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Samuel Washington McCallie.

A preliminary report on the roads and road-building materials of Georgia online

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the same convention, Rev. Dr. Ray stated, ^ that the lands on the
eastern shore of Virginia had increased in value, from $10 to
$100 per acre, in the last few years, chiefly on account of the im-
provement of the highways. The writer has in mind a farm, in
one of the Eastern States, which, a short time ago, was offered
for sale at $20,000. Since the completion of a first-class macad-
amized road through the farm, the owner has refused an offer of
$30,000 for the property. Prof. W. C. Latta, of Purdue Univer-
sity, places the estimated average increase of valuation per acre,
that would result, if all common roads were improved, at $9.00.
Other instances might be indefinitely enumerated, showing large
increases in the values of real estate, brought about, in a great
measure, by the improvement of the highways. However, it is
not necessary to assume such large gains as the above, to show,
that the increase in value of real estate in any commonwealth,
due to the betterment of public roads, must aggregate an im-
mense sum. Let us suppose, that the construction of good public
roads throughout the State of Georgia would increase the value
of our lands $2.00 per acre. This estimate is certainly not over-
rated, as every person will testify, who has experienced the bene-
ficial effect of good roads. Nevertheless, this insignificant
amount, as it may appear to the general reader, would aggregate
more than $70,000,000, a sum equal to about a half of the
present assessed valuation of all the farming lands of the State.
Such an amount of money is ample, not only to grade and mac-
adamize all our leading public roads, but also to pay the entire
State debt, with a sufficient surplus remaining, to bear the ex-
pense of running the State Government for a number of years.
Granting an increased value of only $1.00 per acre, on a belt of
land one mile in width on each side of a road ; even then the
aggregate increase in the value of such a narrow strip of land

' Bulletin No. ii, U. S. Dept. of Agri., Office of Road Inquiry, p. 19.



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32



THE VALUE OF GOOD ROADS



alone would be sufficient to build a first-class road in any part of
the State. That is, any section of the State can construct good
roads, by levying a tax of $i.oo per acre, on all lands lying
within one mile of the proposed road.

Leaving out of consideration entirely the increased value of
real estate and summing up the foregoing estimates, we have a
total aggregate of $6,250,000 annually, chargeable to the bad
roads of Georgia. This amount is sufficient, to construct 3,000
miles of macadamized road, and is nearly twice the annual
assessed State taxes.



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CHAPTER III



ROAD CONSTRUCTION

Location of Roads. — The Roman engineers, in constructing
the imperial roads, as has been previously noted, are said to have
always laid them out, in straight lines from one objective point to
another, regardless of intervening obstacles. Modern highway
engineers no longer follow the rule, adopted by the Romans ; but,
on the contrary, other things being equal, they always locate the
roads along the lines of easy gradient. Gen. Q. A. Gillmore, in
discussing the question of road location, says : ^ ** The considera-
tions, which should govern the engineer in locating the line of or-
dinary wagon-roads, are (i) the present and prospective amount
of traffic over the road; (2) its general character, whether light
or heavy ; (3) the convenience and necessities of the community
tributary to the line ; and (4) the natural features of the country
through which the road must pass." Taking these several con-
ditions into consideration, it is at once evident, that the location
of a road really involves a rather complex economic problem. If
the question of grades is alone taken into consideration, the con-
venience of the road is likely to be sacrificed, to a greater or less
extent ; and, at the same time, the cost of maintenance is mate-
rially increased. On the other hand, if convenience is considered,
the grades may become so great, as to render the road practically
impassable for heavy traffic.

Mr. Austin T. Byrne, in his treatise on highway-construction,
lays down the following general principles, to be observed in
locating highways : — *

Roads, Streets and Pavements, p. 9.
2
Highway Construction, by Austin T. Byrne, p. 316.

(33)



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34



ROAD CONSTRUCTION



''i Follow the route, which affords the easiest grades. The easiest grade for a
given road will depend upon the kind of covering adopted for its surface.

