Directional arrangement of phyllite fragments in phyllite talus slope at the eastern margin of the Tibetan Plateau.

Phyllite fragments are essential for accumulating and generating talus slope at the toes of hillslopes, however, how they are linked to slope failure remains unknown. This paper reports the directional arrangement of phyllite fragments (DAPF) in phyllite talus slope at the eastern margin of the Tibetan Plateau. Field investigation, mathematical statistics and model experiments were performed in order to systematically understand the influencing factors, which include fragment shape, flat ratio, dip angle (α), and fine particle content (c). The results show that the quadrilateral fragment generates a similar imbricate structure more easily than the triangular and rod fragments in the phyllite talus slope. Additionally, the flat phyllite fragments easily accumulate as imbricated structures on the phyllite talus slope. When the dip angle (α) is in the range of 20°–30°, the minimum orientation ratio (P) is more than 50%, which means that the DAPF phenomenon is more obvious in the phyllite talus slope. For the fine particle content (c) at the same dip angle (α), the minimum orientation ratio (P) is 54%, and the minimum orientation ratio (P) correlates positively with the fine particle content (c). Therefore, compared with the homogeneous talus slope, the phyllite talus slope displays a special DAPF phenomenon. This study provides a valuable reference and presents novel knowledge for risk assessment and engineering design against the phyllite talus slope failure mechanism. [ABSTRACT FROM AUTHOR]