Compatibility Of Some Compacted Victorian Soils With Organic Chemicals And Waste Leachates

Compacted soil liners are used as hydraulic barriers in waste containment facilities to reduce the rate of pollution migration from the waste into ground water. It is imperative for these liners to have low hydraulic conductivity, preferably less than 10 −9 m/s, over the design time span of these facilities. During the assessment of a particular soil for liner construction, laboratory hydraulic conductivity tests with water are undertaken to examine whether the field compacted soil can achieve hydraulic conductivities less than the above value. However, in waste containment facilities, compacted soil liners come in contact with various chemical leachates, and it is possible that increases in hydraulic conductivity may result when compacted soils are permeated with some chemical liquids commonly found in leachates. It follows then that tests should be undertaken to assess the compatibility of these chemicals with the selected soil. It is generally considered that hydraulic conductivity tests with chemical leachate would provide direct evidence of the soil compatibility and is commonly undertaken as part of the design process of the facility.

The current paper covers the results of a study on the assessment of the compatibility of two Victorian soils using laboratory hydraulic conductivity tests. Hydraulic conductivity was measured with time permeating with water, leachate, methanol, and modified leachate using flexible wall permeameters (FWPs), consolidation cell permeameters (CCPs) and compaction mould permeameters (CMPs). The study indicates that the compatibility results are heavily dependent on the test method, and the commonly adopted flexible wall method does not usually produce significant change in the hydraulic conductivity whereas CCPs and CMPs produce considerable increases in hydraulic conductivity. The necessity for a better testing method is highlighted on the basis of these results. A new testing technique of zero lateral strain boundary condition was adopted and the results are presented for comparison.