Saturated Soil Research Articles

The roles of microstructure and water mobility in pre-Darcy flow formation in saturated clay soil

Water flow in saturated clay soil at low hydraulic gradients usually occurs via pre-Darcy flow. The occurrence of the pre-Darcy flow phenomenon is attributed to the adsorption of water on pore walls via surface forces. However, a clear understanding of the amount of water that is movable in saturated clay soil and the distribution of movable/immovable in the microstructure of clay soil is lacking. Furthermore, it is difficult to accurately evaluate the effect of water mobility on the seepage characteristics of clay soil. To investigate the effects of water mobility and pore microstructure on pre-Darcy flow in clay soil, nine clay samples were used to conduct constant head permeability experiments. The results showed that the seepage of water in clay deviated from that predicted by Darcy's law, and with increasing hydraulic gradient, the apparent water permeability first increased and then tended to remain constant. The porosity ϕ, average pore radius rp, sorting coefficient Sp, mean pore radius Dm, dry density ρ and tortuosity τ had major influences on the stable apparent water permeability ks. In contrast, the influences of maximum pore radius and median pore radius on ks were relatively weak. Macropores (>1.0 μm) and mesopores (100–1000 nm) were the dominant pore types in the clay and accounted for almost 80 % of the overall porosity. The water in saturated clay can be divided into four types according to interfacial forces. The results showed that weakly bound water (in the outer layer) was the main type of water in the clay. Among the four types of water, ks had the strongest correlation with the proportion of free water. The mobility of water was affected by coupling between interfacial forces and hydraulic gradients. The movable water content was closely related to the permeability of the clay.

Fast Lagrangian analysis of the short-term bearing capacity of shallow foundations in clays on the basis of the cone penetration test

Based on a numerical modelling of the cone penetration test CPT as well as the vertical response of shallow foundation in saturated clays, derivation of the cone factor Nk led to propose a CPT-based method of computation of the bearing capacity. This study was carried out by launching a detailed parametric study using the software FLAC-2D (Fast Lagrangian Analyses of Continua) based on the finite difference method. The soil material was modeled as a homogeneous elastic-perfectly plastic medium obeying the Mohr-Coulomb criterion, and the effects of the soil rigidity index Ir, the cone-soil interface, and the initial depth of the penetration on the cone factor Nk were investigated leading to an analytical formulation of Nk. After a comparative study with those proposed in the literature, the cone factor Nk was used to derive the bearing capacity factor Kc of a shallow foundation. Compared to current CPT-based methods proposed in the literature, this method reasonably predicts the short-term bearing capacity of shallow foundations in saturated clayey soil.

A Study on the Potential of Sand Liquefaction Hazard at Chukai Sentral, Terengganu Using Plaxis 2D

An earthquake is classified as a natural disaster of mother nature. Sometimes, it cannot be predicted when it will occur and difficult to estimate the striking force values and the period of incident. The effect of the earthquake may catastrophic if the magnitude is more than 6 Richter. It had been proved by previous event, an earthquake could cause a huge impact towards the soil condition especially when the saturated soil is soft or loose since the propagation of shear wave and compression could induced the soil liquefaction and gave an effect towards excess pore pressure and effective stress of the soil that may affect the stability of infrastructure such as dam, embankment, and bridge. This study was conducted to analyse the horizontal displacement of soil due to earthquake and to evaluate the possibility of liquefaction at Chukai Sentral, Kemaman, Terengganu, Malaysia. The study was conducted using Plaxis-2D software based on Mohr-Coulomb soil model at magnitude of 5.4 Richter. The Mohr-Coulomb model was selected as its failure occurs when the shear stress acting on the soil reaches a critical value and the shear strength is related to the effective stress acting on it. The analysis was concentrated on the mesh deformation and horizontal displacement. The result shows the mesh deformation and horizontal displacement obtained in the boreholes not more than 6 mm. It is considered as a small deformation and will not trigger to the potential of liquefaction to that area. It can be concluded that the earthquake magnitude of 5.4 Richter is unable to disturb the natural resistance of the soil and structure due to their stiff layer proportion.

