceleration, velocity, and displacement values were obtained from the experiments. Subsequently, finite element analysis (FEA) was performed using the ABAQUS software to determine stress values and volumetric displacements in the pipes, and the model was validated with a 5-7% error margin. In the final stage of the study, a parametric analysis was conducted by modifying the soil cover height above the pipe and the Geocell thickness in the validated finite element model. The parametric study revealed that the displacement value in the pipe decreased by 78% with an increase in soil cover height, while a 16% reduction was observed with an increase in Geocell thickness. The results demonstrate that the soil improvement techniques examined in this study provide an effective solution for enhancing the impact resistance of buried pipeline systems.

Background: Herbicides are chemical agents that promote plant and crop growth by killing weeds and other pests. However, unconsumed and excessively used herbicides may enter groundwater and agricultural areas, damaging water, air, and soil resources. Mesotrione (MT) is an extensively used herbicide to cultivate corn, sugarcane, and vegetables. Excessive consumption of MT residues pollutes the soil, water, and environmental systems. Methods: Henceforth, the potential electrocatalyst of the tungsten trioxide nanorods on the carbon microsphere (WO3/C) composite was synthesized for nanomolar electrocatalytic detection of MT. The electrocatalysts of WO3/C were synthesized hydrothermally, and the WO3/C composite was in-situ constructed by using the reflux method. Significant findings: Remarkably, the as-prepared WO3/C composite displayed a fantastic sensing platform for MT, characterized by an astonishingly nanomolar detection limit (10 nm), notable sensitivity (1.284 mu A mu M-1 cm-2), exceptional selectivity, and amazing stability. The actual sample test was carried out using MT added in food and environmental samples of corn, sugar cane, sewage water, and river water. The minimum MT response recovery in vegetable and water samples was determined to be approximately 97 % and 99 %, respectively. The results indicate that the WO3/C composite is an effective electrode material for real-time MT measurement in portable devices.

This investigation examines the development of titanium slag-flue gas desulfurized gypsum-Portland cement ternary composites (the ternary composites) for the solidification and stabilization of Pb-contaminated soils. The efficacy of the ternary composites is systematically evaluated using a combination of experimental methodologies, including mechanical properties such as unconfined compressive strength, stress-strain behavior and elastic modulus, leaching toxicity, XRD, TG-DTG, FTIR, XPS, and SEM-EDS analyses. The results indicate that the mechanical properties of Portland cement solidified Pb-contaminated soils are inferior to those of Portland cement solidified Pb-free soil, both in the early and later stages. However, the mechanical properties of Pbcontaminated soils solidified by the ternary composites are superior to those of the ternary composites solidified Pb-free soils in the early stage but somewhat inferior in the later stage. The ternary composites significantly decrease the leached Pb concentrations of solidified Pb-contaminated soils, which somewhat increase with the Pb content and with the pH value decrease of the leaching agent. Moreover, with much lower carbon emissions index and strength normalized cost, the ternary composites have comparable stabilization effects on Pbcontaminated soils to Portland cement, suggesting that the ternary composites can serve as a viable alternative for the effective treatment of Pb-contaminated soils. Characterization via TG-DTG and XRD reveals that the primary hydration products of the ternary composite solidified Pb-contaminated soils include gypsum, ettringite, and calcite. Furthermore, FTIR, XPS and SEM-EDS analyses demonstrate that Pb ions are effectively adsorbed onto these hydration products and soil particles.

This study developed a novel geopolymer (RM-SGP) using industrial solid wastes red mud and slag activated by sodium silicate, aiming to remediate composite heavy metal contaminated soil. The effects of aluminosilicate component dosage, alkali equivalent, and heavy metal concentration on the unconfined compressive strength (UCS), toxicity leaching characteristics, resistivity, pH, and electrical conductivity (EC) of RM-SGP solidified composite heavy metal contaminated soil were systematically investigated. Additionally, the chemical composition and microstructural characteristics of solidified soil were analyzed using XRD, FTIR, SEM, and NMR tests to elucidate the solidification mechanisms. The results demonstrated that RM-SGP exhibited excellent solidification efficacy for composite heavy metal contaminated soil. Optimal performance occurred at 15 % aluminosilicate component dosage and 16 % alkali equivalent, achieving UCS >350 kPa and compliant heavy metal leaching (excluding Cd in high-concentration groups). Acid/alkaline leaching tests revealed distinct metal behaviors: Cu/Cd decreased progressively, while Pb initially declined then rebounded. Microstructural analysis indicated that RM-SGP generated abundant hydration products (e.g., C-A-S-H, N-A-S-H gels), which acted as cementitious substances wrapping soil particles and filling and connecting pores, thereby increasing the soil's compactness and improving the solidification effect. Furthermore, heavy metal ions were solidified through adsorption, encapsulation, precipitation, ion exchange, and covalent bond et al., transforming their active states into less bioavailable forms, proving novel insights into the remediation of composite heavy metal contaminated soils and the resource utilization of industrial solid wastes.