2 Connect the places by the .shortest and most direct routes commensurate with
easy grades.

3 Avoid all unnecessary ascents and descents. When a road is encumbered
with useless ascents, the useless expenditure of power is considerable.

4 Give the center line of the road such a position with reference to the natural
surface of the ground, that the cost of construction shall be reduced to the
smallest possible amount.

5 Cross all obstacles, where structures are necessary, as nearly as possible at
right-angles.

6 Cross ridges through the lowest passes.

7 Cross either under or over railroads. Grade crossings are always dangerous
to the users of the highway, and, if possible, should be avoided."

It will be seen from the above principles, that the first thing to
be done in the location of a road is to study the topography of the
section through which the road is to pass. Where topographic
maps of the region have already been made out, they can be used
to a great advantage in locating the most practical line for the
proposed road. When these are not accessible, there must be a
preliminary survey made, showing the location and trend of the
streams, hills and ridges, together with the relative positions of
the objective points, to be reached by the road. Having obtained
this desired information, the highway engineer proceeds to defi-
nitely locate the line of road, which will best accommodate the
traffic, for which it is to be constructed. The easiest grades, the
shortest distances, and the smallest rise and fall consistent with
the cost of construction, all receive due consideration from the
faithful engineer, before the line of road is permanently located.

It may be noted, as a common rule, in mountainous or hilly
countries, that the best and most important highways, like rail-
roads, are located along streams or ridges. Each of these locations
has its disadvantages. Ridge-roads are often dry and destitute of
running water, so that both man and beast are frequently com-
pelled to travel long distances, without water to relieve their thirst.
Furthermore, the descent of these roads to the valleys below are
likely to present difficult problems to the engineer, in securing a
practical grade. The location of roads along valleys, on the other



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ROAD CONSTRUCTION 35

hand, is frequently objectionable, on account of the extra expense
of keeping up bridges. Even if the line of road does not cross the
main stream of the valley, there are always many small tributaries
or deep gorges to be bridged.

The problem, now presented to the advocates of good roads in
the South, is not so much a question of locating new roads, as it
is of changing the location of roads already in existence. This is
especially true of the State of Georgia, where many of the roads
were originally laid out along lot-lines or division boundaries be-
tween properties, regardless of the various obstacles encountered.
These mistakes must be corrected, in a great measure, before it
will be possible to construct first-class roads, of easy grade, through-
out the State, at anything like a reasonable cost. Road Commis-
sioners should by all means see, that their roads are always prop-
erly located before attempting any permanent improvement. It
would probably be no exaggeration to say, that many of the lead-
ing highways in this State would require an expenditure of several
thousand dollars per mile, in grading alone, to put them in first-
class condition for heavy traffic. Such conditions as these are
practically prohibitive of good roads, until they shall be re-located.
Changing the location of established roads frequently presents a
simple problem to the engineer ; but, at the same time, it may
save hundreds of dollars per mile in the cost of construction.

Grades. — By the term grade, as used in highway construction,
is meant the degree of inclination from the horizontal, or the
slope of the surface. When not designated by degrees, the grade
is expressed either in the form of a simple ratio, as, for example,
1 : 20, or by the percentage amount. The ratio 1:20 indicates a
rise of i foot in every 20 feet, or a 5 per cent, grade.

The grade of a road should depend, in a great measure, upon
the character of the traffic, for which the road is to be used. If
the traffic is heavy, and the individual loads are necessarily large,
it is always advisable to reduce the grade to the lowest possible
minimum consistent with the cost of construction. Most high-
way engineers place the maximum grade of macadamized roads at



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36



ROAD CONSTRUCTION



I to 30. Such maximum grades, however, should be as short as
possible ; as they overstrain the team, and render frequent stops
necessary, to relieve the animals from fatigue. By reference to
table No. 3, page 26, it will be seen, that the tractive force, re-
quired to move a given load over a road, with a grade of i to 30,
is nearly three times as great, as that, required to move the same
load over a level road. The maximum load for any team should
always be governed by the maximum grade to be overcome. A
short grade of i to 30, at any point on an otherwise level road,
will reduce the efficiency of a team nearly one-third, and at the
same time increase the cost of transportation in the same ratio.
It is nearly always practicable to reduce the grade of a road to
the above maximum limit, even in mountainous regions, by

