An extended BNWF model for root piles incorporating soil-root interactions under lateral loading

Root piles constitute a new type of pile in which a series of prefabricated reinforced concrete roots are inserted into the surrounding soil to improve the bearing capacity of the pile foundation. To investigate the nonlinear behaviour of root piles under lateral loading, an extended beam on nonlinear Winkler foundation (BNWF) model incorporating the soil-root interactions is proposed in this paper. The proposed model is aimed at simultaneously describing the additional bearing capacity provided by roots and the nonlinear soil-root interactions for laterally loaded root piles. Lateral loading tests are conducted on two full-scale root piles to verify the applicability and reliability of the proposed model. It is demonstrated that the proposed model can describe the lateral behaviour of root piles with a reasonable calculation accuracy. Further parametric analyses are conducted to investigate the lateral bearing behaviour of the root piles. It is found that the root pile increases the lateral bearing capacity of the piles owing to the roots. Increasing the number or length of roots and locating them in shallow soil layers can improve the lateral bearing capacity of the root piles. The obtained results are useful for the design and appli-cation of root piles.