Influence of grain gradation on undrained mechanical behavior of granular materials

©, 2015, Yantu Lixue/Rock and Soil Mechanics. All right reserved.This paper studies the influence of grain gradation on the undrained mechanical behavior of granular materials. A series of conventional undrained triaxial compression tests is carried out on two different materials (glass balls and Hostun sand), which have high degree of shape self-similarity. For each material, 6 samples with similar relative density and different gradations (Cu 1.1-20) are prepared, and then the samples are sheared. Test results show that the grain gradation has an obvious impact on the undrained mechanical behavior of granular material: both deviatoric stress level and undrained shear strength of two material samples decreases as the coefficient of uniformity (Cu) of the material increases, their variations tend to converge as coefficient of uniformity Cu surpasses 5. Based on the evolution of the value of the second-order work of the granular assembly during undrained triaxial loading, potential instability for the selected granular materials is also analyzed. The results demonstrate a significant influence of the grain gradation on stability: the higher of coefficient of uniformity (Cu), the larger of the potential of static liquefaction and the unstabler of materials.