Subgrade Stabilisation Assessments

The subgrade, the natural ground layer beneath a pavement or structure, is critical to long-term performance. Subgrade stabilisation involves improving the engineering properties of these soils to provide a strong, stable, and durable foundation. Atlas Engineering and Technology Group offers comprehensive subgrade stabilisation assessments in Sydney to ensure your earthworks meet design specifications and achieve optimal performance.

Our Subgrade Stabilisation Assessment Services

Our testing services cover all stages of the subgrade stabilisation process, from initial site investigation to post-construction verification. We tailor our approach to your project's specific requirements.

Pre-Stabilisation Investigations

Before stabilisation works commence, a thorough understanding of the existing subgrade material is essential. Our pre-stabilisation investigations include:

  • Soil classification and characterisation (e.g., Particle Size Distribution, Atterberg Limits).
  • In-situ strength assessment (e.g., California Bearing Ratio - CBR, Dynamic Cone Penetrometer - DCP).
  • Moisture content determination.
  • Assessment of material suitability for stabilisation.
  • Laboratory trials to determine the appropriate type and proportion of stabilising agents (e.g., lime, cement, slag, fly ash, or blended products).

Process Monitoring and Control During Stabilisation

Effective quality control during stabilisation is crucial for achieving the desired outcome. We provide:

  • Monitoring of stabilising agent spread rates.
  • Assessment of mixing uniformity and depth.
  • Moisture content control during conditioning.
  • Compaction control testing (e.g., nuclear densometer, sand replacement) to achieve target densities.

Post-Stabilisation Verification

After stabilisation and curing, we conduct tests to verify that the improved subgrade meets the project's performance criteria:

  • In-situ strength testing (e.g., CBR, Plate Load Test, Benkelman Beam).
  • Laboratory strength testing on cured samples (e.g., Unconfined Compressive Strength - UCS, CBR).
  • Assessment of durability and long-term performance characteristics.
  • Compliance checks against project specifications and relevant standards.

Testing Methods and Standards

Atlas Engineering and Technology Group conducts all subgrade stabilisation assessments in accordance with relevant Australian Standards (e.g., AS 1289 series) and specific project or TfNSW (Transport for NSW) specifications. Our experienced technicians utilise calibrated equipment for both field and laboratory testing. We employ a range of methods, including:

Testing CategoryCommon Tests Performed
Field Testing
  • Nuclear Density/Moisture Gauge testing
  • Dynamic Cone Penetrometer (DCP) testing
  • Perth Sand Penetrometer (PSP) testing
  • Clegg Impact Hammer testing
  • Field CBR testing
  • Plate Load Test
  • Benkelman Beam deflection
Laboratory Testing
  • California Bearing Ratio (CBR) – soaked and unsoaked
  • Unconfined Compressive Strength (UCS)
  • Particle Size Distribution (PSD)
  • Atterberg Limits
  • Standard and Modified Compaction tests
  • Moisture Content
  • Stabiliser content verification
  • Durability testing (e.g., wetting/drying, soaking)

Benefits of Our Subgrade Stabilisation Assessments

  • Ensured Performance: Verification that the subgrade will support the design loads over its intended lifespan.
  • Compliance: Meeting project specifications, council requirements, and Australian Standards.
  • Cost Optimisation: Potentially reducing the need for excessive pavement thickness or expensive imported materials by improving existing soils.
  • Risk Mitigation: Early identification of potential issues, minimising the risk of premature failures and costly rework.
  • Independent Verification: Providing reliable, third-party data for quality assurance.