Revised test protocols for the identification of dispersive soils

Abstract

Dispersive soils are prevalent in many areas of South Africa, and the presence of these soils has always posed a problem on road construction sites. The use of dispersive soils in roadway embankments and structures can lead to serious engineering problems if the soils are not accurately identified before use and appropriate mitigation measures taken. The current identification methods include the pinhole, double hydrometer, crumb and chemical tests, which are commonly used in combination to obtain the most reliable outcome. These laboratory tests, however, have not always been entirely consistent, whether used in combination or individually, and it is possible that the reason lies in the actual testing procedures. This paper discusses the observations made during a detailed investigation into the current methods used for testing and identification of dispersive soils. The test methods were thoroughly analysed and shortcomings identified. The differences resulting from different test techniques are examined and solutions to overcome the problems proposed. The paper concentrates mainly on the modification of the physical tests. The recommended solutions and process of identification are also proposed.