Soil Surveys

Level 1 Earthworks

Level 1 Fill – you have probably seen it written on drawings and in our reports, you may know these answers but if you don’t or are not sure, we have put together responses to questions we have been asked in the past.

What Australian Standard outlines Level 1 Earthworks ?
AS 3798-2007 Guidelines on earthworks for commercial and residential developments (the code).

What is Level 1 fill ?
The primary objective of Level 1 Inspection and Testing is for the GITA to be able to express an opinion on the compliance of the work (note this must include site preparation works as well as any filling operations). Obviously to do this the GITA needs to have competent personnel (defined in Section 8.4 of the code).

Are there any other levels ?
The code specifically mentions Level 2 Sampling and testing (note the change in title). In this case the fill is assessed by a GTA using the number and location of tests as deemed by the GTA. It is the responsibility of the superintendent to arrange the visits required and they are responsible for ensuring sufficient sampling and testing is undertaken. Obviously any fill not tested in accordance with the code would be considered uncontrolled. The results of any inspection and testing need to be provided to confirm that the fill is controlled.

I have seen the term controlled fill in reports, how does it relate to Level 1 ?
As defined in the code Structural fill, controlled fill and engineered fill are synonymous. This is any fill required to support structures. Therefore as a minimum the fill would need to be Level 1 and also be deemed to be suitable to support structures.

Can I put my high level footings in Level 1 fill ?
The short answer is “it depends”. The code does discuss the need to limit large fragments within the fill to minimise the impact of excavating through the fill for placement of footings and does suggest minimum relative compactions for fills and recommended design allowable bearing capacity. One aspect that the code does not specifically address is the presence of old fill and the need to remove this. It does note the need for adequate preparation of any surface for the proposed fill with the assumption that this preparation should adequately address future issues. This may be an issue with respect to individual footings founding in the fill being placed. It is for this and several other reasons (soft ground potential settlement of the underlying strata) that placement of footings into Level 1 fill needs to be carefully assessed.

Should I get a report when the filling is completed ?
The code outlines site records and reports that should be provided for earthworks projects. This is particularly needed in the case of Level 1 Fill as the GITA will need to express an opinion on the compliance of the fill. Should footings be required to be placed in the fill as per the design drawings then it should be stated in that report.

Definitions
GITA – Geotechnical inspection and testing authority
GTA – Geotechnical testing authority

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Soil Surveys