Wausau pilot. [volume] (Wausau, Wis.) 1896-1940, 1917-08-07
GOOD 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, Permeability and
Capillary Power.

Structure, Permeabllity and
Capillary Power.
prepared by the United States Depart
ment of Agriculture)
Roads constructed by grading the
natural soil to the required shape,
grade and alignment, without special
surfacing of any kind, usually are des-
ignated as earth, or dirt, roads. The
efficiency of such roads depends ID on
the quality of the soil composing the
roadbed, (2) on proper construction,
and 60 on adequate maintenance.
Soils.
The principal qualities of soils from
the standpoint of road construction de-
pend upon texture and structure, per-
meabiBty and capillary power. Soils
usually are classified as clay, sand,
loan, gravel, mari or gumbo, according
to the material predominating in their
composition. Soils composed of two
different materials mixed in 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, grayelly clay, etc.
Clay.
Clay is 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, hut when mixed with other
materials, such as sand or gravel, its
stability may be increased greatly. In
general, clay road, to be passable, |
must be kept dry, and since clay is very
difficult to drain, it happens seldom
that roads composed entirely of clay
can be kept in good condition at all
seasons of the year. No matter how
we'll such a 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 it will dry
out quickly when the weather becomes |
favorable and may soon be restored
to its 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 ball and placed in water, |
will continue in the original shape for |
{. considerable time, even if thorough |
ly saturated and softened, while COM
pressed balls from other varieties will !
Stake 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 clays." 1t has been observed |
that shaking .clays produce more mud
in 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 |
So ud-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 stabilizing effect by making the
clay more easily drained and increasing |
its bearing power when wet. In fact, |
good quality of clay mixed with |
coarse sand in such proportions that |
the clay fills the voids in the sand and |
cements the individual particles to-
gether produces a soil which possesses |
the good qualities Of both materials
Nnd which overcomes, to great extent, |
she objections to each.
Sand.
Sand is composed of granular par
ticles of mineral or stone which occur |
In nature and which will pass q one
GOurth-inch-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 grains. |
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 it is practically impossible, |
under any circumstances to make a sat |
isfactory road surface of sand alone. |
Dry sand offers almost as great resist |
ance to 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 at their best when |
they are kept moist, and for this rea-
son they should be designed with a |
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
mixing sawdust, straw, pine leaves or
other similar material into the surface, |
but, in general, the sand-clay crust is
the most satisfactory improvement for
roads of this character. This is true
where clay may be obtained |
readily and only limited funds are
available for the improvement.
Loan.
Loan is soil composed of clay and |
sand, mixed WITH a considerable per-
centage of finely divided vegetable mat
ter or humus. The quality of loan
from the standpoint of road building
depends very largely upon the nronor-