Der Selbstfiltrationsindex als Suffosionskriterium für nichtbindige Erdstoffe

The Self-Filtration-Index as an internal stability criterion for granular soils.

Soils susceptible to internal erosion are characterized by a structure consisting out of a load bearing skeleton formed by the coarser particles and embedded fine-grained material. Due to seepage through such soils, fine particles can be eroded if the skeleton is unable to catch these moving grains at the constrictions of the pore network. This process of washing out fine particles is called suffusion. If suffusion cannot occur due to geometrical considerations, soils are called internally stable. The article describes a simple method to assess the internal stability of non-cohesive soils based on the slope of the lower part of its grain size distribution. Suffusion is considered as spatial filtration, were the skeleton acts as filter to catch the embedded mobile particles. A Self-Filtration-Index ISF is introduced which expresses the geometric ratio of the separated grain-size-distribution into the skeleton and the mobile fines. Internal stability of a representative grain-size-distribution and the potential of suffusion can be quantified by ISF. The amount of eroded mass can be estimated.