ROAD MAKING.
One of the most important points towards obtaining a good metalled road
is to ensure a proper foundation for the metal to be consolidated on,
and to see that the sides are well confined or tied in. Where bricks are
used for this foundation they should be whole ones, not bats, be tightly
packed together and then rammed with a wooden rammer. The edging should
consist of bricks-on-end well backed up with earth on the out, or berm
side. The same applies where stone is used for the soling. These must
have flat surfaces, be of fair size, and be well hand-packed together
and rammed. It is not much use doing metalling work on a raised road
until the embankment has at least 2 rains over it to properly
consolidate it. This equally applies to the approaches to bridges on a
kutcha road where the metalled portion should be extended to a length of
at least 10 feet beyond the toe of the approach slope.
[Sidenote: Stone Metal.]
In most municipalities it is financially impossible to thoroughly repair
all the roads each year, nor is it necessary to do so, if the work has
been properly done. A system of biennial or triennial repairs should
therefore be evolved. A diagram showing how this can be arranged is
shown in Fig. 11, page 19.
In the selection of stone metal it is of great importance to see that
stone of equal grade and hardness is used, and that surface, or
weathered rock, is not mixed up with the harder material lying
underneath it in the quarries. The stone should be broken to the size
that the largest piece shall pass freely through a 1½″ diameter ring.
When repairing existing metalled roads it is essential that all old
metal be picked up, and any rounded, or traffic-worn portions re-broken,
as it is impossible to ensure good consolidation unless the edges and
corners of the stone metal be sharp. Consolidation should be done by a
heavy roller. A steam roller for preference. The cost of a 6–ton steam
roller is about Rs. 6,000 and the working cost about Rs. 4 per day, but
this must necessarily vary considerably in different localities,
depending on the cost of fuel and labour.
[Illustration:
DIAGRAM
FIG. 11.
]
_For Oiling Roads._
[Sidenote: Oiling Roads.]
The roadway must first be swept clear of dust and foreign material, when
the mixture composed of one part of coal-tar to 20 parts of oil (liquid
fuel), mixed cold, must be sprinkled on through a watering cart. Men
with hard long handled brushes follow the cart, and brush the mixture
into the roadway, and repeat this operation for the second time in the
reverse direction, when ¼ of a mile has been done. The oiling lasts for
about 2 months, and costs about Re. 1 per hundred square feet.
[Sidenote: Tar-Macadam.]
Although tar-Macadam may be somewhat ambitious for mofussil
municipalities, an abstract of the specification for MacCabe’s
tar-Macadam, which was kindly supplied to me by the Chief Engineer of
the Calcutta Corporation, is of interest, see specification Appendix H,
page 75. The cost of a road so laid is Rs. 2–2–0 per square yard, and
although sufficient experience is not available to predict its life,
some has been down for 3 years and is still good. The materials consist
of two parts Pakoor Stone metal, MacCabe’s patent Bituminous binder of
Gas Co.’s Coal-tar, and Stagg brand English coal-pitch, in the
proportion of 1 of tar to 3 of pitch by weight, with stone chipping, and
sand as a top binder.
[Sidenote: Kunkar Metal.]
All _kunkar_ metal required for metalling or repair work should be
collected, screened, and stacked by the middle of May at latest;
screening must be done in the dry weather, otherwise the meshes of the
screen soon clog up when the _kunkar_ is damp, and the operation is more
or less a farce. A specification for this is given below:—
(1) All _kunkar_ must be washed, cleaned, and screened during the dry
weather months; and must be of such quality that, being re-washed and
rescreened through an expanded metal screen of ⅜″ mesh, set at an angle
of 45°, shall leave a residue of 80 per cent. pure _kunkar_. If _kunkar_
of a lower standard is stacked it must either be rejected, or the cost
of bringing the metal up to specification, deducted from the price paid.
(2) No _kunkar_ should be measured after the 1st June. All _kunkar_
collection must be completed by 15th May.
[Sidenote: Brick Metal.]
Brick metalled roads are rarely successful owing to the difficulty of
ensuring that the metal is of equal hardness throughout, and especially
so in a dry climate, as under heavy traffic the metal soon wears into
brick dust, which either blows away in the dry season in the form of
dust, or is washed away in the rains; on no account should _jhama_, or
vitrified brick, and red brick metal be mixed, as their degree of
hardness is so different.
[Sidenote: Morhum & Kutcha Roads.]
It is of great importance that excessive slope be not given in morhum or
kutcha roads, otherwise they will rapidly gutter during heavy rain. A
rise of 1 in 50 to the centre of the road will generally be found to be
ample.
[Sidenote: Stacking Metal.]
In order to control the collection of material it is essential that all
be stacked to gauge, or in boxes, and that the stacks be of equal size,
thus facilitating measurements.
[Sidenote: Consolidation of Metal.]
Consolidation of metal must invariably be done as soon after the rainy
season sets in as possible, and especially so for _kunkar_. Any heavy
rainfall in a water-bound road after the metal is once laid is
invaluable in helping consolidation, as it fills up all the interstices
which may be left after rolling or ramming; _kunkar_ should be
consolidated by ramming with heavy wooden rammers, although on a new
road a roller will be of use in forcing the _kunkar_ in between the
joints of the soling bricks, and jamming them into the earth, thus
making a solid foundation. A plentiful supply of water should be used in
the process of consolidation; this is most essential. Stone and brick
metalling should be consolidated by heavy rollers, a minimum quantity of
surfacing material being used. It is of great importance to keep the
berms well made up against the metalled portion of a road, otherwise the
metal will rapidly spread out under traffic.
In all cases it is of the greatest importance that the natural aid
afforded by climatic conditions be utilised in making roads; this is a
subject the importance of which is frequently overlooked. When the
consolidation of metal is seen to be going on after the end of the
rains, unless there are exceptional circumstances to justify this, the
official in charge may be condemned at sight as being ignorant or
incompetent.
Long lengths of road should not be taken up for repairs at a time, as
this causes much inconvenience to traffic. A furlong is the uttermost
limit admissible.