Construction World January 2019

PROJECT PROFILE

UPGRADE ON N11 SECTION 10 FROM MIDDELBURG TO LOSKOPDAM HHO Consulting Engineers was appointed in 2010 by the South African National Roads Agency Limited (SANRAL) to carry out design upgrades of the 54 km of road between Middelburg and Loskopdam (N11 - Section 10) in Mpumalanga.

T he route traverses flat to rolling terrain with very shallow cuts and fills over most of its length. There are two passes where there are deep cuts and fills. The road section through the Kranspoort Pass has a very high accident rate due to the sharp bends located at the bottom of the pass. These bends are preceded by a sustained downgrade, resulting in runaway trucks not being able to negotiate the bends. Due to the extensive nature of the distress of the road pavement over this section of the route and the fact that the surfaced roadway was only 7 m wide, it was decided to carry out a rehabilitation of the road. The safety improvements within the Kranspoort Pass was a major component of the upgrades. Cut widenings in the 5 km long pass were needed in order to flatten out certain of the sharp bends, as well as to make provision for an additional lane and two arrestor beds. There are eight major cuttings within the pass, with heights of up to 40 metres and cut slopes as steep as 75 degrees. In order to protect the future road users against falling rocks, various slope stabilisation methods were used. Soil nail anchors with mesh draping is provided along the higher quarzitic sandstone cut faces, while tied back 8-10 metre high gabion walls are

provided in the weathered dolerite sections. Rock traps of 4-6 metre wide and concrete barrier walls are provided at the foot of the cuttings. The blasted material from the cuttings was carted to the on-site crushing facility that was established in order to produce crushed stone material for use in the road layer works, including a new crushed stone base and the bituminous double seal surface. Safety improvements at the Doornkop Village, which included the construction of a 3 km pedestrian sidewalk facility separated from the National Road including access management by means of upgrading the internal village access roads formed part of the project. Community Participation objectives for the project, which included targeted labour and targeted enterprises was set at 18%. The actual expenditure was 32,6% or R112-million of the total project cost of R350-million. The project was completed in December 2017 and opened

to traffic in time for the school holidays. Quality of the Engineering Design

At the commencement of the appointment, a detailed investigation was carried out. The road investigations

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CONSTRUCTION WORLD JANUARY 2019