Tensile Strength of Unsaturated Sand

A theory that accurately describes tensile strength of wet sand is presented. A closed form expression for tensile strength unifies tensile strength characteristics in all three water retention regimes: pendular, funicular, and capillary. Tensile strength characteristically increases as soil water content increases in the pendular regime, reaches a peak in the funicular regime, and reduces with a continuing water content increase in the capillary regime. Three parameters are employed in the theory: internal friction angle (at low normal stress) ${\varphi }_t$ , the inverse value of the air-entry pressure $\alpha$ , and the pore size spectrum parameter $n$ . The magnitude of peak tensile strength is dominantly controlled by the $\alpha$ parameter. The saturation at which peak tensile strength occurs only depends on the pore size spectrum parameter $n$ . The closed form expression accords well with experimental water retention and tensile strength data for different sands.