Effect of Pore-Water Surface Tension on Tensile Strength of Unsaturated Sand: Fid-Bau Portal

Effect of Pore-Water Surface Tension on Tensile Strength of Unsaturated Sand

Jindal, Prateek / Sharma, Jitendra / Bashir, Rashid

Abstract Tensile behaviour of unsaturated sand was investigated both experimentally and theoretically. A custom-built direct tension apparatus was employed to perform direct tension tests on unsaturated sand specimens at different saturations levels and packing dry density. An attempt was made to understand the effect of surface tension of wetting liquid and loading rate on the tensile strength. The magnitude of the tensile strength was found to be dependent on saturation, dry density, loading rate and type of wetting liquid used. It was found that the tensile strength decreases, as the surface tension of the wetting liquid decreases and rate of loading increases; however, the decrease in tensile strength was found to be not proportional to the reduction in the surface tension and unsaturated specimens mobilize higher tensile strength than suggested by the capillary tube model. The experimental results were also compared with the predicted results from two theoretical tensile strength models: the micro-mechanical and the macro-mechanical models. Results predicted using the micro-mechanical model agreed well with the experimental results, but only at lower degree of saturation values. On the other hand, the macro-mechanical model followed the experimental trend for the entire range of saturation reasonably well. At reduced surface tension, both the models under-predicted the experimental results significantly.