Geosynthetics October/November 2020 - 16

Reinforced embankments for the causeway for a North Wales bridge project

Conclusions

FIGURE 6 Construction reinforced embankment north side

FIGURE 7 Construction temporary access south abutment

16

The use of reinforced earthworks
embankments with geogrids and granular
material Class 6B and Class 6N allowed
the construction of the causeway and
access roads for the new bridge, keeping
the existing timber viaduct in service
during construction.
The main challenge for the design of
the reinforced embankments was to keep
the distance from slope edge for piling
rigs and cranes to only 3.3 feet (1 m), with
a maximum slope angle of 1V:1.5H while
coping with the variation of the water levels
due to tidal activity. Tidal levels varied by
up to 15 feet (4.6 m) with very high spring
tides experienced during the construction
phase. In addition, two periods of major
storms and flooding occurred during construction, and no damage occurred to the
causeway or embankments.
The reinforcement of the embankments and access roads using geogrids
also allowed the construction of working
platforms and safe areas for the heavy
plant to operate under all conditions,
even the most extreme tidal conditions.
One of the major benefits was that even
though the platforms were submerged on
a regular basis, very little, or almost no,
remedial work was required after each
tidal event to bring them back into operation. Without the reinforced working
platform solution, the project deliverables
would have been impossible to achieve
within the spatial constraints imposed
by the scheme land boundary and zone
of influence of the operational railway.
A very detailed and careful construction plan was produced to integrate the
permanent embankment construction
with the temporary works and to ensure
that the existing railway line could stay
operational during construction. The
project was successfully constructed in an
efficient and cost-effective way, overcoming all the environmental and operational
constraints of the scheme.

Geosynthetics | October November 2020

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Geosynthetics October/November 2020

Table of Contents for the Digital Edition of Geosynthetics October/November 2020

Geosynthetics October/November 2020 - Cover1
Geosynthetics October/November 2020 - Cover2
Geosynthetics October/November 2020 - 1
Geosynthetics October/November 2020 - 2
Geosynthetics October/November 2020 - 3
Geosynthetics October/November 2020 - 4
Geosynthetics October/November 2020 - 5
Geosynthetics October/November 2020 - 6
Geosynthetics October/November 2020 - 7
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Geosynthetics October/November 2020 - Cover3
Geosynthetics October/November 2020 - Cover4
Geosynthetics October/November 2020 - Geosynthetics Conf. Brochure 1
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Geosynthetics October/November 2020 - Geosynthetics Conf. Brochure 8
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