Abstract: Micro-piles primarily produce anti-sliding effects in soil landslides through significant bending deformations near to the slip surface. When calculating their responses, changes in bending stiffness due to plastic deformation of the pile material should be considered. This paper proposes a computationally efficient p-y method for micro anti-slide piles based on the study of the bending characteristics. Taking the micro-piles made from concrete-filled steel tubes as the object, a refined finite element numerical simulation was conducted to study the nonlinear moment-curvature relationship. This relationship was divided into three stages: elasticity, elastoplasticity, and hardening, according to the evolution of section stress distribution and plastic strain, and was modeled by a three-stage equation. Based on the p-y method for calculating laterally loaded piles, the incremental differential equation of pile deformation considering the nonlinear moment-curvature relationship was derived. Using the incremental method and updating the flexural stiffness at each incremental step, the entire process response of the pile under landslide action can be quickly solved. The proposed method was verified using finite element numerical simulation and limit analysis method. Parameter analysis shows that both ultimate soil resistance and pile flexural strength significantly influence pile response. Higher soil ultimate resistance makes it easier for the micro-pile to reach failure, with failure positions closer to the slip surface. Conversely, a higher pile flexural strength results in failure positions further from the slip surface and mobilizes a larger range of soil resistance, but also increases soil displacement required to reach failure. The proposed p-y method and the associated analysis procedure can be applied to the optimal design of micro anti-slide piles.

Key words: micro anti-slide pile, p-y method, material nonlinearity, moment-curvature relation, ultimate pile resistance