Inextensible (Steel) Reinforcement. With inextensible reinforcements, the
displacement at the leading end is nearly the same as the displacement at the free end
because reinforcement strain is negligible. The friction developed between the
reinforcement and the soil is determined for a leading edge displacement of 20 mm,
and the transfer of load to the soil via friction is uniformly distributed over the full
length of the reinforcement.
In an actual structure, the load is applied to the reinforcement by the soil within the
active zone, which is trying to escape through the wall face. The magnitude of this
earth pressure depends on the vertical stress and the coefficient of lateral earth
pressure. Vertical stress is a function of the overburden pressure, which increases
with depth in the structure, while the coefficient of lateral earth pressure varies from
at rest (Ko) at the top of the structure to active (Ka) at a depth of 6 m and deeper. The
horizontal earth pressure becomes tension in the reinforcements through the
mechanism of friction.
The tension in the reinforcement is greatest at the line of maximum tension
(Figure 3), and decreases gradually over the full reinforcement length until near the
free end, where the tension decreases rapidly to zero. Significant tension is observed
over the full length of the reinforcements.