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


subgrade. These dusty places in III,
tirst course OF gravel need not max,
bad places in the finished gravel ROAD
provided the excess dust end dirt :.
seraped off and enough additions
gayel is applied with the seconf
course TO allow for that lost in the
subgrade. This, l understand is be.
ing done.
when | made my second trip owe,
the road with the county Enginec,
august A. the work was in much
better shape than it was two weeks
before. Two or three miles of SOC.
ond course gravel h2d 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 is
| good and there is no evidence of an
| excess quantity of dirt. 1t is useless
to hope that the engineers will be
ablo to mako, Immediately, herd
eompactcd ro&d surface under the
conditions existing and with the
grade of material being used. It Is
simply a physical impossibility. The
grading Of the gravel and the per
cent Of binding material are not such
as to make it possible to consolidate
it. Rolling would produce no results.
This brings re 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 a 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 ex-
ecution Of 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 u 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 criti-
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 take from the pit, which
| think is fairly representative, shows
the following sieve analysis: dirt 10
per cent sand Go per cent, gravel %
per cent The 10 per cert of dirt
found in the gravel after about one
foot of the is inches of dirt covering
| is scrapcd off is none too much. Some
of the very best road grayels contain
from 10 toe25 per cent Of clay, which
| serves as a binding material The
ideal per cent of earth for a 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 s.
per cent OF material finer than one
quarter inch (sand) and only % per
cent coarser than one-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 we'll graded graycls
having approximately Is per cent
earth, % per cent sand (mineral
matter smaller than one-Quarter
inch) and so 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 of fine and
coarse are reversed, as in the case of
the gravel being used on the La
Crosse-Dusty road, The gravel pit
at Lacrosse contains a largo per cont
of material above two inches in size
including a quantity of large bould-
ers
If the quality of the gravel in the
pit had been anticipated, and the
specifications for the work drawn so
as to require the crushing of al least
a portion of the coarse material and
the screening out of some of the OK
cess fine, a much better grade of ma
terial could have been obtained. II
the specifications had required the
gravel to be crushed and screened in
order to obtain a better graded pro
duct this would probably have in
creased the cost Of the work but, l
believe, the results obtained would
have justified the additional cost.
have one other criticism to make
and that is in regard to the methods
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