Soil & Rock Classification
Atlas Engineering and Technology Group (AETG) provides comprehensive soil and rock classification services as part of our geotechnical investigation offerings in Sydney and throughout Australia. Our experienced geotechnical engineers utilise industry-standard classification systems to accurately identify and categorise soil and rock materials.
Soil Classification
Soil is classified into three primary categories:
- Coarse-grained soils (e.g., sands and gravels)
- Fine-grained soils (e.g., silts and clays)
- Highly organic soils (referred to as "peat")
Each soil type exhibits distinct engineering properties. For instance, sandy soils typically have higher permeability and drainage capacity than clay soils. Most natural soils are mixtures of these categories, with variations influenced by parent rock material, weathering processes, age, chemical composition, topography, and environmental factors.
Our soil classification services include:
- Visual-manual classification according to Australian Standard (AS1726)
- Particle size distribution analysis
- Atterberg limits determination (liquid limit, plastic limit, plasticity index)
- Moisture content assessment
- Density and unit weight measurements
- Strength parameter evaluation
- Compaction characteristics
Rock Classification
Rock classification is crucial for projects involving excavation, foundation design, tunnelling, or slope stability analysis. Our rock classification services include:
- Rock type identification (igneous, sedimentary, metamorphic)
- Weathering grade assessment
- Discontinuity mapping (joints, bedding planes, faults)
- Rock Quality Designation (RQD)
- Point load strength index testing
- Unconfined compressive strength estimation
- Rock mass classification (RMR, GSI, Q-system)
Field and Laboratory Testing
Our field investigations typically include:
- Borehole drilling with core sampling
- Test pit excavation
- In-situ testing (SPT, CPT, vane shear)
- Groundwater monitoring
Laboratory testing complements field investigations with:
- Particle size analysis
- Atterberg limits testing
- Moisture content determination
- Compaction testing
- Strength testing (triaxial, direct shear)
- Rock strength testing
Reporting and Interpretation
Atlas Engineering provides detailed reports that include:
- Soil and rock classification results
- Stratigraphic profiles
- Engineering properties assessment
- Geotechnical parameter recommendations
- Site-specific considerations
- Construction recommendations
Why Soil & Rock Classification Matters
Proper classification of soil and rock is fundamental to any geotechnical project. It provides critical information about:
- Material properties and behaviour under different conditions
- Potential construction challenges and solutions
- Foundation design requirements
- Excavation methods and difficulty
- Slope stability considerations
- Earthwork specifications
Our Classification Methodology
Atlas Engineering employs the Australian Standard AS1726 (Geotechnical Site Investigations) alongside internationally recognised systems, including the Unified Soil Classification System (USCS). Our comprehensive approach includes:
- Field identification and logging by qualified geologists and engineers
- Laboratory testing to confirm visual classifications
- Detailed documentation with standardised terminology
- Integration of classification data into comprehensive geotechnical reports
Soil Classification Parameters
Our soil classification process examines multiple parameters:
| Parameter | Description | Significance |
|---|---|---|
| Grain Size | Distribution of particle sizes | Affects strength, drainage, and compaction characteristics |
| Plasticity | Soil's ability to deform without cracking | Indicates clay content and potential volume change |
| Consistency | Firmness of cohesive soils | Relates to strength and compressibility |
| Density | Compactness of granular soils | Indicates bearing capacity and settlement potential |
| Color | Visual appearance | Can indicate composition and environmental conditions |
| Organic Content | Presence of organic materials | Affects strength and settlement characteristics |
Rock Classification Parameters
Our rock classification includes the assessment of:
- Rock type (igneous, sedimentary, metamorphic)
- Strength (extremely low to extremely high)
- Weathering degree (fresh to extremely weathered)
- Discontinuities (joints, bedding planes, faults)
- Rock Quality Designation (RQD)
- Fracture spacing and orientation
Applications of Our Classification Services
Our soil and rock classification services support a wide range of projects:
- Building foundations
- Retaining structures
- Road and pavement design
- Excavation planning
- Slope stability analysis
- Tunneling projects
- Earthworks specifications
Why Choose Atlas Engineering
With decades of combined experience, our team provides accurate, reliable classification that forms the foundation of sound geotechnical design. Our classifications are performed by Australian Standards, ensuring consistent, high-quality results for every project.
Successfully Completed Jobs by AETG to Date
✔ Proposed Residential Development - Warana Road, Cecil Park NSW
The soil classification report, as assessed in the Site Classification Report by AETG, was determined based on detailed fieldwork and laboratory testing. The subsurface profile encountered across three boreholes consisted of a thin topsoil layer overlying sandy clay fill, which transitioned into residual silty clay soils at depth. Laboratory Atterberg Limits testing of the residual silty clay indicated high plasticity, with a Liquid Limit (LL) of 68%, Plastic Limit (PL) of 19%, and Plasticity Index (PI) of 49, categorising the material as a highly plastic silty clay. Based on these findings, along with Dynamic Cone Penetrometer (DCP) results and site observations, the site was classified as Class H2 in accordance with AS2870, indicating it is subject to very high ground movement due to moisture changes. The residual soil horizon was identified as the preferred founding material for structures, while fill was deemed unsuitable for foundation support without specific remediation measures.
✔ Material Classification - Mill Road, Liverpool NSW
The Material Classification Assessment conducted by AETG at Mill Road, Liverpool, NSW, focused on the soil properties of an onsite stockpile. The stockpiled material was visually and physically assessed as light brown sandy clay with fine-grained sand, low plasticity, and inclusions of asphalt, bitumen, and concrete fragments. Laboratory testing confirmed the material to be free from asbestos, hydrocarbon contamination, and heavy metal concentrations exceeding regulatory limits. Geologically, the site is underlain by Middle Triassic Bringelly Shale with overlying Quaternary alluvium. Soil testing results showed pH levels ranging between 7.6 and 8.8 and low electrical conductivity, indicating neutral to slightly alkaline conditions. Based on the chemical analysis and field observations, the material was classified as General Solid Waste (≤ CT1) under the NSW EPA Waste Classification Guidelines (2014), confirming its suitability for reuse or disposal without special handling for contamination concerns.