Search Results (156)

The present study evaluated the potential of waste glass fiber-reinforced polymer (wGFRP) as a soil reinforcement material for geotechnical applications. Laboratory model footing tests and large-scale direct shear tests were carried out on sandy soils prepared at three relative densities (Dr = 40%, 65%, and 85%) and reinforced with four wGFRP contents (0.5%, 0.75%, 1.0%, and 1.5%) to evaluate bearing capacity, settlement behavior, and shear strength characteristics. Environmental characterization and a performance-based economic assessment were also conducted to assess environmental compatibility and identify the optimum reinforcement content from engineering and economic perspectives. The results showed that wGFRP improved sand performance under all investigated conditions. Optimum performance was achieved at 0.75% wGFRP, where the ultimate bearing capacity increased by up to 92%, settlement decreased by up to 79.2%, and the internal friction angle increased by up to 6.2%. Environmental characterization indicated compatibility under the investigated laboratory conditions, with negligible trace-element release and no significant physicochemical, microstructural, or chemical degradation. The economically optimum reinforcement content depended on the selected engineering objective and the initial relative density. The findings indicate that wGFRP has strong potential as a sustainable, environmentally compatible, and cost-effective soil reinforcement material, offering a high-value reuse pathway in geotechnical applications. Full article

Water retention availability remains a primary constraint on both vegetation restoration and agricultural productivity across the Chinese Loess Plateau. Attapulgite (ATP) has considerable potential as a soil amendment for improving soil water retention and crop performance, yet its effectiveness is likely to depend on soil texture and climatic water availability. Here, we evaluated the effects of five ATP application rates (0%, 1%, 2%, 3%, and 4%, w/w) on soil hydraulic properties and maize (Zea mays L.) grain yield in three representative soils: clay loam, loam, and sandy loam. Soil water retention curves and field maize experiments were conducted to quantify the hydrological and agronomic responses to ATP addition. The classical van Genuchten (VG) model was further modified by incorporating ATP-dependent parameter relationships to better characterize the water retention behavior of ATP-amended soils. The modified model consistently provided a more accurate representation of the relationship between soil water content and matric suction than the original VG model. The derived soil hydraulic parameters were subsequently incorporated into the DSSAT cropping system model, which was calibrated and evaluated against field observations from Yangling in 2019 and 2020. The calibrated model was then used to simulate maize yield responses to ATP application from 2011 to 2020 at three representative sites: Yangling (clay loam), Changwu (loam), and Yan’an (sandy loam). Simulated yield responses varied markedly with soil texture and interannual climatic conditions. In clay loam, maize yield generally decreased with increasing ATP application, although positive responses occurred in relatively dry years. In sandy loam, ATP application generally increased maize yield across most years, whereas the loam soil exhibited stronger interannual variability in yield response. These contrasting responses indicate that the agronomic effectiveness of ATP is governed by the balance between enhanced soil water retention and local climatic water availability. Overall, the coupled soil hydraulic–crop modeling framework provides a mechanistic basis for developing site-specific ATP management strategies and highlights the importance of matching soil amendments to both soil texture and climatic conditions in water-limited agroecosystems. Full article

