Abstract: The spatial variability of gravelly soil landslides arises from the combination of units with varying grain size compositions, degrees of difference, unit sizes, and arrangements. These combinations form fundamental structures, referred to as the basic structures of spatial variability, characterized by distinct strength levels, differences, unit sizes, and arrangements. Understanding the mechanical behavior of these basic structures is essential for assessing landslide stability through displacement characteristics. To address this, the study utilizes field investigations and empirical insights, combined with the discrete element simulation software PFC, to develop numerical models of strip blocks with varying basic structures of spatial variability. The mechanical behavior of these structures is analyzed under the application of a thrust force. The results indicate that the characteristics of the basic structures of spatial variability significantly affect the mechanical behavior of gravelly soil landslides. Interactions among units within these structures result in changes to stress distribution, deformation behavior, and stress-strain relationships, highlighting structural effects such as force transmission and anti-sliding resistance. As a result, displacement characteristics differ across various positions of the landslide. Local yielding and cracking develop from weak units to strong units within the structure, progressing from localized to overall failure. During small deformations, strong units primarily bear the load. In contrast, during large deformations, the load redistributes and concentrates on weak units. The deformation direction of the structure is oriented toward its weak units, which determines the magnitude and direction of the force distributed to the sliding zone. The displacement curve clusters on the landslide surface are shaped by the combined effects of the landslide structure, its mechanical behavior, and external forces. Accordingly, this study proposes a method for identifying landslide structural features based on displacement curve clusters, enabling the assessment of structural characteristics—or even specific structures—using these curves. This approach optimizes the layout of monitoring points, thereby improving the accuracy and reliability of landslide monitoring.

Key words: gravelly soil landslide, push-type, basic structure of spatial variability, mechanical characteristics, structural effects, displacement curve cluster