Structural cell contribution to resistance of trees to uprooting

Key message: Structural cells, as a form of suspended pavement, increases the resistance of urban trees to uprooting failure by confining the roots from growing above ground surface. Abstract: Trees planted in urban environment may be prone to uprooting due to poor root development and lack of anchorage in the soil. The stability of the tree can be improved by implementing suspended pavement system to encourage growth of tree root below ground surface. A type of suspended pavement has been developed and used in this study, subsequently referred to as structural cell (SC). Numerical analyses were carried out to investigate the contribution of the SC on the stability of Samanea saman, a common urban tree in Singapore with a shallow root system. A simplified tree–root–soil model was adopted for a parametric study by varying root length at both sides of the tree from 1 to 3 m with an interval of 0.5 m. The SC was added to the model as a confinement on top of the shallow roots to give additional resistance against uprooting. Results show that the SC implementation increased the load resistance to uprooting by reducing the strain developed in root plate base and the underlying soil. However, the tensile and compressive stress on the top fibre of root plate at the windward and leeward sides of tree trunk increased due to the presence of SC. Overall, the presence of SC increases the tree resistance to wind load by 2.5–3.3 times the resistance of the tree without SC.