Analytical study on the role of tree roots system in slope stability

Abstract

The objective of this paper is to investigate the role of a tree roots system in slope stability through an analytical method. Variations of the diameter and the area ratio of the roots depending on its position in the soil were determined using two actual Japanese cedar trees (Cryptomeria japonica D. Don). The shape of the whole roots of a tree was assumed to be a hemisphere centered at the middle of the tree stump, thus the diameter and the area ratio of the roots is distributed on the surface of the hemisphere with an arbitary radius. The role of the tree roots system was clarified by the Spencer method for two-dimensional analysis. The conventional studies of many researchers have adopted fixed and linear slip surfaces in stability analysis. In this study, the safety factor against slope failure was optimized to determine the critical slip surface of the non-circular shape. The analytical examina tion using model slopes of homogeneous soil material revealed that a tree located at the toe of a slope is far more effective in slope stability than at any other position of the slope, and the role of this system has the function of increasing the critical safety factor against slope failure, on the contrary the depth of the slip surface (i. e. the scale of slope failure) will increase.

Fertilization reduces root architecture plasticity in Ulmus pumila used for afforesting Mongolian semi-arid steppe

“…In particular, it has been widely demonstrated that roots can respond to prevailing winds by selectively increasing root number, diameter, length, and volume to enhance tree anchorage ( Stokes et al, 1995 ; Nicoll and Ray, 1996 ; Danjon et al, 2005 ; Tamasi et al, 2005 ; Danquechin Dorval et al, 2016 ; Saint Cast et al, 2019 ). In particular, for the increase in root diameter observed in the present study, the mechanical enhancement of these roots is due to diameter-dependent characteristics, such as resistance to breakage, tensile maximum force, and stiffness which are generally expressed as a power-law function of the root diameter ( Ziemer and Swanston, 1977 ; Coutts, 1987 ; Nilaweera and Nutalaya, 1999 ; Kondo et al, 2004 ; Genet et al, 2010 ; Vergani et al, 2012 ). Similar findings from other studies were related to the response of roots to environmental stimuli ( Rellán-Álvarez et al, 2016 ) with particular attention to the mechanical forces due to both slope and wind ( Danjon et al, 2005 ; Lombardi et al, 2017 ; Dumroese et al, 2019 ).…”