The annexed engravings illustrate a method of constructing subaqueous
foundations by the use of iron pile planks. These latter, by reason of
their peculiar form, present a great resistance, not only to the vertical
blow of the pile driver (as it is indispensable that they should), but
also to horizontal pressure when excavating is being done or masonry being
constructed within the space which they circumscribe. Polygonal or curved
perimeters may be circumscribed with equal facility by joining the piles,
the sides of one serving as a guide to that of its neighbor, and special
pieces being adapted to the angles. Preliminary studies will give the
dimensions, form, and strength of the iron to be employed. The latter, in
fact, will be rolled to various thicknesses according to the application
to be made of it. We may remark that the strength of the iron, aside from
that which is necessary to allow the pile to withstand a blow in a
vertical direction, will not have to be calculated for all entire
resistance to the horizontal pressure due to a vacuum caused by the
excavation, for the stiffness of the piles may be easily maintained and
increased by establishing string-pieces and braces in the interior in
measure as the excavation goes on.
[Illustration: FIG. 1.--CONSTRUCTION OF A DOCK WALL BEHIND PAPONOTS IRON
PILE PLANKS.]
The system is applicable to at least three different kinds of work: (1)
The making of excavations with a dredge and afterward concreting without
pumping out the water. (2) The removal of earth or the construction of
masonry under protection from water (Fig. 1). (3) The making of
excavations by dredging and afterward concreting without pumping, mid
then, after the beton has set, pumping out the water in order to continue
the masonry in the open air. This construction of masonry in the open air
has the great advantage of allowing the water to evaporate from the
mortar, and consequently of causing it to dry and effect a quick and
perfect cohesion of the materials employed.
[Illustration: FIG. 2.--TRAVERSE SECTION OF TWO PILES CONNECTED BY MORTAR
JOINTS.]
This system may likewise be employed with advantage for the forming of
stockades in rivers, or for building sea walls. A single row of pile
planks will in many cases suffice for the construction of dock walls in
the river or ocean when the opposite side is to be filled in, or in any
other analogous case (Fig. 1).
The piles are driven by means of the ordinary apparatus in use. Their
heads are covered with a special apparatus to prevent them from being
flattened out under the blows of the pile driver. They may be made in a
single piece or be composed of several sections connected together with
rivets. They are designed according to circumstances, to be left in the
excavation in order to protect the masonry, or to be removed in their
entirety or in parts, as is done with caissons. In case they are to remain
wholly or in part in the excavation, they are previously galvanized or
painted with an inoxidizable coating in order to protect them and increase
their durability.
The points of the piles, whatever be their form and arrangement, are
strengthened by means of steel pieces, which assure of their penetrating
hard and compact earth.
[Illustration: FIG. 3.--DREDGING WITHIN A SPACE CIRCUMSCRIBED BY IRON PILE
PLANKS.]
Fig. 2 represents a dredge at work within a space entirely circumscribed
by pile planks. Here, after the excavation is finished, beton will be put
down by means of boxes with hinged bottoms, and the water will afterward
be pumped out in order to allow the masonry to be constructed in the open
air. Fig. 3 shows a transverse section of two of these pile planks united
by mortar joints. This system is the invention of Mr. Papenot.--_Revue
Industrielle._
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