Infrastructure Development Code


Before fill is placed, the Contractor shall notify the Engineer that the fill foundation has been stripped, drained, (including subsoil drains) and prepared as per the Contract Drawings and documents and is ready for the Engineer’s inspection. 

Before compaction, fill materials shall be spread uniformly in horizontal layers and if necessary, be conditioned to an appropriate moisture content by aeration and drying or wetting (as the case may be), and/or by blending and mixing "wet" and "dry" materials. If soil is to be dried, the Contractor shall disc it and allow it to dry uniformly to its full depth. If the soil is to be wetted, this shall be done with sprinklers capable of ensuring uniform and controlled distribution of water in conjunction with blading and disking. In all cases the fill shall be mixed and conditioned thoroughly so that immediately before compaction the material type and its moisture content is reasonably uniform within one area and as close as practical of optimum moisture content. Before compaction the layers shall be less than 250mm loose thickness. All fragments within the loose layer shall be less than 100mm maximum dimension.

No new fill shall be placed over previously compacted material until the construction methodology to be utilised by the contractor has been reviewed and observed by the Engineer and Geo-Professional.  Once the construction methodology has been observed, the Engineer or the Geo-Professional shall confirm whether they are satisfied that continued placement of earth fill will ensure that all earthworks will meet the required compaction standards and testing methodology.

Effective drainage shall be maintained during filling operations to minimise any deterioration of material exposed in excavation areas and in the uppermost fill layers. 

Special care shall be taken to avoid hollows which could pond water. All fill surfaces shall be protected when rain is imminent to minimise erosion and protect the fill from strength loss of the fill due to an increase in moisture content.

Where fill is to be placed against sloping surfaces steeper than 1v:2h, the sloping surface shall be excavated ("benched") such that horizontal benches no greater than 1.0m height intervals are formed.

Filling shall be carried out so that no area of fill is ever more than 0.5m higher than any other adjacent area of filling unless approved by the Engineer.

In order to ensure adequate compaction of the materials forming the final fill surface profile, all fill batter faces shall be overfilled as necessary and carefully trimmed back to the required design profile.

Definitions in this section