Mass haul diagram: characteristics and haul terms

Mass haul diagram and its characteristics

A mass haul diagram is a curve of cumulative earthwork volume (cut positive, fill negative, after correcting for shrinkage or swell) plotted as ordinate against chainage as abscissa. It is used to plan the movement of earth along a road.

 Cum.
 volume
   ^            peak
   |          ,--*--.
   |  A -----'-------'--- B  balancing line
   |      ,'            '.
   | ____/                '.     valley
   |                        '-._*______
   +------------------------------------> chainage
      cut        fill         cut

Characteristics

1. A rising curve shows cut exceeding fill; a falling curve shows fill exceeding cut.
2. A peak marks a change from cut to fill and a valley a change from fill to cut.
3. A horizontal line (balancing line) cuts the curve at points where cut and fill are equal; the earth between these points is balanced.
4. The maximum or minimum ordinate between two such points gives the volume of earth moved from cut to fill in that section.
5. The length of the balancing line gives the haul distance for that balanced volume.
6. Curve above the balancing line means haul is forward (in the direction of chainage); below means backward.
7. The area between the curve and the balancing line is the haul moment, volume times distance (m3-m).
8. A steep slope shows heavy earthwork; a flat curve shows a balanced section.
9. The end ordinate gives the excess (to be wasted) or deficit (to be borrowed) for the whole length.

Definitions

• Free haul distance (FHD): the distance up to which excavated earth can be moved with no extra payment, because it is included in the unit rate of excavation and filling (commonly 100 m in Nepal/India specifications; as per contract).
• Overhaul: hauling beyond the free haul distance; paid as volume times extra distance (m3-station, 1 station = 20 m or 100 m as specified) $=V\times(L-L_f)$.
• Economic haul distance (limit of economic haul): the longest distance for which carrying cut to fill costs no more than excavating from a borrow pit and wasting the cut; beyond it, borrowing is cheaper. $L_e = L_f + \dfrac{\text{cost of borrow and waste}}{\text{overhaul rate per m}^3\text{-m}}$.
• Shrinkage: loose or in-situ soil, when compacted in an embankment, occupies less volume than the bank volume it came from (about 10 to 20 percent for soil); the fill volume is multiplied by a shrinkage factor to get the cut needed.
• Swelling: increase in volume of soil or rock after excavation (loose condition), for example 20-30 percent for common earth and 40-60 percent for rock, so more truck volume is needed.