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STRENGTH CHARACTERISTICS OF ROOT-REI...

DAKESSIAN, SUREN.

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STRENGTH CHARACTERISTICS OF ROOT-REINFORCED SOILS.

Record Type:	Electronic resources : Monograph/item
Title/Author:	STRENGTH CHARACTERISTICS OF ROOT-REINFORCED SOILS./
Author:	DAKESSIAN, SUREN.
Description:	203 p.
Notes:	Source: Dissertation Abstracts International, Volume: 42-01, Section: B, page: 0119.
Contained By:	Dissertation Abstracts International42-01B.
Subject:	Physical Geography. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=8113005

STRENGTH CHARACTERISTICS OF ROOT-REINFORCED SOILS.
DAKESSIAN, SUREN.

STRENGTH CHARACTERISTICS OF ROOT-REINFORCED SOILS. - 203 p.

Source: Dissertation Abstracts International, Volume: 42-01, Section: B, page: 0119.

Thesis (Ph.D.)--University of California, Berkeley, 1980.

Vegetation plays a beneficial role in stabilizing the soil on slopes against shallow slides by two mechanisms: mechanical reinforcement of the soil matrix by the roots and drying the soil, thus increasing the effective stress on the potential slip plane. This experimental work refers only to the reinforcing mechanism.Subjects--Topical Terms:

893400
Physical Geography.

STRENGTH CHARACTERISTICS OF ROOT-REINFORCED SOILS.
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100 1 $a DAKESSIAN, SUREN. $3 1908250
245 1 0 $a STRENGTH CHARACTERISTICS OF ROOT-REINFORCED SOILS.
300 $a 203 p.
500 $a Source: Dissertation Abstracts International, Volume: 42-01, Section: B, page: 0119.
502 $a Thesis (Ph.D.)--University of California, Berkeley, 1980.
520 $a Vegetation plays a beneficial role in stabilizing the soil on slopes against shallow slides by two mechanisms: mechanical reinforcement of the soil matrix by the roots and drying the soil, thus increasing the effective stress on the potential slip plane. This experimental work refers only to the reinforcing mechanism.
520 $a A major purpose of the research was to define the magnitude of cohesion c and friction angle (phi) for a root-permeated soil over a range of low normal stresses (5 to 30 KNm('-2)).
520 $a Water saturated soil samples in which barley, alfalfa, and Harding grass roots were grown were tested in direct shear and triaxial compression. The results indicated that the Coulomb envelope of a root-permeated soil is practically parallel to that of the unrooted soil. The cohesion intercept of the root-permeated soil is much larger than the cohesion of the unrooted soil. This verifies experimentally the correctness of the assumption advanced in the derivation of the expression for the reinforcing effect (DELTA)S, the difference in strength between the rooted and unrooted soil (Waldron, 1977). In both planted and bare soil, the mobilization of cohesion occurs early during shear deformation compared to friction angle mobilization.
520 $a The results show that the reinforcing effect is a continuously increasing function of the shear displacement x over the displacement range investigated, with a small intercept on the x coordinate. This indicates that at very small displacements, the presence of roots decreases soil strength because of a slower mobilization of the friction angle in the root-permeated sample than in the unrooted one. The relatively late mobilization of the friction angle of the rooted soil was found to be normal stress dependent: the larger the normal stress applied, the larger the displacement intercept on the x versus (DELTA)S plot. For both alfalfa and Harding grass, if the maximum shear stress occurring during the run is expressed as S, the ratio S(,planted)/S(,bare) was equal to 2.6 at a normal stress of 5 KNm('-2) and 1.6 at a normal stress of 20 KNm('-2).
520 $a The ratio of the total root cross section over total shear cross section a(,r) and the volume concentration of roots in soil w(,R) were both related to (DELTA)S. The larger these two parameters, the larger (DELTA)S. In both correlations though (a(,r) versus (DELTA)S and w(,R) versus (DELTA)S), there seems to exist a minimum value of a(,r) or w(,R) below which no reinforcement is present.
520 $a When root-permeated samples were tested in direct shear at two rates of displacement (3 mm/day 3000 mm/day), no significant differences were found between the two strength values obtained at large displacements of the shear box (5 to 7 mm). At small displacements (less than 3 mm), the fast rate generated a slightly larger strength.
520 $a The results obtained in this research program provide experimental proof and strengthen the existing view that reinforcement is mainly on increase in soil cohesion, caused by the roots.
520 $a The experimental data can be used in the stability analysis of slopes for which the potential failure plane is shallow and crosses entirely through soil material.
590 $a School code: 0028.
650 4 $a Physical Geography. $3 893400
690 $a 0368
710 2 0 $a University of California, Berkeley. $3 687832
773 0 $t Dissertation Abstracts International $g 42-01B.
790 $a 0028
791 $a Ph.D.
792 $a 1980
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=8113005