Heterogeneous characteristics of stress transmission within finer fraction of gap-graded soils and its relevance to suffusion\suffosion

The heterogeneous transmission of particle stress within the finer fraction has a critical effect on the development of suffusion\suffosion in gap-graded soils, while quantitative evaluations on it are still needed. To this end, the stress transmission within the finer fraction of gap-graded soils with packing fabrics covering all the four typical packing fabrics under isotropic confining pressure were studied using discrete-element simulations. The finer particles with at least one contact, termed connected finer particles are classified into two groups that carry obviously different particle stress and have different contact features: primarily- and secondarily-stressed finer particles, which is well indicated by the gap in the particle stress contribution distribution of the connected finer particles, and meanwhile by the transition limitations of particle connectivity. The primarily-stressed finer particles always play a primary role in supporting the soil skeleton, while the role of the secondarily-stressed finer particles is closely related to the stress-reduction factor, alpha. The transition limit was found to be alpha = 0.146-0.191, over which the secondarily-stressed finer particles play a primary role in supporting the soil skeleton, while below which they play a secondary role. It also sets the borderline to identify the suffusion and suffosion susceptibility of gap-graded soils.