Field Vane Shear Test (VST) in Bundaberg

We recently assessed a soft clay deposit on the northern edge of Bundaberg for a two-storey commercial building. The site had 6 m of estuarine clay over dense sand. A field vane shear test (VST) was the right tool to measure undrained shear strength directly in situ. We deployed the vane at 1 m intervals using a hydraulic rig. Each test took about 20 minutes. The data let the design team set reliable parameters for shallow foundations without over-conservatism. For deeper layers we also ran a presurometer test to compare stiffness values. The vane test is especially useful in Bundaberg because the coastal soils can be highly sensitive. Remoulded strength values help the engineer decide whether the clay will lose bearing under construction traffic.

Bundaberg’s estuarine clays can have sensitivity ratios over 6 — the vane test captures that loss of strength directly in the field.

Methodology applied in Bundaberg

Bundaberg’s soil profile varies from the Burnett River floodplain to the inland basalt ridges. In the floodplain we find soft to firm clays and peat lenses. On the basalt slopes the soils are stiff but may contain old root holes. The field vane shear test handles both scenarios well. In soft clays we use a 65 mm × 130 mm vane with a torsion spring that matches the expected torque. In stiffer soils we switch to a 50 mm × 100 mm vane.

Maximum torque capacity: 200 N·m
Rotation speed: 6°/min (standard)
Data recorded: peak torque, remoulded torque, sensitivity ratio

The test procedure follows AS 1726‑2017. We also compare vane results with a compression simple test on undisturbed tube samples when we need additional confirmation for deep foundation design. The whole setup fits in a ute and can reach most sites around Bundaberg within 30 min from our depot.

Field Vane Shear Test (VST) in Bundaberg – Geotechnical Lab Services

Parameter	Typical value
Vane size (standard)	65 mm × 130 mm
Vane size (stiff clay)	50 mm × 100 mm
Torque capacity	200 N·m
Rotation speed	6°/min
Depth range	0.5 m – 20 m
Typical test time per depth	15–25 min

Typical technical challenges in Bundaberg

AS 1726‑2017 requires that the vane test be performed at a constant rotation rate to avoid strain-rate effects. In Bundaberg’s saturated clays, the main risk is underestimating the remoulded strength if the vane is rotated too fast. We control the rate with a digital torque transducer. Another common issue is rod friction in deep holes. We subtract the friction measured before the vane engages. The test is also sensitive to sand or shell layers. If the vane hits a shell pocket, the torque spike can give a false peak. We always correlate vane data with a granulometry test on samples from the same depth to confirm grain size. This prevents misinterpretation and keeps the foundation design safe.

This service complements our laboratory testing work for a complete project analysis.

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Email: contact@geotechnicalengineering1.xyz

Applicable standards: AS 1726‑2017 (Geotechnical Site Investigation), AS 1289.6.2.1‑18 (Standard Test Method for Field Vane Shear Test in Saturated Fine-Grained Soils), AS 4678‑2002 (Earth Retaining Structures)

Our services

We offer the field vane shear test as a standalone service or as part of a broader geotechnical investigation in Bundaberg. The following sub‑services are available:

Standard Vane Shear Test (VST)

Full field vane shear test at multiple depths using a hydraulic rig. Includes peak and remoulded torque measurement, sensitivity ratio calculation, and a certified report with AS 1726 compliance. Suitable for soft to firm clays and peat.

Wet‑hole Vane Test (WVST)

Modified vane test performed inside a cased borehole with drilling mud. Used when the clay layer is below the water table and the hole would collapse without support. Same torque measurement and reporting as the standard test.

Frequently asked questions

How deep can the field vane shear test reach in Bundaberg soils?

With a standard hydraulic rig we can reach up to 20 m depth. In Bundaberg's estuarine deposits the target is typically between 3 m and 12 m, where the soft clays are thickest.

What is the typical cost of a vane shear test in Bundaberg?

For a standard site with 5 test depths, the cost ranges between AU$890 and AU$2,090 depending on access, depth, and number of vanes. We provide a fixed quote after a site visit.

Do you need undisturbed samples if you run a vane test?

The vane test gives undrained shear strength directly, but we always recommend taking at least one undisturbed tube sample per soil layer for moisture content and Atterberg limits. This helps correlate the vane results and check soil classification.

Can the vane test be used for slope stability analysis in Bundaberg?

Yes. The vane test is the preferred method for measuring shear strength in soft clays for slope stability. The peak strength is used for short‑term stability and the remoulded strength for long‑term or post‑failure conditions. We have used it on several canal and riverbank projects in the region.