The Civil Engineering Contractor July 2019 | Page 8

PROJECT OWNERS
Bridging Limpopo together
Project: Provincial roads
Client: Roads Agency Limpopo
Location: Limpopo
The Roads Agency Limpopo (RAL) is forging ahead
with the construction of a new road that will connect
three villages in the mainly rural Sekhukhune District
Municipality to two provincial roads, including the
D1547 that is administered by the South African National
Roads Agency Limited. When completed in September
2019, the new 13km single carriageway will provide
citizens of Mmotwaneng, Legonaneng and Luckau with
quick access to major urban centres in Limpopo and
Mpumalanga.
On site are Thabiso Phetla, site manager of Lonerock
Construction, and Joseph Myoya, Ubona Engineers’ resident
engineer-on-site. “As a typical Expanded Public Works
Programme project, it has been designed to be extremely
labour intensive. By November 2018, there were as many
as 60 locals working alongside members of our team.
This number will increase when we commence on the
ancillary works, such as the installation of the guardrails
and construction of the storm-water drains, in mid-2019,”
Phetla says.
Myoya adds that one of the challenges was quickly
adapting the original engineering design that was completed
more than eight years ago to current conditions without
delaying the works programme.
“While the engineering design was completed by another
engineering consultancy in 2010, the construction of the
road was delayed by RAL due to limited financing and other
pressing responsibilities. The villages have since rapidly
expanded with many properties located within the planned
route. The road, therefore, had to be extensively realigned to
avoid having to relocate more than 200 affected properties.
Our approach, which also included reducing the width of
the two-metre shoulder in areas, resulted in significant cost
savings for the client, while also mitigating further delays to
delivering this critical infrastructure to the communities,”
he says.
Moreover, the original design of the bridge over the
Mankgatle River had to be adapted to align with the higher
level of the new realigned road. It is one of two major and
technically-complex structures that were built by Lonerock
Construction as part of this project. At six metres in height,
it is significantly taller than the original design and is,
thus, well above the 20-year floodplain. Substantially more
reinforcement steel was required for the taller concrete
abutments and additional precast-concrete elements were
needed to build the larger 20m long and 11.5m wide
superstructure.
The I8 precast-concrete beams and 126 precast concrete
deck planks were manufactured and installed by CoreCivils,
the precast-concrete bridge beam and parapet arm of
6 | CEC July 2019
The new bridge over the Mankgatle River is one of two
large structures along the route.
CoreSlab. The benchmark for quality was confirmed after the
first element had reached a compressive strength of 45MPa
and CoreSlab was instructed by the team to proceed with the
manufacture of the remaining seven beams and deck planks.
The design of the foundations of the bridge also had to be
modified by Ubona Engineers considering that the terrain is
overlain by rocks and large boulders. A decision was taken
to anchor the foundations of the bases of the abutments into
the large boulders as opposed to removing them by drilling
and blasting.
“Mass concrete was cast over the boulders and we then
drilled through them to insert the dowels. This approach
provided some cost savings for our client considering that
up to 45 000m³ of rock had to be removed by drilling and
blasting during the earthworks stages of the construction of
the road. It also mitigated any delays as we decided to first
prioritise the completion of the two large structures before
working on the road,” Myoya says.
Some of this material was crushed and used in the layer works
of sections of the roads and in the foundations of the large cast
in-situ three-barrel culvert. These challenging ground conditions
were compounded by the perched water table in many areas
along the route. Affected areas were excavated and then filled
with crushed rock that was covered with a Bidim geotextile,
before work commenced on the layer works.
The road comprises a bedding layer compacted to 93%
AASHTO density; selected layers compacted to 95%
AASHTO density; and a C3 base course compacted to 98%
AASHTO density. This road will then be primed and sealed
with 13.2mm and 6.7mm thick bitumen layers. Quality G6
material for the sub-base layers was sourced on site from
the various cuttings and the remaining material from two
borrow pits that were opened specifically for this project.
In terms of the stabilisation of the sub-base layers, the
pockets of cement supplied to site by PPC were unpacked
and spread by hand to ensure accuracy and to provide further
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