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.

Pore pressure and suction in soil

Abstract: METHODS USED AT THE ROAD RESEARCH LABORATORY FOR MEASURING SOIL SUCTION AND NEGATIVE PORE-WATER PRESSURE AND FOR INVESTIGATING THE RELATIONSHIP BETWEEN SUCTION AND MOISTURE CONTENT ARE DESCRIBED. METHODS DISCUSSED ARE: (1) SUCTION PLATE, (2) CONTINUOUS FLOW, (3) RAPID METHOD, (4) FIELD TENSIOMETER, (5) PRESSURE PLATE, (6) PRESSURE MEMBRANE, (7) ODOMETER, (8) CENTRIFUGE, (9) FREEZING POINT DEPRESSION METHOD, (10) VACUUM DESICCATOR, (11) SORPTION BALANCE, AND (12) ELECTRICAL RESISTANCE GAUGES. THE SIGNIFICANCE OF SOIL SUCTION AND NEGATIVE PORE-WATER PRESSURE IN RELATION TO SOME ASPECTS OF SOIL MECHANICS ARE CONSIDERED.

A mini drivepoint sampler for measuring pore water solute concentrations in the hyporheic zone of sand‐bottom streams

Abstract: A new method for collecting pore-water samples in gravel streambeds is presented. We developed a mini drivepoint solution sampling (MINIPOINT) technique to collect pore-water samples at 2.5-cm vertical resolution. The sampler consisted of six small-diameter stainless steel drivepoints arranged in a 10-cm-diameter circular array. In a simple procedure, the sampler was installed in the streambed to preset drivepoint depths of 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0 cm. Sampler performance was evaluated in the Shingobee River, Minnesota, and Pinal Creek, Arizona, by measuring the vertical gradient of chloride concentration in pore water beneath the streambed that was established by the uninterrupted injection to the stream for 3 d. Pore-water samples were withdrawn from all drivepoints simultaneously. In the first evaluation, the vertical chloride gradient was unchanged at withdrawal rates between 0.3 and 4.0 ml min− but was disturbed at higher rates. In the second evaluation, up to 70 ml of pore water was withdrawn from each drivepoint at a withdrawal rate of 2.5 ml min−1 without disturbing the vertical chloride gradient. Background concentrations of other solutes were also determined with MINIPOINT sampling. Steep vertical gradients were present for biologically reactive solutes such as DO, NH4+, NO3−, and dissolved organic C in the top 20 cm of the streambed. These detailed solute profiles in the hyporheic zone could not have been determined without a method for close interval vertical sampling that does not disturb natural logic mixing between stream water and groundwater.

Groundwater Flow and Solute Transport in Fractured Lacustrine Clay Near Mexico City

Abstract: A network of piezometers was installed in a surficial lacustrine clay aquitard overlying a thin saline water aquifer of volcanoclastic origin at a study site near Mexico City in the Basin of Mexico. The aquifer is underlain by additional lacustrine sediments which in turn overlie a thick regional freshwater aquifer. The regional aquifer provides approximately 70% of the water supply for 20 million people in the Basin of Mexico. In the study area, major ions, oxygen 18, and deuterium in the pore water of the surficial aquitard exhibit large variations with depth. The nature of these variations suggests that the saline pore water is being displaced downward by infiltrating meteoric water. The infiltration has been induced by strong downward hydraulic gradients imposed two to three decades ago when heavy aquifer pumping of the thin saline water aquifer began. One-dimensional analytical models representing solute transport in both fractured and unfractured porous media were used to simulate the geochemical profiles in the surficial aquitard. The fractured porous medium model, using a realistic mean hydraulic gradient and fracture spacing (1.5 m) and small but significant fracture aperture (30 μm) provide nearly an exact match to the field data. From this we infer that, because of vertical fractures, there is a much greater potential for downward leakage of water and contaminants through the Mexico City clay into underlying aquifers than has been previously thought.