Colluvial landslides are mainly composed of soil-rock mixtures with complex composition and structure, resulting in large uncertainties in mechanical properties. This leads to difficulties in designing stabilizing piles for colluvial landslides. In this study, we derive a predictive model for the ultimate lateral force of stabilizing piles in soil-rock mixtures, and use it to evaluate the factor of safety of a pile- stabilized colluvial landslide. Subsequently, robust geotechnical design is employed to optimize the design of the stabilizing piles. The design robustness is measured by the variation of failure probability, an approach which can overcome difficulties in characterizing uncertainties in soil-rock mixture mechanical properties. Accordingly, we propose a robust design procedure for stabilizing piles for colluvial landslides. The design method and procedure are illustrated using a real colluvial landslide case study, out of which the most preferred design considering the safety, cost, and design robustness is obtained. Moreover, the influences of rock blocks and safety requirements on the optimal designs are discussed. Our results show that the angle of repose of the rock blocks and the volumetric block proportion determine whether the mechanical parameters of the soil matrix can be used to effectively design the stabilizing pile. It is also found that a higher safety requirement can improve the design robustness, but at higher cost. The advantages of the proposed method are illustrated by a comparison with the traditional reliability-based design method. (c) 2025 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society. This is an open access article under the CC BY- NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

This study investigates the vulnerability of expansive soil slopes to destabilization and damage, particularly under intense rainfall, due to their heightened sensitivity to moisture. Focusing on a project in Yunnan Province, numerical simulation software is employed to address slope stability challenges. Meanwhile, the soil mechanical parameters of this study were acquired through experimentation. The analysis considers six conditions: unsupported, conventional anchor and stabilizing pile reinforcement, and NPR (Negative Poisson's ratio) anchor and stabilizing pile reinforcement, evaluated under both normal and rainstorm conditions. The research outcomes reveal noteworthy insights: (1) The efficacy of NPR anchors in mitigating deformation in expansive soil landslides is investigated, broadening their application potential, particularly in restricting maximum slope displacement compared to conventional anchors. (2) No significant difference in safety factors for slope stability is observed between NPR and conventional anchors. Under rainstorm conditions, safety factors are 1.39 and 1.32 for NPR and conventional anchor and stabilizing pile support, respectively, while under normal conditions, they are 1.42 and 1.39. (3) The NPR anchor, in contrast to the conventional anchor, ensures a more uniform force distribution across the stabilizing pile. (4) While combined support structures contribute to slope stabilization, NPR anchors surpass conventional anchors in limiting slope displacement.

The construction of the Three Gorges Reservoir dam in China has led to an increase in reservoir landslide events. To mitigate these geohazards, multiple rows of stabilizing piles (MRSP) have been employed to stabilize massive reservoir landslides. This study utilizes centrifuge and numerical modeling to investigate the behavior of unreinforced landslides and MRSP-reinforced landslides in reservoir areas. The failure mechanisms of unreinforced landslides, as well as the mechanical behavior and stabilizing mechanisms of MRSP under reservoir water level (RWL) fluctuations, are examined. The results indicate that elevated downward seepage forces contribute to prefailure sliding, but are not the sole cause of catastrophic failure. Instead, rapid pre-failure sliding leads to soil particle compression and crushing in the saturated sliding zone, resulting in excess pore water pressure and accelerated overall failure. This excess pore water pressure-dependent mechanism explains the observed steplike deformation pattern and rapid failure pattern in reservoir landslides. Furthermore, the study reveals the formation of soil arches between adjacent MRSP groups, causing stress concentration on boundary columns and necessitating reinforcement. The finding challenges traditional one-dimensional load transfer ratios, advocating for a two-dimensional approach that accounts for variations across rows and columns. Notably, the study also highlights significant variations in load transfer laws within MRSP under different RWL operations, emphasizing the need for a more nuanced understanding of MRSP behavior.

