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Soil Testing and Supervision


Field Densities

In soil testing for civil construction, Field Density testing would be amongst the most common. Its purpose is to determine the Field Dry Density (in t/m3) and Moisture Content (as a %) of the material being tested. The Field Dry Density is usually compared with a laboratory compaction test of the same soil type, to produce a ratio between field and laboratory compaction. (See "Compaction" below)


Australian Standards: AS1289 5.3.1                                  



Compaction testing as carried out in a soil testing laboratory is done to determine the Maximum Dry Density (t/m3) and the moisture content at which that is achieved known as the Optimum Moisture Content (%). 

This data is used to compare to the Field Dry Density (see Field Densities above) to determine the Density Ratio and Moisture Variation

Compactions are either performed as Standard or Modified and sometimes Oversized if the material being tested is of a larger particle size (rock).                    

Australian Standards: AS1289 5.1.1 (Std), 5.2.1 (Mod)    



Particle Size Distribution test results (or Gradings) are used for many reasons such as determining the compliance of manufactured gravels with required standards and specifications in the earthwork and concrete stages  of construction works.

This Soil test is also part of the process used to classify a soil sample in conjunction with Atterburg Limits testing (see below).


Australian Standards: AS1289 3.6.1                                      



Atterburg Limits cover a range of soil tests relating to reactivity to moisture (water), better known as Plasticity. These tests include Liquid Limit, Plastic Limit, Plasticity Index and Linear Shrinkage. Atterburg Limits play an important part when classifying soil types and work in conjunction with Particle Size Distribution tests (above).


Australian Standards: AS1289 3.1.1, 3.1.2, 3.2.1              

                                   AS1289 3.3.1, 3.4.1




CBR stands for Californian Bearing Ratio which is used to determine the compressive strength of a soil usually for the purpose of determining the "Box Depth" of a road pavement. CBRs can be tested wet (soaked) or dry, although wet is the industry standard as it allows a road to be designed to better cope with stresses placed on the subgrade after it has been subject to significant amounts of moisture. Soaked CBRs must remain under water for 4 days before being measured for shrinkage or swell and then tested as to there bearing capacity in that state. (The test usually takes 7 to 10 days in total).


Australian Standards: 

AS1289 6.1.1                                    

Emerson Class

Soil cohesion is vital for structures such as road embankments and the like. Civil Engineers often need to know if a soil will hold together satisfactorily on its own or whether it may need to be supported or even replaced. One group of soil tests used to determine cohesion properties of soils is called the Emerson Class.


Australian Standards: AS1289 3.8.1                                                                       


Level One


Level One Supervision has become a standard requirement or at least a serious recommendation for all building development sites. Following the standard AS3798, ensures an earthworks site has been filled and compacted to a high standard under controlled conditions.

Such conditions include, fill is placed on firm ground, level and on natural ground. All non-certified fill is removed, and replaced or discarded with a material complying to AS3798 or as defined by an overseeing civil engineer.



Australian Standards: AS1289, AS3798



Trench Testing

& Supervision

Trench Testing is normally required by councils to ensure trench backfill is compacted to a satisfactory standard. QGS regularly conducts soil tests on trench backfill to the required specifications .

On occasion, our experienced soil technicians are asked to supervise the placement of trench backfill. One reason for this is backfill of an "untestable" nature is being used such as rock / soil combinations.


Australian Standards: AS1289, AS3798                

© 2006 SMC Pty Ltd (Qld)




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