Issue and Nonissue in Block Walls as Implied Through Computer-Aided Design - Reinforced Soil Engineering: Advances in Research and Practice - page 85

Table 2 Comparison: Pullout Results for Geosynthetic Wall Having Same Geometry
and Vertical Spacing as the Metal Strip Wall in Table 1 (Uniform Length of
Reinforcement; See Fig. 1a and 1b)

Pullout:
Fs
(metal
strip)

F *
C i tan(f)
[C i ¼ 0.8]

Pullout:
Fs
(geosynthetic)

Elevation
(m)

L
(m)

T max
(kN/m) Rc K/Ka a

0.375 1.0 5.50 1.0 0.54 0.80 31.6 20.22 1.75

1.125 1.0 5.50 1.0 0.54 0.80 28.6 18.56 1.59

1.875 1.0 5.50 1.0 0.54 0.80 25.6 16.91 1.79

2.625 1.0 5.50 1.0 0.54 0.80 22.6 15.23 1.51

3.375 1.0 5.50 1.0 0.54 0.80 19.6 13.55 1.51

4.125 1.0 5.50 1.0 0.54 0.80 16.6 11.85 1.50

4.875 1.0 5.50 1.0 0.54 0.80 13.7 10.10 1.58

5.625 1.0 5.50 1.0 0.54 0.80 10.7 8.30 1.61

6.375 1.0 5.50 1.0 0.54 0.80 7.7 6.36 1.57

7.125 1.0 5.50 1.0 0.54 0.80 5.7 3.28 1.60

laboratory tests and design computations. It is important to note that this

generalization is limited to free draining backfill soil.

3 ISSUE (FOR POLYMER REINFORCEMENT)

Demo 82 requires that the long-term connection strength, reduced by a safety
factor, should equal the maximum tensile force in the reinforcement. In many
block wall systems, the connection of the geosynthetic to the block is achieved
via friction. That is, pullout resistive force at the front end of geosynthetic layers
has to be the same as that at its rear end. However, while rear-end pullout
resistance is a nonissue, the front-end pullout (i.e., connection strength) can be an
issue. It should be pointed out that the front-end frictional resistance is achieved
due to the confining pressure of stacked blocks combined with the properties of
the geosynthetic-block interface. Contrary to block walls, achieving connection
strength for walls reinforced with metal strips is a nonissue.
Table 3 shows the factors of safety at the connection as generated by
MSEW software for the original geometry where the layers are spaced at 75 cm.
Block data as well as geosynthetic information are marked in the caption of Table
3. Note that T ult used is unrealistically high (it is 115 kN/m). This high strength
value was selected because of the large spacing and the desire to examine
“failure” only at the facing (i.e., no overstressing of the geosynthetic). While