The characteristics of particle breakage and shear strength of soil-rock aggregate with six rock contents under six normal pressures were studied from macro and mecro perspectives by large-scale direct shear test

particle observation test and particle sieving test. The relationship between macroscopic shear strength properties and mecroscopic particle breakage characteristics was established

thus further revealing the influence mechanism of rock content and particle breakage on the shear strength characteristics of soil-rock aggregate. The results showed that particle breakage mainly occurred near the shear plane. The breakage morphology can be divided into surface grinding

local fracture

complete fracture and complete breakage

resulting from the stress concentration caused by uneven contact forces between particles. Due to particle breakage

the content of fine particles increased

coarse grains decreased

and intermediate grains fluctuated. The relative particle breakage Br increased with the increase of normal pressure ?n or rock content P5

which accorded with the function of two variables. With the increase of normal pressure ?n

the shear strength τ increased nonlinearly and met the modified M-C strength criterion. When the rock content P5 increased

the cohesive force c0 of soil-rock aggregate decreased

the internal friction angle ?0 of soil-rock aggregate increased

and the non-linear parameter Δ? increased. Particle breakage was the direct cause of non-linear strength characteristics of soil-rock aggregate.