Xiaodong Wang, geotechnical laboratory manager for University of Wisconsin-Madison’s Department of Civil and Environmental Engineering, and Civil and Environmental Engineering professor Craig Benson have devised a new, American Society for Testing and Materials-approved invention to improve hydraulic conductivity testing.
Current commercial technology places a sample between two openings (connected to burettes) that have different water levels to create a pressure differential across the sample.
This method has proven reliable but for media with very low hydraulic conductivity, such as tight rock cores, the time to reach a steady state flow of water across the sample can take upward of nearly three weeks.
The new invention includes a constant head system and instruments for measuring the hydraulic conductivity of materials using a closed loop system.
The geological sample is placed within a test fluid under a constant pressure and the fluid flow is regulated so that a constant volume of test fluid is within the sample.
This invention is said to eliminate variation in pressure difference, which is believed to cause errors in the calculation of hydraulic conductivity, and decreases the amount of time needed to reach a steady state flow of water across the sample.
Advantages of this new, simpler process include almost immediate results and a reduction in measurement variation.