Fundamental

mechanisms of fiber reinforcement

The basic mechanism of reinforced earth can be

explained in so many ways. A simple method of explaining the concept is by

Rankines’s method of stress theory. If a two dimensional element of cohesive

less soil subjected to uni-axial stress theory. It will not be able to remain

in equilibrium. The Mohr circle of stress will cut the strength envelope. If

the element is subjected to equal bi-axial stresses, it will undergo uniform

compression, if one of the stresses, say ?1 is increased while ?3 is kept constant

an expansion in the direction of stress ?3 will result. To hold the

element without failure, the lateral stresses must be increased. If

reinforcement is provided in the direction ?3, interaction

tensile stresses will be produced in the reinforcement and a corresponding

reinforcement. It will be analogous to the existence of a pair of planes which

prevent the Mohr circle to the right and away from the failure envelope and the

soil element will remain in equilibrium. The soil reinforcement friction is

fundamental to the concept of reinforced earth. Vidal (1978) describes

reinforced earth as a cohesive material. The cohesion is assumed to be induced

due to introduction of the reinforcement friction is produced in the direction

of reinforcement earth. It has however not been possible to define this

cohesion in a way as to enable its use in the design of reinforced earth

structures.

studies indicate that stress–strain–strength

properties of randomly distributed fiber-reinforced soils are also a function

of fiber content, aspect ratio, and fiber-surface friction along with the soil

and fiber index and strength characteristics. A different view of the influence

of reinforcement on the behavior of soil mass has been advanced in the recent

past.

The reinforcement is assumed to restrict the dilatancy

of the soil leading to an increase in the mobilized shear strength. The

reinforcement also causes a rotation of principal strain directions relative to

the unreinforced case. The most effective directions for the reinforcement can

be estimated by the zero extension characteristics, which are thought to

represent potential slip or rupture surfaces.