Unit Cell Testing of Reinforced Soils - Reinforced Soil Engineering: Advances in Research and Practice - page 55

3 REINFORCED CLAY

It is difficult to restrict the type of soil used for reinforced structures to
cohesionless soil. As cohesive soil behaves differently when compared to
cohesionless soil under otherwise identical conditions, a few research projects
had been pioneered using laboratory tests.

3.1 Triaxial Compression Test

Ingold (1979) performed a theoretical study on reinforced soil. His theory is
basically similar to that of Broms (1977). It considered the compression of a thick
disc of material undergoing compression between frictional platens, which
reached an expression for the strength ratio of reinforced soil to unreinforced soil
at the following four different conditions:

exp tan d
3Kaa

Fully drained : ð 31 Þ

exp tan d
3a

Fully drained at soil reinforcement only : ð 32 Þ

m
4a

Fully undrained : 1 þ ð 33 Þ

1
4a

Internal failure before bond failure : 1 þ ð 34 Þ

where

a 2R is the aspect ratio,

d is the angle of friction between the reinforcement and soil,
mis a factor that relates bond stress to undrained shear strength of clay.

¼ h =

Experiments were conducted on Kaolin clay reinforced with either porous
disc or aluminum foil in unconfined condition. A comparison between the theory
and experimental results under drained condition and rapid shear (undrained) is
given in Fig. 11 . The general trend of relationship between the strength ratio and
the aspect ratio was well depicted.
Ingold and Miller (1983) conducted a study on the drained behavior of
reinforced clay using triaxial compression tests. Kaolin clay and porous plastic
were used. Both unconfined and confined tests were performed. The test results
showed an increase in the compressive strength of the reinforced clay, and the
ratio of increase became greater in the case of smaller reinforcement spacing.