Fig. 5



Cross-section of a Macadam Road (after Shaler) .

making the line of road sinuous or zig-zag. This principle of
highway-construction is admirably illustrated at many of our
Southern mountain resorts, where roads, of easy grade, reach, in
a short distance, elevations of many hundred feet above the val-
leys below. Besides reducing the efficiency of tractive force,
steep grades also greatly augment the cost of keeping roads in
repair. Every observant person has noticed, how difficult it is to
keep a hillside road from forming ruts or gullies, on account of
the erosive action of running water. The erosive power of water
varies, as the square of its velocity ; so it is obvious, that a slight
increase in grade will greatly increase the effective force of this
destructive agent. A practical highway engineer, in discussing
the question of grades, has said, that the extra expense, incurred
in maintaining a road with high grades, will frequently in a short
time aggregate a sum sufficient to pay the entire expense of re-
locating the road.



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ROAD CONSTRUCTION



37



Drainage. — There is no problem, presented to the political
road-builder, of more importance than drainage. Unless a road
is properly drained, it is practically impossible to keep it in first-
class condition. Water must be removed from the roadway, or
it will rapidly destroy the compactness of the surface, and sooner
or later render the road impassable. This is true, not only of
common dirt roads, but of macadamized roads as well.

The drainage of roadways is naturally divided into two divi-
sions, namely, surface drainage and subdrainage. The object of
surface drainage is to conduct the water, which falls on the sur-
face of the road, into the side ditches or drainways, as quickly as
possible, while the subdrainage removes it from beneath the sur-
face.




Cross-section of a Macadam Road.

Surface drainage is accomplished, mainly by giving the surface
of the roadway a slight inclination from its centre to its sides.
This is called " crowning " the road. Engineers differ as to the
shape of the crown of roads. Some contend, that it should be a
convex curve, approximately circular ; and others advocate two
uniformly sloping planes at the sides, connected in the middle of
the road by a small circular arc. '

The angle of the slope, which the crown of the road should
have, depends, in a great measure, upon the character of the ma-
terial used in forming the surface. When the material is easily per-
meated, the angle of slope should be greater than for impermeable
material. The usual grade for the crown of a macadamized road
is about I in 30. That is, a roadway, 60 feet in width, should be
one foot higher at the center than at the sides. The crown of a
dirt road should be somewhat greater ; but in no instance should

See fig^s. 5 and 6.



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38



ROAD CONSTRUCTION



it be SO great as to confine the traffic to its center, by reason of
the sloping conditions of its sides, or to cause an undue erosion
of the surface from heavy rains. The water, as it flows from the
surface of the roadway, should be received in properly constructed
drains, on either side of the road.* These drains should have suf-

Fig. 7
Cross-section of Earth Road Showing Side-Drains.

ficient slope to conduct the water off, as rapidly as it accumulates,
into the cross channels or culverts. Frequently, a road properly
crowned and supplied with suitable side ditches needs no further
drainage. In many cases, however, subdrainage is also necessary,
to secure the desired results. The object of subdrainage is not
only to remove the water, which may penetrate the surface from
above, but also to draw off the water which, by lateral seepage,
enters the roadbed from below.

Fig. 8




Cross-section of a Macadamized Road Showing Central Sub-drain and Side-drains.

Subdrainage is accomplished by the use of either side or cen-
tral drains.^ Side-drains may be open or closed, and should
always have a depth of 2 ^ to 3 feet below the surface of the road-
way, with sufficient slope to carry off the water. Open drains per-
form the double office of carrying off both the surface and the
underground waters ; and, for this reason, they are often preferable
to closed drains. These drains, however, on account of their

See fig. 7. See figs. 8 and 9.