Analytical and experimental study on shaking effects for improved stone column foundations

Stone column technology is a method used to reduce liquefaction in saturated sediments. By using materials with greater permeability than the surrounding soil, stone columns can help drain excess pore water pressure and mitigate liquefaction potential during seismic loading. In this study, analytical solutions are proposed to address the liquefaction problem in saturated soils during earthquakes, taking into account the influence of stone columns and the surrounding soil. These solutions consider the excess pore water pressure at the boundary of the zones and analyze the vertical and horizontal drainages. The study also includes centrifuge tests on sandy soils improved with stone columns, calculating the total seepage flow and converting it into settlement based on the relationship between drainage flow rate and volumetric changes in the soil. The calculated settlement aligns well with the measured value in the centrifuge test, confirming the accuracy of the analytical formula for calculating settlement in stone column foundations. The study also evaluates the combined effects of radial and vertical drainages in stone column foundations using the derived analytical solutions.

PLAXIS 3D numerical analysis of complex geotechnical problems of colossal built heritage

The paper aims to contribute to the preservation of high valuable historic masonry structures and historic urban landscapes through the combination of geotechnical, structural engineering. The main objective of the study is to conduct finite element analysis (FEA) of bearing saturated soft clay soil problems and induced structural failure mechanisms. This analysis is based on experimental and numerical studies using coupled PLAXIS 3D FE models. The paper presents a geotechnical analytical model for the measurement of stresses, deformations, and differential settlement of saturated clay soils under colossal stone/brick masonry structures. The study also discusses the behavior of soft clay soils under Qasr Yashbak through numerical analysis, which helps in understanding the studied behavior and the loss of soil-bearing capacity due to moisture content or ground water table (G.W.T) changes. The paper presents valuable insights into the behavior of soft clay soils under colossal stone/ brick masonry structures. The present study summarized specific details about the limitations and potential sources of error in Finite Element Modeling (FEM). Further field research and experimental analysis may be required to address these limitations and enhance the understanding of the studied soft clay soil behavior. The geotechnical problems in historic monuments and structures such as differential settlement are indeed important issues for their conservation since it may induce serious damages. It deserves more in-depth researches.

A hybrid Eulerian–Lagrangian approach for non-self-similar expansion analysis of a cylindrical cavity in saturated and unsaturated critical state soils

AbstractThis paper proposes a powerful hybrid Eulerian–Lagrangian (HEL) approach for the analysis of cavity expansion problems. The new approach is applied to analysing the non-self-similar expansion process of a hollow cylinder of critical state soils, considering arbitrary saturation states of soils and both drained and undrained conditions. A closed-form solution for the stresses and displacements in the elastic zone is presented, taking the state-dependent soil moduli and outer boundary effect of the soil cylinder into account. Adopting large strain theory in the plastic zone, the non-self-similar cavity expansion process is formulated into a set of partial differential equations in terms of both Eulerian and Lagrangian descriptions, which is solved by a newly proposed algorithm. The HEL approach is compared with the conventional Eulerian and Lagrangian approaches for the cavity expansion analyses. It is found that the new approach can reduce to the Eulerian approach when the self-similar assumption is satisfied and to the Lagrangian approach when stress–total strain relationships are obtained analytically. Finally, the expansion process is proven to be non-self-similar by showing the stress and deformation paths, and the finite thickness of soil cylinders may greatly influence the cavity expansion behaviour, especially with a small thickness ratio. The HEL approach can provide useful tools for validating advanced numerical techniques for both saturated and unsaturated soils and interpreting pressuremeter tests in small-size calibration chambers.

