Rigid wall, constant head, saturated hydraulic conductivity

The saturated hydraulic conductivity testing of wildfire ash mixtures was performed in a rigid wall permeameter (D = 11.4 cm) under constant head (ASTM D2434 2000). Samples were prepared by placing a thick layer of wildfire ash (4 – 6cm) above a layer of compacted Silver #20 sand (10 cm). This was done to both conserve the quantity of ash for other testing and to simulate a field scenario where ashes are deposited above native soils following a wildfire event. The compacted sand had a unit weight of 15.8 kN/m3, and the wildfire ash layers were prepared in both a loose state (target 50% relative compaction) and a dense state (target 85% relative compaction). Prepared specimens were saturated for a 24-hour period and then tested for saturated hydraulic conductivity at hydraulic gradients of 3 – 4 (depending on the final height of the specimen after saturating). The equivalent hydraulic conductivity method was used to estimate the saturated hydraulic conductivity of the ash layer, assuming that vertical flow dominated (Budhu 2011).