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ROAD CONSTRUCTION



39



depth and their proximity to the roadway, are frequently danger-
ous. Gen. Gillmore meets this objection by suggesting, that open
under-drain ditches be placed on the field side of fences or hedges
in the agricultural districts, where accidents to vehicles are most
likely to occur. The width of an open drain and the slope of its

Fig. 9




Cross-section of a Macadamized Road Showing Lateral Sub-drains.

sides should be governed by the amount of water to be carried off ,^
and by the character of the soil. Jf the soil is sandy or friable,
the sides of the ditch should slope at a low angle ; otherwise, they
will cave and soon render the ditch practically useless for drain^
age purposes.

Closed drains are variously constructed. One of the simplest,
and, at the same time, most cheaply constructed closed drains is
shown in fig. lo. It consists of a narrow, properly-graded ditch^
about three feet in depth, and partly
filled with stones. In constructing a
drain of this character, it is always ad-
visable to use rounded stones, placing the
largest on the bottom and the smallest
on the top. Such an arrangement gives
ample space at the bottom for the free
circulation of the water, and prevents the
washing in of the earth from above. To
guard more completely against the filling

of the spaces between the stones by earth,

., . -^ , ^ X 1 ^t '^..i Cross-section of a Blind

It IS often best to overlay them with j^^^.^ ^^^^^ Spalding).

grass or straw before filling the upper

part of the ditch with earth. There are several modifications o£



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ROAD CONSTRUCTION



this plan of stone drain differing mainly in the arrangement of the
lower layers of the stones.' Where stones are not to be had, a
drain can be made of logs, poles and brush, which will answer

all practical purposes. The foUow-
^*^* ^' ing description of such a drain is

given by Mr. Charles W. Irish in
Bulletin No. 8, published by the U.
S. Office of Road Inquiry : —

*'The materials used are a few
waste logs and some brush, of any
kind handy, and some poles for cov-
ering the brush. ^ Supposing the
trench ^, / ^, A is 3 feet wide on the
bottom, f^g. I put in, at the sides

Cross-section of a Stone Drain. ^^ ^^^ ^^O logS, a, a, each about 8 or

10 inches in diameter. Between
these logs, I place brush, laid criss-cross, and thoroughly rammed
and tramped into place, filling up the space to a height of 3 or
4 inches above the logs. On the top of the small bush, so rammed
into place, I lay poles about 3 or 4 inches in diameter, one or two
courses deep, and then fill in the
trench to the top with earth well ^*^* "

rammed."

A drain, constructed after this
manner, was found by Mr. Irish to
be in good condition after a use of
twenty years.

The most durable and satisfactory
material for use in the construction
of underground drains are bricks

and tiles. The different methods of cross-section of a stone Drain,
using bricks for underground drain-
age is shown in figs 14, 15, 16 and 17, taken from Gillmore.^ In
order to make this method of drainage as effective as possible, it is

See figs. II and 12. See fig. 13.

^ Roads, streets and Pavements, by Q. A. Gillmore, p. 56.



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ROAD CONSTRUCTION



41



^essential, that the lower part of the ditch be filled with stones,
gravel or coarise sand, so as to allow the water an easy access to the
opening below. Drains properly constructed of brick will last for
an indefinite period and always give satisfactory results.

Tile-drains are probably the best and most effective of all under-
ground drains. The form of the tile, employed in under-draining,
is usually round, and varies in diameter from 3 to 6 inches, ac-
cording to the amount of water to be carried off. The tiles should
be evenly laid, and have a slope of about i foot in icx>, insuring an

Fig. 13



Cross-section of a Brush Drain, e-f-g-hy the Trench, a-a. Logs, 10 inches in
Diameter, b. Brush, c-d^ Poles, 2-4 inches in Diameter.

effective flow. The ditch, in which the tiles are placed, should be
partially filled with stones,^ as in the case of brick-drains.

The cost of tile-drains is said to be less than either stone or
brick-drains. Mr. Henry F. French, in discussing the cost of
drains, says : " Drainage with tiles will generally cost less than
one-half the expense of drainage with stone, and will be incom-
parably more satisfactory in the end." The following price-list
of tiles suitable for underground drainage is taken from Mr. Isaac
B. Potter's excellent booklet on Macadam Roads: —



See fig. 18.



