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The N3 Toll Route is a key transport node linking the largest port, Durban Harbour, to South Africa’s economic hub, Gauteng. For this reason, the company managing the N3 Toll Route, the N3 Toll Concession’s road safety efforts, includes upgrade and maintenance programmes to ensure the extended lifespan of this important road link.
Geotechnical investigations revealed that the release depth of the superficial slope failure measured approx. 1- 2 m and caused one road line to collapse and slip down. The total project area covered 1’750 m2 The stabilized area was 100 m long and up to 10 m high with a 65° steep slope.
The geology is characterized by shales, mudstones, and fine-grained sandstone. The area falls within the Grassland Biome with topography that is mainly flat and rolling but includes the escarpment itself. The climate condition in the area is characterised by heavy and frequent rainfalls, significantly increasing during the rainy season.
The slope stability work on the N3 involved the following work: On the one section, there was a diameter of 100 mm holes drilled by DTH up to 8 meters length. Steel anchors (32 mm galvanized gewi) had been installed with their necessary centralizers and tremie pipe for the injection of grout. A 30mpA grout mix was used. After seven days, the TECCO® mesh was installed. The anchors were secured onto the mesh with P66/50 galvanised spike plates on section 5a. A 13mm galvanized cable was used for the boundary rope.
On the slope section of this contract, two kinds of soil anchors, a 25 mm galvanized gewi of 8 meters length plus R32S self-drilling anchors of 16 meters length, were used. Holes were drilled 100 mm for the 25 mm gewi bars, and a 110 mm bit was used for the R32S self-drilling rod. While drilling, the grouting process was done simultaneously. On this section, we also used the TECCO® G65/4 with a P33/40 spike plate and 13 mm galvanized cable for the boundary rope. A total of 2514.50 meters had been drilled on this project.
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