Earthworks is one of the most important aspect of road construction projects and often among the costliest. Earthworks may begin from stripping of topsoil where these are present. However, this is not usually considered among roadwork excavation. Unlike roadwork excavation that is measured in cubic metres (m3), stripping of top soil is measured in square metres (m2) and payment is made in m2.
Roadwork excavation consists of the total quantity of measured fill together with the quantity of unsuitable materials and/or excess cut placed to spoil which are determined from the cross-sections of the road.
Earthworks shall be measured by super-imposing the specified finished formation levels on the initial cross-sections taken by the contractor at 30 m intervals or closer if necessary, along the centerline of the road. The levels of such cross-sections shall be agreed by the Engineers Representative (ER).
Ideally,
i. The net volume of the suitable materials excavated from cuttings or side drains shall be determined by deducting the quantity of unsuitable material placed to spoil from the total quantity of cut as determined from the cross-sections.
ii. The total volume of filling placed in embankment shall be found from the cross-sections.
iii. The volume of suitable excess cut placed to spoil shall be taken as the volume found in (i) less the volume found in (ii) with an adjustment made to the latter to allow for compaction. The adjustment which shall be made for compaction shall be based on the ratio of the maximum dry density (MDD) of the filling at 100% BS compaction to the insitu density of the material in the cutting or side drain.
iv. Added haulage rates of the trucks hauling these materials would be based on the nearest acceptable road making materials to the section of the road under construction.
