Timaru Main Trunk Sewer Renewal

Timaru Main Trunk Sewer Renewal
Timaru District Council
3 x 400m drives of 2.5m diameter ring beam and lagging tunnel with multiple curves in each section of tunnel.
Ring beam and lagging tunnel through varying ground conditions.
“Extensive planning to avoid uplift and deformation.”

The project involved the construction of a 2.5m ring beam and timber lagged tunnel through ground conditions ranging from soft clays to cannington gravels/boulders and solid basalt.


An Akkerman ring beam and lagging machine was used together with an Akkerman EX50 Excavator in the softer ground, and conventional drill and blast methods in the harder ground to complete tunnel construction.


Following construction, two PE pipes were pulled through the tunnel length and grouted into place. This operation required extensive planning to avoid uplift and deformation during the curing period. Additional difficulties encountered within the project were curved drives to avoid private land boundaries and stay within the council owned reserve.

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Abergeldie Harker
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PO Box 9888, Newmarket, Auckland 1149, New Zealand

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