Confronted with severe global challenges, including water scarcity, excessive use of chemical fertilizers and pesticides, and heavy metal contamination in soils, conventional agricultural technologies exhibit marked limitations in integrated water–fertilizer management and non-point source pollution control. Leveraging their excellent water retention capacity, intelligent sustained-release properties, and environmental responsiveness, hydrogels offer innovative solutions to advance sustainable agricultural development. This review comprehensively outlines the fundamental types, crosslinking mechanisms, and key functional properties of hydrogels, with a focused discussion on their agricultural deployment as high-efficiency soil conditioners, fertilizer vectors, and pesticide carriers; it deciphers the microscopic water-holding mechanisms under the tristate water model, delineates the divergent water-uptake and retention behaviors between ionic and non-ionic hydrogels, and clarifies the cyclic water-holding and release mechanisms of hydrogels during soil amelioration. Thise paper further synthesizes hydrogel-enabled environmental remediation applications, in which heavy metals and pesticide residues in soils and aquatic systems are removed via functional-group coordination adsorption or photocatalytic degradation; concurrently, hydrogels have been shown to activate plant systemic immunity through calcium-signaling pathways, thereby inducing broad-spectrum antiviral defense responses. Moreover, hydrogels can be integrated into precision agriculture frameworks to enable real-time monitoring of crop physiological status and to support targeted irrigation and fertilization management. This work also evaluates the role of hydrogels in promoting seed germination, root system development, crop metabolic regulation, and stress resilience, while introducing tailored application strategies across distinct plant growth stages. Their documented economic advantages include water conservation, enhanced crop yields, reduced dependence on synthetic fertilizers, and lower labor costs. Nevertheless, the large-scale implementation of hydrogels continues to face multifaceted challenges—particularly poor degradability and latent ecological risks, as conventional polyacrylamide (PAM)-based gels resist soil mineralization and retain potentially neurotoxic monomers, leaving a critical gap in multi-annual field data concerning their non-target interference with native soil aggregate evolution, pore distribution, and rhizospheric carbon–nitrogen footprints. Mechanistically, many hydrogels with tensile strengths below 1 MPa are highly susceptible to three-dimensional network collapse under high-salinity osmotic shock and tillage mechanical stress, exhibiting a precipitous drop in water retention after more than three wet–dry cycles due to deficient long-term structural stability. Compounding these technical gaps are elevated production costs and low farmer adoption, driven by the absence of texture-specific performance thresholds—such as an available water increment ≥ 40% for sandy soils—and the lack of established life-cycle cost models and farmer incentive mechanisms for bio-based hydrogels. Moving forward, hydrogel technology should pivot toward materials innovation and cost-reduction engineering to broaden its applicability, employ ≥3-year, multi-habitat regional trials to delineate ecological benefit–risk boundaries, and ultimately position hydrogels as pivotal enablers of sustainable, green agricultural paradigms. Full article

Small-scale excavations with depths of approximately 1 to 3 m are widely conducted for purposes such as the repair of underground pipelines. In confined construction spaces, earth-retaining systems consisting of lightweight sheet-piles with struts and walers are frequently used. However, comprehensive investigations of the influence of ground conditions on member forces have not yet been conducted. Furthermore, since these temporary structures are generally not designed with seismic considerations, they may suffer damage during earthquakes depending on the soil conditions. Accordingly, this study conducted a comprehensive parametric numerical investigation to evaluate how differences in soil type, such as sandy and cohesive soils, and loading conditions during excavation and earthquake loading affect the internal forces in the supporting members. Excavation analyses using PLAXIS 3D confirmed that as the soil strength parameters (cohesion and internal friction angle) decreased, the demand on the supporting members increased and larger internal forces developed. Dynamic analyses using LIQCA 3D revealed complex behavior in which (i) earth pressure acting on the wall generated compressive forces in the struts, (ii) lateral deformation of the excavation face reduced axial forces in the struts, and (iii) when the ground liquefied, it exhibited a vibration-isolation effect, and the vibration components generated in the structural members became smaller. Full article

Staged upward seepage can trigger particle migration and pore-structure adjustment in graded sandy soils, but the resulting transition behavior remains difficult to identify quantitatively. In this study, three representative sandy soils from a deep overburden deposit in southeastern Tibet were tested using a laboratory vertical upward seepage apparatus. Eight specimens with different nominal preparation states were subjected to stepwise increases in hydraulic head difference. Local hydraulic gradient, seepage velocity, hydraulic conductivity, and macroscopic outflow phenomena were monitored. Apparent seepage-transition hydraulic gradients were identified by combining abrupt changes in k–i curves, conductivity ratios between eligible staged records, and observed seepage responses. The clearest transition occurred in the nominal loose specimen of Soil 2, where the temperature-corrected hydraulic conductivity k₂₀ increased from 1.76 × 10⁻³ to 2.25 × 10⁻² cm s⁻¹ as i increased from 0.20 to 0.25, giving k_20,2/k_20,1 = 12.80 and i_c = 0.225. A clear transition was also identified for the nominal dense specimen of Soil 3, with k_20,2/k_20,1 = 6.61 and i_c = 0.583. Clear transitions were identified in the tested specimens only for Groups D and H, whereas the remaining specimens showed weak or phenomenon-assisted responses, local high-gradient fluctuations, or anomalous loading-path records rather than uniformly identifiable transition points. These results show that apparent transition gradients are path-dependent and should be evaluated together with loading history, seepage-velocity evolution, conductivity ratios, and macroscopic observations. Full article

