Abstract: As for the accumulation landslides with steep-sliding planes, the calculation of the anchorage depth of anti-sliding piles is one of the key technique problems of support structure design. Taking the K285 landslide along Neijiang-Liupanshui railway as instance, based on the similarity principle, the physical modelling tests of the interaction between anti-piles and sling mass is adopted to study the stress state and failure characteristics of sliding bed in front of the piles. The results show that: (1) The resistance force of sliding masses in front of piles is triangular distribution; and the resistance force at the sliding belt is the largest. (2) The maximum bending moment point of the piles decrease gradually along the piles with the loading increasing, and the bedding rock in front of the piles occurred wedge fracture, of which the depth corresponded to the maximum bending moment position. (3) As the length of the anchorage section increase, the position of wedge fractures of the bedding rock in front of the piles gradually move closer to the sliding surface; and its fracture angle decreased gradually. Based on the above analysis, the anchorage depth can be divided into non-resistance anchorage section, invalid anchorage section and effective anchorage section. Furthermore, the length formula of such three sections and the total anchorage depth of the anti-pile are deduced respectively. When the research results are applied to optimize the anchorage depth of the anti-slide piles of K285 landslide, the total length of the piles is reduced by 6 meters on the basis of ensuring the effectiveness of the treatment. The research has important engineering practical value.

Key words: steep-sliding accumulation landslide, anti-sliding pile, anti-sliding pile interacts with the surrounding rock and soil, physical modelling test, anchorage depth, rupture angle