APPARATUS AND METHOD FOR PREPARING A NEW ROADBASE FROM A DETERIORATED PAVED ROAD

DISPOSITIF ET PROCEDE POUR LA PREPARATION D'UNE NOUVELLE COUCHE DE BASE A PARTIR D'UNE VOIE PAVE DEGRADEE

English Abstract

Apparatus for preparing a new roadbase from a deteriorated paved road is described. The deteriorated road comprises a layer of deteriorated pavement atop a gravel roadbed atop a soil sublayer. The apparatus comprises a smooth drum roller selectively operable in a vibratory rolling mode or in a non-vibratory rolling mode and a plurality of roller cams mountable on the drum roller. The roller cams are sized to crumble substantially all of the layer of deteriorated pavement into fragments when the drum roller is operated in a non-vibratory rolling mode, and to drive substantially all of the fragments into mixture with the roadbed when the drum roller is operated in a vibratory rolling mode. A method of preparing a new roadbase from such a deteriorated paved road comprises crumbling substantially all of the layer of deteriorated pavement into fragments with a drum roller having a plurality of roller cams mounted thereon, driving the fragments downwardly into the gravel roadbed to produce a mixture of substantially all of the fragments with the roadbed, and compacting said mixture into consolidation with said sublayer to produce a new roadbase.

French Abstract

Appareil pour la préparation d'une nouvelle couche de base à partir d'une route pavée détériorée. La route détériorée comporte une couche de pavés détériorés au-dessus d'une plate-forme de gravier au-dessus d'une sous-couche de terre. L'appareil comporte un rouleau à cylindre lisse fonctionnant de manière sélective dans un mode de roulement vibratoire ou dans un mode de roulement non vibratoire et une pluralité d'excentriques à cylindre pouvant être montés sur le rouleau à cylindre. Les excentriques à cylindre sont dimensionnés pour désagréger substantiellement toute la couche pavée détériorée en fragments lorsque le rouleau à cylindre fonctionne en mode non vibratoire, et pour faire se mélanger substantiellement tous les fragments avec la plateforme lorsque le rouleau à cylindre fonctionne en mode de roulement vibratoire. Méthode de préparation d'une nouvelle couche de base à partir d'une route pavée détériorée comprenant la désagrégation de substantiellement toute la couche pavée en fragments avec un rouleau à cylindre doté d'une pluralité d'excentriques à cylindre montés dessus, l'entraînement des fragments vers le bas dans la plate-forme de gravier pour produire un mélange de substantiellement tous les fragments avec la plate-forme, et le compactage dudit mélange en consolidation avec ladite sous-couche pour produire une nouvelle couche de base.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of preparing a new roadbase from a deteriorated paved road, said
road
comprising a layer of deteriorated pavement atop a gravel roadbed atop a soil
sublayer,
said method comprising:
(a) crumbling substantially all of said layer of deteriorated pavement into
fragments with a drum roller having a plurality of roller cams mounted
thereon;
(b) driving said fragments downwardly into said gravel roadbed to produce a
mixture of substantially all of said fragments with said roadbed; and,
(c) compacting said mixture into consolidation with said sublayer to produce
said new roadbase.
2. A method as defined in claim 1, wherein:
(a) said drum roller is selectively operable in a vibratory rolling mode or a
non-vibratory rolling mode;
(b) said crumbling step is performed with said drum roller operating in a
non-vibratory rolling mode; and,
(c) said driving step is performed with said drum roller operating in a
vibratory
rolling mode.
3. A method as defined in claim 1 or 2, wherein said compacting step is
performed
with a smooth drum roller operating in vibratory rolling mode and is continued
until
further compaction by said smooth drum roller is substantially refused.
4. A method as defined in claim 1 or 2, further comprising dismounting said
roller
cams from said drum roller and, while said roller cams are dismounted,
performing said
compacting step with said drum roller operating in said vibratory mode until
further such
compaction is substantially refused.
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5. A method of preparing a new roadbase from a deteriorated paved road, said
road
comprising a layer of deteriorated pavement atop a gravel roadbed atop a soil
sublayer,
said method comprising:
(a) providing a smooth drum roller selectively operable in a vibratory rolling
mode or a non-vibratory rolling mode,
(b) removably mounting a plurality of roller cams on said drum roller, said
roller cams being sized to crumble said layer of deteriorated pavement into
fragments;
(c) while said roller cams are mounted on said drum roller.
(i) crumbling substantially all of said layer of deteriorated pavement into
fragments with said drum roller operating in said non-vibratory
rolling mode; and,
(ii) driving said fragments downwardly into said gravel roadbed with said
drum roller operating in a vibratory rolling mode to produce a mixture
of substantially all of said fragments with said roadbed;
(d) dismounting said roller cams from said drum roller to provide a smooth
drum surface; and,
(e) while said roller cams are dismounted from said drum roller, compacting
said mixture into consolidation with said sublayer with said drum roller
operating in said vibratory rolling mode.
6. A method as defined in claim 5, wherein said compacting step is continued
until
further compaction with said drum roller is substantially refused.
7. A method as defined in any one of claims 1 to 6, wherein said roller cams
each
have a contact area of about one inch by three inches.
8. Apparatus for preparing a new roadbase from a deteriorated paved road, said
road
comprising a layer of deteriorated pavement atop a gravel roadbed atop a soil
sublayer,
said apparatus comprising:
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(a) a smooth drum roller selectively operable in a vibratory rolling mode or
in
a non-vibratory rolling mode; and,
(b) a plurality of roller cams mountable on said drum roller, said roller cams
being sized each with a contact area substantially less than 3 inches by 6
inches to crumble substantially all of said layer of deteriorated pavement
into fragments when said drum roller is operated in said non-vibratory
rolling mode, and to drive substantially all of said fragments into mixture
with said roadbed when said drum roller is operated in said vibratory
rolling mode.
9. Apparatus as defined in claim 8, wherein said roller cams each have a
contact area
of about one inch by three inches.
10. Apparatus as defined in claim 8 or 9, wherein said roller cams are
removably
mountable on said drum roller.
11. Apparatus as defined in claim 8 or 9, wherein said roller cams are affixed
to a pair
of semi-cylindrical shells removably mountable on said drum roller.
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Description

