In Bundaberg, many sites show a tricky contrast between loose sandy layers near the surface and stiff clayey deposits deeper down. We run the Flat Dilatometer Test (DMT) to capture the full stiffness profile without disturbing the soil fabric. It gives us the horizontal stress index and modulus directly, which is essential when we're designing shallow or deep foundations in these variable alluvial soils. For projects needing a baseline of strength, we often cross-reference DMT readings with a compression test on intact samples to validate the unconfined compressive strength. The DMT blade penetrates at a steady 20 mm/s, and we log pressure readings at every 200 mm depth interval. That level of detail helps us pick up thin layers that a standard SPT might miss entirely.
DMT captures soil stiffness and lateral stress in-situ, critical for foundation design in Bundaberg's layered alluvial profiles where SPT alone misses thin clay seams.
Methodology applied in Bundaberg
Typical technical challenges in Bundaberg
Cyclonic rain events here can saturate the upper sands in hours, which changes the effective stress and makes DMT readings drift if you don't correct fast. We've seen pore pressure lag cause p0 values to read high right after heavy downpour, so we always monitor barometric pressure and apply the standard ASTM correction. Another risk is hitting buried ferrous debris in old cane farm sites — the blade can get nicked or refuse to penetrate. That's why we pre-scan with a magnetometer and keep spare membranes on hand. Missing a thin clay seam between sand layers can lead to underestimating settlement by 40 percent, so we never skip the 200 mm logging step.
This service complements our laboratory testing work for a complete project analysis.
Our services
We deliver the Flat Dilatometer Test as part of a broader geotechnical investigation package tailored to Bundaberg conditions. Our team holds NATA accreditation for field testing and follows ISO 17025 procedures in the lab.
DMT Profiling with Real-Time Data Logging
We deploy a 15-tonne CPT truck for DMT pushes up to 30 m deep, recording p0, p1, p2 at every 200 mm. Results are plotted on-site so the engineering team can adjust the testing grid immediately. We provide a full report with ID, KD, ED profiles and interpreted settlement modulus.
Combined DMT and SPT Investigation
For projects requiring both stiffness and penetration resistance, we run DMT alternating with SPT in the same borehole. This gives you a complete picture: DMT for modulus and lateral stress, SPT for blow counts and sample recovery. Ideal for bridge footings and wharf structures near the Burnett River.
Frequently asked questions
What does the Flat Dilatometer Test measure that SPT does not?
The DMT directly measures in-situ horizontal stress (K0) and soil stiffness (modulus) without the dynamic disturbance of a hammer blow. SPT gives you blow counts and a disturbed sample, but it cannot capture the stress history or the small-strain stiffness that governs settlement. In Bundaberg's layered soils, DMT picks up thin clay seams that SPT often punches through.
How deep can the DMT penetrate in typical Bundaberg soils?
With our CPT truck, we routinely reach 25 to 30 m in the alluvial sands and clays around the city. In the cemented layers near the coastal dunes, we may stop at 15 m if refusal is met. We always pre-drill through any gravel or calcrete caps before pushing the blade.
Is the DMT suitable for soft soils and sensitive clays?
Yes — the DMT is excellent in soft clays because the blade expansion is only 1.1 mm, which causes minimal disturbance. In Bundaberg's estuarine clays, we get clean p0 and p1 readings that correlate well with oedometer modulus. We just need to correct for pore pressure lag in very low permeability soils.
What is the typical cost range for a DMT investigation in Bundaberg?
For a standard 15 m profile with full reporting, the cost ranges between AU$1,210 and AU$1,570. This includes mobilization within the Bundaberg area, one membrane set, and a PDF report with ID, KD, ED profiles. Volume discounts apply for multiple test locations on the same site.
How long does a DMT test take on site?
A single 15 m push takes about 45 minutes including setup and membrane calibration. For a typical investigation with 4 to 6 locations, we complete the fieldwork in one day. Real-time data is available on screen, so we know immediately if we need extra depth or additional points.