The soil-rock mixture is an important construction material in practical engineering. Its physical properties, especially soil-water properties, are particularly important for on-site construction, while both matrix suction and electrical resistivity in unsaturated soils depend on the magnitude of moisture content, and a certain relationship can be established between the two physical quantities. Therefore, in this paper, we designed a matrix suction–electrical resistivity synergistic test device and conducted indoor physical tests on common soil-rock mixtures in the Chongqing area to investigate the correlation between matrix suction and electrical resistivity in soil-rock mixtures. The electrical resistivity comprehensive parameter was used to represent the electrical resistivity characteristics of rock and soil. Based on the experimental results, a matrix suction–electrical resistivity comprehensive parameter model applicable to soil-rock mixtures was established, and the sensitivity analysis of the model parameters was carried out. The results show that the soil-water characteristic curve of the soil-rock mixture has a double-step shape, and the shape of the curve under different compaction degrees is similar. The matrix suction and mass moisture content of the soil-rock mixture were positively correlated with the compaction degree. There was good consistency between the experimentally measured matrix suction and the matrix suction reflected by the electrical resistivity in the model. Moreover, the model curve was able to reflect the drainage process of pores in the soil for soil–stone mixtures with a bimodal pore size distribution, thus providing a new way to measure the matrix suction of unsaturated soil–stone mixtures in practical engineering.
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