Western liberal. (Lordsburg, N.M.) 1887-1919, 1917-06-22

come Of sufficient Importance to war
rant a highly improved surface, the
maximum grade usually is fixed with
reference to this feature about as fol-
lows:
Coastal plain and prairie regions. - TO 3
Average rolling country ..............4 to s
Hilly or mountainous regions........6 to 8
The question Of minimum grade is
of Importance only as regards the side
bitches. These should have adequate
fall to empty the water that collects
In them at a sufficiently rapid rate to
prevent damage to the road. Ordinar-
lily 1t is desirable to give the side
bitches a fall of about one foot per 100
feet of length, though a somewhat less
fall has proved satisfactory some
times.
Wherever changes in grade occur
the change should be made by mean
Of a vertical curve, and not by an
abrupt angle
Slopes.
The slope at which earth win stand
when faced up in a cut or placed in an
embankment depends 1l on the char
acter of the earth and (2) on the eli
mate. In cuts, a good quality of non
shaking clay usually will stand on a
slope of about As degrees, or, as slope
is expressed usually, one horizontal to
one vertical, even where fairly deep
freezing occurs, and in some Of the
Southern states such material has been
known to stand for many years on a
slope of less than One-half to one. On
the other hand, clay that Stakes very
easily, may require a slope Of three to
one, or eve four to one, under the most
favorable condition Of climate, but
this latter extreme Is very unusual.
The usual slope for clay in cuts is n
to one in warm climates and one and
One-half to one in cold climates.
While in the case Of entertainments
clay usually can be deposited on an
initial slope of about one to one this
steep slope seldom can be maintained
unless the material is Of An exceptional
quality and the climate very favorable.
Ordinarily clay embankments should
have a slope of about two to one in
cold climates and ut least one and one
half to One in warm climates; and If
the clay be of questionable quality
these values should be increased. En-
bankment slopes require more care In
construction than excavation slopes,
because any fiattening Of an embank-
ment slope by the action Of weather
after the road is completed is very
likely to damage the road Rlrface;
while the sliding I'm of excavation
slopes usually does nc further damage
than to Obstruct the side bitches,
which can be reopened readily.
Sand of average quality usually re-
quires n slope of about two TO one in
cuts and three to one in embankments,
regardless of climate. Moderately
coarse sand mixed with gravel will
stand on a sleeper slope than fine
sand, because the former is not moved
so readily by the action of storm wa
ter.
Solid rock excavation usually car be
done on an average slope of about one
fourth to one, except where the rock
occurs in slOping strata separated by
slippery clay seams. In the latter case
the average slope may be as much as
One-half to n or three-fourths to one
The faces of rock cuts usually are not
| dressed down to even an approximate
Iy smooth slope, as is done in eartf
cuts. In %excavating solid rock only
4 such material is moved as is actually
necessary to obtain the desired widtf
Y at the bottom of the cut or as has beer
lOOsened in blasting. The fuces should
Of course, be cleared Of all materia
which is loose, or which might b'
lOOsened subsequently by frost anC
e slide down upon the road. Stone EN-
e bankments usually will stand on
d slope Of about one to one.
t In order to prevent damage by wash
ing all earth slopes In either excava
ton or e%mbankmept should be protect
C ed by a growth of grass as soon a
e practicable after they are formed.
n In many localities where the soil
t fertile and a good quality Of grass
native no seeding of the slopes Is nee
D essary. In other cases the soil may no
e possess sufficient fertility to grO'
r grass, even when the slopes are SEED
ed. and in which event 1t may be yer
% desirable to cover the slopes with Gu
d sod. This latter process usually !
very expensive, and should be en-
10 plOyed only where it is known tina
ID thorough seeding and fertillzing wOul
a fail to secure a covering of sod.
d Another precaution frequently nece.
sary In order to prevent the washin
4. away of excavation slopes Is to int
:" cept water from the natural grOun
80 surface which otherwise would flo
SSSS down over the excavation slope! Tn
So is done by means of a bern" ditC
be constructed well back from the top
H. the slope. Figure ? illustrates a co
he dltiOn which makes a "berm' ditto
C. desirable and also shows hIw such
e, ditch is constructed.