Volume 30, Issue 4 (July 2007)
An In-situ Device for Rapid Determination
This paper describes a new in-situ Air Permeameter Test (APT) device developed for estimating the hydraulic conductivity of drainable granular base materials. The device is assembled from commonly available components including air flow meters and differential pressure gages. Using prescribed air flow and pressure measurements from the APT, a theoretical relationship is derived to calculate the saturated hydraulic conductivity. The geometric factors for the device, sample boundary conditions, partial saturation, compressibility and viscosity of the permeant fluid (i.e. air), and the Brooks-Corey pore size distribution index are considered in the derivation. Attempts at correlating in-situ APT calculated hydraulic conductivity values for compacted granular base materials to hydraulic conductivity values from reconstituted laboratory compaction mold permeability tests show that the in-situ values are generally higher and more variable. The in-situ variability is attributed to segregation and is shown to be spatially correlated to the fines content (passing No. 200 sieve).