Ripping Frozen Ground with
an Attachment for Dozers
PAUL V. SELLMANN AND DALE R. HILL
compacted or bonded by ice or some chemical
INTRODUCTION
cement. Rippers greatly expand the capability of
tractors, providing a means to break up and
Objective
A ripper attachment was mounted on the dozer
disagregate hard surface materials, preparing an
blades of commercial crawler tractors and on a
area for more rapid excavation by conventional
military dozer (the M728 Combat Engineer Ve-
methods. In some quarry and mining operations,
hicle, CEV) in an attempt to improve performance
large ripper-equipped tractors are used in coal
for work in hard and frozen soil when more con-
and rock, eliminating the need for drilling and
ventional rear-mounted rippers are not available.
blasting. Russian experiments with a ripper
The tractors were selected to help predict the rip-
mounted on a modified military T-34 tractor indi-
ping performance of smaller military and com-
cated that ripping hard ground was 15 times less
mercial dozers, and that of a military dozer with a
expensive than drilling and blasting (Zelenin et
suspension system. This was done for a better
al. 1985). Some manufacturers of crawler tractors
understanding of how a blade-mounted ripper
equipped for ripping provide data on ripability
could be used for combat engineering operations
of materials to aid estimates of ripper performance
during the winter, such as construction of fight-
and productivity (Nichols 1976, Caterpillar 1989),
ing positions and denial structures. Observations
which helps to allow cost comparisons with other
were made at several sites with a range of ground
alternatives, such as drilling and blasting. Rip-
conditions, including sites with seasonal frost
ping is an appealing concept for military opera-
greater than 2 ft (0.6 m) thick. Some of these ob-
tions because a minimum amount of equipment
servations were made during military exercises
and manpower is required.
and during field demonstrations.
Rippers on dozers are commonly rear-mounted
on a hydraulically operated linkage that is usu-
ally a permanent accessory to the tractor. This
Background
Combat engineers have a number of missions
report discusses a less common ripper attachment
that require excavation, including constructing
used on the blades of crawler tractors. This device
fighting positions for combat vehicles, construct-
can be rapidly installed on most tractors that have
ing obstacles, and maintaining and constructing
a conventional dozer blade to provide some rip-
roadways, runways, and other facilities in all ter-
ping capability. It can be easily transported to the
rain and weather. The difficulty of these missions
field and installed with no modifications. For some
significantly increases when construction is in
tasks it can also be more versatile and less re-
hard and frozen ground. Reduced availability of
stricted by its location than a rear-mounted rip-
the D7 tractor with a rear-mounted ripper and
per. When mounted on part of the blade that is
poor performance in hard ground of other avail-
visible to the operator, it can be used to hook and
able equipment further complicate this problem.
remove rocks, barriers, and debris from the
Dozers that lack ripping capability are usually
ground, and to trench for burying cables or small
restricted to operating in ground that is not highly
utility lines.
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