in figure 4-3. These forces consist of an actuating

(3) The conventional assumption is that criti-

force composed of lateral earth pressure and a

cal slip circles will be the same for both the

resisting force created by frictional resistance be-

geotextile-reinforced and nonreinforced embank-

tween the embankment fill and geotextile. To

ments although theoretically they may be differ-

provide the adequate resistance to sliding failure,

ent. Under these conditions, a stability analysis is

the embankment side slopes may have to be

performed for the no-geotextile condition, and a

adjusted, and a proper value of soil-geotextile

critical slip circle and minimum factor of safety is

friction needs to be selected. Lateral earth pres-

obtained. A driving moment or active moment

sures are maximum beneath the embankment

(AM) and soil resistance moment (RM) are deter-

crest. The resultant of the active earth pressure

mined for each of the critical circles. If the factor

per unit length

for the given cross section

of safety (FS) without geotextile is inadequate,

may be calculated as follows:

then an additional reinforcement resistance mo-

ment can be computed from the following equa-

(eq 4-2)

tion:

where

(eq 4-1)

= embankment fill compacted density-force

per length cubed

where

H = maximum embankment height

T = geotextile tensile strength

= coefficient of active earth pressure (di-

R = radius of critical slip circle

mensionless)

RM = soil resistance moment

FS = factor of safety

For a cohesionless embankment fill, the equation

AM = driving or active moment

becomes:

This equation can be solved for T so that the

(eq 4-3)

geotextile reinforcement can also be determined to

provide the necessary resisting moment and re-

Resistance to sliding may be calculated per unit

quired FS.

length of embankment as follows:

in an analysis for embankment sliding are shown

(eq 4-4)

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