Roadway Design: Earthwork Calculation

Earthwork in Roadway Design

• Earthwork includes excavation of existing earth material and placement of fill material for constructing embankments.
• The manual method for determining earth excavation and embankment amounts involves three steps:
  • Placing cross sections of the proposed highway on original ground cross sections
  • Calculating areas in cut and fill
  • Computing volumes between sections

Cut and Fill

• Cut and fill refer to areas in a section, while excavation and embankment refer to volumes.
• Methods for manually calculating cut and fill areas are presented in most surveying textbooks.

Mass Diagrams

• Mass diagrams (or mass-haul diagrams) are plots of cumulative volumes of cut and fill along an alignment.
• The diagram is typically plotted below a profile of the route, with the ordinate at any station representing the sum of volumes of cut and fill up to that station.
• The rising curve on the mass diagram indicates excavation, while a descending curve indicates embankment.

Balance Line

• A horizontal line drawn to intersect the mass diagram at two points indicates equal excavation and embankment (adjusted for shrinkage) between the two stations represented by the points of intersection.
• Such a horizontal line is called a balance line, because the excavation balances the embankment between the two points at its ends.

Economics of Earthwork Distribution

• The most economical way to handle the distribution of earthwork volumes can be determined from the mass diagram.
• Highway engineers strive to balance the amount of cut and fill during a highway construction project to avoid costly hauling of materials.