They were able to establish a correlation between the relative breakage rate, normal stress, and stone content. The results indicate that particle breakage increases with increasing normal stress and stone content. Another study by [PERSON] et al. [8] utilized laboratory testing to develop a direct shear numerical model for analyzing the strength parameters of soil-rock mixtures. They also quantified particle breakage and demonstrated a hyperbolic connection with normal stress. Microscopic analysis revealed that the soil-rock mixture experiences both tensile and shear failure under shear stress. Despite compositional differences, previous academic studies [10; 11; 12; 13; 14; 15] on soil-rock mixtures and similar materials have shown consistent mechanical characteristics. These findings offer valuable insights for further research on soil-rock mixtures. [PERSON] et al. [10] and [PERSON] et al. [11] studied the effect of scaling on the shear strength of coarse-grained soil and reported that the shear strength index is strongly influenced by the particle size. [PERSON] et al. [12] investigated the particle breakage of rockfill during triaxial shear testing under varying conditions of gradation, relative density, and confining pressure. Their findings demonstrated that particle breakage is significantly affected by gradation and confining pressure. They developed a relationship function based on fractal dimension to analyze the strength and dilatancy characteristics of the gradation and confining pressure. Additionally, [PERSON] et al. [13] developed a relationship between the breakage index and the gradation equation using the concept of the gradation equation. They established an evolution model of gradation with stress-strain by establishing a relationship function between the breakage index and stress-strain state. This model can be used to predict the change in the particle breakage process during the shear stage. [PERSON] et al. [15] established the repeated compaction characteristic curve of graded macadam through repeated compaction and screening of graded macadam. The correlation between fractal dimension of particle size distribution and repeated compaction times, water content, and dry density were analyzed. Particle breakage in granular soil-rock mixtures is a critical engineering parameter that significantly influences their strength and deformation characteristics [16; 17; 18]. A precise characterization of this parameter is essential for analyzing the engineering strength and stability of such mixtures. To gain a better understanding of the particle breakage law during triaxial shearing of soil-rock mixtures, the breakage index \(B_{W}\), introduced by [PERSON] et al. [5], is enhanced to more accurately measure the particle breakage characteristics. This improvement aims to simplify the particle breakage index test and facilitate a comparative evaluation of the degree of particle breakage. Furthermore, a fractal dimension will be employed to validate the test's validity. The dilatancy characteristics will be elucidated by examining the phase transition stress ratio under different dry density and confining pressure conditions. The gradations before and after shear will also be analyzed. This paper investigates the deformation strength characteristics of soil-rock mixtures using an improved breakage index, \(B_{C}\). The concept of the failure dilatancy rate is introduced, demonstrating the correlation between the breakage index and failure dilatancy rate and explaining its dilatancy behavior. This study establishes a link between the breakage index and the nonlinear internal friction angle to demonstrate the shear strength of the sample.