In Hervey Bay, we see sandy soils and coastal clays that change behavior with the water table. A simple field guess on permeability can lead to drainage failures. That is why we run laboratory permeability tests under controlled conditions. We use falling head for fine soils and constant head for sands. Every sample is compacted to field density before testing. The results give you a reliable k-value for foundation design, retaining walls, or pavement subgrades. Before we start, we often recommend a classification of soils to pick the right test method. That step saves time and avoids retesting.
A falling head test on Hervey Bay clay gave k = 3.2 × 10⁻⁹ m/s, confirming the need for subsurface drainage.
Service characteristics in Hervey Bay
Critical ground factors in Hervey Bay
A commercial development in Pialba relied on a single field infiltration test. The design assumed k = 10⁻⁵ m/s. After heavy rain, the basement wall leaked. We ran laboratory permeability tests on split-spoon samples. The actual k was 10⁻⁷ m/s. The difference meant the drainage system was undersized by 40%. The fix cost three times the original test budget. In Hervey Bay, where the water table fluctuates seasonally, lab permeability data prevents that kind of error. It is cheap insurance against structural damage.
Our services
We offer two standard laboratory permeability services tailored to Hervey Bay soil profiles.
Falling Head Permeability
For fine-grained soils: clays, silts, and clayey sands. Uses a flexible-wall permeameter. Confining pressure matches estimated overburden. Test duration 3 to 7 days depending on sample thickness. Report includes k at 20°C, void ratio, and saturation level.
Constant Head Permeability
For coarse soils: clean sands and gravelly sands. Rigid-wall permeameter. Flow is measured under constant head difference. Typical test takes 2 to 4 hours. Results are used for dewatering design, filter layers, and drainage blanket specifications.
Frequently asked questions
What is the difference between falling head and constant head permeability tests?
Falling head is used for fine soils with low permeability (k < 10⁻⁴ m/s). The water level drops over time, and the rate of fall gives the k value. Constant head is for coarse soils with higher permeability. Water flows through the sample at a steady head, and the collected volume is measured. Both methods follow AS 1726 and ASTM standards.
How much does a laboratory permeability test cost in Hervey Bay?
A standard falling or constant head test costs between AU$680 and AU$1000 per sample. The price depends on specimen preparation, test duration, and whether remolding is required. We provide a fixed quote after sample receipt.
How long does it take to get results?
Falling head tests take 5 to 10 business days because of the slow flow in fine soils. Constant head tests are faster, typically 2 to 3 business days. Urgent requests can be prioritized for an additional fee.
Do you test disturbed or undisturbed samples?
Both. Undisturbed tube samples (U50, U63, U100) are preferred for falling head tests on clays. Remolded samples compacted to field density are used for constant head tests on sands. We always note the sample condition in the report.