Human health risk assessment of vapor intrusion caused by organic pollutants is commonly based on steady-state predictions of partition and vapor migration in the subsoil. This study develops a pseudo-dynamic, process-based Partition–Diffusion Risk Model (PDRM) using a one-dimensional numerical model for organic mixtures to assess the time evolution of cancer and non-cancer risks, indoor air concentrations, and non-aqueous phase liquid (NAPL) formation. The model has been applied to a low-carbon sandy soil without microbial degradation, which might be a worst-case scenario. Six simulation scenarios combined two source concentrations (1000 and 3000 mg/kg) and three source depths (1, 3, and 5 m) over 30 years. Results show that source depth governs exposure dynamics: shallow contamination poses unacceptable risks rapidly but declines quickly, whereas at greater depths, unacceptable levels appear later and persist throughout the exposure period. NAPL formation may act as a secondary source, sustaining vapor release and extending indoor exposure under high-loading conditions. Multicomponent partitioning induces nonlinear, compound-specific behavior, with the first 3–5 years representing a critical period for rapid risk changes. Conventional models show that neglecting NAPL formation and time variability may lead to an underestimation of cancer risk by up to an order of magnitude. These findings highlight the importance of incorporating depth and time-dependent characterization to reduce uncertainty in vapor intrusion risk assessments. Full article

Polyacrylamide (PAM) is widely used to improve sandy muck in shield tunneling due to its excellent physicochemical properties. During shield excavation, the temperature of excavated soil varies with geological depth and equipment heat transfer, making it necessary to investigate the temperature effect on the performance of PAM-modified sandy muck. In this study, molecular dynamics (MD) simulations are employed to construct a (PAM, H₂O)/α-SiO₂ interfacial model. The microstructural evolution and interfacial interaction characteristics between PAM molecules and the α-SiO₂ substrate are analyzed at the nanoscale under different temperature conditions. A structure–performance–mechanism relationship is established, forming a conceptual framework of the “configuration–interaction energy–stability” mechanism for PAM-modified sandy muck. The main findings are as follows: (1) The PAM exhibits the most stable interfacial bonding with α-SiO₂ between 278 K and 318 K, primarily governed by electrostatic attraction and hydrogen-bond synergy. (2) Within this temperature range, PAM forms a dense and stable interfacial adsorption structure, whereas both thermodynamic stability and structural integrity decline outside it. (3) At 318K, the PAM/α-SiO₂ system shows the most favorable hydrogen-bonding behavior, with orderly alignment of PAM and H₂O molecules and optimal chain flexibility and adhesion capacity. Therefore, 318 K is the upper temperature limit reference point at which the improvement effect of PAM remains the most stable, providing theoretical guidance for temperature-controlled soil conditioning in shield tunneling. Full article

