Kingscote Streets Upgrades - Kangaroo Island Council

5 Pavement Subgrade
This section of the specification details the requirements for preparation of the pavement subgrade
and shall be read in conjunction with the earthworks section of this specification and the pavement
design schedule as detailed on the drawings.
The subgrade shall include the top 200 mm of the formation directly under the pavement.
5.1 Construction and Workmanship
5.1.1 General
Preparation of the sub-grade shall follow formation of the earthworks, as detailed in the Site
Preparation and Earthworks section of this specification.
5.1.2 Subgrade Preparation
Following the earthworks formation the subgrade shall be trimmed to produce a tight dense surface
to the tolerances specified.
The subgrade shall be systematically compacted to the full width with appropriate compaction
equipment to the specified compaction as detailed in the pavement design of the subgrade.
Where required the subgrade shall be moisture conditioned and compacted as detailed on the
pavement design schedule. Moisture conditioning may include tyning of the subgrade and aeration
to reduce the moisture content, prior to spreading and recompaction. Care shall be taken to ensure
the subgrade is not affected by inclement weather during moisture conditioning process.
Trafficking of the subgrade by construction activities shall be kept to a minimum to reduce “pumping”
of moisture from lower layers into the subgrade.
Subgrades shall be finished with adequate drainage to ensure the water runoff without ponding.
5.1.3 Maintenance of Subgrade
The Contractor shall maintain the subgrade to ensure that the shape and degree of compaction
immediately prior to the placement of the first pavement course conforms to the requirements of the
specification.
Trafficking of the subgrade by construction activities shall be kept to a minimum.
Subgrade that area affected by moisture subsequent to achieving the specified requirements shall
be re-worked as required to achieve the specified requirements.
5.1.4 Proof Rolling
The Contractor shall undertake proof rolling in the presence of the Superintendent by moving a
heavy vehicle over the subgrade to identifying unsuitable material. Proof Rolling shall be carried out
within 24 hours of completion subgrade preparation or prior to any trafficking by construction traffic
of the subgrade.
The Contractor shall ensure that the approved vehicle (a fully laden water cart or similar) for proof
rolling is on site when required for proof. Payment will not be made for transportation of the proof
roll vehicle around the site.
The Superintendent will determine whether a section of subgrade shall not be proof rolled (e.g. over
utility service with limited cover) and the method of proof rolling for small areas.
Ref No. 20120236SA1 Kingscote Streets Upgrades Technical Specification 22