Research on the effect of rock content and sample size on the strength behavior of soil-rock mixture

The mechanical behaviors of soil-rock mixture (S-RM) are very complicated and significantly affected by its rock block content and gradation composition. A systematic study was performed on how the strength and failure characteristics of S-RM can be affected by the rock block content, the “oversize rock block” processing methods adopted, and the sample size in triaxial tests. Both the deviator stress ratio and friction strength of S-RM increase together with the rock block content, but the former tends to decrease as the confining pressure increases. In the case of S-RM samples with the same gradation, these two parameters tend to decrease as the sample scale becomes larger. The development of deviator stress over axial strain of samples prepared using the equal quantity substitution method is similar to that of the samples of the natural gradation. During the shearing process, some large rock blocks in S-RM will be broken. The breakage mode of the rock blocks can be primarily divided into four categories according to its mechanism, namely, disintegration, corner breakage, fracturing, and breakage along bedding faces. As a result of the breakage, the strength envelope curve of S-RM follows a power function.