2026· E3S Web of Conferences· Vol 729, pp. 01003· 0 citations· 1 references
Abstract
Seasonal soil-moisture flux causes time-varying soil resistivity and earthing resistance, which can compromise the safety of power-system earthing installations. Using representative sites in South Africa and Nigeria under comparable climates, this paper quantifies how temperature and relative humidity drive changes in topsoil suction and influence variation in subsoil resistivity and earthing resistance. The sites span four Köppen-Geiger climate classes: Aw (tropical savanna), BSh (hot semi-arid steppe), BWh (hot desert), and Cwb (subtropical highland). To study climate effects, a two-layer subsoil (silty top layer over sandy clay) with two earthing configurations: bare vertical rod and earthing enhancement material (EEM) embedded rod is modelled in COMSOL Multiphysics and simulated under the monthly suction values computed from the monthly average temperature and humidity data (1991-2021) of the sites. From postprocessing, the resistance of bare and EEM-embedded rods was computed and compared with analytical equivalents. Results show consistent resistance reduction with EEM across months and climates. Earthing sites in BWh and BSh exhibit wider suction ranges and larger resistance variations than those in Aw and Cwb. Similar climate classes show comparable seasonal patterns, but their rainfall days and sunshine hours provide plausible contextual differences in resistance magnitude and variation.
Increasing extremes in atmospheric drought associated with climate change raise growing concerns on the potential impact of climatic actions on the geotechnical stability of regional dykes in the Netherlands. Accurate quantification of seasonal soil strength variations under in-situ conditions is essential to assess this impact. Cone penetration testing (CPTu) is widely adopted to assess material strength, however, the influence of seasonality on CPTu data is largely overlooked in current practice. This contribution presents the results of CPTu investigations repeated at one regional dyke location under variable atmospheric conditions, ranging from winter wetness to severe summer drought. The observed differences in resistance and pore pressure between the CPTu data collected over different seasons highlight the impact of drought on soil strength. It is shown that conventional interpretation tool for saturated soils cannot be used straightforwardly to analyse the data. In the variably saturated zone, clear derivation of strength is hindered by current knowledge gaps. Possible interpretation of CPTu data for constant water content shear strength is discussed for both the saturated and the unsaturated zones in view of dyke stability assessment, with the aid of expected soil physical behaviour and parallel data from in situ hydro-mechanical monitoring.
I. De Wolf, Cristina Jommi· E3S Web of Conferences· 0 citations
(English) The top layer of soil on a slope is highly dynamic, influenced by atmospheric forces and the presence of vegetation. The vegetation condition plays a crucial role in determining the amount of water transpiration and evaporation from the slope surface, thus affecting slope performance by altering temperature, water content, and pore water pressure within the soil mass. Many numerical models often neglect the vegetation impact on soil performance. To capture these effects, this study employs a finite element model in CODE_BRIGHT that integrates vegetation and climate-driven interactions, aiming to bridge the gap between reality and simulation. A specialized boundary condition is developed to simulate soil–vegetation–atmosphere (SVA) processes with hydraulic hysteresis, linking canopy resistance to solar radiation, vapor pressure deficit, and soil saturation. Model validation using three years of field data from the Agropolis slope in Barcelona shows strong agreement, confirming its ability to reproduce vegetation effects on slope hydrothermal behavior. Results reveal pronounced daily temperature variations in the root zone, higher temperatures on south-facing slopes, and stronger drying under vegetation during hot, dry periods.
Parametric analysis identifies leaf area index (LAI), root density, and vegetation fraction as key factors influencing soil moisture. Root density and LAI most strongly affect water retention, dense roots lower summer saturation by up to 40%, while high LAI reduces surface drying by 30%. Vegetation fraction enhances winter storage but intensifies summer drying.
To better represent unsaturated soils, a hysteretic soil–water retention model is implemented in CODE_BRIGHT, coupling suction and void ratio changes to improve accuracy in scenarios such as rainfall-induced landslides.
