Unit Cell Testing of Reinforced Soils - Reinforced Soil Engineering: Advances in Research and Practice - page 45

apparatus. Leighton Buzzard sand and River Welland sand were used with a heat-
bonded nonwoven geotextile. In a dense state, the reinforcement weakened the
sand, but it strengthened the sand in loose states. The axial strain to peak strength
was increased for reinforced specimens. The effect of angle of inclination of
reinforcement on the strength of a reinforced specimen was also studied. The
sand was weakened at certain inclination angles, which are close to the zero-
extension line. McGown et al. (1978) reported a similar study using the plane
strain cell, but focused specifically on “extensible” and “inextensible” materials
in which Leighton Buzzard sand was used with a heat-bonded nonwoven
geotextile, aluminum foil, and aluminum mesh. The difference in performance of
reinforced sand with extensible and inextensible reinforcements was reported.
Tatsuoka (1986a) and Tatsuoka and Yamauchi (1986) performed a study
on reinforced sand using different materials as reinforcement in a plane strain
apparatus. Moreover, a theoretical study was conducted to investigate the
reinforcement effect due to the reinforcement and soil properties, spacing, and
initial confining pressure. In the study, the reinforcement material is assumed to
be isotropic and linear elastic (Fig. 6a).
Consider a reinforced soil composite that has been consolidated
isotropically to a stress state s 1 ¼ It was then sheared to failure at

the major principal stress s 10 ¼ K p s 30 ; where K p ¼ð 1 þ sin f 0 Þ=ð 1 2 sin f 0 Þ:
Due to the restraining effect of reinforcement

s 2 ¼ s 3 :

in the composite, the

confining pressure in the composite is enhanced to a value

s 3R ¼ s 30 þ Ds 3 ð 13 Þ

Figure 6 Reinforced sand under plane strain conditions: (a) schematic sketch; (b) stress-
strain curves; (c) relationships between R and Et. (From Tatsuoka and Yamauchi, 1986.)