Soil water availability, salinity dynamics, and nitrate transport are key factors controlling agricultural sustainability in arid environments characterized by limited water resources and high evaporative demand. This study evaluated the combined effects of soil texture, nitrate–nitrogen application, and sawdust mulching on soil water retention, evaporation losses, salinity redistribution, and nitrate movement in loamy sand and sandy clay loam soils under controlled greenhouse conditions. Results showed that soil texture was the dominant control on hydrochemical behavior, with sandy clay loam exhibiting higher water retention and lower drainage than loamy sand. Sawdust mulching significantly improved soil water conservation by reducing evaporation and stabilizing moisture distribution, while the 4 cm mulch treatment achieved the highest overall CSI performance. Evaporation strongly governed salinity accumulation in surface layers, whereas mulching reduced salt build-up and promoted a more uniform salinity profile. Nitrate transport closely followed water fluxes, resulting in higher leaching in loamy sand and greater retention in sandy clay loam. Increasing nitrogen application enhanced nitrate mobility and leaching in both soils. A Composite Sustainability Index (CSI) was developed to integrate soil water conservation, evaporation reduction, salinity control, and nitrate retention into a unified metric. Sensitivity analysis demonstrated that treatment rankings were largely unaffected by alternative weighting schemes, confirming the robustness of the CSI framework. The CSI identified mulch application, particularly the 4 cm mulch treatment, as the most effective management option based on overall sustainability performance. The CSI framework provides an integrated decision-support tool for evaluating coupled water–salt–nitrate interactions and improving water use efficiency and salinity management in arid agricultural systems. This study offers a novel integrated CSI-based framework for simultaneously quantifying hydrological and hydrochemical soil responses under mulch management in arid environments. Full article

Seismic damage has been observed not only in liquefiable sandy soil layers but also in thick deposits of soft clayey soils, which are characterized by the destruction of the soil structure, leading to strain softening. Previous studies conducted numerical simulations and defined this phenomenon as soil disturbance, which refers to the simultaneous reduction in stiffness and peak shear strength. To fill the research gap, this study systematically compares the post-cyclic degradation behavior of stiffness and peak shear strength of UDS and REC specimens derived from the same material. Based on the experimental results, the peak shear strength and rigidity of the UDS specimens simultaneously decrease, as the number of cycles increases. In contrast, the peak shear strength degradation effect is absent in the REC samples; both specimens exhibited loss in stiffness. The reduction in stiffness of UDS specimens was slower than that of REC specimens due to aging effects. Nevertheless, both effects on UDS and REC specimens are due to soil disturbance, which is defined in the numerical simulations of previous studies. Hence, the effects of soil disturbance can be summarized as (1) a reduction in the initial stiffness of soft clay and (2) a reduction in the mean effective stress during cyclic loading. Full article

Submarine landslides pose severe marine geological hazards. Their movement and deposition behaviors can seriously threaten marine engineering stability and coastal safety. The propagation characteristics of landslide-generated tsunamis are therefore critical for hazard assessment. Physical model experiments provide an effective approach for investigating the underlying mechanisms of tsunami generation and propagation. To investigate the complete process from landslide motion to wave generation and propagation, this study developed an underwater soil-movement physical model test system. The system integrates controllable landslide initiation, real-time monitoring of landslide motion, wave height measurements, and full-field image acquisition, enabling synchronous observation of landslide movement and water body response. By controlling the main variables influencing submarine landslide dynamics, a series of physical model experiments were conducted to investigate water surface waves generated under different test conditions. The study examines the complete process from the initial water disturbance caused by submerged landslide motion to tsunami generation and propagation. The effects of landslide volume, particle size, initial submergence depth, and slope angle on tsunami parameters, including wave height, wave velocity, and wave period, were evaluated. Using 21 experimental datasets for each landslide type, namely, cohesionless sandy slides and muddy debris flows, empirical formulas for maximum surge height were established through dimensional analysis, SPSS (v25)-based multiple nonlinear regression, and validation against experimental results. The validation results show strong agreement between the empirical predictions and the physical model test data. Full article

The rapid advance of urbanization and social development has intensified the complexity of engineering projects, especially where geotechnical constraints play a decisive role. Expanding cities increasingly occupy areas with challenging soil conditions, such as collapsible soils, which demand careful investigation and innovative design solutions. These geotechnical factors directly influence the safety, durability, and cost-effectiveness of infrastructure, making integrated analysis essential from the earliest stages of project planning. An experimental study with lateritic sandy soil was performed to investigate the effect of rice husk ash (RHA) on collapsible soil behavior. Collapsible soils occur worldwide in diverse geological and geotechnical conditions and can result in costly structural damage. Due to intense leaching during tropical weathering, lateritic soil structures and textures show high collapse potential, with substantial volume reduction under constant stress when wetted. The investigated soil was collected in a tropical area of the Paraná Basin (Brazil) and is considered representative of large regions with similar geological conditions. Soil samples and mixtures (2, 4, 6, 8, 10, 12, and 14 wt.% RHA) were tested using standard geotechnical procedures such as grain size distribution and compaction tests. Collapsibility behavior (i.e., collapse potential, CP) was measured using oedometer tests. Tests were conducted with realistic compaction degrees (~80%), representing conditions found in nature and in civil works involving collapsible soils. The results show that RHA can considerably reduce the collapse potential of lateritic fine sandy soils, mainly due to its packing effect, which reduces volumetric changes with increased moisture. The CP was significantly reduced from 9.83% to 1.93% in the mixture containing 14% RHA. Full article

