A novel optimal plane arrangement of stabilizing piles based on soil arching effect and stability limit for 3D colluvial landslides

• A novel flattened ellipsoid model was proposed to describe 3D sliding mass of colluvial landslides.
• A reasonable interval model for stabilizing piles was deduced base on friction soil arching effect.
• Inherent relations among pile spacing, driving force, and pile cross-section were revealed.
• Stability limit was put forward to confine rational arrangement scope for stabilizing piles.
• The Erliban landslide illustrates that optimal scheme can reduce a large number of piles.

The paper presents a novel optimal plane arrangement of stabilizing piles in terms of the provided half simplified flattened ellipsoid model, which can be used to describe the three-dimensional characteristics of sliding mass for colluvial landslides. By studying the friction soil arching effect between the adjacent stabilizing piles, a reasonable pile spacing model for stabilizing piles was deduced in consideration of the driving force and shear strength of sliding mass as well as the dimension of pile cross-section. The results indicate that the net pile spacing is in direct proportion to the height of pile cross-section and shear strength parameters of sliding mass, but in inverse proportion to the driving force intensity. Consequently, the net pile spacing should steadily increase from the major slip profile to the profiles near the boundaries accordingly, which can be called the non-uniformly spaced arrangement principle of stabilizing piles for colluvial landslides. In view of the scale factor and groundwater in the different cross sections of landslide, the improved formula of stability coefficient based on the Fellennius method was proposed accordingly. Furthermore, the concept of stability limit was put forward to confine the rational arrangement region for stabilizing piles; consequently, the region beyond the rational arrangement region is not necessary to set piles any more. The case study of the Erliban landslide in the Three Gorges Reservoir Region of China shows that the quantitative optimal plane arrangement scheme based on the proposed reasonable pile spacing model and stability limit only requires 25 stabilizing piles rather than 31 stabilizing piles in the conventional uniformly spaced arrangement scheme, with an obtainable savings of 19.4% in the number of stabilizing piles.