On estimation of the constriction size distribution curve for cohesionless soils

Abstract

Internal stability against suffusion and filter efficiency are two important issues in geotechnical engineering. To well assess them, the constriction size distribution (CSD) of soil particles must be determined accurately. Both the Silveira model and the modified Silveira model have been widely used to mathematically simulate CSD curves and then to simulate filtration process in filters, for example. In the Silveira model, it was assumed that the constrictions are formed among groups of four soil particles at the loosest state, while the constrictions are assumed to be formed among four particles at any relative density in the modified model. We took a close look at the models and found that some groups of the possible four soil particles were not taken into account. As a result, the number of groups computed in the models is fewer than the number of actual unique groups. To demonstrate the effect of this difference on model prediction, we obtained the CSD curves using numerical and experimental tests and compared these curves with those predicted using the modified Silveira model and the Silveira model. Our comparison indicated that this difference has a significant effect on the CSD results using the modified Silveira model while it has a negligible impact on those calculated using the Silveira model. For the former, proper fitting factors are needed to have an accurate prediction of the CSD curves.

Keywords:

• constriction size distribution
• constriction size model
• probabilistic model
• cohesionless soils