TM 5-818-8/AFJMAN 32-1030
B. METHOD OF REPRESENTING TRAFFIC LIVE LOADS
Figure 7-2.
Procedures for Computing Live Load Stresses on Geotextile Reinforced Retaining Walls.
or triaxial tests (ASTM D 2850). The unit weight,
three locations along the wall are checked to
, will be determined in a moisture density test
determine the most critical.
(ASTM D 698). Generally, 95 percent of ASTM D
d. Composite Pressure Diagram. The earth pres-
698 maximum density can be easily attained with
sure and live load pressure diagrams are combined
granular materials. However, other densities can
to develop the composite diagram used for design
be specified so long as the friction angle used is
as shown in Figure 7-1b.
consistent with that density. The saturated unit
e. Vertical Spacing of the Fabric Layer. To deter-
weight is used in lateral pressure calculations.
mine the vertical strength of the fabric layer, the
b. Lateral Earth Pressure Diagram. Using the
fabric allowable tensile strength, S , is set equal to
properties of the retained soil, calculate the pres-
the lateral force calculated from
, where
is
sure coefficient,
The lateral earth
the lateral pressure at the middle of the layer.
pressure expression:
Thus, knowing the fabric tensile strength, and
value of
the fabric vertical spacing, X , can be
calculated. The fabric strength should be divided
is used to calculate the triangular shaped pressure
by the appropriate safety factor. The equation for
distribution curve for the height of retaining wall
fabric spacing is:
desired.
c. Live Load Lateral Pressure Diagram. It is
(eq 7-6)
first necessary to determine the design load. Lat-
eral pressure diagrams must be developed for each
f. Length of Fabric Required to Develop Pullout
vehicle or other equipment expected to apply loads
to the retaining wall using equation 7-3. The
, is used to solve for the pullout
equation is solved for each wheel and the results
resistance which can be developed at a given depth
added to obtain the lateral pressure. This pressure
geotextile length combination or to solve for d ,
is calculated at 2-foot vertical intervals over the
the depth required to develop
. The usual case
height of the retaining wall. Normally, from one to
for walls is to set
equal to the geotextile
7-4
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