Pore water pressure

About: Pore water pressure is a research topic. Over the lifetime, 11455 publications have been published within this topic receiving 247670 citations. The topic is also known as: pwp.

Effect of antecedent rainfall on pore‐water pressure distribution characteristics in residual soil slopes under tropical rainfall

Abstract: Characteristics of changes in pore-water pressure distribution are the main parameters associated with slope stability analysis involving unsaturated soils, which are directly affected by the flux boundary conditions (rainfall infiltration, evaporation and evapo-transpiration) at the soil-atmosphere interface. Four slopes were instrumented in two major geological formations in Singapore to provide real-time measurements of pore-water pressures and rainfall events on the slopes. The field monitoring results were analysed to characterize pore-water pressure distributions under various meteorological conditions and to study the effect of antecedent rainfall on pore-water pressure distributions in typical residual soil slopes under tropical climate. Slope stability analyses were also conducted for the best and worst pore-water pressure distributions recorded in each slope to determine the range of factor of safety for the slopes. Results indicate that, antecedent rainfall, initial pore-water pressures prior to a significant rainfall event as well as the magnitude of the rainfall event play a crucial role in the development of the worst pore-water pressure condition in a slope. The role of antecedent rainfall in the development of the worst pore-water pressure condition was found to be more significant in residual soils with low permeability as compared with that in residual soils with high permeability. Pore-water pressure variation due to rainfall was found to take place over a wide range in residual soils with higher permeability as compared to residual soils with lower permeability. The worst pore-water pressure profiles occurred when the total rainfall including the 5-day antecedent rainfall (in most cases) reached a maximum value during a wet period. The factor of safety of residual soils with low permeability was found to be unaffected by the worst pore-water pressure condition.

Temperature Dependence of Water Retention Curves for Wettable and Water-Repellent Soils

Abstract: The capillary pressure (ψ) in unsaturated porous media is known to be a function of temperature (T). Temperature affects the surface tension (α) of the pore water, but possibly also the angle of contact (y). Because information on the temperature dependence of (γ) in porous media is rare, we conducted experiments with three wettable soils and their hydrophobic counterparts. The objectives were (i) to determine the temperature dependence of the water retention curve (WRC) for wettable and water-repellent soils, (ii) to assess temperature effects on the apparent contact angle γ A derived from those WRCs, and (iii) to evaluate two models (Philip-de Vries and Grant-Salehzadeh) that describe temperature effects on (. Columns packed with natural or hydrophobized soil materials were first water saturated, then drained at 5, 20, and 38°C, and rewetted again to saturation. Capillary pressure and water content, 0, at five depths in the columns were measured continuously. The observations were used to determine the change in γ A with T, as well as a parameter β 0 that describes the change in ( with T. It was found that the Philip-de Vries model did not adequately describe the observed relation between ( and T. A mean value for β 0 of -457 K was measured, whereas the Philip-de Vries model predicts a value of -766 K. Our results seem to confirm the Grant-Salezahdeh model that predicts a temperature effect on γ A . For the sand and the silt we studied, we found a decrease in γ A between 1.0 to 8.5°, when the temperature was increased from 5 to 38°C. Both β 0 and γ A were only weak functions of 0. Furthermore, it seemed that for the humic soil under study, surfactants, i.e., the dissolution of soil organic matter, may compound the contact angle effect of the soil solids.

Ionic‐strength effects on colloid transport and interfacial reactions in partially saturated porous media

Abstract: [1] Contaminant migration through the vadose zone may be influenced by the presence of mineral colloids that are mobilized during infiltration events. In this work, we report model calculations and experimental data on the role of pore water ionic strength in the transport of silica colloids through water-saturated and unsaturated porous media. The transport model solves the advection-dispersion equation, together with kinetics equations for straining, air-water interface capture, and mineral-grain attachment. Parameters for air-water and solid-water interfacial area required by the transport model are derived through the application of a published liquid-vapor configuration model that accounts for dual-phase (i.e., air and water) occupancy of pore spaces. Comparison of experimental and modeled results reveals that the dominant colloid-immobilization mechanism transitions from straining, to air-water interface capture, and finally, to mineral-grain attachment as the ionic strength increases from 2 × 10−4 M to 0.2 M. The results of this research provide a basic framework for interpreting how interactions between moisture content and pore water chemistry affect colloid mobility in the vadose zone.