Effect of Water Table Level and Soil Layering on Hydraulic Conductivity and Inverse Air Entry Suction Using Tension Disc

Hydraulic conductivity is one of the important physical properties of the soil used extensively in water and soil science. Most of the soil processes take place in unsaturated soil conditions. This study was conducted in order to evaluate the effect of soil layering and water table on saturated and unsaturated hydraulic parameters using a tension disc in five suction heads, i.e. 0, 5, 10, 15, and 20 cm. The experimental tests were done on three same samples with 56 cm diameter and 85 cm height in three compacted layers with soil bulk densities of 1.18, 1.38 and 1.68 gr.cm-3 and water table depths of 85 (no water table) 50, and 25 cm. Additionally, we considered a one-layered sample to investigate the effect of bulk density. The experimental results showed that soil layering caused changes in the values ​​of saturated and unsaturated hydraulic conductivity. Also, sensitivity of the saturated hydraulic conductivity to soil layering was more than that of the inverse air entry suction(α). Compared with the treatment with no water table, the saturated hydraulic conductivity of the layered soil in treatments with water table depths of 25 cm and 50 cm decreased by 52 % and 27.6 %, respectively.