Mechanical properties hysteresis of unsaturated granular soil

Abstract

The soil-water characteristic curve reveals that the studied very dense crushed sand and gravel proves unable to maintain a saturated state under a positive matric suction. Capillary physics explains how this could result from the presence of millimetre size pores. An innovative pendular model gives insight on why consolidated drained triaxial tests give higher mechanical properties after drying followed by wetting than after drying alone. The model shows how particle tilting induced by shearing may squeeze pendular water into the funicular regime and provoke drainage as observed during both contraction and dilation phases. It also highlights that particle tilting produces changes of matric suction within pendular water and why dilation increases with applied matric suction while confinement stress yields the opposite.