Western liberal. (Lordsburg, N.M.) 1887-1919, 1917-08-03
EARTH ROADS
Much Depends on Soil, COnstruC-
ton and Maintenance.
LEADING QUALITIES OF SOILS
From Standpoint Of Road Building
They Depend on Texture and
Structure, Permeabllity and
Capillary Power.

Roads constructed by grading the
natural soil to the required shape,
grade and alignment, without special
~surfacing of any kind, usually are des-
lgnatcd as earth, or dirt, roads. The
efficiency of such roads depends u) on
the quality of the soil composing the
roadbed, (2) on proper construction,
and (3) on adequate maintenance.
Soils.
The principal qualities Of soils from
the standpoint of road construction de-
pend upon texture and structure, per-
meability and capillary power. Soils
usually are classified as clay, sand,
loan, gravel, mari or gumbO, according
to the material p~redOminating in their
composition. Soils composed Of two
different materials mixed ia such pro-
portions that the character Of the mix
ture is decidedly intermediate may be
designated conveniently by naming
both components, as sand-clay, sand
gumbO, gravelly clay, etc.
Clay.
Clay is a soil of very fine texture
which results from the complete de-
composition of rocks or minerals. Pure
clay Is very ~retentive Of moisture, and
usually becomes plastic and unstable
when wet, but when mixed with other
materials, such as sand or gravel, its
stability may be increased greatly. In
general, a clay road, to be passable,
must be kept dry. and since clay is very
difficult to drain, 1t happens seldom
that roads composed entirely of clay
can be kept in good condition at all
seasons of the year. No matter how
well such n road may be graded and
crowned, the surface absorbs water in
wet seasons and subsequent traffic will
produce mud. But when the road is
shaped and drained properly 1t will dry
out quickly when the weather becomes
favorable and may soon be restored
to it's original shape. On the other
hand, clay roads, when very dry, usu-
ally produce considerable dust under
traffic, and for this reason may become
very insanitary in extended dry sea
sons.
The extent to which clay roads are
subject to the objections mentioned
above usually varies according to the
sO-called shaking" qualities of the clay.
Some varieties of clay, when COM
pressed into a ball and placed in water,
will continue in the original shape for
Il considerable time, even If thorough
ly saturated and sOftened, while ON
pressed balls from other varieties will
slake or break down almost immedi-
ately upon being placed In water. Clays
of the aforementioned variety are called
''nonslaking clays," and of the latter,
shaking cluys." 1t has been observed
that shaking clays produce more mud
i'm wet weather and more dust in dry
weather than those of the nonslaking
variety. This characteristic of clays IS
further considered in the discussion of
Sand-clay roads appearing in another
part Of this bulletin, where methods
for testing clay are suggested.
Most clays, as they occur in nature,
contain more or less sand or gravel
which, as pointed out above, usually
has n stabilizing effect by making the
clay more easily drained and increasing
its bearing power when wet. In fact,
Il good quality of clay mixed with
coarse sand in such proportions that
the clny fills the vOids in the sand and
cements the individual particles to-
gether produces a soil which possesses
the good qualities of both materials
and which overcomes, to Il great extent,
the objections to each.
Sand.
Sand is composed of granular par
ticles of mineral or stone which occur
in nature and which will pass u One
fOurth-lnch-mesh screen. The one
fOurth-inch-mesh screen is fixed arbi-
trarily as the dividing line between
sand and gravel and is generally,
though not universally, accepted as
such. Nearly all sand consists essen
TALLY of quartz grains that are very
hard and durable. But there Is no CO.
herence between the different gruins,
and therefore soils composed princi-
pally of sand are unstable, except when
confined in some way. If properly CON
fined and protected from undermining,
sand foundations may, under favorable
climatic conditions, prove entirely sat
~isfactOry for almost any type of road
crust, but 1t Is practically impossible,
under any circumstances to make a sat
isfactOry road surface of sand alone.
Dry sand offers almost as great resist
ance "a traffic as mud, and except In
very wet seasons sandy roads are likely
to dry out to a considerable depth. The
reason for this is that the capillary
power of sand is comparatively low
and the ground water elevation may be
lowered practically to the prevailing
level of surface streams in extended
dry seasons.
Sand roads are ut their best when
they are kept moist, and for this rea-
son they should be designed with n
view to retaining moisture In the sand
rather than to effective drainage, as is
the case with clay roads. Such roads
sometimes are improved temporarily by
mixfnu cn~urfIugt ofpour min, Io,.... a.