Since the catastrophe of the red-bed soft rock is closely related to the water-rock interaction on the surface

the research on the interface process is of great significance to reveal its catastrophic mechanism. However

at present

the study on the red-bed soft rock softening mainly focuses on the macroscopic phenomenological characteristics

and the study on its interface process is still in the exploration and initial stage

which needs further improvement. The characteristics of the interface process of the red-bed soft rock softening are analyzed

which shows the soft rock particles on the water-rock interface are continuously dissolved

and the water diffuses in the soft rock to form a new water-rock interface. Based on this result

the standard entropy of soft rock is established to characterize the soft rock softening

and the evolution of the standard entropy is consistent with that of the softening and disintegration of soft rock over time. At the same time

the dynamics model of soft rock softening interface is constructed by using the Fick diffusion law

which can describe the formation rule of the water-rock interface well. Finally

in the DEM-CFD model of red-bed soft rock

the particle connection fracture in soft rock softening process represents the generation of water-rock interface. Comparing the dynamics models of the interface process

a better fitting result is achieved. The results of this study have certain significance for the exploration of soft rock softening interface.