During the construction of long engineering projects such as roads, pipes lines and canals there may be a considerable quantity of earth required to be brought on the site to form embankment and to be removed from the site during the formation of cutting.
The earth brought to form embankment may come from another section of the site such as tie formed from excavated material ( known as spoil heap) or may be imported on to site from a near by query.
Any earth brought on to the site we said to have been borrowed. The earth excavated to form cutting may be deposited in tips at regular intervals along the project to form spoil heaps for later use in embankment formation of maybe wasted either by spreading the earth at right angles to the center line to form verges or by carting it away from the site area and depositing it on suitable local areas.
This movement of earth through the site can be very expensive and since the majority of the cost of such project is usually given over to earth moving it is essential that considerable care is taken when planning the way in which materials is helded during the construction. The mass haul diagram is a graph of volume against chain age which is greatly helps planning such earth moving.
The X-axis represents the chain age along the project from the position of zero chain age. And they axis represents the aggregates volume material up to any chain age or station from the position of zero station when constructing the mass haul diagram. Volumes of cut are considered and volumes of fill are considered negative.
The vertical and horizontal axis of the mass haul diagram usually drawn at different scales to exaggerate the diagram and there by facilitate its use.
The mass haul diagram considered any earth moved longitudinal to the direction on direction of the center line of the project and does not take in to account any volume of material moved at right angles to the center since the mass haul diagram is simply a graph of aggregate volume against station it will be noted that if the volume is continually decreasing with the station, the project is all embankment and all the material will have to be imported on to the site, since there will be no fill material will available for use such an occurrence will involve a great deal of earth moving and obviously not an ideal solution .
It is better attempt if it has been laid in the section of suitable formation level such that some areas of cut were balanced out by some areas of fill a more economical solution would result.
5.4.1. Economic of mass haul Diagram
When costing the earth moving there are four basic costs which are included in the contract for the project.
1-Cost of Free Haul:- Any earth moved over distances greater than the free haul distance changed both for it’s volume and for it’s distance in access of the free haul distance over which it is moved.
2- Cost of over Haul: – Any earth moved over distance greater than the free haul distance changed both for its volume and for its distance in access of the free haul distance over which it is moved.
3- Cost Borrow: – Any material which must be brought on the site to make up a deficiency is also usually changed on units of volume.
4- Cost of waste: – Any sample or unsuitable materials which must be removed from the site and deposited in a tip is usually changed on units of volume.
Uses of mass haul diagram
Mass diagram can be used in several ways in design.
In section 5.1 the relation ship between mass hauling and formation level was discussed if several formation levels are tried and as mass haul diagram constructed for each. That formation that gives the most economical result and maintains any stipulated standards, for example gradient restrictions in vertical curve design, can be designed and also for determination of earth quantities.
In Financing: – Once the formation level has been deigned the mass haul diagram can be used to indicate the most economical method of moving the earth around the project and a good estimate of the over all cost of the earth moving can be calculated.
The required volume of material are known before construction begins enabling suitable plant and machinery to be chosen sites for spoil heaps and borrow. Pits to be located and directions of haul to be established.
In planning a head
The mass haul diagram can be used to indicate the effect that of her engineering works, for example- funnels and bridges with in over all projects.