This paper investigates the participation of the fines fraction in the load-carrying structure of binary mixtures of granular soils.For this purpose,various fractions of two fine sands were added to two coarse sands with the same particle size distribution,but different particle shape characteristics.Based on the results of 144 direct shear tests,it was found that fines participation in the load-bearing structure increases with fines content.At the same fines content,the participation of the fines in the load-carrying structure of loose mixtures is greater than in samples that were initially compacted.In addition,it was observed that fines participation rises with the increase in the average size of the fines fraction. This paper investigates the participation of the fines fraction in the load-carrying structure of binary mixtures of granular soils. For this purpose, various fractions of two fine sands were added to two coarse sands with the same particle size distribution, but different particle shape characteristics . Based on the results of 144 direct shear tests, it was found that fines participation in the load-bearing structure increases with fines content. At the same fines content, the participation of the fines in the load-carrying structure of loose mixtures is greater than in samples that were initially compacted.In addition, it was observed that fines participation rises with the increase in the average size of the fines fraction.