Geotechnical Engineer : Moore, Spence & Jones (pty) Ltd
Date Of Works : Sept 2001
3300Nº Soil nails and rock bolts
220Nº Auger piles for Contiguous piled wall
120Nº Permanent Ground Anchors
Magoebaskloof pass between Pietersburg and Tzaneen
General project description
In February 2000 Cyclone Elina caused extensive flooding in the Northern Province including the scenic Magoebaskloof pass between Pietersburg and Tzaneen which is an important tourist route in the Province.
It was a condition of the tender and contract that the road remained open to light traffic and coaches throughout the duration of the contract. The road consisted of three lanes (two up, one down) but after the floods, this was reduced to two lanes in many sections. Stop/go sections were in operation where piling / drill rigs occupied an additional lane. The road was opened to 2 lanes last night. It was necessary to close the road for the day on four occasions where felling of trees was necessary.
The road damage can be divided into two categories. The slips (landslides) which occurred in the cuttings (cut slopes) and the slips/washaways, which occurred on the road, fill slopes. The fill slopes were repaired using two methods which were determined by the geological strata ad topographical factors. The small core drilling rigs were used initially to determine the geological formation. The first solution was a contiguous pile was anchored with permanent anchors.
The second method used was gabion walls. Galvanised mesh boxes (crates) were tied back into the fill using a mat, which extended 4 to 5 metres back into the fill and these were in turn fastened onto 12m long soil nails.
For the cut slopes, to prevent these slipping again, they were anchored back using soil nails (a lightweight version of a rock anchor) and gabions at the bottom of these slopes at road level. Because of the height of some of these cut slopes, the drill rigs drilling the soil nails were suspended from a crane.
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