Do I need a site classification?
Site classifications are requested by councils and developers to determine the suitability of a site for construction and the optimal foundation type. Site classifications are completed in accordance with AS 2870-2011 Residential slabs and footings. The site classification consists of three parts, a
- Desktop study
- Site inspection
- Soil investigation and testing
Site desktop Study
The site desktop study is used to identify the planning, geographic and environmental factors which influence the design and construction of a development. Site mapping data is obtained from local council and state departments to identify hazards such as acid sulfate soils, salinity and slope stability.
The site classification inspection involves inspecting the site for signs of distress in the landscape. Signs of distress (in terms of a site classification) can include lack of vegetation growth, erosion, slumping ground and high water levels. A survey of the trees, waterways, services and ground slope helps identify factors which may cause distress or foundation failure in the future.
Soil investigation and testing
Borehole drilling is used to collect soil samples, create bore logs and perform in-situ and laboratory testing. The borehole drilling uses thin-wall tubes which are hydraulically hammered into the ground. Thin-wall tube sampling maintains the soil structure and layering for accurate in-situ identification, logging and classification. Laboratory tests are used when specific soil properties are required. Site classification soil testing includes soil reactivity (shrink and swell), soil plasticity and bearing capacity.
Site reactivity classification
The three stages of the site classification collectively determine the reactivity and suitability of the proposed development allowing the structural engineer to choose the most cost-effective foundation type. AS 2870 provides a list of site classifications based on the soil reactivity:
|Site Class||Site Classification Description||Characteristic surface movement (ys) mm|
|A||Most sand and rock sites with little or no ground movement from moisture changes|
|S||Slightly reactive clay sites, which may experience only slight ground movement from moisture changes||0 - 20mm|
|M||Moderately reactive clay or silt sites, which may experience moderate ground movement from moisture changes||20 - 40mm|
|H1||Highly reactive clay sites, which may experience high ground movement from moisture changes||40 - 60mm|
|H2||Highly reactive clay sites, which may experience very high ground movement from moisture changes||60 - 75mm|
|E||Extremely reactive sites, which may experience extreme ground movement from moisture changes||> 75mm|
|P||Sites which include filled sites (refer to AS 2870-2011), soft soils, such as soft clay, silt or loose sands; landslip; mine subsidence; collapsing soils; soils subject to erosion; reactive sites subject to abnormal moisture conditions; tree affected; fill containing deleterious materials (wood, metal, plastic) or in a marine environment.|
Broadcrest offer a five business day turnaround time for site classifications from the date of the site inspection, all in accordance with AS2870-2011.
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