Model Development and Experimental Verification for Permeability Coefficient of Soil–Rock Mixture

A soil–rock mixture consists of soil and broken rocks mixed proportionally, and it has more complicated seepage characteristics than pure soil or broken rocks. Current research on the seepage characteristics of soil–rock mixtures is still limited to empirical equations. This paper presents an improved theoretical compound seepage model for the permeability coefficient of soil–rock mixtures and relative concentrations of individual constituents (i.e., pure soil and pure broken rocks). This model considers the gap filled by particle grains in a soil–rock mixture under the same compaction level, as well as the reduced porosity of the mixture and the decreased permeability caused by the fine particles serving as a filler. A revised version of the seepage model of soil–rock mixtures consisting of a combination of the proposed model and the Kozeny-Carman seepage model is also suggested, and the precision of the model is verified against experimental results. The model provides a straightforward and effective quantification for the permeability coefficient of soil–rock mixtures.