In this paper, through extensive on-site research of the plain concrete composite foundation for the Jiuma Expressway, the study conducted proportional scaling tests. This study focused on the temperature, moisture, pile-soil stress, and deformation of this foundation under freeze-thaw conditions. The findings indicate that the temperature of the plain concrete pile composite foundation fluctuates sinusoidally with atmospheric temperature changes. As the depth increases, both temperature and lag time increase, while the fluctuation range decreases. Furthermore, the effect of atmospheric temperature on the shoulder and slope foot is more significant than on the interior of the road. During the freeze-thaw cycle, the water content and pore-water pressure in the foundation fluctuate periodically. The pile-soil stress fluctuates periodically with the freeze-thaw cycle, with the shoulder position exhibiting the most significant changes. Finally, the road displays pronounced freeze-thaw deformations at the side ditch and slope toe. This study provides a valuable basis for the construction of highway projects in cold regions.

Waste red layers have the potential to be used as supplementary cementitious materials after calcination, but frequent and long-term dry-wet cycling leads to deterioration of their properties, limiting their large-scale application. In this study, the feasibility of using calcined red layers as cement replacement materials under dry-wet cycling conditions was analyzed. The damage evolution and performance degradation of calcined red layer-cement composites (RCC) were systematically evaluated via the digital image correlation (DIC) technique, scanning electron microscopy (SEM) analysis and damage evolution mode. The results show that the calcined red layer replacement ratio and number of dry-wet cycles affect the hydration and pozzolanic reactions of the materials and subsequently affect their mechanical properties. Based on the experimental data, a multiple regression model was developed to quantify the combined effects of the number of dry-wet cycles and the replacement ratio of the calcined red layer on the uniaxial compressive strength. As the number of dry-wet cycles increases, microcracks propagate, the porosity increases, and damage accumulation intensifies. In particular, at a high substitution ratio, the material properties deteriorate further. The global strain evolution process of a material can be accurately tracked via DIC technology. The damage degree index is defined based on strain distribution law, and a damage evolution model was constructed. At lower dry-wet cycles, the hydration reaction has a compensatory effect on damage. The pozzolanic reaction of the calcined red layer resulted in an increase in the number of dry-wet cycles. The RCC samples with high replacement ratios show significant damage accumulation with fast damage growth rates at lower stress levels. The model reveals the nonlinear effects of dry-wet cycling and the calcined red layer replacement ratio on damage accumulation in RCC. The study findings establish a scientific foundation for the resource utilization of abandoned red layers and serve as a significant reference for the durability design of materials in practical engineering applications.

Soil-steel composite bridges (SSCBs) are commonly utilized as overpasses. In the majority of existing studies, the transverse structural performance of SSCBs is primarily focused on, while neglecting their longitudinal structural performance. The aims of this paper are to clarify the longitudinal properties and compensate for the paucity of research on the longitudinal structural performance of SSCBs. In current study, field tests were conducted on a SSCB case bridge in a mining area, both in the construction stage and post-construction stage. Subsequently, longitudinal differences in the structural settlements, deformations, and hoop strains were analyzed. Additionally, a refined three-dimensional finite element model was developed and verified to analyze the transfer behavior of soil pressure above the structure along the longitudinal direction. The results indicate that in the construction stage, the difference in the soil-covered height primarily account for the differences in structural performances along the longitudinal direction. At the end of backfilling, the settlements, deformations, and hoop strains in the middle are all greater than those in the end sections. In the post-construction stage, further developments of longitudinal structural characteristics occur due to creep deformation of the foundation soil and disturbances from mining trucks. One year after construction, the structural characteristics have stabilized. The maximum settlement reaches -1.014 m and the maximum settlement difference reaches 0.365 m. The differential settlement ratio, at 0.62 %, remains within the 1 % limit specified in the CHBDC code. Due to longitudinal settlement differences, the soil pressure in the higher settlement zone is transferred to the lower settlement zone by the longitudinal soil arching effect, which benefits the load-bearing capacity of SSCBs.

