Hervey Bay grew quickly from a quiet fishing town into a major coastal centre, especially after the 1990s. That development pushed construction onto sandy coastal plains and reclaimed lowlands where the water table sits just a few metres down. For any project here, understanding lateral soil stiffness and in-situ stress history is critical. The Flat Dilatometer Test (DMT) provides exactly that data without the disruption of drilling. Before we run a DMT, we often combine it with a test pit program to log stratigraphy and confirm soil layering in the upper profile. This gives us a complete picture of how the ground behaves under load at depth.
Loose coastal sands and shallow groundwater make the DMT the most reliable tool for lateral stiffness assessment in Hervey Bay.
Service characteristics in Hervey Bay
- Material index (Id) for soil type identification
- Horizontal stress index (Kd)
- Dilatometer modulus (Ed) in MPa
- Constrained modulus (M) for settlement analysis
- Undrained shear strength (Su) in clay layers
Critical ground factors in Hervey Bay
AS 4678:2002 for earth retaining structures and AS 1726:2017 for geotechnical site investigations both apply directly to the DMT. In Hervey Bay, the risk of underestimating lateral soil movement is real — coastal infill and soft alluvial pockets can settle unevenly under foundation loads. Using the dilatometer test early in the design phase reduces that risk by providing site-specific stiffness values that standard penetration tests alone cannot offer. We see this especially on subdivisions near the Urangan marina or waterfront developments along the Esplanade.
Our services
We offer two complementary DMT service levels tailored to Hervey Bay projects.
DMT Sounding with Full Parameter Report
Includes blade insertion at 20 cm intervals, real-time readings of A and B pressures, and a complete report with Id, Kd, Ed, M, and Su profiles. Suitable for residential subdivisions, commercial slabs, and retaining wall design.
Combined DMT + Borehole Verification
DMT soundings paired with one borehole per site for soil sampling and laboratory classification. Recommended for multi-storey buildings or infrastructure projects where correlation with lab strength tests is required.
Frequently asked questions
How does the Flat Dilatometer Test differ from a CPT in Hervey Bay sand?
The CPT measures cone tip resistance and sleeve friction, which are great for soil profiling. The DMT measures lateral stress and stiffness directly, giving you the horizontal stress index (Kd) and constrained modulus. In loose coastal sands like those in Hervey Bay, the DMT is more sensitive to stress history and overconsolidation effects, making it better for settlement and lateral movement predictions.
What is the typical cost range for a DMT in Hervey Bay?
The cost for a standard DMT sounding with full parameter report in Hervey Bay ranges between AU$1.360 and AU$1.450 per test point, depending on depth, site access, and number of readings. Volume discounts apply for multiple soundings on larger subdivisions.
Can a DMT be performed in very loose wet sand near the water table?
Yes. The DMT blade is pushed hydraulically from a CPT rig, so even loose saturated sands do not prevent insertion. In fact, the test performs well in these conditions because the membrane inflation is independent of groundwater. We regularly run DMT soundings within 5 metres of the Hervey Bay foreshore with no issues.