Abstract: Shallow quaternary deposited and sedimentary soil-rock mixtures (SRMs) are widely distributed on the earth. One of the most effective approaches to solve the increasingly complex geotechnical problems is to study the mechanical properties of SRMs from their structural characteristics. At present, the quantification of the structure of SRMs is mainly and indirectly described by macroscopic indicators, such as density, stone content, and void ratio; while the multiscale correlation between microscopic and mesoscopic structural indexes is still a technical bottleneck. To better understand the influence of the structure on the mechanical behavior of SRMs, the layered distribution form of rock blocks created in the deposited and sedimentary evolution was quantified via the standard variance based on the idea of comprehensive structural potential. The structural parameter (m_s) was defined as the ratio of the deviator stress of uniform SRMs to that of non-uniform SRMs. The variations of m_s with the axial strain (ε₁), the non-uniformity (s) and the confining pressure (σ_3c) were examined, and the quantitative expression of m_s was obtained and incorporated into an elastic-plastic constitutive model with double yield surfaces. The results show that the variation of m_s well reflects the influence of the layered structural characteristics on the mechanical behavior of SRMs. The comprehensive structural potential of SRMs is released almost completely as the axial strain reaches 5%, and the feature value (i.e., m_s (5%)) reflects the macroscopic influence of structural characteristics on the mechanical behavior of SRMs. Meanwhile, the modified constitutive model with m_s improves the accuracy of the deviator stress by about 28%. It proves that the modified constitutive model can reasonably reflect the macroscopic mechanical properties of layered SRMs.

Key words: soil-rock mixture, layered, structural characteristics of rock blocks, structural parameter, modified constitutive model