The large-scale development of urban underground spaces has resulted in hundreds of millions of cubic meters of accumulated shield soil dreg waste, occupying huge amounts of land resources and potentially causing groundwater pollution and soil salinization. In this study, shield soil dreg waste is recycled and activated to substitute cement in ultra-high performance concrete, aiming to promote solid waste management and sustainable construction. The slump, mechanical performance, and autogenous shrinkage of the concrete are investigated through macro-scale tests, and the underlying mechanism is revealed via micro-scale experiments. The incorporation of calcined shield soil dreg reduces flowability and leads to a 10.2 % deterioration in compressive strength of the ultra-high performance concrete while mitigating autogenous shrinkage. The primary reason is due to the low CaO content of shield soil dreg, which limits the formation of calcium silicate hydrate, and its high SiO2/Al2O3 content slows hydration kinetics. The environmental and economic benefits of the concrete are determined via life cycle analysis. Recycling shield soil dreg waste into concrete results in about 35 % reduction in carbon emission and 22 % reduction in energy consumption. According to multi-criteria assessment, the overall performance of the concrete considering economic cost, environmental benefit, as well as physical and mechanical properties increases compared to the pristine concrete, achieving well-balanced economic feasibility, environmental sustainability, and engineering performance. The findings of this study provide an effective approach for recycling shield soil dreg and preparing low-carbon concrete, thus promoting solid waste management and sustainable construction.

The grouting method plays a critical role in preventing seawater intrusion in submarine tunnels, particularly in regions with highly weathered rock that are susceptible to erosion and shifting seawater. The long-term properties of the strength and impermeability of the grout-soil composite are related to the durability of the tunnel lining structure, which is an important focus of the present research. This study introduces a new method for calculating material ratios to determine the optimal proportions of each component in grout-soil composites. A specialized experimental setup was designed to replicate the erosive conditions of seawater in environments characterized by significant rock weathering. The primary objective of this investigation was to analyze the weakening effects of seawater ions (e.g., Mg2+, SO42-, Cl-) on the grout-soil composite under dynamic seawater flow conditions. Therefore, the influence of water-cement (W-C) ratio, grouting pressure, and erosion duration on the compressive strength and permeability coefficient of the composite was studied. Furthermore, microscopic analyses were conducted to investigate the microstructure and composition of the weakened composite specimens. Finally, the model of damage weakening in grouted composite has been established. The experimental results indicate that the erosive ions (Cl-, SO42-) initially enhance and then weaken the strength and impermeability of the grouted composite, while Mg2+ ions continuously degrade the strength of the composite. Reducing the water-to-cement ratio and increasing the grouting pressure can improve the strength and impermeability of the grouted composite, but once a certain threshold is reached, the enhancement effect becomes negligible. Under different dynamic water environments and with various erosive ions (Cl-, SO42-, Mg2+, and seawater), the compressive strength of the specimens at the end of the erosion process decreased by 25.49%, 31.21%, 50.34%, and 39.70%, respectively, compared to static freshwater. The permeability coefficient increased by 8.5 times, 3.2 times, 5.8 times, and 8.9 times, respectively. As the W/C ratio increased from 0.8 to 1.2, the compressive strength decreased by 27.67%, 38.97%, 65.70%, and 44.58%, respectively, and the permeability coefficient increased by 55.24%, 59.70%, 134.23%, and 44.49%. As the grouting pressure increased from 1.5 MPa to 2.5 MPa, the compressive strength increased by 48.90%, 162.60%, 163.71%, and 48.35%, respectively, while the permeability coefficient decreased by 53.76%, 40.05%, 73.69%, and 32.89%. The findings of this study offer valuable insights into the erosion mechanism of grout-soil composites induced by seawater ions, thereby contributing to enhanced durability and longevity of submarine tunnel infrastructure.

Stinging nettle (Urtica dioica L.) has been observed to grow spontaneously on metal-contaminated soils marginalised by heavy industrial use, thereby presenting an opportunity for the economic utilisation of such lands. This study explores the potential of nettle as a fibre crop by producing short fibre-reinforced polylactic acid (PLA) composites through compounding and injection moulding. Whole stem segments from three nettle clones (B13, L18, and Roville), along with separated fibre bundles from the L18 clone, were processed. The fibre bundles were separated using a roller breaker unit and a hammer mill. From separation with the hammer mill, not only cleaned fibre bundles but also the uncleaned fibre-shive mixture and the undersieve fraction were processed. The Young's modulus of all composites exceeded that of unreinforced PLA, with mean values ranging from 5.7 to 8.1 GPa. However, the tensile strength of most composites was lower than that of pure PLA, except for the two composites reinforced with cleaned fibre bundles. Of these two, the reinforcement with fibre bundles from separation with the hammer mill led to superior mechanical properties, with a higher Young's modulus (8.1 GPa) and tensile strength (61.8 MPa) compared to those separated using the breaking unit (7.2 GPa and 55.9 MPa). This enhancement is hypothesised to result from reduced fibre damage and lower fibre bundle thickness. The findings suggest that nettle cultivation on marginal lands could be a viable option for producing short-fibre composites, thereby offering a sustainable use of these otherwise underutilised areas.