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Case Study
Bruce Highway, QLD
ROCKFALL MESH
Project: Gunalda Range Cutting - Bruce Highway
Location: Gympie, Queensland
Client: Henry Walker Eltin
Principal: Queensland Main Roads
Part of Bruce Highway works 30 km North of Gympie involved a significant rock cutting through the Gunalda range. The cutting was excavated in three separate cuts. Each cut was about 10-15m high giving an overall height about 40metres. The cut faces were separated by narrow benches which in some cases provide access and a working platform for the rock mesh installation.
The preparatory rock scaling operations to remove any loose debris from the newly exposed rock face was commenced in August 2000 but was soon suspended while the Main Roads Geotechnical Engineers reviewed their proposed design.
Rock bolts were drilled and installed at strategic locations on the face to support any loose formations. Galvanised 20mm Reid Bar was used for these rock bolts.
Once the scaling was completed the rock mesh installation could commence. This involved the drilling and installation of anchor points at the top and base of each face. A wire rope was then threaded through the anchors to provide a continuous connection for the rockfall mesh.
Rock mesh was then installed using a combination of absailing and "cherry picker" techniques. Once in place the mesh was permanently connected to the top and bottom anchor ropes.
The upper cuttings were completed first followed by a brief delay while further excavation and scaling was done.
During the last excavation the lowest access benches were deemed to be unstable and were therefore removed. A revised work method was therefore adopted for the lowest cutting as a convenient working platform was no longer available.
A total of about 600 anchors and 12,000sq.m of mesh were installed following the various design modifications and work was completed in December 2000.
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