LAUSR

Abstract Fault activity is a factor causing geological disasters and controlling their spatial distribution. The information on fault activity can be recorded by the microstructure of the fault gouge sliding surface, which provides an approach to study the macroscopic mechanical behavior of faults. In this study, the ring shear test was used to simulate the shear sliding behavior of a fault gouge under different stress states and water contents, and the microstructure of the shear sliding surface was quantitatively analyzed using scanning electron microscopy (SEM). The results revealed an evident relationship between the microstructure and macroscopic mechanical properties of the fault gouge. The microstructure, represented by sliding scratches, was primarily created by the movement of coarse particles, such as sand and quartz. An index of the sliding scratch ratio was proposed to characterize the microstructure. The sliding scratch ratio is negatively correlated with water content and normal stress, and a multivariate model of sliding scratch ratio was established with water content, normal stress and coarse particle contents. Allying the model to natural scratches of the fault gouge reveals that the observed sliding scratches were formed during slope sliding, which proves the influence of fault on the occurrence of the studied landslide. Influenced by the “Gully Land Consolidation” projects in the Loess Plateau of China, the groundwater level may increase and then weaken the shear strength of fault gouge, reducing the stability of slopes crossed by fault zone. Therefore, more attention should be paid to potential geological disasters induced by faults in gully filled areas