Civil Engineering Project Management (4th Edition)

Site surveys, investigations and layout 139
not seriously disrupt the surface. In most cases roads have to be designed for
haulage trucks, which can impose heavy wheel loads when laden. Roads for
them must be of adequate thickness, suitably topped (or constantly regraded)
to prevent rutting and ponding, and well drained. Any attempt to save money
by building an access road of inadequate thickness, without proper drainage
ditches either side and a surface kept to a camber to shed rainwater, is a
false economy. It will quickly break up and cause repeated delay to the job. Flat
tracked machines can pass occasionally over metalled, waterbound, or sprayed
and chipped roads without causing much damage. Machines with gripped
tracks, such as large dozers, will quickly break up the surface of any road.
The consequence of the foregoing is that internal roads on site have to be
designed according to the anticipated usage of them. For maximum output
from motorized scrapers it is important that haulage roads should have easy
gradients. Laden haulage trucks are also frequently slow on steep gradients,
both uphill and downhill. Mud is a particular nuisance when trucks have to
go on public roads; frequent cleaning of the road and hosing of traffic leaving
the site will be needed if public objection is to be avoided.
Planning bulk excavation
The order in which an excavation is to be undertaken has to be planned. The
excavating machine must be able to work to its maximum capacity attended
by a continuous flow of dump trucks in and out. As bulk excavation proceeds,
formation trimming and minor excavation will follow, then the placing of fill
or concrete. For speed of execution these follow-on operations will need to be
started before the bulk excavation is completed. Hence the excavation must be
planned in such a manner that the different operations carried on simultaneously
do not interfere with each other, and that excavating machines can withdraw
without difficulty after their work is completed.
Concrete production plant
This needs to be positioned to give easy delivery to the parts of the work where
the main concrete is required. Delivery lorries to the stockpiles of aggregates
should preferably not follow the same routes as muck-shifting plant, or they
will pick up mud and track it into the aggregate bays. The bays should have
concrete floors laid to a fall so the aggregate can drain.
Power generators and compressors
These may need to be housed, even if mobile, because their noise can create
a nuisance to local residents. Their siting should be such that the noise they