|Title||Pneumatic permeameter for transient tests on coarse gravel|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||Judge AI, Ostendorf DW, Degroot DJ, Zlotnik VA|
|Journal||Journal of Hydrologic Engineering|
|Keywords||Gravel, hydraulic conductivity, Laboratory test, Models, Optimization, Porosity, Soil water, Tortuosity, Underdamped, Water flow|
A new permeameter is proposed for performing laboratory hydraulic conductivity tests on gravels with hydraulic conductivity values ranging from 0.1 to 1 m/s1 m/s. A small diameter riser is connected to a large diameter cylinder, which holds the coarse-grained specimen saturated in a water bath. The release of pneumatic pressure, applied to the free surface in the riser, induces an underdamped oscillatory response of the water level in the riser, similar to an underdamped in situ slug test response in monitoring wells. A closed-form model is used to analyze the measured oscillatory hydraulic head data to calibrate the minor losses in the permeameter and the hydraulic conductivity of the specimen by performing tests without and with a specimen. The average model error of calibrated pressure head values in the riser for the tests considered are about 5% of the initial displacement of about 2 cm. The hydraulic conductivity values are calibrated considering the replicate tests, the tests of different specimen lengths, and the different time periods within a test to verify that the results reflect the hydraulic conductivity of the specimen alone. The Kozeny-Carman equation, which considers the specific surface area of the tested material, gave a hydraulic conductivity value within 5% of the measured value for the marbles, which is a good comparison because the uniform marbles have a known specific surface area. For all the various tests performed on each specimen, most of the hydraulic conductivity values were within 10% of the average, while the specimens with hydraulic conductivity greater than 1 m/s1 m/s were within 10 to 20% of the average.