Predicting permeability coefficient in soil-rock mixtures using parameters from the negative exponential continuous grading equation

Abstract

Soil-rock mixtures (SRMs) are widely utilized for embankment filling of highways in mountainous areas. The permeability characteristics of SRMs must be investigated as mountain highways are often exposed to strands of rainwater subjected to extreme rainfall. For the same species of SRM, its permeability is determined by its pore distribution and grading characteristics, which can be considered as an expression of particle grading and pore parameters. The predictive model of the SRMs permeability coefficient encompassing gradation coefficients and porosity was proposed based on the negative exponential continuous gradation equation and the Kozeny–Carman model. The applicability of the prediction model was verified based on the existing literature and performing SRMs seepage tests. The findings indicated that the permeability coefficient formula for SRMs established on the particle grading parameters and porosity was reasonable. Nevertheless, its current applicability is limited to the prediction of permeability coefficients for continuously graded SRMs. Consequently, further investigation is required to assess the suitability of the model for intermittently graded SRMs.