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CONSTRUCTION WORLD
APRIL
2015
PROJECTS AND CONTRACTS
The detail design for the rehabilita-
tion and re-alignment of the road,
including upgrades on 11 culverts,
one river bridge and one road-over
rail bridge, as well as the new in-situ culvert
with a fill height of 9,7 m and wall thickness
of 700 mm and the new Elands River bridge
was done by the SANRAL appointed AECOM/
DMV Baeletsi joint venture.
The construction works were scheduled
to start in November 2012, but were delayed
by environmental issues until April 2013.
The construction time allowed for comple-
tion of the project is 30 months. Currently,
after 24 months into the project, work is well
underway and the initial backlog is slowly
but surely diminishing every month.
Construction challenges
The road rehabilitation specification has an
embargo on the use of stop/go systems. The
challenge, therefore, is to keep the traffic
flowing in both directions while the opposite
side of the road is being constructed. The
available road widths at certain places were
such that the traffic had to be accommo-
dated on freshly built bypasses in the middle
of the rainy season.
This, at times, led to crisis management
solutions to enable the free-flow of traffic.
A rapid increase in heavy vehicles contrib-
uted to the traffic accommodation chal-
lenge on this project. The speed limit was
reduced to 60 km/h at work zones assisted
by the placing of removable speed humps.
The absolute minimum road width to use
was found to be 3,3 m and a working space of
1,6 m was required for the adjacent construc-
tion activities, road signs and flag people.
There were, however, instances along the
route where the road had to be constructed
in third-width sections. Fortunately these
were only applicable for about 8 km of
the road. Traffic in these sections were
separated during phase two to run both
sides of the work zone, a situation which
required extra care and effort from the
contractor’s personnel.
Another aspect that had to be intro-
duced was the construction of temporary
seals during the winter period to allow for
the traffic to be transferred to the newly reha-
bilitated road, as existing old road sections
were deteriorating very quickly and became
unsafe and uneconomical to repair.
Winter seals have been an aspect of
investigation and research by SANRAL and
other entities like the bitumen manufac-
turers and consultant/contractor companies
to try and overcome the big loss in produc-
tion during the embargo period for sealwork
in South Africa (May to September). On the
basis of these research findings, temporary
sealwork was allowed with the use of a speci-
fied bitumen emulsion [SC E1(t)] with 9,5 mm
pre-coated stone, covered by a well designed
slurry mix. Using this design the safe flow of
the traffic as well as the construction produc-
tion could be successfully maintained.
The cuttings in the new alignment
section were done by blasting up to the
required levels. Traffic along the N5 was
re-routed through QwaQwa and for the
remaining traffic on the N5 the time lost due
to waiting for the blasting and clearance of
debris was never more than one hour.
Some sub-surface drainage challenges
were encountered between km 20 and 25.
After an on-site investigation, it was found
that due to the high water table in this area,
several natural springs existed in the road
prism. This problem was solved using a
herringbone system of sub-soil drains.
The Elands River tributary culvert was
done in 11 stages. The floor of the culvert was
completed in total to allow for the collapsible
internal shutter to be pushed along rails to
the adjacent section. The shutter was then
erected again only once the previous section
had been cured.
A total of 120 cub.m of concrete was
cast for the walls and deck of each of the 11
sections. Proper care had to be taken with
the fill adjacent and on top of the culvert.
The final fill reached a height of 9,7 m above
the top of the deck of the culvert. This implies
a static load of 20 ton/m
2
of the culvert deck
slab. The total static weight of material on
the deck slab range in the order of 17 600 t.
The new main Elands River Bridge has
five spans, each consisting of 10 precast
concrete beams. These beams are covered by
an in-situ deck slab of 250 mm, with perma-
nent precast shutters between all beams.
The two abutments are supported by 4 piles
each, which on average have been founded
to a depth of 19 m, while piers 1 and 4 each
have five piles in the order of 9 m deep. Piers
CHALLENGING ASPECTS
of N5 rehabilitation
Werner Venter, contracts engineer
from the DMV/AECOM JV.
Edgar Dube, project manager
from SANRAL.
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