Matakuliah
Tahun
Versi
: S0182/Studi Kasus Dalam Teknik Sipil
: Juli 2005
: 01/01
Pertemuan 05
<<Judul>>
1
Learning Outcomes
Mahasiswa dapat memperhitungkan
berbagai kemungkinan dan memilih
alternatif yang terbaik bagi penyelesaian
masalah.  C3, C4
2
Outline Materi
• Kasus yang selalu dijumpai di proyek
• Kasus yang mungkin terjadi dengan
kondisi khusus
• Analisa pemecahan masalah
3
• "Fatted-up" Surface Dressings
The most common sites where
retexturing with "High Pressure Water"
is undertaken are fatted up surface
dressings as shown to the left.
You will see on this site large areas of
the road surface have completely fatted
up leaving a smooth surface with no
texture at all.
4
Pavement Design
• The road pavement is the actual surface on which the vehicles will
travel. It's purpose is two fold, to provide friction for the vehicles and
to transfer normal stresses to the underlying soils. The procedure
described in this page is that in the Design Manual for Roads and
Bridges, Volume 7 (Available on-line at http://www.archive.officialdocuments.co.uk/document/ha/dmrb/index.htm.)
• The design Process can be split up into different areas. These are
as follows:
• Foundation Design - That is the design of the Subgrade and subbase
• Thickness Design - That is the design of the actual road surface
• Unfortunately to include both of the areas on this page would cripple
your browser so they have been split up and this page contains only
the introduction and links to the different areas.
5
PAVEMENT
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There are four types of pavement currently in use in the United kingdom at
present:
Flexible - pavements with a bitumen bonded surfacing and roadbase.
Flexible Composite - The surfacing and upper road base are bituminous
on a lower roadbase of cement bound material
Rigid - Pavements with a concrete surface slab which can be un-reinforced,
joint reinforced or continuously reinforced.
Rigid Composite - continuously reinforced concrete slab with a bituminous
overlay.
Although there has been considerable advance in the theoretical design of
pavements, most of the current work is based on empirical methods and
design charts. For this reason only these methods will be covered in these
pages.
Normally a design is carried out for each of the alternatives and then the
most economical chosen. However, if for environmental or technical
reasons one is impractical then it may be omitted.
The general form of the different types of pavement is shown below. It can
be seen that common to all types of construction is the Sub-base and
subgrade. It is this aspect of the design which is treated first. However, it is
first necessary to decide on a failure criteria on which to base the design.
6
FAILURE CRITERIA
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This has been the subject of extensive research and is the result not of
theory but of full scale tests and observations of real life situations. Croney1
states that permanent deformation in the near side wheel tracks of a flexible
pavement of 20mm, when measured from a 1.8m straight rule, was
normally accepted as the point at which reconstruction was considered
necessary.
It was also noted that at this point the surface was beginning to crack. This
led to water ingress and subsequently rapid deterioration.
The critical condition was much harder to define although it was found
generally that overlays were being provided between deformations of 10
and 20mm. Cracking at these points was generally limited to longitudinal
cracks in the wheel tracks.
The advantage of this method is that it is easily measured by visual
inspection and a straight edge.
Methods used in the United States including asking passing motorists to
rate the trafficability between 0 and 5 and a slope variance device. Salter2
contains more information on both these methods as well as other relevant
ones.
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8
Pavement Design - Thickness Design
The thickness design of the
pavement is the determination
of the overall thickness of the
road and the thickness of the
individual layers. This is of
course dependant on the type
of material chosen for the road.
This is explained in more detail
below. The procedure
described in this page is that in
the Design Manual for Roads
and Bridges, Volume 7.
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• Before and after high pressure water
treatment
The photographs below are before and after
sections of the fatted up surface dressing,
you will see the pressure of the water has
successfully removed the excess bitumen
and left an excellent texture.
This process is so effective that the biggest
danger is "blasting" out sections of the road
surface, so great care is needed by the
machine operators to ensure the integrity of
the road surface is not weakened by the
process.
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• High pressure water retexturing / declogging
machine
Below are pictures of a typical machine for
doing this type of retexturing, it has to be
able to carry large amoiunts of clean water
so its basic shape is that of a "tanker".
It has a row of spinning heads at the rear of
the machine which actually spray the water,
there is usually just one jet on each spinning
unit and complete coverage of the road is
due to the spinning action.
If the head stops spinning while the jet is still
spraying you will quickly have a small hole in
the road surface.
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• Relative Hydraulic Conductivity
This particular machine carried its own apparatus for testing the
relative hydraulic conductivity ( porosity ) of "Porous Asphalt" when
the machine was being used for "de-clogging" the open texture of
that surfacing material.
This test is a measure of how quickly the water will drain through the
porous asphalt matrix..
Initially the test will be performed shortly after laying to check that
the material/surface complies with the specification.
The method of the test is to be found in BS DD 229 : 1996.
It will also be performed from time to time to test that the
interconnecting voids which allow drainage have not become
clogged, and to test the effectiveness of any "declogging"
operations.
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• Description of the Process
The rotating assembly of bars carrying the individual discs is
positioned very accurately above the road surface so that only
slight contact is made with the aggregate at the road surface.
In this position the aggregate is successfully roughened
without causing damage to the road surface.
The accuracy of this positioning with this process cannot be
over emphasised, because if it is set to low not only will the
surface course layer receive damage, you may well create a
road surface that has longitudinal groves that could be cause
for concern for motorcycle traffic.
However, performed correctly by an experienced gang this is
an excellent process.
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• The Rotating Assembly
This picture illustrates the way the individual
discs are mounted on the rotating bars.
The discs are not fixed but loosely mounted
with the bar passing through the central hole
of the disc with a considerable clearance,
this is so that the once the disc has impacted
with the road aggregate it will bounce up as
there is no downward pressure from the
machine other than centrifugal force.
This is providing the rotating assembly is
correctly positioned.
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