抄録
Physical disintegration of aggregates as a response to externally imposed disruptive forces to soil or the physico-chemical dispersion and swelling of soil clays (soil intrinsic behavior) are often reported to cause deterioration in the hydraulic properties of soils. The joint effect of these two mechanisms on column hydraulic conductivity (HC) of different soils was studied. Three prewetting rates (PWR) of 1,6 and 30 mm/hr and a water quality characterized by sodium adsorption ratio (SAR)10 and total electrolyte concentration (TEC) of 0.5,0.05, 0.01 Molc L 1 and distilled water (DW) were used. The results showed that absolute values of HC and its relative changes over time depended on the type of soil, the PWR, the TEC, and the aggregate size. HC decreased with an increase in the silt and clay content, with an increase in the PWR, and with a decrease in the TEC of the percolating solution. Soils that slaked into microaggregates under the effect of fast PWR, showed a substantial decrease in HC with an increase in the PWR. In structurally unstable soils, fast PWR caused more slaking and physical disintegration of aggregates that restricted water flow leading to low HC. HC of the columns that sustained greater slaking also deteriorated more under the effect of dilute solutions. The larger the aggregate size fraction, the more pronounced was the PWR effect on HC apparently due to greater pore throttling by the slakes. development of cohesive forces between clay structural units with time (aging) was suggested to counteract HC deterioration as observed for smaller aggregate size fraction of this soil. HC of less aggregated or structurally stable soils were less affected by the PWR. The study also indicated that PWR effects on soil HC could be satisfactorily predicted from soil aggregate stability tests.
