Abstract: Now，the soil between the piles is usually considered to be elastic in many calculation models of portal double-row anti-slide piles. Because of the soil being the elastoplastic material, the results of elastic models are not consistent with the reality. A new plane link finite element model is established. The soil between the piles is considered to be the elastoplastic in this model which combined the linear elastic model and the plastic model. A calculation method for calculating internal force of the fore-pile and the rear-pile is developed, which is based on structural mechanics, soil constitutive relationship and numerical method. First, the soil total stress between the piles is acquired by calculation based on the displacement of pile top used in the displacement method. Then the internal force of portal double-row anti-slide piles is calculated by numerical method, linear elastic elements and plastic elements of this numerical method, whose basic parameters are derived according to the Lade-Duncan constitutive model. Last, combining with engineering example, the internal force of portal double-row anti-slide piles is calculated with the finite element program ANSYS. Compared with the monitoring data and the calculating results of elastic model, the calculating results of elastoplastic model are more consistent with the monitoring values.

Key words: double-row anti-slide piles, elastoplastic model, plane bar system finite element model, landslide