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The Yudonghe landslide is located in a upcoming reservoir region of a 233-m-high Shuibuya rockfill dam, 2,300 m away from the dam site. It consists of a massive landslide with upper and lower segments and two secondary slides, i.e. an eastern secondary slide and a western secondary slide. In this paper, values of factor of safety (FS) for various masses were calculated in a scenario of reservoir impounding-induced increase in groundwater levels, using a method of three-dimensional (3D) limit equilibrium. Results showed that the smallest value of FS for the massive landslide is 1.12 computed on the presupposition of reactivating along a bottom slide zone in case of an earthquake. The smallest FS value of the lower slide mass is 1.12 in a possible direction, given earthquake occurrence and a groundwater level of 225 m above the sea level. This FS value shows that the lower slide mass is stable in case of groundwater increasing. In addition, by the calculation of the 3D limit equilibrium method, the FS value of the east secondary slide is approximately 1.0 in different groundwater levels under consideration of earthquake occurrence, which reflects that this mass is prone to reactivate when external factors are taken into effect.

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The interaction mechanism between micropiles and soil landslides is comprehensively investigated through static model tests and numerical simulations. The results show that the deformation damage mode of micropiles is mainly bending and shear damage. Because of bending deformation, cracks appear at the rear and front of the pile, respectively, about three times the pile diameter from the sliding surface. In addition, the plastic damage becomes more severe when approaching the back edge of the landslide body. Micropiles in the landslide body play a significant role in load sharing; more importantly, there is a certain pattern between the miniature piles. According to the experimental and numerical simulation results, the recommended load-sharing ratio for micropile design under static conditions is as follows: rear-row pile:middle-row pile:front-row pile = 0.411:0.348:0.241. The research in this paper reveals the good effect of micropiles against landslides, explains the mechanism of pile–soil interaction, and provides a theoretical reference for the research and application of micropiles in engineering.

Earthquake-induced landslide has various spatial characteristics that can be effectively described with the frequency–area curve. Nevertheless, the widely used power-law curve does not reflect well the spatial features of the distribution, and the power exponent does not show the association with the background factors. There is a lack of standards for building the relationship, and its implication on the spatial distribution of landslides has never been analyzed. In this study, we propose a new form of frequency distribution and explore the parameters in the typical watersheds along the highway from Dujiangyan to Wenchuan in the Wenchuan earthquake region. The obtained parameters are related to the landslide density and proportions of the large-scale landslides. Furthermore, a hot spot analysis of landslides in the watersheds is conducted to assess the relationship between the parameters and the spatial cluster patterns of landslides. The hot spots highlight the size and distance of landslide areas that cluster together, whereas the distribution parameters reflect the density and proportions of landslides. This research introduces a new method to analyze the distribution of landslides and their association with the spatial features, which can be applied to the landslide distribution in relation to other influential factors.