Rockhampton expanded rapidly during the 1860s gold rushes, with early builders placing structures directly on the floodplain's deep alluvial and colluvial fills. Those fills now support houses, commercial blocks, and roads across the city. Our team analyses these man-made ground layers to determine how they will behave under load. We combine borehole logging, SPT testing, and laboratory classification to produce a clear picture of fill thickness, composition, and compaction. This analysis is the foundation of any safe design. Before you pour concrete, we recommend running a subgrade assessment for pavements to compare fill performance across your site, and if the fill is deep, a plate load test equivalent gives us the stress-strain response directly.
Fill from the 1920s can hide loose zones, organic pockets, or even buried stumps. Our analysis digs into that variability.
Scope of work
- Dynamic cone penetrometer (DCP) profiles to map strength layers
- Moisture-density correlation via nuclear gauge and sand cone
- Atterberg limits and soil classification on suspect samples
Area-specific notes
Rockhampton sits at just 14 m above sea level on the Fitzroy River floodplain, and the water table can rise within 1 m of the surface after heavy rain. That shallow water turns poorly compacted fill into a sponge. When loaded, it consolidates unevenly, cracking slabs and tilting walls. We have documented differential settlements of 40–80 mm in fills less than 2 m thick in the Depot Hill area. Without proper foundations on fill analysis, you risk structural damage that costs far more than the geotechnical investigation. Our team flags these risks early so you can design deep footings or Improvement before construction begins.
Standards used
AS 1726 – Geotechnical Site Investigations, AS 4678 – Earth Retaining Structures, AS 1289.5.4.1 – Compaction control (sand replacement)
Linked services
Standard Fill Assessment (Residential)
For house slabs and small commercial pads. Includes 2 boreholes to 3 m depth, DCP profiles, moisture-density tests, and a report with bearing capacity and settlement estimates.
Deep Fill Investigation (Industrial / Subdivision)
Covers fills deeper than 3 m. Adds SPT borings, undisturbed sampling, consolidation testing, and settlement-time predictions. Suitable for large warehouses, retaining walls, and road embankments.
Typical parameters
FAQ
How much does a foundations on fill analysis cost in Rockhampton?
A standard residential analysis typically costs between AU$1,340 and AU$2,100, while a deep fill investigation for industrial sites ranges from AU$2,500 to AU$4,300. Final price depends on borehole depth, number of tests, and site access conditions.
What signs indicate that fill on my site is poorly compacted?
Look for cracks in the slab, doors that stick after rain, or noticeable dips in the ground surface near the building perimeter. Our DCP and density tests confirm whether the fill meets the required 95% MDD standard.
Can I build on fill without any geotechnical analysis?
Technically yes, but it is a high-risk shortcut. Unanalysed fill can settle 30–60 mm under a standard house load, causing slab cracks and service line breaks. Most Rockhampton councils require a geotechnical report for new structures on fill deeper than 0.5 m.