A micro-mechanical approach to swelling behavior of unsaturated expansive clays under controlled drainage conditions

The focus of this work is to elucidate the effect of drainage conditions on the swelling behavior of unsaturated expansive clay soils using a new drainage controlled uniaxial swelling (DCUS) cell developed by the authors. The researc`h would aim at identification of the complicated micro-structures and distinguishing the mechanisms for the micro deferred alteration phenomena (the alteration of the swelling media by the end of the swelling process) of the porous swelling media, by swelling under K0 constraint, constant volume condition using scanning electron microscopy (SEM) technique taking into account the influence of drainage condition as the remarkable environmental factor. It shall be noted that the micro deferred alteration concerns the phenomena in which the swelling media would be altered (in particle's arrangement and size) in micro-scale, by the end of the swelling process and not during the swelling process. Three types of clay have been evaluated of wide range of plasticities. Results demonstrate the promotion of swelling pressure for specimens compacted statically at optimum moisture level and below the optimum value, as the drainage condition converts to multilateral drainage. Furthermore, irrespective of the type of clay, the sensitivity of swelling pressure value to the drainage conditions increases as the initial dry unit weight increases.