Influence of Root Volume, Plant Spacing, and Planting Pattern of Tap-like Tree Root System on Slope Protection Effect

Vegetation slope protection has been widely utilized as an eco-friendly approach for slope stability. Up to now, research on the slope protection effect of shrubs and herbaceous vegetation is more than those of trees, which can be attributed to the challenge of evaluating the slope protection effect of tree root systems that can be influenced by many factors, such as root morphology, root volume, plant spacing, and planting patterns. Therefore, this study takes tap-like tree root systems as the research object, constructs the corresponding root-soil composite model by using 3D printing technology, and carries out a series of physical model experiments on slopes supported by tap-like tree root systems, examining the anti-sliding force, slope surface displacement, sliding range, and slope cracks throughout the entire process of deformation and the damage to shallow slopes, to finally evaluate the effectiveness in the slope protection effect of tree root systems from multiple perspectives. The results indicate that: (1) the peak anti-sliding force of the slope supported by tree root systems correlates positively with the root volume and negatively with plant spacing generally, and the influence of tree plant spacing on the peak anti-sliding force is weaker than that of the root volume; (2) the displacement of slopes supported by tree root systems in the square planting pattern is generally less than that in the staggered planting pattern, and the displacement of slopes has a negative correlation with the root volume and a positive correlation with the plant spacing; (3) the sliding range of the slope supported by tree root systems is significantly reduced compared with that of the unsupported slope, and the tree root system can prevent the occurrence of slope surface cracks to a certain extent, which makes the sliding-body show better integrity. The above understanding enriches the study on the slope protection effect of the tree root system, reveals the influence of the tree root volume, plant spacing, and planting pattern (square distribution and staggered distribution) of the tap-like tree root system, and offers some guidance for the engineering application of tree slope protection in practice.