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CQ Soil Testing provides site classifications for large subdivisions and individual allotments. We have the capability to carry out both the fieldwork and laboratory testing necessary for a site classification.
We engage professional engineers to interpret results and provide appropriate footing designs quickly and accurately.
A Site Classification is carried out in accordance with the Australian Standard AS2870: “Residential Slabs and Footings”. Classes include S (slightly reactive), M (moderately reactive), H1-H2 (highly reactive), E (extremely reactive), or P (problem site). Classes S, M, H1-H2, and E refer generally to sites in which clayey soils will form the founding strata.
The classification indicates how reactive the clay subsoil is to changes in moisture content. The reactivity (shrinking and swelling) of the clay can have a significant impact on the footings / slabs of a building slab which need to be designed to counteract the movements of the clay soils, otherwise damage (cracking) of the house may occur.
Sites classified as Class P may present difficulties for the proposed construction. The P classification often suggests deep and/or uncontrolled fill, which cannot provide suitable bearing for the house. In these situations, the house is either founded on the stable materials beneath the fill (i.e., deep footings / piers), or the fill is removed and replaced with compacted, controlled fill.
CQ Soil Testing are able to provide site classifications for either large subdivisions or individual allotments. We have the facilities to carry out both the fieldwork and laboratory testing necessary for a site classification, whilst our association with professional engineers are able to interpret the results and provide the appropriate footing designs in a short period of time.
Some of the soil properties analysed when preparing a soil site investigation include:
Other factors that need to be included in the classification of a site are external influences such as:
Class |
Foundation |
|---|---|
| A | Sand and rock site with no ground movement from moisture changes. |
| S | Characteristic Surface movement 00 mm – 20 mm. Slightly reactive clay sites with only slight ground movement from moisture changes. |
| M |
Characteristic Surface movement 21 mm – 40 mm. Moderately reactive clay or silt sites, which can experience moderate ground movement from moisture changes. |
| H1 | Characteristic Surface movement 41mm – 60mm. Highly reactive clay sites, which can experience high ground movement from moisture changes. |
| H2 | Characteristic Surface movement 61 mm – 75 mm. Highly reactive clay sites, which can experience very high ground movement from moisture changes. |
| E | Characteristic Surface movement > 75mm. Extremely reactive sites, which can experience extreme ground movement from moisture changes. |
| P |
Sites which include uncontrolled fill, soft soils, such as soft clay or silt or loose sands; landslip; mine subsidence; collapsing soils; soils subject to erosion; reactive sites subject to abnormal moisture conditions or sites which cannot be classified otherwise. For Class M, H and E this includes sites with existing or recently removed/altered dwellings which are likely to have created abnormal moisture conditions across the site. |
For Classes M, H1-H2 and E further division based on the depth of the expected movement is required. For deep-seated movements, characteristic of dry climates and corresponding to a design depth of suction change, Hs, greater than 3m, the classification shall be M-D, H1-D, H2-D, or E-D as appropriate.