Geospatial Liquefaction Modeling of the 2023 Türkiye Earthquake Sequence by an Ensemble of Global, Continental, Regional, and Event-Specific Models

Abstract A global geospatial liquefaction model (GGLM-2017) was previously developed (Zhu et al., 2017) using logistic regression (LR) and is currently used by the U.S. Geological Survey as the preferred liquefaction model to map liquefaction probability immediately after the occurrence of earthquake events. This research proposes an ensemble modeling approach to improve the performance of the GGLM-2017 for geospatial liquefaction modeling of the 2023 Türkiye earthquakes using an updated inventory of liquefaction occurrence locations in Europe (the OpenLIQ database, which includes prior events occurring in Türkiye) and a new inventory from the 2023 Türkiye earthquakes (gathered from multiple sources). Using the same geospatial proxies for soil saturation, soil density, and earthquake loading, and the same non-liquefaction sampling strategy used to develop GGLM-2017, the proposed ensemble method is validated on the data of the 2023 Türkiye earthquakes by integrating four models, including global (GGLM-2017), continental (LR model trained on eight European events), regional (LR model trained on three historical events in Türkiye), and event-specific (LR model trained on partially available data from the 2023 Türkiye earthquakes) models. The inventory from the 2023 Türkiye earthquakes is split into two batches, in which the first batch (163 liquefaction occurrences) resulted from the preliminary reconnaissance and is used for training the event-specific model, and the second batch (284 liquefaction occurrences) resulted from a more complete reconnaissance (which was made available later) and is used for validating all models. The rationale for using the first batch for training the event-specific model is to exploit the information as they become available to optimize the performance of global model in liquefaction prediction. The final ensemble probability assignment is done by averaging the probabilities derived by the four individual models, and a 50% threshold is used for classification accuracy evaluations. Comparative analysis of the ensemble model’s performance with the GGLM-2017 showed improved predictive accuracy, resulting in higher liquefaction detection for the specific event under study (the 2023 Türkiye earthquakes). The ensemble model also provides an estimate of model uncertainty.

Testing the hydrodynamic behavior of a loam soil by beerkan infiltration runs with six heights of water pouring

Interpreting and simulating rainfall partition into infiltration and surface runoff has to consider that surface soil hydraulic properties, including saturated soil hydraulic conductivity (Ks) and sorptivity (S), could change even at very short temporal scales. Soil deterioration due to water impact can be tested in the field by the multi-height beerkan (MHB) method, that is, by pouring water on the infiltration surface from different heights. Soil hydraulic properties can be estimated coupling the MHB method with the steady version of the Beerkan Estimation of Soil Transfer parameters procedure (BEST-steady). The MHB method with six heights of water pouring (H) in the range 0.03–2 m was applied on a relatively dry loam soil to investigate height of water pouring effects on i) the established infiltration process, and ii) Ks, S, the scale parameter of the water retention curve (hg) and the characteristic microscopic pore radius (λm). Higher heights of water pouring generally induced a slowdown of the infiltration process, smaller S, Ks and λm values and higher |hg| values. The S, Ks, |hg| and λm vs. H relationships were statistically significant but the fitted relationships for S and Ks were stronger than those for |hg| and λm, indicating a different sensitivity of the considered parameters to the height of water pouring. Small or negligible soil deterioration was observed for both small (H ≤ 0.25 m) and large (H ≥ 1.5 m) heights. Between these two extremes, the soil deteriorated as H increased, suggesting that the external solicitations were high enough to overcome the resistance of the porous medium but not so high to determine a complete soil alteration. The tested methodology appears promising to determine the effects of water impact on the soil hydrodynamic behavior and it could be applied to perform a soil hydraulic characterization usable for modelling hydrological processes.