The purpose of this study was to evaluate how an alkali activator, specifically soluble glass, influences the geotechnical performance of sandy-pebble soil when combined with biomass bottom ash (BMA) as a sustainable stabilizing material. This work focused on understanding whether alkali activation could increase the strength, compactness, and overall engineering suitability of these mixtures while also examining how the activator affects permeability. To accomplish this, mixtures containing different proportions of BMA were prepared and treated with soluble glass at controlled water-to-activator ratios, followed by standard geotechnical procedures including Proctor compaction and California Bearing Ratio testing to assess density and load-bearing capacity. The results showed that soluble glass substantially improved the mechanical behavior of the mixtures, with both Proctor density values varying from 1.48 to 2.04 Mg/m³, depending on BMA content and activator dosage, while CBR values more than doubled for mixtures containing 20% BMA at a water-to-soluble-glass ratio of 1:3. Water permeability decreased with increasing BMA and activator content, from 8.11 × 10⁻⁵ to 5.91 × 10⁻⁵ m/s, although the permeability threshold of ≤2 × 10⁻⁵ m/s was not reached. These enhancements were linked to better packing of soil particles due to the void-filling effect of BMA and the formation of new binding compounds produced through alkali-activation reactions, including N-A-S-H and C-S-H gels. However, this study also found that higher amounts of soluble glass reduced water permeability, an effect associated with the denser microstructure created during geopolymerization. Overall, the findings demonstrate that stabilizing sandy-pebble soil with alkali-activated BMA is an effective approach to improving essential geotechnical properties while simultaneously offering environmental benefits by repurposing biomass waste in ground-improvement applications. Full article

A thorough understanding of the resistivity response characteristics of ethanol-contaminated soil is of great significance for the development of non-destructive geophysical detection techniques and for supporting contaminated site investigation and assessment. This experimental study aims to systematically investigate the resistivity behavior of ethanol-contaminated sandy soils, with a focus on the coupled mechanisms of multiple factors, including water content, ethanol concentration, particle size distribution, and contamination time. It is hypothesized that water content serves as the dominant factor controlling resistivity, whereas ethanol concentration and contamination time regulate resistivity by altering the physicochemical properties of the pore fluid. Under laboratory conditions, silt, fine sand, and medium sand were selected as the test materials. Resistivity was systematically measured using a Miller Soil Box with increasing water content, Wenner array configuration across varying water contents (3–24%), ethanol concentrations (40–98%), and contamination durations (0–144 h). The experimental results indicate the following: (1) Regardless of the presence of ethanol contamination, the resistivity of sandy soil decreases with increasing water content following a power-law relationship. The decrease is most pronounced at low water contents (3–9%), and gradually stabilizes at higher water contents. The results show that, at a constant water content, resistivity systematically and consistently follows the order: silt > medium sand > fine sand. (2) The influence of ethanol concentration on resistivity is constrained by water content levels, and the overall increase in resistivity is primarily attributed to ion dilution and the obstruction of conductive pathways. (3) Over time, resistivity exhibits a two-stage increasing trend, associated with ethanol volatilization and water loss. Resistivity changes in fine sand samples contaminated with ethanol at concentrations ranging from 75% to 95% follow a two-stage pattern. The initial phase of growth is characterized by a gradual increase over a period of 0–48 h, followed by a more rapid increase during the subsequent phase, which extends from 48 to 144 h. The results show that higher initial ethanol concentrations enhance the sensitivity of resistivity to temporal changes. Comprehensive analysis indicates that the resistivity variation mechanism under multi-factor coupling conditions can be summarized as follows: the water content is the dominant factor in the regulation of the conductive pathways; the particle size distribution determines pore structure and the characteristics of the particle interface; ethanol concentration and contamination time dynamically alter pore fluid properties, collectively regulating the resistivity response. Although the experiments were conducted under controlled laboratory conditions and the results have certain limitations, they provide a preliminary reference for interpreting resistivity responses in relatively homogeneous sandy contaminated sites and offer theoretical support for the application of resistivity methods in contamination identification and dynamic monitoring. Full article

