disengaged. Additionally, set the brake, and lower the
. When towing a heavy load downgrade, keep the
dozer in low gear. Coasting is dangerous. A coasting
dozer with a towed load is likely to jackknife.
. Before dismounting a dozer and at the end of a
workday, secure the dozer blade by lowering it to the
ground. Lowering the blade prevents the dozer from
rolling; more importantly, it eliminates the possibility of
the blade falling on someone. Whenever it is necessary
to work on the dozer with the blade up, especially when
changing cutting edges, the blade must be securely
blocked to prevent it from falling accidentally.
l Wear required personal protective equipment,
such as steel toe safety shoes and hard hats.
Any time soil is disturbed, it becomes expanded and
very loosely packed. During the construction of a fill or
subgrade, this loose soil must be compacted into a solid
mass. The process of compressing The loose soil into a
solid mass is called compaction. If the soil is not
properly compacted during construction, it will settle
causing roads, building foundations, or runways to
Soil may be compacted naturally (settled) by
weather and time. If the soil is porous, settlement may
be speeded by soaking it and allowing it to dry. This
process is slow and cannot be depended upon to produce
the high densities required by project specification.
Another method of compaction is through chemical
stabilization that involves the application of one or
more chemicals to a soil to achieve a desired change in
its characteristics. Mechanical compaction is normally
required to supplement chemical stabilization. To
accomplish mechanical compaction, you can use
various compaction techniques and types of compaction
equipment, such as vibratory rollers, pneumatic-tired
rollers, and steel-wheeled rollers.
Vibratory rollers provide compactive force by a
combination of weight and vibration of their steel
compaction rolls, commonly referred to as drums.
Those used for compaction are self-propelled and vary
in weight from 7 to 17 tons.
Propulsion for single-drum models is provided by
pneumatic-tired wheels, as shown in figure 11-39. The
Figure 11-39.Vibratory roller.