Simulation of groundwater-flow dynamics in the U.S. Northern High Plains driven by multi-model estimates of surficial aquifer recharge

There is growing interest in incorporating higher-resolution groundwater modeling within the framework of large-scale land surface models (LSMs), including processes such as three-dimensional flow, variable soil saturation, and surface water/groundwater interactions. Conversely, complex groundwater models (e.g., the U.S. Geological Survey Groundwater-Flow Model, MODFLOW) often use simpler representations of land surface dynamics (e.g., surface vegetation, evapotranspiration, recharge) and may benefit from higher process fidelity and temporal resolutions in these inputs. This study investigates the potential of improving groundwater representation in LSMs and land surface dynamics in MODFLOW through forcing MODFLOW with recharge from LSMs. Groundwater simulations build on an existing and well-calibrated MODFLOW model of the U.S. Northern High Plains aquifer, a hydrologically complex basin under the dual impacts of conversion of native vegetation to intense irrigated agricultural fields and climate change. Simulated groundwater recharge from four different land models are used to drive MODFLOW groundwater simulations. Results show relatively large discrepancies between recharge estimates among simulations. Forcing MODFLOW using recharge simulated by some of the LSMs in place of a simple water balance model marginally improves MODFLOW groundwater simulation. Further, our results support the efficacy of coupling LSMs to a sophisticated groundwater model such as MODFLOW. The coupling results in notable improvements in matching the historical groundwater levels through reduction of the skewness coefficient in percent bias histogram (from 1.50 and 1.41 in original LSMs to 0.44 and 0.27, respectively, when MODFLOW is forced by groundwater recharge from LSMs) and reduction of bias. This modeling effort seeks to identify the best compromise between comprehensive land surface processes from global LSMs and advanced representation of groundwater from regional models.

Temporal variations in soil aggregate re‐formation behaviors after disturbance by tillage

AbstractAggregate re‐formation after a disturbance is important for maintaining soil hydraulic status and carbon stabilization. A study investigating the re‐formation of aggregates after disturbance by spring tillage was conducted at a site located on a south‐facing (6%) slope with a silt‐loam soil at Arlington‐Wisconsin in 2018 and 2019. Treatments were conventional tillage (CT) and no‐tillage (NT) with winter application of solid manure (SM) and no manure in a complete randomized design. Soils under NT had a higher proportion of larger aggregates (>1 mm), whereas the proportion of smaller (<1 mm) aggregates was greater under CT. Soil organic carbon, total nitrogen, bulk density, soil water retention, and micropores of NT treatments were higher compared to CT systems at 0‐ to 5‐cm depth. However, the impacts of manure application on soil properties were not significant, except for those of soil organic carbon (SOC) and total nitrogen. Harvesting in 2018 decreased the relative proportion of aggregates smaller than 1 mm and hydraulic conductivity of saturated soil. These results indicate that the immediate effect of tillage is to decrease larger aggregates, SOC, and total porosity, whereas harvesting decreases the proportion of smaller aggregates. Comparatively, aggregates smaller than 1 mm were mainly influenced by the long‐term effects of the management operations. It appears that larger aggregates can recover on an annual basis, but aggregates smaller than 1 mm do not. In long‐term studies, there is a need to monitor aggregates, including their size distribution and pore structures, to identify aggregate turnover time and rate, which will augment our understanding of aggregate formation.

Estimating the electrical conductivity of a saturated soil paste extract (ECe) from 1:1(EC1:1), 1:2(EC1:2) and 1:5(EC1:5) soil:water suspension ratios, in calcareous soils from the Mediterranean Islands of Malta

