A structural bounding surface constitutive model for unsaturated soils and its verification

Most soils have both unsaturated and structural properties. The establishment of a constitutive model of unsaturated soils considering the structure is of great significance for analyzing the mechanical properties of unsaturated soils. On the basis of the volume variation equation of saturated structural soil, the influence of matrix suction is considered for the structural parameters, combined with the LC yield curve of BBM model, a new volume variation equation of unsaturated structural soil is established, and the deconstruction law is introduced to consider the structure disturbance during isotropic compression under constant suction. The structural strength and its decay law are introduced to consider the influence of the structure on the shear strength, and the deformation characteristics of the unsaturated soil in the three-dimensional state are described based on the bounding surface plasticity theory framework. Parameter calibration and model verification were carried out using the experimental data of unsaturated intact loess in Gorgan area and Xi'an Q₂ unsaturated intact loess. The results show that the established model can effectively predict the deformation characteristics of unsaturated structural soil.