The sandy coastal soils around Bunbury often sit above a shallow water table, especially near the Leschenault Estuary and the Preston River floodplain. In our experience, these soils can appear well-graded but compact poorly if moisture control is ignored. That is why running a Proctor test early in the project stage is a necessary step — it defines the optimum moisture content and maximum dry density for any fill material before the roller even arrives. For earthworks in Bunbury, combining the Proctor test with a placa de carga field plate load test gives you both laboratory compaction targets and on-site modulus verification.
The Proctor curve from Bunbury’s sandy loams typically shows a sharp drop-off on the wet side of optimum, meaning moisture control during compaction is tight.
Methodology and scope
- Maximum dry density (MDD) in t/m³
- Optimum moisture content (OMC) in percent
- Dry density vs. moisture curve shape
- Zero air voids line for saturation check
Local considerations
Bunbury sits on the Swan Coastal Plain, where the underlying Tamala Limestone formation transitions into deeper alluvial sands and clays near the coast. With an average annual rainfall around 740 mm concentrated between May and September, earthworks scheduled during winter months often face moisture levels above OMC. If compaction targets are set without a site-specific Proctor curve, the contractor risks placing fill that will settle under service loads. In 2023, a subdivision project near Bunbury’s Vittoria Road required re-compaction of 4,000 m³ of imported fill after field densities showed only 92% of the laboratory MDD — a problem solved by re-running the Modified Proctor and adjusting the moisture regime.
Applicable standards
AS 1289.5.1.1 – Soil compaction and density tests: Standard compactive effort, AS 1289.5.2.1 – Soil compaction and density tests: Modified compactive effort, AS 1289.5.1.1-12e2 – Standard Proctor (reference for international projects), AS 1289.5.2.1-12e1 – Modified Proctor (reference for high-energy compaction)
Associated technical services
Standard Proctor (AS 1289.5.1.1)
Suitable for fill compaction control in residential subdivisions, light commercial sites, and road shoulders. Uses a 2.5 kg rammer dropped 300 mm in three layers. Reported parameters include MDD, OMC, and the dry density curve.
Modified Proctor (AS 1289.5.2.1)
Required for heavy-traffic pavements, port hardstands, and deep fill embankments in Bunbury. Uses a 4.54 kg rammer dropped 450 mm in five layers, delivering four times the energy of the standard method.
Typical parameters
Frequently asked questions
How long does a Proctor test take from sample drop-off to results?
For a single sample, the laboratory procedure takes about 24 hours including drying. In practice, we issue the report within 48 hours of receiving the bagged sample at our NATA-accredited facility.
What is the difference between Standard and Modified Proctor in terms of application?
The Standard Proctor simulates light compaction equipment (e.g., small vibrating plate), while the Modified Proctor replicates heavy rollers used on major roads and airfields. For Bunbury’s industrial zones, Modified is the default.
Can you run a Proctor test on sandy or gravelly soils common in Bunbury?
Yes. Sandy soils with up to 19 mm particles fit the standard mold. For coarser material up to 37.5 mm, we use the modified mold. Oversize particles are scalped and corrected using the replacement method per AS 1289.5.1.1.
How much does a Proctor test cost in Bunbury?
The typical cost range is between AU$180 and AU$350 per sample, depending on whether you need Standard or Modified compactive effort. Volume discounts apply when submitting multiple samples from the same project.