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ROAD CONSTRUCTION



PRICE-UST OF HARD BURNED DRAIN-TILE



Size



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2 inch

3 inch

4 inch

5 inch

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8 inch

9 inch
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15 inch
18 inch

20 inch

21 inch
24 inch





3.141


3


1 20.00


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7.068


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12.566


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45 -00


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19.625


9


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28.274


12


80.00


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38.484


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110.00


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50.265


22


150.00


.70






63.617


26


200.00


75


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78539


33


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1. 00






II3090


44


325 00


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176.710


60


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254460


92


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314.160


106


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345 000


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452.390


150


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0.50
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6.50



8,000
6,000
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2,20O'

2,000

1,250

1,000

850

750

500

350

250

225

200



Central drains made of stone, brick or tile, are often used b>^
highway engineers for subdrainage, in the place of lateral drains.
The material employed, and the method of constructing such
drains, are similar to that adopted in closed side-drains. Cross-
drains are also, in many cases, found to be essential, in order to-
secure satisfactory drainage of a roadway. These are closed drains,
made of stone, brick or tile, and connected with the side or cen-
tral drain, into which they deliver the water. Cross-drains on a
grade should be in the form of a V, with the apex directed toward
the ascent.

Besides the above-named drains, there is another important class-
of waterways in common use in road construction. These drains
are called culverts, and are often waterways of considerable size.
The object of culverts is to conduct under the roadway the water,
which collects from the side-ditches ; also, to furnish a free passage
to the smaller streams intersecting the road. It is usually best,
especially in building first-class macadamized roads, to construct



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ROAD CONSTRUCTION



45



the culverts of stone or brick. Good examples of such water-
ways, and the plan of their construction, may be seen and studied
in all railroad culverts. Where the amount of water to be con-
ducted beneath

the roadway is Fig. 14

limited, large-size
drain-tiles answer
all purposes, and
can be put in
place at a small
cost. Wooden

culverts soon un- Cross-section of a Drain.

dergo decay ; and

for this reason, they should never be used in permanent first-class

highways.

ROAD SURFACES

Having graded and properly under-drained the roadway, the
next process in highway building is to construct a suitable surface^

over which the traffic is to pass. This is
Fig. 15 accomplished in all first-class highways^

by covering the specially prepared road-
bed, to the depth of several inches, with
broken stones, or some other unyield-
ing material. Numerous methods are
adopted by highway engineers in con-
structing hardened surfaces for roadways.
One of the oldest methods, to be gener-
Cross-section of a Drain. ally adopted by practical road-builders,

and one, that is still in common use,
is the Telford method.^

The Telford Road. — The Telford plan of road construction,
as previously stated, was invented and inttoduced by Telford in
1820 ; and it is best described in his own specifications : ^ '* Upon

^ See fig. 3. Roads, Streets and Pavements, by Q. A. Gillmore.



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44



ROAD CONSTRUCTION



a level bed, prepared for the road materials, a bottom course or
layer of stones is to be set by hand, in the form of a close, firm
pavement. The stones, set in the middle of the road, are to be
seven inches in depth ; at nine feet from the center, five

inches ; at twelve from the center,
Fig. i6 four inches; and at fifteen feet, three

inches. They are to be set on their
broadest edges and lengthwise across the
road^ and the breadth of the upper edge
is not to exceed four inches in any case.
All the irregularities of the upper part
of the said pavement, are to be broken
off by the hammer, and all the interstices
Cross-section of a Drain. are to be filled with stone chips, firmly

wedged or packed by hand with a light
hammer, so that, when the whole pavement is finished, there shall
be a convexity of four inches in the breadth of fifteen feet from
the center.

" The middle eighteen feet of pavement is to be coated with
hard stones to the depth of six inches. Four of these six inches
are to be first put on and worked in, by
carriages and horses, care being taken to ^*S- ^7

rake in the ruts, until the surface be-
comes firm and consolidated, after which


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Online LibrarySamuel Washington McCallieA preliminary report on the roads and road-building materials of Georgia → online text (page 3 of 22)