Study on the anchorage depth of anti-sliding piles in steeply slipping colluvium landslides
In order to study the anchorage depth of anti-sliding piles in steeply slipping colluvium landslides, the anchorage depth is divided into non-resistance anchorage section, invalid anchorage section and effective anchorage section according to the stress of the anchorage section of the piles and the working state of the bed rock mass. Three model tests of the bed rock destructive characteristics were carried out with geometric similarity ratio equal to 50 and with different anchorage depth of the piles. The K285 landslide typical section in Neijiang to Liupanshui railway was used as the prototype in the model tests. The results show that, in the first and second model test, the maximum bending moment point of the piles is gradually going down along the piles with the loading increase and the bed rock mass before the piles is wedge fracture. The wedge failure depth is corresponding to the maximum bending moment position, and the rupture angle is 35° to 38°, the diffusion angle is 23° to 24°. In the third model test, the maximum bending moment point is located near the slipping surface before the piles, and the local damage in the bed rock mass before the piles is also in the same position. In the three model tests, the anti-slide piles are bent. On this basis, the calculation formula of the non-resistance anchorage section, the invalid anchorage section, the effective anchorage section and the total anchorage depth are obtained respectively. Combined with numerical analysis, the rupture angle estimated value is calculated to the mean value of slipping surface angle and bed rock internal friction angle, and the diffusion angle estimated value is to take 24°. According to these formulas, the single anti-slide pile length of the original design in K285 landslide can be reduced by 6 m. The research has important economic and social benefits.