One-dimensional compression tests and deformation rules of unsaturated soils

In order to study the deformation rules of unsaturated soils under lateral confinement, a series of one-dimensional compression tests are carried out under controlled initial dry density and matric suction. The concepts of tangent compressibility coefficient and tangent volume compression coefficient are proposed. Results of the study indicate that the tangent compressibility coefficient and tangent volume compression coefficient decay exponentially with the increasing net vertical pressure. Based on this law, two empirical models, which can describe the variations of void ratio and vertical strain with the net vertical stress, are established. The rationality of the proposed models and their applicability to various types of unsaturated soils are verified using the test data in other literatures. The proposed models can be used to calculate the mean compressibility indexes within arbitrary pressure interval, to compute the slaking deformation of unsaturated soils due to the increase of moisture content, and also to describe the variation of void ratio with the matric suction.