Vertical pullout tests of orchard trees for bio-inspired engineering of anchorage and foundation systems

Abstract

Application of bio-inspired design in geotechnical engineering shows promise for improving the energy and material efficiency of several processes in infrastructure construction and site characterization. This project examines tree root systems for use in future bio-inspired design to improve the capacity of foundations used to support, for example, buildings and bridges. Foundation and anchorage elements used in industry are comprised almost solely of linear elements with a constant cross-sectional geometry. This functional form has remained the same for more than a century, primarily due to material availability and installation simplicity. Knowledge and understanding of the mechanisms that contribute to capacity development of natural nonlinear or branched foundation systems, such as tree root systems, could make foundation design more sustainable. The experiments described herein show that the root systems studied are 6–10 times as efficient as a conventional micropile system in developing tensile capacity on a per volume basis, with some systems displaying nearly 100 times efficiency in comparison to a conventional shallow footings. This paper explores the relationship between root system architecture and force–displacement behavior of tree root systems to better understand how to improve foundation capacity and demonstrates the potential for a more efficient use of materials and energy as compared to conventional pile and footing approaches.

Architecture characterization of orchard trees for mechanical behavior investigations

“…Results from our previous study in Burrall et al [20] suggest that differences in the root architecture can help explain differences in the mechanical pull-out responses. Primarily, the spatial distribution of thick structural roots, which can be described through a combination of branch length, branch angle, and diameter allocation aforementioned, plays a signi cant role in load transfer to the soil that provides support through frictional resistance.…”

“…Ten root systems were subjected to vertical pullout in the UC Davis Plant Science Department teaching orchard [20]. The orchard trees, the scion and the rootstock, were selected for testing based on apparent differences in root architecture and perceived differences in anchorage performance from past usage in the orchard.…”

“…In total, four Lovell, three Marianna, and three Myrobalan rootstocks were tested. Details of the test program and their pullout capacities are described in Burrall et al [20].…”

“…Coarse root architecture has been studied using various geometric descriptors such as biomass allocation, branching angle, rooting depth and cross-sectional area [18,19]. Recent innovations in imaging techniques such as photogrammetry, Xray computed tomography, LiDAR, and MRI enable acquisition of 3D models of root systems, which provides a basis for detailed geometric analysis [20][21][22][23]. Geometric descriptors for tree root systems can have wide variations with associated statistical distributions.…”

Architecture characterization of orchard trees for mechanical behavior investigations

“…This study explores the architectural characteristics of ten 3-year old orchard tree root systems (including Lovell, Marianna, and Myrobalan rootstocks) that were extracted from the ground by vertical pullout [20]. Following pullout, the orchard tree roots were cleaned and scanned with 3D photogrammetry.…”