Background
The Newman to Roy Hill Transmission Line extends from the existing Mt Whaleback electrical substation, located 2.5km west of Newman, to the proposed Roy Hill mine site development to the north over a distance of approximately 120km. From Newman, the alignment follows the Great Northern Highway for approximately 6km to the southeast after which it turns to the north and approximately follows the alignment of Marble Bar Road to Roy Hill.
Scope
CMW carried out a geotechnical investigation incorporating the following works:
- Intrusive ground investigation by drilling boreholes and excavating test;
- Electrical resistivity testing;
- Laboratory testing on recovered soil and rock samples; and
- Factual and interpretative reports describing the work carried out along with design recommendations.
Findings/Challenges
The geotechnical field investigation was carried out over the period 14 May to 10 June 2013. All permits and plans were completed prior to mobilisation including, Health & Safety, Environmental and Quality.
Resistivity testing
The 28 day investigation campaign involved a total of 34 boreholes, with SPT’s and thin walled push tubes, and 12 test pits. DCP’s were performed at all test locations.
Field in-situ soil electrical resistivity tests were undertaken at nineteen locations and tests were run with electrode spacings at 1m, 2m, 4m, 8m and 15m using the Wenner Test method.
A total of 190 soil laboratory test were carried out along with an additional 203 rock laboratory test.
CMW provided 2 design recommendations for foundation types which were proposed in concept drawings being bored sockets and shallow pad footings.
CMW was awarded additional packages of work for this project in relation to design testing and construction of anchor foundations.