Finally, an enhanced Barcelona Basic Model (BBM-VEG) is formulated within a thermo-hydro-mechanical (THM) framework. The model introduces a strain-dependent reinforcement factor (Rpveg), correlated with root mass fraction and activation strain, allowing soil stiffness and strength to evolve dynamically. Validated with triaxial and tensile tests, it accurately captures the mechanical response of rooted soils. Slope simulations under hydraulic (infiltration rates of 0.001–0.003 and 0.0005 kg/s) and thermal (15–60 °C) cycles show that vegetation limits infiltration, enhances evapotranspiration, expands the unsaturated zone, and reduces deformation by up to 70% compared to bare slopes.
(Català) La capa superior del sòl en un talús és altament dinàmica, influïda per les forces atmosfèriques i la presència de vegetació. L’estat de la vegetació té un paper crucial en la determinació de la quantitat de transpiració i evaporació d’aigua des de la superfície del talús, afectant així el seu comportament mitjançant l’alteració de la temperatura, el contingut d’aigua i la pressió intersticial dins de la massa de sòl. Molts models numèrics sovint descuiden l’impacte de la vegetació en el comportament del sòl. Per capturar aquests efectes, aquest estudi utilitza un model d’elements finits a CODE_BRIGHT que integra les interaccions impulsades per la vegetació i el clima, amb l’objectiu de reduir la bretxa entre la realitat i la simulació. Es desenvolupa una condició de contorn especialitzada per simular els processos sòl–vegetació–atmosfera (SVA) amb histèresi hidràulica, vinculant la resistència del dosser amb la radiació solar, el dèficit de pressió de vapor i la saturació del sòl. La validació del model amb tres anys de dades de camp del talús d’Agropolis a Barcelona mostra una forta concordança, confirmant la seva capacitat per reproduir els efectes de la vegetació en el comportament hidrotermal del talús. Els resultats revelen variacions diàries pronunciades de temperatura a la zona radicular, temperatures més elevades als talussos orientats al sud i un assecat més intens sota vegetació durant períodes càlids i secs.
L’anàlisi paramètrica identifica l’índex d’àrea foliar (LAI), la densitat radicular i la fracció de vegetació com a factors clau que influeixen en la humitat del sòl. La densitat radicular i el LAI afecten amb més intensitat la retenció d’aigua: arrels denses poden reduir la saturació estival fins a un 40%, mentre que un LAI elevat disminueix l’assecat superficial en un 30%. La fracció de vegetació millora l’emmagatzematge hivernal, però intensifica l’assecat estival.
Per representar millor els sòls no saturats, s’implementa a CODE_BRIGHT un model histèric de retenció sòl–aigua que acobla la succió i els canvis en el volum de buits per millorar la precisió en escenaris com ara esllavissades induïdes per la pluja.
Finalment, es formula un Model Bàsic de Barcelona millorat (BBM-VEG) dins d’un marc termo-hidro-mecànic (THM). El model introdueix un factor de reforç dependent de la deformació (Rpveg), correlacionat amb la fracció de massa radicular i la deformació d’activació, permetent que la rigidesa i la resistència del sòl evolucionin dinàmicament. Validat mitjançant assaigs triaxials i de tracció, el model captura amb precisió la resposta mecànica dels sòls amb arrels. Les simulacions de talussos sota cicles hidràulics (taxes d’infiltració de 0,001–0,003 i 0,0005 kg/s) i tèrmics (15–60 °C) mostren que la vegetació limita la infiltració, potencia l’evapotranspiració, amplia la zona no saturada i redueix la deformació fins a un 70% en comparació amb talussos nus.
(Español) La capa superior del suelo en una ladera es altamente dinámica y está influenciada por las fuerzas atmosféricas y la presencia de vegetación. El estado de la vegetación desempeña un papel crucial en la determinación de la cantidad de agua transpirada y evaporada desde la superficie de la ladera, afectando así su comportamiento al modificar la temperatura, el contenido de agua y la presión de poros dentro de la masa del suelo. Muchos modelos numéricos suelen pasar por alto el impacto de la vegetación en el desempeño del suelo. Para capturar estos efectos, este estudio emplea un modelo de elementos finitos en CODE_BRIGHT que integra las interacciones impulsadas por la vegetación y el clima, con el objetivo de reducir la brecha entre la realidad y la simulación. Se desarrolla una condición de contorno especializada para simular los procesos suelo–vegetación–atmósfera (SVA) con histéresis hidráulica, vinculando la resistencia del dosel a la radiación solar, el déficit de presión de vapor y la saturación del suelo.
