Experimental study on strength characteristics and micromechanism of rubber-sand mixtures

To illustrate the variation laws of strength characteristics and micromechanism of rubber-sand mixtures, a series of laboratory tests including direct shear tests, unconfined compressive strength tests and scanning electron microscopy analysis are conducted to study the effects of rubber fraction, vertical stress and curing time on the shear strength, internal friction angle, stress-strain characteristics and unconfined compression strength of sand-rubber mixtures. Moreover, the variations of microstructure of rubber-sand mixtures are qualitatively evaluated, and the micromechanisms of the mixtures are also discussed. The experimental results show that the density of rubber-sand mixtures decreases linearly with the increase in rubber fraction. Addition of rubber chip can reduce the shear strength and unconfined compression strength of mixtures. The relationship between internal friction angle and rubber fraction is linear. The stress-strain characteristics of rubber-sand mixtures exhibit a tendency to change from “brittle” to “ductile” with the increase in rubber fraction. Some force chains are generated to support the external loading when the rubber fraction is low. Rubber chips often play an important role in preventing the slipping and buckling of sand particles. The rubber-sand mixtures with high rubber fraction mainly rely on the large deformation of rubber chips to support the loading.