Seepage plays a crucial role in the mechanical behavior and damage modes of geotechnical materials. In this work, based on the unsteady seepage equation, a hydraulic coupling numerical simulation algorithm combining interpolation finite difference method (FDM) and discrete element method (DEM) is proposed to explore the intrinsic mechanism of the interaction between geotechnical materials and the seepage process. The method involves constructing an irregular fluid calculation grid around each particle and deriving the two-dimensional unsteady seepage governing equation and its stability conditions using interpolation and the FDM. The efficiency of the seepage calculation was investigated by numerically varying the parameters of the difference format. The method was applied to simulate the generation of gushing soil in a sinking area of a sunk shaft under hydraulic drive conditions. The results indicate that the improved FDM can effectively simulate the two-dimensional seepage of soil with high calculation efficiency. The hydraulic conductivity and time step positively correlate with the calculation efficiency of the difference format, whereas the spatial step has a negative correlation. The proposed method also accurately reflects the process of gushing soil damage. These results provide a solid theoretical basis to study the geotechnical seepage field and its associated damage mechanisms.

In cold regions, the strength of soil-rock mixture (SRM) is gradually reduced by freeze-thaw (F-T) cycles, in order to study the deterioration mechanism of mechanical properties of SRM under F-T cycles, indoor triaxial tests were carried out by taking into account the effects of the number of F-T cycles, the rock content and the confining pressure, and combined with the numerical simulation of particle discrete elements to analyze the microscopic deformation of the failure characteristics of the SRM, as well as the development law of the shear surfaces and the contact force chain. The results showed that the F-T cycle did not have much effect on the stress-strain curve morphology, but the peak and initial slope of the stress-strain curve increased with the increase of the rock content. The F-T cycle has a more obvious deterioration effect on the failure strength, elastic modulus and cohesion of the samples, but has less effect on the internal friction angle. The failure strength and elastic modulus of the samples increased with the increase of the confining pressure. With the increase of rock content, the failure strength, elastic modulus and internal friction angle of the samples increased, but the cohesion decreased. Under the flexible loading condition, the SRM samples exhibit swell failure, and the shear zone formed after failure is roughly distributed in an X shape, and the failure morphology of the SRM samples, as well as the morphology and size of the shear zone, are all affected by the rock content and the confining pressure. The contact force between particles in the SRM samples increases with the increase of rock content, and the chain of coarse force is mainly distributed in the vicinity of rock particles, but the F-T cycle will weaken the contact force between particles, thus reducing the strength of the SRM.