Abstract: At present, there is no suitable scale method for seepage and seepage stability test of coarse soil. Based on the equivalent alternative method, a new scale method for seepage and seepage stability test was proposed by keeping the particles finer than d30 (the grain size corresponding to 30% finer in particle size distribution) and particles finer than 5 mm unchanged. If the particle content finer than 5 mm in the original particle size distribution is larger than or equal to 30%, the oversized particles are replaced by the particles ranging from the largest allowable particle of specimen and particles larger than 5 mm; if the particle content finer than 5 mm in the original particle size distribution is less than 30%, the oversized particles are replaced by the particles ranging from the largest allowable particle of specimen and particles larger than d₃₀. A list of seepage and seepage stability tests on coarse soils was carried out to verify the proposed scale method. The results indicate that the proposed scale method is suitable and effective. The seepage failure mode does not change after scaling, the permeability of the coarse soils after scaling is also close to that of the original soils, and the critical hydraulic gradient and failure gradient of seepage instability are basically consistent with the original soils. Consequently, the seepage and seepage stability characteristics of the coarse soils after scaling can represent the original coarse soils.

Key words: coarse soil, seepage and seepage stability test, scale method, equivalent alternative method