Our field crew deploys a track-mounted drill rig on Hervey Bay sites, typically paired with a portable dynamic cone penetrometer to log soil response in real time. The rig retrieves undisturbed tube samples from depths up to 6 meters, which we seal and transport to our NATA-accredited lab for oedometer testing. This setup is standard for collapsible soil evaluation in Hervey Bay because the shallow water table and dune sands demand careful handling to preserve in-situ moisture content. We also conduct in-situ density tests using the sand replacement method right after extraction.
Saturation of dune sands in Hervey Bay can trigger immediate collapse settlements exceeding 50 mm under moderate loads.
Service characteristics in Hervey Bay
- Double-oedometer consolidation for collapse index
- In-situ moisture and density by sand cone
- Comparison with local collapse records
Critical ground factors in Hervey Bay
Hervey Bay expanded rapidly along the foreshore from the 1980s, with many subdivisions built on former dune systems. These aeolian sands are loose and metastable — they support structures when dry but can densify abruptly when water infiltrates from broken drains or heavy rain. Without a proper collapsible soil evaluation, a residential slab can settle unevenly, cracking walls and floors. The risk is highest in Torquay and Scarness, where the water table sits within 2 metres of the surface. Identifying collapse-prone zones early avoids costly retrofitting.
Our services
We offer three complementary services tailored to Hervey Bay's ground conditions, each feeding into a complete collapsible soil evaluation.
Double-Oedometer Collapse Test
Two identical samples are loaded — one at natural moisture, one soaked — to measure the difference in void ratio. The collapse potential index is calculated and compared to the Jennings & Knight criteria.
In-Situ Density & Moisture Survey
Sand replacement and nuclear gauge methods determine dry density and water content at multiple depths. Data is used to assess the initial state parameter of the soil.
Shallow Settlement Analysis
Using collapse test results, we model immediate settlement under proposed footing loads. Output includes differential settlement estimates for single-storey homes and light commercial slabs.
Frequently asked questions
What is collapsible soil and why does it matter in Hervey Bay?
Collapsible soil is a loose, metastable material that loses strength and compresses suddenly when wetted. In Hervey Bay, the coastal dune sands are particularly susceptible because they have a honeycomb structure that collapses once water breaks the inter-particle bonds. If ignored, a house slab can sink 30–60 mm after the first heavy rain.
How much does collapsible soil evaluation cost in Hervey Bay?
The typical cost for a complete collapsible soil evaluation in Hervey Bay ranges from AU$1,370 to AU$3,500. The final fee depends on the number of test pits, depth of sampling, and whether double-oedometer tests are required. We provide a fixed quote after reviewing the project scope.
Which standard governs collapsible soil testing in Australia?
The primary standard is AS 1726-2017 for geotechnical site investigations. For the collapse test itself, we follow AS 1289.7.1, which defines the collapse potential index and the laboratory procedure for double-oedometer testing.
How long does the evaluation take from sampling to report?
Field sampling takes one day for a standard residential block. The double-oedometer consolidation test requires 5 to 7 days to reach the final load stage. The full report, including settlement analysis, is usually delivered within 10 working days.
Can I build a slab on collapsible soil without expensive ground improvement?
Yes, in many cases. If the collapse potential index is below 1%, a stiffened raft slab designed per AS 2870 can accommodate minor differential movement. For higher collapse indices, pre-wetting, dynamic compaction, or deep soil mixing may be needed. The evaluation report will state the acceptable foundation option.