Controlled Irrigation to Estimate Field-Scale Hydraulic Conductivity of a Landfill Final Cover

摘要

Hydraulic conductivity of engineered earthen covers increases over its life due to the formation of macropores. Macropores are formed during construction and service due to shrinkage, desiccation, freeze-thaw cycles, vegetation root growth and death, rodent holes, and worm holes. Field-scale test section of a compacted clay cover was constructed to investigate the changes in its hydraulic properties over a four year period. Saturated hydraulic conductivity was measured in laboratory on compacted samples and in the field immediately after the test section was constructed. Irrigation tests were used to evaluate transient changes in the hydraulic conductivity. Two irrigation tests, first during the first year and the second during the fourth year after the construction of the test section were carried out. The effective field hydraulic conductivities were calculated using the measured percolation rate in the lysimeter assuming steady-state flow and a unit downward gradient. The effective field hydraulic conductivity calculated after the second irrigation test was about nine times the effective field hydraulic conductivity of the compacted clay measured during the first year.