Root tensile strength of 3 typical plant species and their contribution to soil shear strength; a case study: Sasumua Backslope, Nyandarua District, Kenya
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Date
2011-04Author
Osano, Simpson Nyambane
Sixtus, Kinyua Mwea
Type
ArticleLanguage
enMetadata
Show full item recordAbstract
The effect of root reinforcement depends on the
morphological characteristics of the root system,
the tensile strength of individual
roots, the soil-root cohesive st
rength, and the distribution of the
root system in the soil.
This research looks into Sasumua B
ackslope in Kenya, where a great deal
of erosion is responsible for large soil loss
es. Shallow mass movements are evident throughout
the slope. Root reinforcement effect of ni
ne typical species was assessed, using Wu
et al
. (1979)
model. The plant species comprised of shrubs (
Atriplex
halimus
), grasses (
Pennisetum
clandistenum
and
Themeda triandra
), and tree ferns (
Asparagus species
). Physical counting of
roots per depth class was conducte
d to obtain root ar
ea ratio (RAR) values
of the individual
species. For each species, single root specimens we
re sampled and tested for tensile tests in the
laboratory using the Hounsfield Tensometer a
pparatus. Maximum RAR values were located
within 0.1 m for all the species, with maximum
rooting depth of 0.7 m for fern tree. Shrubs
species showed high RAR values between 0.1
– 0.3 m depth. Tensile force increases with
diameter. Generally shrubs break at high tensil
e force (160 N maximum), followed by tree ferns
(maximum 90 N) and lastly grass (maximum
75 N). Root tensile st
rength decreases with
increasing root diameter, and follows a power law equation of the form
k
ax
x
f
=
)
( . Generally,
tensile strength can be well predicted by root
diameter. The maximum root tensile strength
values recorded was 39 N/mm
2
for grass. The results presented in this paper contribute to
expanding the knowledge on root resistance behavior
and on root density di
stribution within the
soil. The studied location has allowed the impl
ementation of soil–root reinforcement models
initially used by Wu
et al.
(1979) and the evaluation of the
vegetation contribution to soil
stability
URI
http://profiles.uonbi.ac.ke/sites/default/files/sosano/files/tensile_strengths.pdfhttp://erepository.uonbi.ac.ke:8080/xmlui/handle/123456789/32029
Citation
Journal of Civil Engineering Research and Practice Vol. 8 No.1, April 2011, pp. 57 - 73Publisher
Univesity of Nairobi Department of Civil and Construction Engineering