Construction World September 2016

A Furukawa drill rig drilling 200 mm diameter holes for soil nail installation.

Pictured is a typical section through lateral support wall.

Gunite consists of crusher dust, sand and cement. On site water is added to this dry mixture while being sprayed with a compressor at +-7 bar. The lateral support to the new office of the Prime Minister is a permanent gunite wall, i.e. no addi- tional structure will be constructed in front of it, and it must support the retained soil over the three-metre spans between the slabs of the building for the lifetime of the building. These lateral support walls will require two layers of reinforcing mesh and gunite with a design strength of 25 MPa.

the walls, consisting of 7 200 metres of temporary soil nails with a permanent 4 170 m 2 gunite wall. The wall movement of all four walls was measured weekly throughout the 26-week duration of the project. This measurement process, undertaken to guarantee quality, includes the surveying of fixed points on the wall by means of a total-station as well as a plumb-bob system at the highest points of the walls. Every morning, prior to work commencing on site, the plumb-bob system was measured and recorded in the daily site diary. Surveying of all wall movement reflectors was undertaken on a weekly basis,

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usually on a Friday morning at sunrise before any operations on site would start. The lateral support project ran over a period of 105 days and was completed on schedule in the middle of May 2015. The construction of the buildings have however been put on hold due to the drought the country is experiencing.

The Stefanutti Stocks Geotechnical site crew, comprising of South African expats and a number of local Namibian residents who have been trained as rockcreter operators and nozzlemen.

CONSTRUCTION WORLD SEPTEMBER 2016