Abstract: To research the effect of seepage on mesostructural change of soil-rock mixtures, a laboratory seepage test was applied on soil-rock mixtures with the ratio of 7:3. Nuclear magnetic resonance (NMR) analysis system was applied to monitor the mesostructure change of soil-rock mixtures under different hydraulic gradients and different time periods, such as pore distribution, movable fluid porosity, etc. According to NMR results, it was found that: 1) Seepage pressure caused change of soil-rock mixture properties such as pore distribution, pore size and pore connectivity, which can damage structural characteristics of soil-rock mixtures. 2) With the increase of hydraulic gradient and time, porosity, mobile fluid porosity and NMR permeability all increase, and the NMR permeability growth rate is increased. Besides, mobile fluid porosity has a more significant contribution to permeability than irreducible porosity. 3) Under low hydraulic gradient, the coefficients of Kua and Kca have small change, which reveals low erosion scales and low degree of seepage failure. Under high hydraulic gradient, the coefficients of Kua and Kca have significant change and erosion scales become higher. The soil-rock mixtures form seepage channel and seepage failure.

Key words: soil-rock mixtures, nuclear magnetic resonance (NMR), mesostructure, pore distribution, NMR permeability, erosion