P. Cofie et Aj. Koolen, Test speed and other factors affecting the measurements of tree root properties used in soil reinforcement models, SOIL TILL R, 63(1-2), 2001, pp. 51-56
Measured values of the mechanical properties of tree roots are found to be
affected by a number of factors. Shear properties of tree roots are found t
o be partly influenced by size of the testing equipment. level of soil comp
action. deformation of the root material and estimated width of the shear z
one in the soil etc. Among others. tensile root properties are found to be
affected by factors such as season, age, root types or species, root prepar
ation before experiment, clamping procedure of the root, and rate of elonga
tion used. The aims of this paper were (1) finding an appropriate clamping
procedure for root measurements: and (2) studying the effect of elongation
rate on stress-strain relationships of beech (Fagus sylvatica L.) roots. It
was found that problems associated with root clamping (i.e., in root exper
iments) such as breakage of the root sample close to the jaws of the clampi
ng devices and slippage may be eliminated by introducing wooden blocks of a
ppropriate hardness within the jaws of the clamps and exerting a suitable c
lamping force, respectively. An appropriate wood hardness and suitable clam
ping force were found by conducting a number of initial trial experiments.
Tensile experiments conducted with beech roots pairs showed that elongation
rate does influence the stress-strain relationships of roots. In general,
stress values of beech roots were found to increase between 8 and 20% for a
n increase in the rate of elongation from 10 to 400 mm/min. Similar finding
s have been reported in textile fibres. (C) 2001 Elsevier Science B.V. All
rights reserved.