Effect of Water Quality on the Dispersive Characteristics of Soils Found in the Morwell Area,Victoria, Australia

The paper details an investigation into non-dispersive soils, carried out as part of the geotechnical site investigation for the Morwell River and Strzelecki Highway relocation project at Morwell, Victoria, Australia. The investigation revealed that the quality of water used for Emerson testing could change the concept of soil dispersion. Water quality, in terms of total dissolved solids (TDS) in water, changed the dispersive properties of clays found in the area. Increase in TDS tends to decrease the dispersive/erosive characteristics of soils. As a consequence, soils can be identified as non-dispersive if the TDS levels of the water used in testing ranges from 100 to 200 mg/L. This was further evident in pinhole tests carried out on dispersive soils in river water (as opposed to distilled water) with a TDS of 200 mg/L. The pinhole testing for dispersive soils in river water did not show any erosion, whereas the same samples showed higher erosion in distilled water. Further research was conducted into establishing a turning point TDS (where water quality would not allow dispersive clays to form a colloidal cloud around a soil sample or where water quality will stop the dispersive/erosive characteristics of dispersive clays). The turning point TDS was identified as 105 mg/L.