Modeling of tensile strength on moist granular earth material at low water content

While most research has mainly focused on the volume change, flow, and shear strength of unsaturated earth materials, investigations of tensile strength of unsaturated earth materials especially granular materials have not received much attention except for cemented and clayey materials. Thus, direct tension experiments were carried out to quantify the actual magnitude of tensile strength induced by water in moist granular soil at especially low water contents (w<4%). The magnitudes of the measured tensile strength are significantly different from zero. A simple experimental tensile strength model is proposed. Practicing engineers can use this model for approximate estimation of the tensile strength of unsaturated granular soils without experiments and for precise design or analysis of most engineered facilities relying on the unsaturated granular soils in the vadose zone. The experimental data are also compared with a theoretical model developed for monosized spheres at low water contents, and its application for a real granular earth material having a variety of particles is discussed. The nonlinear behavior of the tensile strength for moist granular soil is appropriately simulated with a model.