## 1 Introduction
This iterative freeze-thaw cycle will cause damage to the micropore structure and mechanical properties of the soil-rock mixture, which will lead to the unstable slide of slope engineering. In recent years, many experts and scholars have gradually paid attention to the influence of freeze-thaw cycles on the mesopore structure and macroscopic mechanical properties of soil-rock mixtures in low-temperature environments [11]. [PERSON] carried out triaxial and nuclear magnetic resonance tests on FSRM (frozen soil-rock mixture) at different temperatures to elucidate the mechanism of the internal degradation of FSRM. The results show that under the action of temperature rise, the locking effect of the particle ice film is weakened, and the increase in water weakens the strain energy generated by the work of interlocking friction between particles in the shear process, which leads to the decrease in strength [12]. [PERSON] carried out research on the effect of freeze-thaw cycles on the mechanical properties of triaxial and shear tests of soil-rock mixtures with different water content and stone content [13]. The results showed that under repeated freeze-thaw cycles, the triaxial compressive strength of the soil-rock mixture has a linear relationship with the confining pressure, with the mechanical strength showing an increasing trend with the gradual increase in the confining pressure [14]. The number of freeze-thaw cycles and the stone content had a significant impact on the cohesion and internal friction angle. In addition, repeated freeze-thaw cycles weaken the bonding strength between soil and stone and between stone and stone, weakening their macroscopic physical properties [15]. [PERSON] conducted the indoor freeze-thaw cycle test and shear test of the earth-rock mixture and detected the microscopic pores of samples with different freeze-thaw cycles based on the nuclear magnetic resonance system, discussing the influence of freeze-thaw cycles on the micropores and macroscopic mechanical properties [16]. The experimental results showed that with the increase in the number of freeze-thaw cycles, the internal porosity showed a trend of first increasing, then decreasing, and then increasing. The skeleton structure inside the specimen would loosen, with the peak shear strength showing a clear decreasing trend [17]. In summary, freeze-thaw cycling has obvious effects on the micropore structure and macroscopic mechanical properties of soil-rock mixtures. However, through previous studies, it can be found that most studies mainly analyze the macroscopic mechanical behavior of soil-rock mixtures, and there are few studies on the microstructure of soil-rock mixtures under cyclic freezing and thawing. The detection of soil-rock mixtures by nuclear magnetic resonance systems also has certain limitations. There is also a lack of research on the establishment of the internal relationship between the microscopic parameters of the soil-rock mixture and the macroscopic mechanics. So, in this paper, an indoor freeze-thaw cycle test and a uniaxial compression test were carried out on the soil-rock mixture taken from the surface layer of a graphite mine in Jixi City, Heilongjiang. Based on the electrochemical comprehensive test system, the impedance spectra of soil-rock mixtures under different freeze-thaw cycles were detected. The mechanism of freeze-thaw cycles in the microscopic pore structure of the soil-rock mixture was analyzed with the characteristic parameters of impedance spectroscopy, with the intrinsic relationship between the characteristic parameters of the impedance spectrum and the macroscopic mechanical properties established. In addition, the uniaxial compression test of the soil-rock mixture under different freeze-thaw cycles was numerically simulated by combining the particle flow program (PFC2D), and the crack propagation law of soil-rock mixturesunder different freeze-thaw cycles is discussed.