CA 02339895 2003-08-25
APPARATUS AND METHOD FOR PREPARING A NEW
ROADBASE FROM A DETERIORATED PAVED ROAD
FIELD OF THE INVENTION
The present invention relates to road construction and, more particularly, to
apparatus and methods for preparing a new roadbase from a paved road having
deteriorated pavement.
BACKGROUND TO THE INVENTION
Compacting rural gravel roads prior to first paving the roads was unknown 4(?
years ago at the start of greatest paving activity on such roads. This has led
to problems
to because a paved but uncompacted gravel roadbed resting on sublayer soils of
varying
densities and permeabilities, and subject to vibration and the cumulative
compacting effect
of wheeled traffic, eventually settles at random within its gravel layers.
Subsidence in the
paved surface then develops, and is followed by varying degrees of pavement
deterioration.
Many paved rural roads show extensive pavement deterioration and repairs.
Costs
for reconstructing uncompacted, settled roadbeds, which have become
prohibitive in
recent years, have prompted resort to several processes of road surface
rehabilitation prior
to repaying. These procedures give the appearance of long-term improvement,
but fail to
compact an existing roadbed into its sublayers to produce maximum density in a
2o reconsolidated roadbase structure.
Current methods of roadbed reconstruction and road surface rehabilitation
include:
reconstruction reconstruction of roadbed;
rehabilitation gravel overlay (covering over pavement);
rehabilitation asphalt mix overlay on deteriorated pavement (recapping);
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CA 02339895 2003-08-25
rehabilitation 'mulching' pavement into roadbed gravel;
rehabilitation grinding pavement in place and repaying ('mill-and-fiil')
However, the durability of such reconstructed or rehabilitated roadbases is
relatively limited and there is a need for a reconsolidation method which
produces a
denser, more durable roadbase, and which raises the prospect of prolonging
pavement
service life beyond the unmet technical goal of 20 years.
SUN1NIARY OF THE INVENTION
The present invention includes a method and apparatus to reconsolidate an
uncompacted gravel roadbed and its deteriorated pavement. The method includes
an
to intensive compacting effort from the deteriorated surface downward.
Preferably, the
method is implemented with a vibratory smooth-drum roller fitted with a shell
on which
cams are welded. The roller cams are sized to crumble rutted and deteriorated
pavement
in situ, and to drive pavement fragments into the roadbed gravel.
More particularly, the main component of asphaltic concrete pavement is
crushed
t5 gravel; therefore deteriorated pavement when crumbled into fragments is
wholly
compatible with roadbed gravel. A drum roller in accordance with the present
invention
serves to intensively compact the mix of fragments and roadbed gravel, and to
drive the
compacted mix into consolidation with the roadbed's sublayer soils. The
purpose of such
intensive compacting is to develop resistance in the sublayer soils equivalent
to the load
20 imposed by the mix of pavement fragments and roadbed gravel which is
displaced into
sublayers, and by the weight of gravel to be added to restore zones of
displacement in the
road surface.
In one aspect of the present invention, there is provided a method of
preparing a
new roadbase from a deteriorated paved road, the road comprising a layer of
deteriorated
25 pavement atop a gravel roadb~ atop a soil sublayer. The method comprises
crumbling
substantially all of the layer of deteriorated pavement into fragments with a
drum roller
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CA 02339895 2003-08-25
having plurality of roller cams mounted thereon; driving the fragments
downwardly into
the gravel roadbed to produce a mixture of substantially all of the fragments
with the
roadbed; and, compacting the mixture into consolidation with the sublayer to
produce the
new roadbase.
Preferably, the drum roller is selectively operable in a vibratory rolling
mode or a
non-vibratory rolling mode. The step of crumbling the layer of deteriorated
pavement
into fragments is performed with the roller operating in its non-vibratory
mode. The step
of driving the fragments into the gravel roadbed to produce the specified
mixture is
performed with the same drum roller, still fitted with the roller cams, but
now operating in
to a vibratory rolling mode.
Preferably the method of the present invention comprises providing a smooth
drum
roller selectively operable in a vibratory rolling mode or a non-vibratory
rolling mode and
removably mounting a plurality of roller cams on the smooth drum roller. As
