###### Abstract
The surface roughness (wave distance \(<\)1 mm) of rock blocks, rather than the macroscopic rock block shape (wave distance \(>\)10 mm), is another important factor that affects the mechanical properties of a soil-rock interface [21]. In contrast, less attention has been placed on rock block surface roughness, especially in terms of numerical simulation analysis. Smooth particles or particle clumps are commonly used as rock blocks in SRMs. [PERSON] [13] constructed a mesostructure concept model of a rock block via a digital image processing technique, and the results showed that the boundary of the rock block should be smooth enough for meshing of the geometry model for the SRM. The influence of the rock block's surface roughness on the soil-rock interface remains unknown, especially for cementation SRMs, such as frozen SRMs. In recent years, with the rapid emergence of engineering construction in cold regions, a series of geotechnical problems have drawn the attention and interest of many engineers; however, studies on frozen soil-rock mixtures (FSRMs) are lagging behind frozen soil studies. The freezing properties of fine soil may differ significantly from those of coarse-grained soil [22]. This topic has rarely been studied. [PERSON] [23] studied the structure, strength, and deformation behavior of substrate from Suess Glacier, Southern Victoria Land, Antarctica, with a large-scale direct shear device. [PERSON] and [PERSON] [24] studied the effects of the ice content and normal load on frozen coarse granular debris shear strength properties. They found that the Mohr-Coulomb failure envelopes displayed very distinctive parabolic curvilinearity. [PERSON] et al. [25; 26] observed the freezing process of coarse-grained sand and the creep and strength properties of rock glacier samples in triaxial stress conditions. [PERSON] et al. [27] studied the influence of temperature, ice content, and normal stress on the shear strength of soil-rock mixtures via large direct shear tests; however, adjustments to the mesostructure (such as the rotation of rock blocks and changes) and the development of internal injures (crack propagation and breakage of rock blocks, etc.) were the crucial causes of the different macro-mechanical responses. Unfortunately, there are a few relevant clues toward frozen soil-rock interface properties, especially in terms of the morphology and cracking characteristics of the frozen soil-rock interface. According to freezing adhesion theory [28], ice adhesion is strongly affected by surface roughness. The contact angles of liquid decrease with the increasing surface roughness of material, where the smaller the contact angle, the higher the contact area, which causes stronger ice adhesion; however, as mentioned in previous studies detailed above, the soil-rock interface is the stress concentration area. The number of stress concentration points increases with an increasing surface roughness of rock blocks. The interactions between blocks and frozen soil matrices are more complex than the interactions at normal temperature. Microscopic representations and the deformation of the frozen soil-rockinterface and the influence of rock block surface roughness on mechanical properties still require further exploration and correlation with physical materials. Here, the aim of this research was to explore soil-rock interface properties and their influence on the strength of FSRMs. The purpose of this study was to investigate the macroscopic failure pattern and deformation of a FSRM sample. Moreover, the strength effects, interface morphologies, and crack propagation modes of soil-rock interfaces composed of rock blocks with different surface roughness are discussed. First, a series of uniaxial compressive tests and Brazilian tests of FSRM samples were conducted with different frozen temperatures. Simultaneously, to further understand the stress field, we used acoustic emission (AE) and ultrasonic plus velocity (UPV) methods during the compression tests.