Numerical simulation and field tests on vertical load bearing behaviour of bored root piles

Bored root piles are a new type of pile in which the load-bearing capacity can be significantly improved by jacking prefabricated roots into the soil through reserved holes. In this study, numerical simulations and computations are incorporated with field tests to fully investigate the complex load-bearing behaviour of bored root piles under vertical loading. The established numerical model is validated using a measured load-displacement curve obtained from self-balanced field tests. Using the validated numerical model, the load-transfer mechanism is investigated in terms of the load-displacement curve, axial force, shaft friction, and load-share ratios of different components. Results show that the roots share a significant proportion of the load, whereas the load-share ratios of the different root layers indicate temporal and sequence effects. Parametric studies are performed to investigate the effects of different root configurations on the vertical load-bearing behaviour of bored root piles. The results show that root layer spacing is the most important factor affecting the load-bearing capacity. Three failure modes of bored root piles are formulated in terms of root layer spacing. The results of this study can facilitate the design and application of bored root piles.