Measurement and modelling effect of street trees distress on asphalt pavements by using experimental and 3-D finite element methods

• “An integrated framework combining PCI field surveys, ANN clustering, and 3D FEM was developed to quantify tree-induced pavement distress.” This study used Artificial Neural Networks (ANN) to investigate correlations between the type and severity of distresses with a group of factors related to the trees and site conditions to identify the tree species that lead to pavement distresses and damage by using Pavement Condition Index (PCI). A Finite Element Model (FEM) was developed to represent two scenarios, with and without the trees, for both curb trees and median trees to highlight the effects attributed solely to the trees. The analysis results provide strategies and plan for tree farming along roads depend on the research results and scientific. In a finite element model that ignores tree-root effects, deformation achieves an upper limit of 0.57 mm below the outer vehicle wheel, while the internal load produces 0.43 mm of deformation, with strains in the x, y, and z directions far below failure limits. When tree-root movements are observed on a traffic-free road, deformations around the roots may reach over 25 mm, affecting a seven-fold wider area than the root zone. In Model 1, vertical displacements above the roots vary between 0.6 cm and 3 cm, indicating pavement expansion. Root pressure causes tension and compression zones to emerge, which can lead to injury. The stress and displacement characteristics in Model 2 are unbalanced due to the trees being planted in the median. Vertical displacements around the roots might reach four centimeters, suggesting serious damage. Longitudinal displacements indicate tensile cracking, suggesting a potential for additional pavement failure due to root growth. The observed types of pavement failure were longitudinal cracking and swelling. For roadside trees located at the outer edge, the failures occurred within 0 to 2 meters of the pavement edge. In the case of median trees, the pavement failures extended from 0 to 5 meters from the median. According to the field study, these failures correspond to the distress types associated with Cluster 1 and Cluster 2 species. The extent and type of modeled distresses were consistent with the on-site observations. In contrast, such distress patterns were absent in areas with Cluster 3 species (California Fan Palm, Elm, Golden Rain, Olea europaea, Pagoda Tree, and Quercus robur), where the induced strains were well below the failure threshold.