Experimental investigation and conceptual modelling of water-limited transpiration as hydraulic boundary condition in geotechnical engineering problems
Water uptake through plant transpiration is a critical hydraulic boundary condition in modelling geostructures under climatic loading. Transpiration occurs in two regimes: energy-limited, controlled by atmospheric evaporative demand; and water-limited, governed by soil hydraulic conductivity around roots. While energy-limited (potential) transpiration is generally modelled using a physically based approach, the water-limited regime is usually modelled macroscopically by way of an empirical transpiration reduction function. This paper first presents an experimental investigation into the influence of soil hydraulic behaviour and potential transpiration rate on water-limited transpiration. Two soil textures were tested – silty sand and clayey-silty sand – planted with Medicago sativa. The use of high-capacity tensiometers enabled the investigation of an unprecedented suction range in clayey soils. Results show that the water-limited branch of the reduction function is non-linear, and its decay is strongly influenced by unsaturated hydraulic conductivity. Furthermore, the suction marking the transition from energy- to water-limited regimes varied with potential transpiration rate and soil hydraulic behaviour. A novel physically based, closed-form reduction function is then formulated to advance water uptake modelling in the water-limited regime. This function is shown to compactly capture the combined effects of soil hydraulic conductivity, root system architecture expressed through root length density and potential transpiration rate on transpiration in the water-limited regime, consistent with observations from both this experimental campaign and the literature data.
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
This paper introduces a nonlinear mathematics model of plant root water uptake in heterogeneous soil based on the coupled soil–plant hydrodynamics. The process of variably saturated water flow and moisture extraction mechanisms is described by Richards' partial differential equation integrated with spatially distributed root uptake sink functions. Discretization for numerical approximation is used on adaptive heterogeneous grids: finite difference and finite element discretization schemes. The model includes the variability in hydraulic conductivity, soil water retention relationships, and uptake dynamics that are dependent on stress. The iterative Newton–Raphson formulations are used to study the stability and convergence for the nonlinear coupled system. Numerical modelling shows that under different boundary conditions, the moisture distribution, the hydraulic gradient and the ability of the root zone to extract water from the soil are markedly influenced by the degree of soil heterogeneity.Moisture distribution, hydraulic gradient and root-zone extraction efficiency vary significantly as a function of soil heterogeneity under different boundary conditions, as demonstrated by numerical modelling. The proposed framework enhances the prediction of irrigation and sustainable agriculture water management.
Devkant Varde, Sangita M.Jaybhaye, Chandrakant D. Kokane et al.· Journal of Intelligent Decis...· 0 citations
Seasonally frozen soils strongly influence infiltration, runoff generation, and infrastructure performance in cold regions. However, infiltration modeling in partially saturated sandy soils remains poorly constrained due to limited experimental characterization of hydraulic parameters under freezing conditions. This study investigates coupled thermo–hydraulic behavior in sandy soils using laboratory column experiments and finite element modeling implemented in COMSOL Multiphysics. Instrumented soil columns were subjected to controlled freeze–thaw cycles to measure transient temperature and liquid water content profiles. A coupled TH model incorporating the van Genuchten–Generalized Clausius–Clapeyron formulation was used to represent phase change and cryosuction. The soil freezing characteristic curve and impedance factor were experimentally determined. Model simulation reproduced measured thermal and hydraulic responses with good agreement. Results show that frozen hydraulic conductivity is highly sensitive to the impedance factor and initial moisture conditions, with an approximately exponential relationship. Freeze–thaw cycling caused hysteresis in the soil–water retention behavior, which is attributed to pore structure modification caused by ice formation and thawing. These results improve parameter estimation for frozen sandy soils and establish a validated framework for simulating coupled heat and moisture transport in cold-region environments.
Ali Behdad, Incheol Kim, Yuan Feng et al.· Canadian geotechnical journa...· 0 citations
This paper describes the formulation of a numerical model for simulating environmentally driven one-dimensional (1D) ground movements of expansive clay. The formulation is based on a finite-element model that simulates the redistribution of matric suction through a diffusion-type equation, explicitly accounting for volume changes due to wetting and drying of the clay. We synthesize and modify highly nonlinear constitutive relationships for (1) hysteretic soil water retention; (2) reversible soil shrinkage and expansion of clay; and (3) hydraulic conductivity, explicitly incorporating desiccation cracks through a multidomain framework and assuming a critical surface crack depth. These models are well-calibrated to published laboratory tests on a reference expansive clay, Denver bentonite. We demonstrate capabilities of the proposed formulation to simulate the response of a homogeneous expansive clay to periods of drying and wetting, considering the initial matric suction, saturated hydraulic conductivity of the intact clay, and critical crack depth as three primary sources of uncertainty. We compare ensemble model simulations with measured ground movements from an instrumented expansive clay test site in Texas over a 3-year period using detailed records of potential evapotranspiration and precipitation. By assigning weights to the ensemble simulations based on their performance, we constrain the ranges of the three key uncertain parameters. The results showed very reasonable first-order agreement with the measured data and highlight the potential of the proposed formulation. We anticipate that more reliable predictions can be achieved through direct measurements of actual in situ evaporation rates and local soil properties.
Mahdi Seyyedan, Jiali Ma, Ivo Rosa Montenegro et al.· Journal of Geotechnical and...· 1 citation
Soil hydraulic properties govern the movement and storage of water in soils and are essential inputs for hydrological and land surface models, influencing water‐holding capacity, matter and energy transport, erosion susceptibility and plant water availability. However, direct measurement of these properties is labour‐intensive and thus often limited in spatial coverage. Therefore, pedotransfer functions (PTFs) are widely used to estimate soil hydraulic properties from readily available soil characteristics. We present a spatial dataset of soil hydraulic properties for Europe at 0–20 cm depth, developed using harmonised soil property maps derived from the LUCAS dataset and the improved PTFs (EUPTFv2) proposed by Szabó et al., which are developed on the European Hydropedological Data Inventory. The derived dataset includes water content at saturation, field capacity (at −10 and −33 kPa), wilting point (−1500 kPa), saturated hydraulic conductivity and their associated uncertainty maps. In addition, we derived available water capacity and air capacity (air‐filled porosity) from the predicted properties. The input datasets (LUCAS‐based soil maps) used in this study are derived from harmonised data in terms of measurement methods and spatial consistency. This is expected to improve the reliability of the resulting maps compared with existing products. The generated dataset is freely available and can therefore support a wide range of environmental and modelling applications.
Surya Gupta, C. Alewell, C. Ballabio et al.· Hydrological Processes· 0 citations
Wicking geotextiles are specialized geosynthetics designed to regulate soil moisture through a combination of capillary-barrier and lateral-drainage mechanisms. Laboratory and field studies demonstrate their effectiveness in reducing volumetric water content, restricting capillary rise, and maintaining subgrade and base stability under rainfall, dry–wet cycles, freeze–thaw cycles, and traffic loading. Performance is influenced by soil type, fines content, installation depth, edge exposure, and environmental conditions. Field applications show benefits in pavements, expansive soils, pumping-prone sections, cold-region roadbeds, and permeable urban infrastructure. Multi-layer and composite geotextiles further enhance hydraulic and mechanical performance. Despite these advantages, gaps remain in standardized testing, long-term monitoring, design methods, and durability assessments under aggressive conditions. This review synthesizes recent experimental and field evidence, highlighting mechanisms, performance factors, and research needs to guide the optimal design and application of wicking geotextiles in geotechnical engineering.
Muhammad Shahbaz, Jun Guo, Jiajun Liao et al.· Applied Sciences· 0 citations