ABSTRACT The standard method to determine soil salinity is by measuring the electrical conductivity (EC) of a saturated soil paste extract (ECe). Models that convert EC of soil:water suspensions (EC(soil:water)) to ECe are soil specific and are not universal models. This study aimed to develop models to convert EC(1:1; 1:2; 1:5) to ECe for the calcareous soil of Malta. Moreover, the effect that soil texture, carbonate and organic matter content might have on these models was investigated. Using 114 soil samples with contrasting textural, carbonate and organic matter characteristics, the general models followed the equation ECe = 10(a(logEC(soil:water))+b) with good correlation coefficients (r2 = 0.91–0.93, p < .001). Models specific to fine and medium textured soil, soils with carbonate content between 35% and 50%, and soils with organic matter content between 2.5% and 4.2% showed a higher correlation coefficient (mean r2 = 0.96). Validation of the models using 22 independent soil samples showed that the general models are reliable (RMSE = 0.93, 0.87, 0.97 dS m−1; NSE = 0.96, 0.97 and 0.95 for 1:1, 1:2 and 1:5, respectively). Except for the models developed from coarse textured soil, all the parameter-specific models were reliable. This study suggests that the general models could be used for soils of Malta having contrasting characteristics except for those with high sand content.

Mobility and transport of pharmaceuticals nalidixic acid and niflumic acid in saturated soil columns

Pharmaceutical compounds often coexist in mixtures rather than as individual entities. However, little is known about their co-adsorption and co-mobility in soil and groundwater. In this study, we investigated the adsorption of a quinolone antibiotic (nalidixic acid, NA) and an anti-inflammatory agent (niflumic acid, NFA) onto two soils from France and Sweden in water-saturated soil columns. Despite its lower hydrophobicity, adsorption of NA is much greater than NFA, which can be ascribed to the presence of both carbonyl and carboxylic groups in NA molecule. The data suggest that chemical adsorption to soil components can mainly take place through hydrogen bonding and surface complexation mechanisms, prevailing over hydrophobic interactions. Accordingly, more sorption of NA and NFA was observed in the Swedish soil because it contains more clay content, and much greater Al and Fe contents than the French soil. Injection of NA/NFA mixture in the column did not modify the breakthrough behavior compared to single systems, although cooperative adsorption was observed under static batch conditions. Ca2+ inhibited NA adsorption by forming a soluble NA-Ca2+ complex but promoted NFA adsorption both in single and binary systems. Their mobility in soil columns was well predicted using a new transport model that accounts for both kinetics and binding reactions of NA and NFA to soil constituents. This work will help in accurately predicting the mobility of coexisting pharmaceutical compounds in soils.

A new state-dependent constitutive model for cyclic thermo-mechanical behaviour of unsaturated vegetated soil

Climate change has resulted in increasing attention being paid to the effects of temperature and humidity on vegetated soil. However, existing constitutive models rarely investigate the thermo-mechanical behaviour, such as the accumulation of plastic strain under non-isothermal conditions, of unsaturated vegetated soil. To address this issue, this study developed a comprehensive constitutive model by adopting state-dependent dilatancy in conjugation with loading, memory, and bounding surfaces. Moreover, root-induced hardening due to pore occupancy and internal bonding is modelled with dependence on the root volume ratio. The performance of this newly developed constitutive model is then evaluated using previous laboratory element tests. Comparisons between the computed and measured results reveal that the model is capable of capturing variations in soil state at a range of temperatures, suctions, and root volume ratios. The shearing behaviour of vegetated soil, especially its volumetric response, is well predicted by the model, as confirmed by comparing it with triaxial compression test results. Moreover, the model predicts that the accumulated volumetric strain of unsaturated vegetated soil (0.2%) is significantly less than saturated bare soil (1.1%) after four thermal cycles. These computed results imply that vegetation can mitigate the effects of climate change on soil through both transpiration-induced suction and mechanical reinforcement.

Transport of sulfanilamide in saturated porous media under different solution chemistry conditions: role of physicochemical characteristics of soils.

