Abstract: In order to study the evolution law and physical mechanism of permeability performance of compacted clayey soil-rock mixtures, a series of dynamic compression tests and triaxial permeability tests were conducted. The compaction curves of soil-rock mixtures show obvious unimodal patterns similar to those of pure clayey soils when rock content CR < 70%. When CR > 70%, the compaction effect begins to decline. A peak for the maximum dry density of the mixtures can generally be achieved when the CR is around 70%. In addition, increasing CR will decrease the optimum water content of the soil mixtures, but this almost does not change the water content of clay matrix at the optimum compaction state. Clay matrix can be compacted to the densest state when CR < 30%, beyond which the clay matrix void ratio gradually increases. When CR > 70%, the clay matrix void ratio presents a sharp increase. The permeability shows constant or a slight decrease as the rock content increases from zero to about 30%. The lowest permeability can be achieved when CR is around 30%. Beyond this amount, the permeability coefficient increases rapidly with a further increase in rock content. Based on the soil-rock meso-structural distribution and clay matrix void ratio, a concept model for flow path in clayey soil-rock mixtures was proposed. The flow path in compacted soil-rock mixtures can be divided into four kinds: low permeability path in compacted clayey soil matrix, ultra-low permeability path in compacted clayey soil matrix with gravels, medium permeability path in soil-rock interfaces, high permeability path in skeleton voids of rock aggregates.

Key words: soil-rock mixtures, clay matrix, rock content, compaction, triaxial permeability, meso-structure