Grundodrill 7XP bores under a highway in South Africa

Rolkon’s previous experience with No Dig techniques has been with their ever-growing range of Grundomat soil displacement hammers. Due to Rolkon’s continued success they decided to expand their trenchless capabilities and purchased a Grundodrill 7X plus from the TT Group product supplier Reef Pneumatics based in Primrose, Germiston near Johannesburg.

 

The Grundodrill 7X plus combined with the MA010 mixing system arrived in Durban early 2011 Rolkon/Reef then subsequently employed the services of TT-UKs Horizontal Directional Drilling (HDD) specialist Jim Albarella to carry out a thorough training and technical/transfer to Rolkon’s designated drilling crew. One practice bore was carried out beneath a grass verge before attempting the N3 toll route highway project.

 

The N3 toll route highway bore length crossing was 64 metres, a pilot bore was carried out across the highway which took 2.5 hours to complete. The ground conditions were a mixture of bolder rock and sandy clays, the bolder rock in various parts of the bore was very difficult at times and a great deal of patience was needed to negotiate through difficult areas of the bore. Once the pilot bore was completed a pre-reaming operation was carried out using a 155 back reamer at the same time drill rods were added to the special adapter on the back reamer. These were pulled into the pilot bore which ensured that the borehole was not lost during the pre-reaming operation.

 

Once the pre-reaming operation had been completed the back reamer was exchanged with a Grundoream body 2, this type of back reamer has exchangeable cutting blades, the size of blades used was 350mm. As the Grundoream was pulled into the bore to expand the bore diameter the 3x110mm PE pipes SDR 17 which would subsequently house electric cables were installed at the same time. This final part of the back reaming operation took 4.5 hours to complete due to the challenging ground conditions of bolder rock and sandy clays.

 

Finally the bundle of PE pipes were installed to the satisfaction of the client Eskom.