above, the
roller cams are sized to crumble the layer of deteriorated pavement into
fragments. Then,
while the roller cams are mounted on the smooth drum roller, substantially all
of the layer
of deteriorated pavement is crumbled into fragments with the roller operating
in its
non-vibratory rolling mode - followed by the step of driving the fragments
downwardly
into the gravel roadbed with the roller operating in its vibratory rolling
mode to produce a
mixture of substantially all of the fragments with the roadbed. Next, the
roller cams are
2o dismounts from the roller drum to provide a smooth drum surface and, while
the roller
cams are dismounted, the mixture is compacted into consolidation with the soil
sublayer
with the drum roller operating in its vibratory rolling mode.
Preferably, compaction is continued until further compaction with the drum
roller
is substantially refused (viz. a stage where the compacting drum roller makes
negligible
impression in the road surface). Density of the roadbase may be measured by
geotechnical
instruments. The condition of 'refusal' to continued compacting effort is
desirable to
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CA 02339895 2003-08-25
prevent settling of the roadbase, and eventual subsidence in a layer of new
pavement
applied thereto.
In cases where a smooth drum roller is used in vibratory and non-vibratory
operating modes, and where roller cams are removably mountable on the roller,
it will be
evident that the steps of crumbling a layer of deteriorated pavement into
fragments,
driving the fragments into mixture with the gravel roadbed, and compacting the
resulting
mixture into consolidation with the soil sublayer, advantageously can be
performed using
a single drum roller.
In another aspect of the present invention, there is provided apparatus for
preparing
a new roadbase from a deteriorated paved road, the road comprising a layer of
deteriorated
pavement atop a gravel roadbed atop a soil sublayer. The apparatus comprises a
smooth
drum roller selectively operable in a vibratory rolling mode or in a non-
vibratory rolling
mode, and a plurality of roller cams mountable on the drum roller. The roller
cams are
sized to crumble substantially all of the layer of deteriorated pavement into
fragments
when the drum roller is operated in a non-vibratory rolling mode, and to drive
substantially all of the fragments into mixture with the roadbed when the drum
roller is
operated in a vibratory rolling mode.
Preferably, the roller cams are removably mountable on the drum roller so that
drum roller may be used either with or without the roller cams, in the latter
case offering a
smooth drum surface for the purpose of compacting operations. To enable the
roller cams
to be quickly and efficiently mounted on or dismounted from the smooth drum
roller, they
advantageously may be affixed to semi-.cylindrical or half shells that are in
turn
removably mountable to the drum roller.
The foregoing and other features and advantages of the present invention will
now
be described with reference to the drawings.
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CA 02339895 2003-08-25
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a steel shell with roller cams welded thereto
in
accordance with the present invention.
FIG. 2 is a perspective view of a conventional smooth drum roller which is
selectively operable in a vibratory rolling mode or a non-vibratory rolling
mode.
FIG. 3 is a perspective view of one of two semi-cylindrical or half shells
used to
form the shell shown in FIG. l..
FIG. 4 is a detail view, in perspective, showing on one end of one side the
half
shells shown in FIG. 1 locked by a steel pin through the double and single
locking cams.
to FIG. 5 is a view in plan, elevation and perspective of a roller cam in
accordance
with the present invention.
FIG. 6 is a perspective view of a conventional padfoot vibratory roller.
FIG. 7 is a photographic view of a vibratory soil-compactor crumbling
deteriorated
pavement.
FIG. 8 is a photographic view of pavement fragments.
FIG. 9 is a photographic view of pavement fragments in a mix with uncompacted
roadbed gravel.
FIG. 10 is a photographic view of a road compacted to a stage approaching
'refusal'.
2o FIG. 11 shows a cross-section A of ~vement on an uncompacted roadbed gravel
resting on sublayer soils, and a cross-section B, of pavement fragments and
roadbed gravel
reconsolidated in sublayer soils.
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CA 02339895 2003-08-25
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
The steel shell shown in FIG. 1 comprises two longitudinal semi-cylindrical
half
