Undisturbed Sampling (Shelby Tube) in Hervey Bay

A common mistake we see in Hervey Bay is relying only on disturbed samples from test pits or auger holes. The sand and clay layers here, especially around the coastal suburbs, can look uniform on the surface but behave very differently under load. Without undisturbed sampling using a thin-walled Shelby tube, you risk underestimating settlement or overestimating bearing capacity. That leads to foundation redesigns or costly repairs later. We take undisturbed samples to preserve the in-situ structure, moisture content, and stress history. That allows us to run reliable triaxial or consolidation tests back at our NATA-accredited lab. For projects near the Urangan marina or the new estate developments, this level of precision is non-negotiable.

A Shelby tube sample preserves the in-situ fabric of the soil — the difference between a safe design and a costly failure in coastal sands.

Service characteristics in Hervey Bay

Hervey Bay sits on Quaternary coastal deposits with interbedded sands, silts, and soft clays. The water table is shallow, often less than 2 m deep. That makes undisturbed sampling tricky but essential. Our Shelby tube procedure follows AS 1726-2017 to the letter. We push the tube hydraulically at a steady rate, extract it carefully, and seal it immediately to preserve moisture. Back in the lab, we log each sample for recovery ratio, disturbance indicators, and visual classification. The key parameters we measure include undrained shear strength (cu) via ensayo triaxial, compressibility from consolidation tests, and sensitivity. Each sample tells us how the soil will react under the actual foundation load. Without this data, your geotechnical model is just a guess.

Undisturbed Sampling (Shelby Tube) in Hervey Bay – Geotechnical Soil Testing

Parameter	Typical value
Tube diameter	50 mm, 75 mm, 100 mm
Wall thickness	1.5 mm (thin-walled, area ratio < 10%)
Recovery ratio	> 95% typical in cohesive soils
Sample length	450 mm to 900 mm
Sealing method	Wax seal + end caps + moisture barrier
Storage temperature	4°C, in sealed PVC tubes
Transport time limit	Within 48 hours to lab
Standards	AS 1726-2017, AS 1289.6.0

Critical ground factors in Hervey Bay

Compare the soils in Pialba with those in Point Vernon. Pialba has firmer sands and gravels from old alluvial fans. Point Vernon has soft estuarine clays that can squeeze under load. If you use a standard split-spoon sampler in those clays, you get a disturbed lump that tells you nothing about the real strength. Undisturbed sampling with a Shelby tube captures the actual undrained shear strength and sensitivity. That is the difference between a foundation that works and one that settles unevenly. Knowing the local variability early saves weeks of redesign and thousands in remedial work.

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Applicable standards: AS 1726-2017 (Geotechnical site investigations), AS 4678-2002 (Earth retaining structures), AS 1289.6.0 (Standard Practice for Thin-Walled Tube Sampling), AS/NZS 1170.0-2002 (Structural design actions – general principles)

Our services

We provide a complete suite of undisturbed sampling services tailored to Hervey Bay’s coastal conditions. Each service is backed by NATA-accredited lab procedures and experienced field crews.

Shelby Tube Sampling – Cohesive Soils

Thin-walled tube sampling for clays, silts, and soft sands. Hydraulic push method, 50–100 mm diameter. Sealed and transported to the lab within 48 hours. Ideal for consolidation and triaxial testing.

Block Sampling – Very Soft Clays

For extremely sensitive clays where tube disturbance is unacceptable. We carve a hand-cut block sample, wax-seal it, and test for undrained shear strength and sensitivity. Used in Point Vernon and Urangan soft zones.

Piston Sampling – Continuous Profiles

Fixed-piston sampler for continuous undisturbed cores up to 1.5 m. Reduces sample disturbance further. Used for detailed settlement analysis and slope stability studies in Hervey Bay’s coastal developments.

Frequently asked questions

What is the difference between disturbed and undisturbed soil sampling?

Disturbed sampling (from augers or split-spoon) breaks the soil structure and changes moisture content. Undisturbed sampling with a Shelby tube preserves the in-situ fabric, water content, and stress history. That allows accurate lab tests for strength, compressibility, and consolidation — critical for foundation design in Hervey Bay's soft coastal soils.

How much does undisturbed sampling (Shelby tube) cost in Hervey Bay?

The typical cost range for undisturbed sampling with a Shelby tube in Hervey Bay is between AU$700 and AU$1,440 per sample, depending on depth, tube diameter, and number of tests requested. Volume discounts apply for multiple samples. Contact us for a fixed quote based on your project scope.

When is Shelby tube sampling required instead of standard SPT?

Shelby tube sampling is required when you need undisturbed specimens for triaxial, consolidation, or permeability tests. Standard SPT (split-spoon) gives only blow counts and a disturbed sample. For settlement analysis, slope stability, or foundation design in soft clays — like those found in Point Vernon or Urangan — Shelby tube sampling is essential.