Identification of the transport of sulfonamide antibiotics in soils facilitates a better understanding of the environmental fate and behaviors of these ubiquitous contaminants. In this study, the mobility properties of sulfanilamide (SNM, a typical sulfonamide antibiotic) through saturated soils with different physicochemical characteristics were investigated. The results showed that the physicochemical characteristics controlled SNM mobility. Generally, the mobility of SNM was positively correlated with CEC values and soil organic matter content, which was mainly related to the interactions between the organic matter in soils and SNM molecules via π-π stacking, H-bonding, ligand exchange, and hydrophobic interaction. Furthermore, higher clay mineral content and lower sand content were beneficial for restraining SNM transport in the soils. Unlike Na+, Cu2+ ions could act as bridging agents between the soil grains and SNM molecules, contributing to the relatively weak transport of SNM. Furthermore, the trend of SNM mobility in different soil columns was unaffected by solution pH (5.0-9.0). Meanwhile, for a given soil, the SNM mobility was promoted as the solution pH values increased, which was caused by the enhanced electrostatic repulsion between SNM- species and soil particles as well as the declined hydrophobic interaction between SNM and soil organic matter. The obtained results provide helpful information for the contribution of soil physicochemical characteristics to the transport behaviors of sulfonamide antibiotics in soil-water systems.

Bio-protection of cementitious materials below ground: The significance of natural soil environments

This study explores the potential impact of natural soil on concrete crack self-healing in sub-surface structures. Three types of pre-cracked cement mortar samples were prepared for laboratory experiments, with some samples inoculated with bacterial healing agents, others supplemented with nutrients to attract indigenous soil bacteria, and plain mortar served as controls. The samples were placed within saturated soil under two conditions: slightly organic natural soil and sterilised soil. After 100 days, crack closure was evaluated through microscopic inspection, water absorption tests, and SEM-EDX scanning. The results indicated calcite precipitation on crack surfaces across all samples, but with varying ratios of crack closure (16%–81%). Notably, most samples incubated in natural soil exhibited an overall increase (up to 59.4%) in healing ratio compared to those in sterilised soil, highlighting the potential of indigenous soil microorganisms and their microbial activity in enhancing the biogenic mineral precipitation and thus protecting sub-surface concrete structures.

Formulation factors affecting foam properties during vacuum foam-drying

This paper explores how vacuum foam-drying of a protein is influenced by formulation parameters by investigating the foam structure, physical properties of the foam, and the stability of the protein. Recombinant human bile salt-stimulated lipase was used as a model of a protein drug. The stability of the lipase was evaluated through activity measurements. Two disaccharides (sucrose and trehalose), strongly tending to an amorphous form, were used as matrix formers, and the physical properties were assessed through residual water content, glass transition temperature, and crystalline state. Moreover, some formulations included surfactants with different sizes and structures of the head group. The alkyl chain length was kept constant to only investigate the impact of the surfactant head group, in the presence of the lipase, on the foamability and surface coverage of the lipase. The study demonstrated that the lipase allowed for a dry, solid foam with a foam overrun of up to 2600 %. The wall thickness of the dry, solid foam was estimated to be 20–50 µm. Clear differences between sucrose and trehalose as matrix former were identified. The lipase showed no tendency to lose activity because of the drying and rehydration, despite a proportion of the lipase covering the surfaces of the dry material.

Investigation of measurement methods for soil thermal conductivity based on optical frequency domain reflection technology

Thermal conductivity is an important parameter reflecting the heat transfer capacity of soil. In engineering applications, the thermal conductivity of soil varies with influencing factors such as particle size, porosity, water content, saturation, and seepage velocity of soil. At present, the thermal probe method and the traditional thermal response test method are mainly used to determine the thermal conductivity of soil. However, these methods can only perform point temperature measurements and require an inversion calculation based on a particular heat transfer model to obtain the value of soil thermal conductivity. Compared with this and other temperature monitoring methods, optical frequency domain reflectometry (OFDR) offers the advantages of distributed measurement, high measurement accuracy, high spatial resolution, and fast speed. In this paper, an OFDR-based measurement of soil thermal conductivity is designed. Taking sand as an example, the influence of different influencing factors on the measured value of thermal conductivity of soil was studied through the measurement test of thermal conductivity of soil, and the results are compared with the calculation results of the theoretical model of thermal conductivity and the results measured by the thermal probe method. The test results showed that when there was no seepage in the soil, the thermal conductivity of the soil exhibited an “S"-shaped growth trend with increasing water content; when the soil had seepage, the thermal conductivity of the soil was larger than that without seepage, and the thermal conductivity showed a positive linear increase with the increase in seepage velocity; With the increase of heating power, the measurement results tend to be stable. By comparing with the results obtained by other methods, the measurement results of the thermal conductivity measurement method proposed in this study have high accuracy.

