A universal method for assessing intrinsic expansiveness of soils.
Many of the attempts made over the past six decades to find a universal system for assessing expansiveness of soils using soil index data have failed to follow the basic principles of soil mechanics. By overcoming most of these limitations Gourley and Schreiner (1993a) developed a new procedure that allows comparison of intrinsic expansiveness of soil samples prepared to have stable micro-fabric and consistent stress history. In this research, the same procedure is used on twenty-seven natural clayey soil samples of varying geological, geomorphological and geographical origin obtained from Kenya, Sudan, Eritrea and South Africa. Each of these samples was tested for Atterberg limits, volume change behaviours and soil suction. Statistical analysis was conducted on different soil parameters derived from these tests to obtain a significant relationship with their intrinsic expansiveness using measured swell. The analysis confirmed that most of the significant relationships obtained contain swell index, C*5' showing the identicalness of the soil properties responsible for volume change behaviour of both saturated and unsaturated clayey soils. Depending on the cost and the significance, the analysis recommended three major models that can be used as a screening system in the assessment of intrinsic expansiveness. For any soil it is possible to obtain preliminary information regarding its intrinsic expansiveness using the cheapest of the recommended models that needs liquid and plastic limit tests and hydrometer analysis, which are the routine tests of geotechnical site investigation. A more detailed assessment can be achieved by including only t he shrinkage test. The most reliable assessment needs addition of consolidation test with the unloading stage. All of the models allow obtaining information regarding the intrinsic expansiveness of soils as early as site investigation stage for successful engineering design. Moreover, they are anticipated to promote worldwide exchange of information regarding these problematic soils.