shells like the half shell shown in FIG. 3 and is sized to be removably
mounted to the
drum of the smooth drum roller shown in FIG. 2. A plurality of roller cams 6
as shown in
detail in FIG. 5 are affixed by welding on the shells and are
circumferentially positioned
around the shells. Roller cams 6 are sized to crumble deteriorated pavement
into
fragments when the drum roller is operated in a non-vibratory rolling mode,
and to drive
substantially all of the fragments into mixture with a gravel roadbed when the
drum roller
is operated in a vibratory rolling mode. Since the half shells are removably
mountable to
to the drum roller, it follows that roller cams 6 which are affixed to the
shells may be
considered as removably mountable to the drum roller.
To enable each half shell to be locked on the drum to the other half shell,
each half
shell includes two pairs of single roller cams 1 which serve as locking cams,
and two pairs
of double roller cams 2, 2 which cooperatively serve as locking cams. As shown
in FIG.
t5 4, roller cams 2, 2 are spaced to enable a roller cam 1 to fit therebetween
and to be locked
with the roller cam 1 by a removable steel pin 3. From FIG. 2, it will be
appreciated that
the two half shells overall include four sets of single roller cams 1 and
double roller cams
2, 2.
Each roller cam as shown in FIG. 5 preferably has a contact area of about 1
inch by
20 3 inches which is substantially less than the contact area (e.g. 3 inches
by 6 inches) of
cams 7 on a conventional padfoot roller (FIG. 6) which are not designed to
crumble
deteriorated pavement into fragments suitable for mixing with a gravel
roadbase. More
particularly, a roller cam with a contact area of about 1 inch by 3 inches is
considered to
be particularly suited to the present invention because it provides about 6
times the loading
25 or crumbling effort of a conventional padfoot roller, and the resulting
fragments have a
workable size for mixing purposes.
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CA 02339895 2003-08-25
As noted above, the conventional drum roller shown in FIG. 2 is selectively
operable in a vibratory rolling mode or a non-vibratory rolling mode.
Operating in a
non-vibratory mode with the half shells mounted, the drum roller is passed
over a layer of
deteriorated pavement 8 and underlying roadbed gravel 9 resting on sublayer
soils 10
(which may be of varying densities and permeabilities) as shown in cross--
section A of
FIG. 11 to crumble substantially all of the deteriorated pavement into
fragments.
Then, operating in a vibratory mode with the half shells still mounted, the
drum
roller is passed over the crumbled pavement to drive substantially all of the
fragments into
mix with uncompacted roadbed gravel 9.
to Later (e.g. one day), on the section of pavement previously crumbled into
fragments and mixed with roadbed gravel 9, the drum roller with the shell now
removed
and operating in a vibratory mode is used to compact the mix of pavement
fragments and
roadbed gravel 9 downwardly to 'refusal' in consolidation with sublayer soils
10 as
depicted in cross-section B of FIG. 11 where the consolidated mix is depicted
by the
numeral 11. By reason of the compacting effort, it can be seen in FIG. 11 not
only that
mix 1 I includes sublayer soils 10 within the mix but also that the sublayer
base has been
compressed downwardly in relation to the level of soils 10 on either side of
the road. It
follows that the resulting roadbase is both dense and durable.
On the resulting reconsolidated roadbase, fresh crushed gravel 12 as shown
2o FIG. I I normally will be spread, graded evenly and compacted, preparatory
to repaying.
The method of the present invention may be considered as a dynamic
'preloading'
of a roadbed with its sublayer soils by mechanically displacing pavement
fragments and
roadbed gravel therein. The method may be likened to a static 'preload' of a
building site
on which granular materials are spread in depth to compact site sublayers over
time.
Environmentally, the method of the present invention can conserve gravel
stocks
by re-using, rather than replacing roadbed gravel, by reducing machine fuel
use and

CA 02339895 2003-08-25
exhaust emissions, and by eliminating the wasting of excavated road material
with its
asphalt content, from leaching into groundwater.
Various modifications and changes to the embodiment that has been described
can
be made without departing from the scope of the present invention. The
invention is not to
be construed as limited to the particular embodiment that has been described
and should
be understood as encompassing all those embodiments that are within the spirit
and scope
of the claims that follow.
_g_

Representative Drawing