Thermal effects on the shear behaviour of saturated coarse-grained soils with reference to post-earthquake deposits

Thermal effects on the shear behaviour of saturated coarse-grained soils with reference to post-earthquake deposits

Repeated Aqueous Film-Forming Foams Applications: Impacts on Polyfluoroalkyl Substances Retention in Saturated Soil.

Historical practices at firefighter-training areas involved repeated aqueous film-forming foams (AFFFs) applications, resulting in source zones characterized by high concentrations of perfluoroalkyl and polyfluoroalkyl substances (PFAS). Repeated applications of AFFF composed of 14 anionic and 23 zwitterionic perfluoroalkyl substances (PFAS) were conducted on a single one-dimensional saturated soil column to quantify PFAS retention. An electrofluorination-based (3M) Milspec AFFF, which was above the mixture's critical micelle concentration (CMC), was at application strength (3%, v/v). Retention and retardation of PFAS mass increased with each successive AFFF addition, although the PFAS concentration profiles for subsequent applications differed from the initial. Greater degree of mass retention and retardation correlated with longer PFAS carbon-fluorine chain length and charged-headgroup type and as a function of AFFF application number. Anionic PFAS were increasingly retained with each subsequent AFFF application, while zwitterionic PFAS exhibited an alternating pattern of sorption and desorption. Surfactant-surfactant adsorption and competition during repeat AFFF applications that are at concentrations above the CMC resulted in adsorbed PFAS from the first application, changing the nature of the soil surface with preferential sorption of anionic PFAS and release of zwitterionic PFAS due to competitive elution. Applying a polyparameter quantitative structure-property relationship developed to describe sorption of AFFF-derived PFAS to uncontaminated, saturated soil was attempted for our experimental conditions. The model had been derived for data where AFFF is below the apparent CMC and our experimental conditions that included the presence of mixed micelles (aggregates consisting of different kinds of surfactants that exhibit characteristics properties different from micelles composed of a single surfactant) resulted in overall PFAS mass retained by an average of 27.3% ± 2.7% (standard error) above the predicted values. The correlation was significantly improved by adding a "micelle parameter" to account for cases where the applied AFFF was above the apparent CMC. Our results highlight the importance of interactions between the AFFF components that can only be investigated by employing complex PFAS mixtures at concentrations present in actual AFFF at application strength, which are above their apparent CMC. In firefighter-training areas (AFFF source zones), competitive desorption of PFAS may result in downgradient PFAS retention when desorbed PFAS become resorbed to uncontaminated soil.

Vertical seismic response of end-bearing piles in nearly saturated soil

This paper presents a study on the effect of the degree of saturation of the foundation soil on the vertical seismic response of end-bearing piles subjected to P-waves. The research focuses on nearly saturated soil, where the air phase is not continuous and air bubbles are dissolved in the pore water, and thus can be treated as two-phase material. The response of the two-phase soil–pile system is quantified by means of a rigorous coupled hydromechanical model, which is based on Biot’s theory for poroelastic media and treats the air bubbles–pore water mixture as a homogeneous fluid obeying Boyle’s law. Numerical results are used to illustrate the influence of the degree of saturation of the soil layer on the seismic strong motion transferred to the pile head, i.e., the capacity of piles to filter seismic wave energy. This work bridges the gap between single-phase and two-phase saturated soil models, which predict profoundly different pile head displacements at incident wave frequencies of practical interest, and elucidates the mechanisms that lead to these differences.