La validación del modelo con tres años de datos de campo del talud de Agropolis en Barcelona muestra una fuerte concordancia, confirmando su capacidad para reproducir los efectos de la vegetación en el comportamiento hidrotermal de la ladera. Los resultados revelan variaciones diarias pronunciadas de temperatura en la zona radicular, temperaturas más altas en laderas orientadas al sur y una mayor desecación bajo vegetación durante periodos cálidos y secos.
El análisis paramétrico identifica el índice de área foliar (LAI), la densidad radicular y la fracción de vegetación como los principales factores que influyen en la humedad del suelo. La densidad de raíces y el LAI afectan más intensamente la retención de agua: las raíces densas reducen la saturación estival hasta en un 40%, mientras que un LAI elevado disminuye la desecación superficial en un 30%. La fracción de vegetación aumenta el almacenamiento invernal, pero intensifica la desecación durante el verano.
Para representar mejor los suelos no saturados, se implementa en CODE_BRIGHT un modelo histerético de retención agua–suelo, acoplando los cambios de succión y relación de vacíos para mejorar la precisión en escenarios como los deslizamientos inducidos por lluvia.
Finalmente, se formula un Modelo Básico de Barcelona mejorado (BBM-VEG) dentro de un marco termo-hidro-mecánico (THM). El modelo introduce un factor de refuerzo dependiente de la deformación (Rpveg), correlacionado con la fracción de masa radicular y la deformación de activación, lo que permite que la rigidez y la resistencia del suelo evolucionen dinámicamente. Validado con ensayos triaxiales y de tracción, el modelo reproduce con precisión la respuesta mecánica de los suelos con raíces. Las simulaciones de laderas bajo ciclos hidráulicos (tasas de infiltración de 0.001–0.003 y 0.0005 kg/s) y térmicos (15–60 °C) muestran que la vegetación limita la infiltración, mejora la evapotranspiración, amplía la zona no saturada y reduce la deformación hasta en un 70% en comparación con laderas desnudas.
Land-atmosphere interactions provide a key pathway through which land-surface anomalies shape regional climate variability. Using ERA5 reanalysis data for 1985–2024, we examine the impacts of soil moisture on monthly precipitation during the rainy season in South China (SC) from both local and non-local perspectives. Singular value decomposition (SVD) and correlation-based diagnostics are combined to isolate coupled patterns and to trace their underlying physical processes. Enhanced soil moisture in July increases local evaporation and atmospheric humidity, thereby contributing to greater total rainfall. Concurrently, the augmented latent and sensible heat fluxes lower surface temperatures, reduce boundary layer depth, and boost convective available potential energy. The synergy between these favorable moisture and dynamic conditions underpins the positive soil moisture–precipitation feedback observed at a cross-monthly timescale. Beyond local feedbacks, anomalously wet soils over northern Indochina in July exert a robust positive influence on August rainfall in SC by modifying atmospheric circulation and moisture transport. A comprehensive synthesis indicates a synergistic effect between local soil moisture in SC and that in northern Indochina, collectively promoting increased precipitation in August. These findings shed light on the regional linkage mechanism of soil moisture–precipitation feedback across monthly scales, offering valuable insights for understanding the drivers of rainy-season precipitation in SC and improving short-term climate predictions.
