Geometrical method for assessing the internal stability against suffusion of cohesionless soils based on controlling constriction size

Abstract

Suffusion is an internal erosion mechanism which can occur in cohesionless soils composed of a bimodal structure, where a sufficient seepage force leads to the detachment of loose finer particles and their transport through the constrictions formed by the primary coarser skeleton. The assessment of the susceptibility of cohesionless soils to suffusion is based on the evaluation of their capacity to filter erodible particles. Compared to models based on the grain size distribution analysis of soil, the approaches focused on the constriction size distribution are most suitable to provide a physical description of soil retention capacity. However, some important soil parameters are not taken explicitly in these models. In this research work and on the basis of the results of an experimental study conducted on mixtures of sands (dmax = 2 mm) and fines (dfmax = 100 μm) under different testing conditions, the main parameters that can influence the soil’s response to erosion were identified. Considering the contribution of these parameters to the suffusion development probability, new empirical formula has been proposed to calculate a control diameter characterizing the soil coarser fraction. This control diameter will be compared with the characteristic diameter of the loose finer fraction to assess the soil stability against suffusion. The application of the proposed model to the tested soils gives a good stability assessment as compared to other models.