Civil Engineering Reference
In-Depth Information
Marking the ground to guide the excavator
Products used to mark the excavation
There are various ways of marking the surface of the site. The least offensive ecologically
is to create lines on the ground with lime or plaster dust. I have even seen the use of white
sand as a marker. There are ground-marking paints specifically for the task which come
in pressure packs and are designed to be sprayed upside down as opposed to normal
pressure packs. They come in a variety of fluorescent colours and are quite simple to use.
Most good hardware stores will either have these products or be able to order them in
for you.
When marking the site for excavation start with the area of hard excavation as
opposed to the filled area. If the site has a significant gradient you will need to allow
additional area due to the fall in the land. If in doubt add a little more area than
necessary, as there is nothing worse than having to wait for the excavator to return to
extend the cutting. Earthmovers charge travelling time plus hours worked. You do not
want to duplicate the charges for travelling.
If the building is an odd shape then it would be beneficial for the cutting to emulate
the shape of the building, and this can be accommodated.
Marking the site to guide the excavator
Mark the ground at the outer corners of the area that is to have the solid excavated area
(see Figure 2.4).
Figure 2.4
Establish the required cut and fill area
Next you will need to mark the total area of the cutting including any area of fill and
the allowance for the treatment of the face of the cutting. Mark the extremities of this
with a simple mark that distinguishes it from the excavated flat area markings. If you
mark the base cutting area with a cross you might use a simple dot as marking for the
outer limits. The next part of the process is easiest with two people. Take a string line and
stretch it first of all over two of the external markings that represent an edge of the
cutting thereby forming a straight line between the two marks. Extend the string line
ideally 3 or 4 metres past the actual marked position and hammer in a robust peg. A
short star dropper is ideal. On a residential block it is unlikely that you will have the space
to extend the lines so far in each direction, so fit these pegs against a fence. The reason the
pegs are fitted so far from the actual excavation is to prevent the machine from
