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Anchor tests confirm safety on Lake Narracan and Glenmaggie dams rock solid after winter stability checks and maintenance

Anchor testing at Lake Narracan and Glenmaggie confirms both dams are secure. Regular inspections and monitoring ensure ongoing safety, with tests conducted every 5 - 10 years per national guidelines.

By news@gippsland - 7th August 2025 - Back to News

We've been busy this winter completing anchor testings at Lake Narracan and Lake Glenmaggie to ensure the strength and stability of the dam structures meet the required standards. The results show they're both rock solid and we wanted to share what's involved in anchor testing and why it's important.

We use calibrated hydraulic or electrical load cells to measure anchor force, lifting it slightly with a jack to assess performance

What are anchors?

A dam anchor is typically a large bundle of high-strength steel strands that is installed by drilling a hole through the dam and inserting and grouting it into the bedrock to secure the structure. They act like massive bolts, helping to hold the dam wall down and improving its stability against hydraulic or seismic forces, such as earthquakes. Dam anchors comprise three key components:

• Anchorage head: This is the connection between the anchor and the dam structure, enabling the transmission of the anchor forces to the dam via the bearing plate
• Anchor free length: This is the section of strand from the anchorage head to the near end of the anchor's fixed length
• Anchor fixed length (also known as the Bond Length): This is the length of strand by which the tensile force is transmitted to the surrounding ground through the grout

The steel strands are tensioned (stretched) after installation and then locked in place, effectively anchoring the dam to the foundation bedrock.

Dam anchors are tensioned steel strands grouted into bedrock, stabilising the dam against water pressure and earthquakes through secure structural connections

How we test the anchors?

We use a load cell - a heavy and sturdy sensor - that measures the force or load applied to the anchor. Load cells can be either hydraulic or electrical, and they help to provide real-time data on the anchor's performance, which is crucial for dam safety and maintenance.

Before testing, the load cells undergo careful calibration and any necessary refurbishment to ensure accurate and reliable measurements during the anchor test. The load cell is screwed onto the anchor, and using a hydraulic jack, we perform a test lift - raising the anchor 1.0 millimetre clear of the bearing plate.

Pictures from Southern Rural Water website.

Source: http://gippsland.com/

Published by: news@gippsland.com