Simplified One-Dimensional Models for Pile-Soil-Pile Interactions of a Duo-Pile System-Paper

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The study develops simplified one-dimensional (1-D) models to represent pile–soil–pile interactions in a duo-pile foundation, an alternative to monopiles and conventional pile groups for elevated transport structures. Because lateral pier deflection affects serviceability and structural stability, the models aim to reproduce the response of more computationally demanding three-dimensional (3-D) analyses.<br /><br />The researchers examine four interaction mechanisms: transverse edge effects, longitudinal shadow effects, vertical-load interaction, and couple interaction. The latter arises when the pile-cap beam transfers moment as equal and opposite vertical forces to the two piles. The authors identify this couple effect as an interaction that has received little attention in previous studies.<br /><br />Linear-elastic 3-D finite-element models of two piles and piers were created in OpenSees. Pile spacing, soil stiffness, and loading direction were varied. The models were checked against single-pile solutions and showed close agreement. For each loading case, the 3-D pile displacement was used as a target for calibrating the spring stiffness in a corresponding 1-D model.<br /><br />The study proposes spring-constant factors for edge, shadow, and vertical interactions, along with a new arrangement of vertical interaction springs between the piles to capture couple effects. The vertical and couple factors were found to be largely independent of soil Young’s modulus; the lateral factors varied with soil stiffness and pile spacing. The calibrated 1-D models approximate the 3-D responses while offering a simpler approach for analysis.<br /><br />These factors can be incorporated into full 1-D models of duo-pile foundations and potentially pile groups, reducing modelling effort. The findings are based on idealized, homogeneous, linear-elastic soil and perfectly bonded pile–soil interfaces, so further validation is needed for more complex field conditions.

Keywords

duo-pile foundation

pile-soil interaction

1-D models

3-D finite-element analysis

lateral pier deflection

spring stiffness calibration

edge effects

shadow effects

vertical interaction

couple interaction