The stabilizing pile represents a promising solution for enhancing the seismic resilience of unsaturated slopes. This study introduces a novel analytical framework for assessing the stability of unsaturated slopes reinforced with piles, amalgamating the minimum potential energy approach with the pseudo-dynamic method. The formulation of the external potential energy arising from the self-weight of the landslide mass and seismic forces is derived. Furthermore, traditional plasticity theory is extended to unsaturated soil slopes to account for the augmenting influence of matric suction on the lateral pressure exerted by stabilizing piles. The efficacy of reinforcing unsaturated soil slopes with piles is gauged through the definition of the safety factor (SF), delineated as the ratio of resistance moment to sliding moment. Additionally, a fresh interpretation of the critical slip surface (CSS) for unsaturated soil slopes is proposed, alongside an original criterion for identifying CSS, introduced herein for the first time. The validity of the proposed methodology is substantiated through examination of three case studies, yielding results indicative of its efficacy and rationality. The analysis underscores the substantial fortifying impact of matric suction on the stability of unsaturated slopes, as well as the reinforcing influence of piles. Moreover, an exploration into the ramifications of seismic and pile-related parameters on slope performance and CSS is conducted. In conclusion, this approach serves as a valuable reference for the design of unsaturated slopes fortified with stabilizing piles.

With the construction of the Three Gorges Reservoir dam, frequent reservoir landslide events have been recorded. In recent years, multi-row stabilizing piles (MRSPs) have been used to stabilize massive reservoir landslides in China. In this study, two centrifuge model tests were carried out to study the unreinforced and MRSP-reinforced slopes subjected to reservoir water level (RWL) operation, using the Taping landslide as a prototype. The results indicate that the RWL rising can provide lateral support within the submerged zone and then produce the inward seepage force, eventually strengthening the slope stability. However, a rapid RWL drawdown may induce outward seepage forces and a sudden debuttressing effect, consequently reducing the effective soil normal stress and triggering partial pre- failure within the RWL fluctuation zone. Furthermore, partial deformation and subsequent soil structure damage generate excess pore water pressures, ultimately leading to the overall failure of the reservoir landslide. This study also reveals that a rapid increase in the downslope driving force due to RWL drawdown significantly intensifies the lateral earth pressures exerted on the MRSPs. Conversely, the MRSPs possess a considerable reinforcement effect on the reservoir landslide, transforming the overall failure into a partial deformation and failure situated above and in front of the MRSPs. The mechanical transfer behavior observed in the MRSPs demonstrates a progressive alteration in relation to RWL fluctuations. As the RWL rises, the mechanical states among MRSPs exhibit a growing imbalance. The shear force transfer factor (i.e. the ratio of shear forces on pile of the nth row to that of the first row) increases significantly with the RWL drawdown. This indicates that the mechanical states among MRSPs tend toward an enhanced equilibrium. The insights gained from this study contribute to a more comprehensive understanding of the failure mechanisms of reservoir landslides and the mechanical behavior of MRSPs in reservoir banks. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

In loess slopes, landslides are easily caused by rainfall and can be prevented by using retaining structures of stabilizing piles. This paper investigated the deformation and mechanical behaviors of the cantilever and fully buried stabilizing piles under complex pile-soil interactions. The deformation and mechanical behaviors, failure modes, and soil pressure distributions of two types of stabilizing piles were analyzed based on field model tests. Further, a calculation method for stabilizing piles considering nonlinear pile-soil interactions was proposed. Also, the numerical solution of the pile deformation and force was obtained by using the finite difference method and Newton's iterative method. The results showed that the deformation and mechanical behaviors of fully buried piles are superior to those of cantilever piles. Fully buried piles and cantilever piles have plastic double-hinged and single-hinged failure modes and undergo bending damage and shear damage, respectively. Besides, the landslide thrusts and soil resistances acting on the pile showed a parabolic distribution pattern. Compared to the model test results, the traditional calculation method overestimated the deformation and internal force of the stabilizing pile by 37.32%, and the newly proposed calculation model considering nonlinear pile-soil interactions was more consistent with the measured values. The study results help to guide the design and calculation of stabilizing piles under complex pile-soil interactions.