Strength & Penetration Testing

A.D. Envirotech offers two types of strength and penetration tests within our NATA accredited scope of testing:

 

  • Dynamic Cone Penetrometer (DCP) testing and;
  • California Bearing Ratio (CBR) testing.

 

It is important to undertake strength and stiffness testing on material prior to works involving loading the soil surface or subsurface to avoid problems arising during the construction phase of the sub/superstructures. This is due to the fact that the soil may be unable to withstand the design load applied to the material leading to the failure of soil (e.g. If a  crane was placed on untested weak soil, the outriggers may shift whilst transporting a heavy load due to soil failure). A load bearing capacity assessment (DCP or a CBR) should be undertaken to determine the strength of the material in order that a proper design load or footing size can be applied during the design process.

 

DCP Testing

 

DCP Testing is used to determine the strength of the subsurface and design load of the soil. Once the maximum design load of a soil is known, these results can be used to calculate appropriate footings and foundations for sub/superstructures to be placed on or within the soil.

 

DCPs performed in-situ to give an estimation of the load bearing capacity which a soil can withstand. This is achieved by measuring the extent of penetration into the ground of a calibrated tip or cone and weight which is dropped from a standardised height. Stiffer soils will yield a lower penetration rate while softer soils will result in increased penetration.

 

All DCP tests which ADE conducts comply with AS1289.6.3.2 and AS1289.6.3.3.

 

CBR Testing

 

CBR testing is conducted to determine the strength of a material (usually a subgrade) when it is at its maximum compaction. This purpose of this is to determine the required thickness of a structural layer or asphaltic layer (e.g. a footpath) to be placed on top of the tested material. This test ensures that the strength requirements outlined by the scope of works are satisfied.

 

To perform this test, a maximum dry density is required to be undertaken on the material prior to testing to determine the remoulded density of the sample. The specimen is commonly remoulded at 100% of standard compaction (or the relative compaction achieved onsite) to determine the strength of the material. This test will require the time taken for a maximum dry density to be undertaken, and then a four day soak to determine the reactivity of the soil prior to testing.

 

This value is given as a percentage as compared to a standardised material (California Limestone) where a low value corresponds to weak fill and a high value to strong filling.

 

ADE carries out all CBR testing according to AS1289.6.1.1 or RMS T117.

 

Both DCP and CBR testing are overseen and conducted by qualified geotechnical engineers from ADE’s geotechnical department. In general, DCP testing takes one day for fieldwork and one day for reporting. In contrast, CBR testing takes an average of 10 working days including fieldwork, analysis and reporting.