Abstract: Soil-rock aggregate mixture is one type of non-homogeneous dispersion material mixed by rock and soil. Its shear strength is mainly affected by the moisture content, rock content, particle gradation and the degree of compaction, etc. On the basis of previous studies and the lab large-scale direct shear tests, this study considers the effect of gradation parameters, attains the required degree of compaction level by controlling the quality and volume of samples, and analyzes the influence of the main parameters on the shear strength. The results show that, in well-graded case, as nonuniformity coefficient increases, the shear strength increases first and then decreases, and achieved peak when the coefficient is around 22.99, while little impact by the coefficient of curvature. The shear strength of soil-rock aggregate mixture increases with the increasing rock content and compaction degree respectively, but the increases less when the degree of compaction is more than 92.5%. The shear strength decreases after the first increase with the increasing moisture content, and peaks at near optimum moisture content. Based on the Matlab’ multivariate linear regression analysis, the order of primary and secondary influencing factors on the shear strength is rock content > moisture content> degree of compaction > nonuniformity coefficient > coefficient of curvature. Through the regression analysis of test results, fitting formulas of it’s shear strength are obtained with correlation index R2 bigger than 0.9.

Key words: soil-rock aggregate mixture, direct shear tests, grading parameter, compaction degree, shear strength