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.

Calcite dissolution in sediments of the Ontong‐Java Plateau: In situ measurements of pore water O2 and pH

Abstract: We present in situ electrode measurements of sediment resistivity, pore water oxygen, and pore water pH from three stations between 2300 and 3000 m depth on the Ontong-Java Plateau in the western equatorial Pacific. One of these stations is also the site of a concurrent benthic chamber incubation experiment [Jahnke et al., 1994]. The pore water oxygen data and a steady state diffusion and reaction model constrain the depth-dependent rate of oxic respiration in the sediments and imply a diffusive flux of oxygen to the sediments of 10–21 μmol cm−2 yr−1. Given these respiration rates, the pore water pH data cannot be explained without calcite dissolution driven by metabolically produced CO2. The dissolution necessary to explain the observations, quantified by a statistical approach, is 3.5–6 μmol cm−2 yr−1, which corresponds to at least 20–40% of the calcite rain to these sediments. Over 65% of the total dissolution is driven by metabolic CO2. Oxygen fluxes and net calcite dissolution constrained by the electrode data are compatible with the benthic chamber measurements of Jahnke et al. [1994]. The dissolution flux, while a significant part of the early diagenesis of calcite in these sediments, is less than would be predicted by earlier models of dissolution, and Jahnke et al. [1994] probably could not distinguish it from zero with the benthic chamber technique. The dissolution rates found in this study are lower than previous estimates because the respiration reaction is concentrated near the sediment-water interface, and the calcite dissolution rate constants are very small. The statistical evaluation of the pore water pH data and model constrain the calcite dissolution rate constant to 0.005–0.16% d−1, following the general trend of lower values determined by in situ techniques rather than by laboratory methods.

Temperature Effects on Clay Soil Consolidation

Abstract: The influence of increasing the temperature in a consolidating soil is examined by consideration of the thermal energy input from the temperature change. This energy provides the potential necessary to cause flow through physical changes in the pore water and at the soil water interface. A consolidometer was adapted to provide temperature changes through a heating element, the temperatures being measured by thermocouples at the soil sample surface. The quantity of deformation induced by increasing boundary temperatures at a given stress level was measured for three series of increases: low-long time, high-long time, and high-rapid time. It was observed that the magnitude of the resulting deformation depended directly on the magnitude of the temperature increase, and that the deformation pattern was similar to the temperature patttern. Deformation ceased when the temperature increase was halted.