Bryan daily eagle and pilot. [volume] (Bryan, Tex.) 1909-1918, 1915-09-30
CONSTRUCTION OF
GRAVEL ROADS.


Highway Engineer, A. & NJ. College
OF Texas.
There are two systems OF gravel
road construction: The first. surface
construction. and the second. trench
construction. In the first the sub
grade Is graded and rolled at a very
Fat slope and then the gravel applied
in one or more layers with the maxi
mum thickness OF the material at the
center, the thickness gradually d.
minishing toward the edge OF the
gravel roadway. The second. or
trench construction. was planned to
save gravel and to coniine Il to that
part OF the roadway where II would
give the greatest amount OF service.
In this case the subgrade is usually
made to a slope approximately paral.
lei to that OF the finished roadway.
and earth shoulders are built up to
confine the gravel In trench nine
to twenty feet In width. depending on
the quantity OF traffic that the road
must handle. The gravel Is then
placed In this trench In one or more
layers and when finished the gravel
surface and the earth shoulders make
one smooth slope TO the side bitches.
this slope becoming sleeper as II ap.
nroaches the ditch.
In constructing gravel road care
should be taken that the coarsest
gravel Is at the bottom. the finer
material on the surface. First. be.
cause the coarser material will not
sink into the subgrade as easily as
the fine material. and secondly. be.
cause the fine material will make a
smoother roadway Where the gravel
Is not over six inches In thickness the
best results will be obtained by using
a bottom course Of gravel composed
Of pebbles varying from one and one
fourth inches to three inches In
diameter. The top course should be
composed OF material. none OF which
should be over one and one-hal
inches In diameter and about two
thirds Of which should 20 through q
one-half inch mesh screen.
The gravel should be laid In a
least two layers. as better results are
always Tins obtained. Where th'
gravel Is thicker than six inches 4
would be well to use three layers. II
any case no layer should be laid dowr
so that after rolling It's thickness ex
ceeds four inches. After a layer o.
gravel has been laid down and spread
by shovels Il should be narrowed
thoroughly with an ordinary spike
tooth harrow. The reason for Thu
Is that the gravel Is brought on thu
road In wagons or trucks and dumped
in piles ON the subgrade. II Is ther
spread out by shovel with the result
that where the gravel was original!
dumped II viii he denser than wher'
n is spread out by the shovel. I
this II not corrected. and traffic 4
turned on the road. there will be
series Of hard and soft spots on Thu
roadway, resulting In an uneven sur
face similar to that which can b
found on at least 90 per cent OF al
the gravel roads In the State OF Texas
On the other hand. II each layer o
gravel Is thoroughly narrowed as |
Is put down. the hard spots are thor
oughly broken up and the entire laye
will have an even density. After haI
rowing each layer OF gravel shout
be rolled n II Is possible to obtail
a roller. as this helps to solidify tn
material and hastens. the day whel
a smooth surface will be secured
Excellent gravel roads. however. hav
been built without the use OF tn
roller. and II is much more importan
that the gravel be thoroughly hal
rowed than 1t be rolled. After tn
last layer OF gravel has been placed
narrowed and rolled. the road may b
thrown open to traffic.