Pullman herald. [volume] (Pullman, W.T. [Wash.]) 1888-1989, 1917-09-07

. O9O uUoNy places IN the
llrst course OF gravel need not make
bad places in the finished gravel road
provided the excess dust end dirt is
scraped off and enough additional
gaYel is applied with the second
course to allow for that lost in the
subgrade. This, l understand is he
ing done.
Nhen l made my second trim over
the road with the county Engineer
august ~ the work was in much
better shape than it was two weeks
before. Two or throo miles Of SOC
ohd course gravel hcd been placed
new gravel had been spread in the
worst places on the first course and
there was evidence to show that the
drag was being used when necessary
Though the finished gravel road is
rutting up badly the general grade ie
good and there is no evidence of an
excess quantity of dirt. 1t is useless
to hope that the engineers will be
able to make, Immediately, a herd
compacted road surface under the
conditions existing and with the
grade of material being used. II IS
SIMPLY physical impossibility. The
grading of the gravel and the par
cent OF binding material ere not such
as to make it possible to consolidate
1t. Rolling would produce no results.
This brings ne to my main criti-
cism Of the entire work. In making
this criticism | realize that it is the
easiest thing in the world to find
fault with piece of engineering or
construction work, but everybody
does it, Quite often the fewer the
data one has in hand and the less
that is known about the actual condi-
tions that control the design and ey-
ecution of a piece of engineering
work, the easier it is to make dis
paraging statements Good engin-
eering is the adjusting of the design
and execution Of given piece Of
work to the existing facts and condi-
tons for the best economic results
This rarely ever makes it possible to
do the ideal thing, hence the critf-
cism.
The criticism | have to make re-
rates to the quality of the gravel be-
ing used on the road A sample of
the gravel taken from tine pit. which
| think is fairly representative, shows
the following sieve ANALYSIS: dirt 10
per cent, sand s. per cent, gravel %
per cent. The 10 per cert of dirt
found in the gravel after about one
foot of the / s inches of dirt covering
is scraped off is none too much. Some
of the very best road gravels contain
from 10 to-25 per cent Of clay. which
serves as a binding material. The
ideal per cent of earth fer given
gravel is not a fixed per cent. but de-
ponds upon the grading Of the gravel
and the physical properties of the
stone composing the gravel The
fact that the product of the pit be-
low two inches in size contains 65
per cent of material finer than one
quarter inch (sand) and only % per
cent coarser than onc-quartcr inch
is the main objection. This excess
fine material is one of the reasons
why it is impossible to obtain a hard
compacted surface. EXtreme dry
weather, of course, is another rea-
son, 1t has been proven beyond a
question that well graded grayels
having approximately - per cent
earth, 25 per cent sand (mineral
matter smaller than one-quarter
inch) and 60 per cent gravel (min-
eral matter larger than one-quarter
inch and smaller than two inches)
will bind together easier and make a
more durable gravel surface than
whore the percentages Oh Inc ana
coarse are reversed, as IN the case OF