Compaction Conditions and Scale-Dependent Hydraulic Conductivity of Compacted Clay Liners

摘要

A database was compiled containing index properties, compaction data, and hydraulic conductivity data from 51 clay liners. The hydraulic conductivity data included large-scale field measurements (K_F) and small-scale laboratory measurements (K_L) on specimens collected from the field in 74-mm-diameter sampling tubes. Analysis of the database shows that K_F is comparable to K_L when compaction is wet of the line of optimums, but K_F can be up to 266 times larger than K_L when compaction is dry of the line of optimums. Similar results were obtained from a stochastic simulation model. Discrepancies between K_F and K_L exist when macropores are present (i.e., compaction dry of the line of optimums), because macropores are inadequately represented in small laboratory specimens. To achieve, K_F ～ K_L compaction specifications should require that the percentage of data falling wet of the line of optimums (P_o) exceed 80-90% and the difference in initial saturation (ΔS_i, which is the mean degree of saturation at compaction less the degree of saturation corresponding to the line of optimums) exceed 2 to 4%. A "line of optimums" compaction specification is recommended to facilitate achieving these recommended values for P_o and ΔS_i.