This is the first in a series of two papers presenting a decoupled methodology for the design of slope stabilising piles. The proposed methodology combines the widely accepted analytical calculations to obtain the required stabilising force, with non-linear finite elements analysis to obtain the ultimate lateral capacity of piles. The soil and pile constitutive model is validated against experimental and observational data. The simplified numerical model results are compared satisfactorily with 3D Finite Elements analyses and theoretical studies.