An Investigation of the Natural Microscale Mechanisms That Cause Volume Change in Expansive Clays.

摘要

The report concludes a study of the natural microscale mechanisms which cause volume change in expansive soils. The mechanisms were defined,and attempts were made to delineate the roles of the mechanisms in the volume change process by inferring the respective influence from observed physical,physicochemical,and mineralogical data. The three major microscale mechanisms which cause the volume change are clay particle attraction,cation hydration,and osmotic repulsion. These three major mechanisms can be represented by the total soil suction which is composed of two components,matrix and osmotic. The matrix component represents the clay particle attraction and cation hydration mechanisms. The osmotic component represents the osmotic repulsion mechanism. For the materials and range of moisture contents tested it was concluded that the clay particle attraction and cation hydration mechanisms play the major role in causing volume change. At higher moisture contents and higher cation concentration environments the osmotic repulsion mechanism provides a secondary influence on volume change. The thermocouple psychrometric technique was shown to be a simple,quick,and reliable method for evaluating soil suction.