Wisconsin Alumni Research Foundation

Improved Pressure Plate Extractor for Characterizing Soils
WARF: P01425US

Inventors: Xiaodong Wang, Craig Benson

The Wisconsin Alumni Research Foundation (WARF) is seeking commercial partners interested in developing an improved, leak-free design for pressure plate extractors.
The soil water characteristic curve (SWCC) is an essential parameter for characterizing the hydraulic and mechanical behavior of soils. SWCC is typically determined by using a pressure plate extractor – a device composed of a pressure chamber and a porous drain plate (usually ceramic) that holds the soil sample and receives water from it when the chamber is pressurized.

To measure SWCC, a soil sample is saturated with water and placed inside the chamber atop the drain plate. A known pressure is then applied and water expelled from the soil is collected and measured. SWCC is determined by calculating the amount of water expelled at several different pressures.

A major problem with current pressure plate extractors is they tend to leak air, resulting in invalid test results and significant losses of time and money. (SWCC tests can take from two weeks to several months to run.) To prevent leakage, practitioners try to tighten the seal between the pressure chamber lid and the ceramic drain plate; however, this often causes the plate to crack because the clamping force is applied to the plate itself.
The Invention
Two UW-Madison civil engineers have now devised an improved, leak-free design for pressure plate extractors. Specifically, their design incorporates a gasket that sits in a channel around the perimeter of the drain plate rather than on top. When the chamber lid is clamped onto the gasket, the gasket expands laterally to tightly engage the drain plate, the side walls of the chamber lid and the pressure chamber base.
  • Characterizing the hydraulic and mechanical behavior of soils
Key Benefits
  • Provides a new leak-free pressure plate extractor with low probability of drain plate failure
  • Suitable for measurements at both high and low pressures
  • Potentially provides much higher measurement accuracy than previous designs
Additional Information
For More Information About the Inventors
For current licensing status, please contact Emily Bauer at [javascript protected email address] or 608-960-9842