A method for simulation of upward root growth pressure in compacted sand

In order to model the impacts of tree root growth under pavement as a layered design, the behavior of the components need to be defined or assumed. Since the behavior of materials and the design of pavement sections work on the presumption of loading from the pavement surface downward, it is reasonable to check engineering behavior assumptions with a testing method for controlled loading upward from a growing perennial root. A root simulation, was developed to inflate with water to known input pressure. Sand displacement in response to increasing input pressure was tracked over several sand density-moisture level pairings. Load cells tracked the translation of sand displacement to load at a simulated pavement surface to develop data plots of a line-load spreading wider with increasing distance between root and pavement. The results from the laboratory experiments were compared to the results from numerical simulations using finite elements to develop better understanding of the mechanisms of load generation due to the root growth. Sand was modeled as a Mohr-Coulomb type material for that purpose. The numerical results are qualitatively in agreement with the experimental results.