Soil thermal conductivity is a key parameter in modeling heat transfer, temperature-driven moisture migration, artificial ground freezing, and geothermal systems. However, most existing thermal-conductivity models do not account for temperature effects. This study aims to determine the temperature-dependent thermal conductivity of silty and fine sandy soils at elevated temperatures using a steady-state heat cell method, addressing the limitations of transient probe techniques, which are affected by air voids and heat loss at the needle–soil interface. The experiment employs a heat cell under one-dimensional steady-state heat-transfer conditions, with sufficiently small temperature gradients to prevent temperature-induced moisture migration, and measures the soil’s thermal properties at steady state by indirect temperature and heat-flux measurements using various sensors. The test observations showed well-correlated thermal conductivity readings from steady state and transient probe methods at room temperature. Furthermore, the measured thermal conductivity of the sandy soil demonstrated a near-linear increase with temperature, with the highest dependence at 15.1% and 22.5% saturation for Benbrook (SM) and fine-grained Ottawa (SP) sands, respectively. Several commonly used existing thermal conductivity models were used to fit the measured thermal conductivity. A new thermal conductivity model was developed, incorporating a temperature-dependent correction based on the best-fit model. The proposed model could more accurately capture the increased thermal conductivity of soils with temperature. The findings will significantly improve the modeling of soil-temperature-dependent multi-physics behavior. Full article

Coastal reclaimed areas are characterized by complex strata and high groundwater levels, and pile foundations in such areas often suffer from insufficient uplift resistance. Compared with conventional cast-in-place piles, squeezed branch piles exhibit superior uplift performance; however, studies on squeezed branch piles in reclaimed areas remain limited. To investigate the uplift bearing performance of squeezed branch piles in the complex strata of coastal reclaimed areas, in situ full-scale uplift tests were conducted in the Shenzhen Binhai Avenue (Headquarters Base Section) traffic reconstruction project. Based on the actual physical and mechanical properties of the soil strata, a three-dimensional numerical model was established and validated against the load–displacement curves obtained from the in situ full-scale uplift tests. On this basis, the uplift bearing performance of squeezed branch piles, the differences in uplift bearing performance between branch and plate structures, and their applicable strata were analyzed. The plate structure and different branch configurations of squeezed branch piles exhibit distinct symmetric configuration characteristics, and these configuration differences influence the overall uplift bearing performance. The results show that the load–displacement curves of the uplift piles are generally smooth, without obvious abrupt rises or drops, exhibiting a gradual variation pattern, and the maximum pile-head displacements are all less than 100 mm. The mobilization of the bearing capacity of the branch and plate structures exhibits a distinct temporal and sequential pattern, with the plate structures at shallower embedment depths mobilized earlier than those at greater depths. Compared with conventional cast-in-place pile foundations, the presence of branches and plates endows squeezed branch piles with better elastic mechanical behavior and higher rebound ratios during unloading. Under identical stratum and loading conditions, the uplift bearing performance of the plate is 133% higher than that of the six-radial-branch configuration, while that of the six-radial-branch configuration is 34% higher than that of the four-radial-branch configuration. It is recommended to adopt the six-radial-branch configuration in clayey sandy gravel strata and the plate configuration in gravelly clayey soil and completely weathered coarse-grained granite strata, whereas neither branches nor plates are recommended in soil-like strongly weathered coarse-grained granite strata. Full article