Methodology
Our DPL Light Dynamic Probing procedure follows Australian Standard AS 1289.6.3.2 and international best practice. A 10 kg hammer is dropped freely from a height of 500 mm to drive a 32 mm diameter cone at a controlled rate of 15 to 30 blows per minute. Blow counts (Nd) are recorded every 100 mm of penetration, with typical refusal defined at 100 blows per 100 mm or when penetration is less than 1 mm per blow. The equipment is calibrated before each deployment to ensure hammer energy efficiency exceeds 80%. Data is processed in real time and correlated with soil classification from adjacent boreholes. For comparison with deeper strata, we often combine DPL with Cone Penetration Test (CPT) to obtain continuous profiles to 30 m depth.
Reference Technical Parameters
| Parameter | Reference Value |
|---|---|
| Hammer Mass | 10 kg ± 0.1 kg |
| Drop Height | 500 mm ± 2 mm |
| Cone Diameter | 32 mm (60° apex angle) |
| Rod Diameter | 22 mm (internal flush) |
| Blow Count Range | 0–100 blows per 100 mm |
Local Considerations — Australia
Australia's diverse geotechnical landscape demands a regionally adaptive DPL approach. In the soft alluvial soils of Brisbane and the Gold Coast, blow counts are typically low (Nd < 5) to depths of 3–5 m, requiring careful correlation with shear wave velocity. In contrast, the dense cemented sands of Perth and the basaltic clays of Melbourne's western suburbs often yield Nd values exceeding 20 within 2 m. Our team calibrates the DPL procedure for each city's dominant soil type and seismic zone (AS 1170.4). For projects in Adelaide, Albury Wodonga, or Ballarat, we incorporate local geological maps and previous borehole records to optimise test spacing. This local knowledge ensures reliable data for foundation design under AS 2870.
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Our team reviews your project and issues an initial report at no cost.
Or write us directly at contact@standardpenetrationtest.org
Applicable Standards
- AS 1289.6.3.2 – Soil strength and consolidation tests: Determination of the penetration resistance of a soil using a 9 kg dynamic cone penetrometer (light)
- AS 1726 – Geotechnical site investigations (referenced for field procedures)
- AS 2870 – Residential slabs and footings (design using DPL-derived bearing capacity)
- Eurocode 7 (EN 1997-2) – Referenced for international correlation methods
Frequently Asked Questions
What is the maximum depth achievable with DPL Light Dynamic Probing?
Typical maximum depth is 8 metres in medium-dense soils, though refusal may occur earlier in gravels or cemented layers. In soft clays or loose sands, depths of 10–12 m are possible with specialised rods. Our equipment is limited to 15 m due to rod buckling constraints.
How does DPL differ from Standard Penetration Test (SPT)?
DPL uses a lighter hammer (10 kg vs 63.5 kg) and continuous 100 mm recording, while SPT samples at 1.5 m intervals. DPL provides a high-resolution profile of relative density but cannot retrieve disturbed samples for laboratory testing. Both methods are complementary under AS 1726.
What is the typical turnaround time for a DPL investigation?
On-site testing for a single probe to 5 m depth takes approximately 30 minutes. A standard project with 10 probes across a 1 ha site is completed in one day. Preliminary blow count profiles are provided within 24 hours; final report with bearing capacity analysis within 5 business days.
How much does DPL Light Dynamic Probing cost in Australia?
Costs range from $1,620 to $6,480 per project, depending on depth, site accessibility, number of test points, and mobilisation distance. For example, a single probe to 5 m in metropolitan Sydney is approximately $1,800; a 20-probe program in a regional area may reach $6,000. Contact our team for a site-specific quotation.