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This requirement was reflected in both nonlinear finite-element analysis and
observations during construction. The postconstruction movements of the
abutment walls have been monitored for a liability period before full payments
were released to the GRS wall contractor. It is the author's understanding that the
payment was fully released, thus verifying satisfactory performance, although the
monitored results have not yet been released.
5.4 Modular Block Walls
Modular block walls are relatively popular in the state of New South Wales
because of their cost-effectiveness and aesthetic appeal. Both HDPE and
high-tenacity polyester geogrids have been used. In New South Wales
(probably also in Australia), the first modular block wall for the SRA was
constructed in1992 at Gosford (a coastal town located about 50 km north of
Sydney). The wall is up to 3.1m high. Crushed sandstone was used as the fill
material, and the blocks were laid with a small setback of 1(H) in 8(V).
Since then, a number of modular block walls have been constructed for
several milestone projects. As reported in Won (1994), the applications range
from road widening to foreshore protection (as sea walls). The wall height is
generally limited to 4m. Setbacks in laying the blocks may or may not be
specified. The reinforcement density is generally one layer every two to three
blocks. In the case of an abutment wall, the bridge deck is supported
independently by piers, with the exception of the wall described in Section
5.3. Multitier walls, also referred to as terrace walls, have been used to
achieve higher heights. A recent example is the widening of the F6 freeway
(from 4 to 6 lanes) at Wollongong, a coastal city about 75 km south of
Sydney. A multitier wall was used to achieve, more effectively, a higher
retained height of about 6m. The tallest section of this wall is presented in
Fig. 17
.
The reinforcement content of this type of wall is often governed by overall
stability, with the potential slip surface passing through some of the
reinforcement layers. As such, the reinforcement distribution is often close to
uniform, and additional conservatism is exercised in the design.
6 CONCLUSION
In Australia, the construction of GRS walls for SRA projects has a relatively short
history. However, GRS walls have gained market acceptance, despite being
under a very demanding contractual system. This attests to the cost-effectiveness,
versatility, and strength of GRS walls.
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