Xirui Xu, Chunqiao Lin, Luchi Song et al.· Journal of Applied Meteorolo...· 0 citations
The behaviour of expansive clay soils is highly influenced by climatic variations that govern the hydric exchanges between the atmosphere and the ground surface. These fluctuations cause changes in soil suction, leading to significant volumetric variations in expansive soils and resulting in differential settlements of lightweight structures, which can induce structural damage. Despite the critical role of these hydroclimatic processes, few models are able to describe the evolution of soil suction under realistic boundary conditions. In this study, a two-dimensional diffusion model is proposed to simulate the temporal and spatial evolution of suction beneath a structure, considered as impermeable, under the influence of climatic fluctuations and over selected time steps. The model is based on the numerical solution of the diffusion equation in unsaturated porous medium, formulated in terms of suction. The boundary conditions incorporate a surface water balance accounting for infiltration and evaporation, using meteorological data from the Météo-France SIM2 model. Hydraulic soil parameters, such as unsaturated permeability and water retention curve expressing suction as a function of water content, are defined from empirical relationships reported in the literature. The model is applied to a clay soil whose parameters are derived from the Chaingy experimental site (France) using daily climatic data for the year 2025. The simulations highlight a strong seasonal variability of suction concentrated within the upper soil layers, while the presence of an impermeable surface zone representing the structure significantly attenuates suction fluctuations beneath the foundation and induces marked horizontal gradients during dry periods.
Mathilde Lefebvre, M. Morvan, A. Chateauneuf et al.· E3S Web of Conferences· 0 citations
Soil moisture is a key indicator of agricultural and hydrological drought, but its meteorological controls vary across temporal scales. Using ESA CCI soil moisture products from 2010 to 2022, this study investigated soil moisture variability in the Yangtze River Basin at weekly, monthly, and annual scales. The product was first validated using ground observations and ERA5 reanalysis data, and a generalized additive model (GAM) was then applied to quantify the relative contributions of precipitation, temperature, wind speed, and VPD under normal conditions and during three extreme drought events. The validation showed that ESA CCI soil moisture captured basin-scale variations well, with mean absolute deviations of 0.0460, 0.0434, and 0.0072 m3/m3 in the upper, middle, and lower reaches, respectively, and a basin-wide RMSE of 0.0127 m3/m3 against ERA5. The attribution results revealed a clear scale-dependent shift in soil moisture controls. At the weekly scale, VPD dominated soil moisture variability, with a basin-wide average contribution of 47.04% and a maximum contribution of 55.92% in the lower reaches, indicating that short-term soil drying is mainly driven by VPD. At the monthly scale, precipitation became the primary control, with a basin-wide average contribution of 36.62% and a maximum contribution of 44.65% in the upper reaches, reflecting the role of accumulated rainfall recharge in maintaining soil moisture storage. During extreme drought events, the monthly-scale dominance of precipitation weakened, and precipitation, VPD, temperature, and wind speed each contributed approximately 20–30%, suggesting that drought development results from the combined effects of reduced water input and enhanced atmospheric water loss. These findings indicate that precipitation-based drought monitoring may underestimate rapid soil drying risks, whereas incorporating atmospheric demand indicators such as VPD can improve drought early warning and water resource management under a warming climate.
Yucheng Liu, Ran Huo, Bowen Zhu et al.· Atmosphere· 0 citations
The 2023–2024 drought reduced water availability worldwide, yet its impacts on soil moisture remain unknown in ungauged Andean catchments. Therefore, we assessed drought-induced soil moisture changes across seven catchments in Ecuador using a multivariable approach that integrates Sentinel-1 A SAR interferometry (InSAR)-derived vertical ground displacement as a relative indicator for soil moisture, soil moisture anomalies, ERA5 precipitation, and land cover data. Ground subsidence indicated a progressive decline in soil moisture. The magnitude of decline varied with elevation and land cover, with the lowest impacts in the uplands (4000–4400 m a.s.l) covered by páramo vegetation (tussock grass and cushion plants) and the strongest impacts in the lowlands (≤ 3400 m a.s.l) covered by grazing pastures. These patterns reflect climatic and hydrologic gradients, better-preserved upland soils and vegetation, soil degradation, and lower water-use efficiency in lowland pastures. InSAR has potential to monitor soil moisture during hydrological drought in the Andean data-scarce catchments, and reveal contrasting drought resilience among land covers, which provide evidence towards improved natural resources management.
