U.S. patent number 3,765,783 [Application Number 05/159,764] was granted by the patent office on 1973-10-16 for composite drain to be used in soil types having low water premeability.
This patent grant is currently assigned to Orebro Pappersbruks AB, Perstorp AB. Invention is credited to Oleg Wager.
United States Patent |
3,765,783 |
Wager |
October 16, 1973 |
COMPOSITE DRAIN TO BE USED IN SOIL TYPES HAVING LOW WATER
PREMEABILITY
Abstract
Embankments for roads, railways etc are made by using material
having low water permeability, such as clay. The material is laid
up in different layers, which are separated from each other by
means of horizontally arranged strips of drains. The drains
comprise an inner core having wave-shaped surfaces and outer sheets
of water filtering material, so that water from the clay may go
through the outer sheets into the space between the inner core and
the outer sheets and flow out.
Inventors: |
Wager; Oleg (Bromma,
SW) |
Assignee: |
Perstorp AB (Perstorp,
SW)
Orebro Pappersbruks AB (Orebro, SW)
|
Family
ID: |
26654365 |
Appl.
No.: |
05/159,764 |
Filed: |
July 6, 1971 |
Foreign Application Priority Data
|
|
|
|
|
Jul 10, 1970 [SW] |
|
|
9649/70 |
Feb 26, 1971 [SW] |
|
|
2446/71 |
|
Current U.S.
Class: |
404/2; 428/116;
428/188; 405/270; 428/178 |
Current CPC
Class: |
E01F
5/00 (20130101); E02B 11/00 (20130101); E02D
3/10 (20130101); Y10T 428/24149 (20150115); Y10T
428/24661 (20150115); Y10T 428/24744 (20150115) |
Current International
Class: |
E01F
5/00 (20060101); E02B 11/00 (20060101); E02D
3/10 (20060101); E02D 3/00 (20060101); E01f
005/00 () |
Field of
Search: |
;94/22,4,33
;161/68,127,139 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Byers, Jr.; Nile C.
Claims
I claim:
1. A composite drain to be used in soil types having low water
permeability, characterized in that it consists essentially of an
inner core of water-impermeable material having wave-shaped
surfaces and that the core on at least one surface is combined with
a filtrating, water-permeable, sheetlike material, which maintains
drainage channels formed between the core and the sheetlike
material, said sheetlike material permitting the passage of water
but preventing the passage of soil particles therethrough.
2. A composite drain according to claim 1, characterized in that
the core comprises a strip-shaped, elongated material having
wave-shaped surfaces on both sides.
3. A composite drain according to claim 1, characterized in that
the core comprises a strip-shaped, elongated plastics material
having wave-shaped surfaces on both sides, which both sides are
combined with paper.
Description
METHOD FOR MAKING EMBANKMENTS FOR ROADS, RAILWAYS, HOUSES ETC
The present invention relates to a method for making embankments
for roads, railways, houses etc using material having low water
permeability, such as clay. The invention comprises also a drain
suitable for carrying out the method.
Clay and similar soil types are usually regarded as bad basic
materials due to their low ability to let water penetrate through
them. For this reason, it has hitherto been necessary to carry out
extensive piling, if construction works shall be done on a clay
base, or it has been necessary to take away large quantities of
clay and replace them with better basic materials. This is a
serious disadvantage giving rise to high construction costs.
If, however, these materials having a low water permeability could
be kept dry, they would be extremely hard and make a good base for
construction works. To lower the construction costs, many attempts
have been made to arrange a good drainage. Such an attempt is to
put clay in layers alternating with layers of gravel, so that
horizontal drainage of the clay is obtained. Also this method is,
however, expensive partly due to high costs of transportation and
partly due to the difficulty in spreading the gravel in uniform
layers. This latter difficulty is especially apparent when the
gravel shall be spread over relatively large areas, as heavy
machines cannot be moved on the clay.
A special drainage problem is present for instance with road
constructions, where it is desired to use fine-grained,
water-saturated soil types like clay from open cuts as embankment
filling material. As the clay taken away usually cannot be used as
embankment filling material without special measures, it is mostly
transported to certain dumping-grounds. This causes large extra
costs and is also unsuitable from a nature point of view. At
present there is no practical and economical method for draining of
clay in embankments. Generally, the filling must consist of gravel,
which often has to be taken from open side cuts. In many areas, the
supply of gravel is unsufficient, which causes high prices. Such
open side cuts do also often come into conflict with nature
interests. It is accordingly desired that the clay could be used
for filling of road embankments. One condition for doing so is that
the clay can be quickly dewatered by suitable measures, e g by
means of drains.
Another example where drains advantageously can be used in
connection with e g road construction is when the work is carried
out winter-tide with frozen material in the embankment filling. The
pore water in the frozen soil (the water in the cavities between
the minerial grains) is frozen. When the spring comes, the soil
thaws, and on account of the excess of water therein a pore water
pressure arises, which substantially decreases the shearing
strength of the soil. In fine-grained soils, it can take a very
long time for the water to disappear, which often results in
floating out and slides of the filling materials. By arranging
drains in the frozen filling masses during the filling work, the
drainage of these is facilitated when thawing. No appreciable pore
water pressure arises and the risk for floating out and slides is
eliminated.
According to the present invention, the above-mentioned
disadvantages are eliminated. The invention comprises a method for
making embankments for roads, railways, houses etc using materials
having low water permeability, such as clay. The method is mainly
characterized in that the material is laid up in several, mainly
horizontal layers, which are separated from each other by means of
sheets of a material having fine pores, so that predominantly
horizontal drainage of the embankments is obtained.
A drain according to the invention, which is suitable for carrying
out the above-mentioned method, comprises an inner core having
wave-shaped, channeled surfaces. The core shall at least on one
surface be equipped with a water permeable, filtrating sheet-shaped
material, such as paper or the like, so that channels are formed
between the core and the sheet-shaped material. It is advantageous
that the drain comprises a disk-shaped, elongated material having
wave-shaped surfaces on both sides and being included in paper.
Paper, which should preferably be unsized and have a surface weight
of approx. 100 g/m.sup.2, may also be used as draining material.
The papers is then arranged with the direction of the fibres in the
same direction as the draining shall occur, i.e. across the road
when embankments for roads are made.
When for instance roads are made in accordance with the invention,
the embankment is laid up in such a way that a clay layer having a
thickness of about 20 cm is spread out, which is thereafter covered
by a layer of drains, a further layer of clay, another layer of
drains thereon etc.
When road embankments are made according to conventional methods,
it is usual that the embankment as it is built serves as a road for
the transportation of filling material. By the method according to
the present invention, however, the embankment is laid up from the
direction toward which it is built.
The invention has made it possible to build road embankments at
substantially reduced costs compared to conventional methods,
primarily due to the highly reduced costs of transportation. The
arrangement of the drains may be carried out by very simple
means.
The invention shall be described more in detail in connection with
the enclosed drawings, wherein FIG. 1 shows an embankment when
being built and FIG. 2 shows a cross section of an embankment. The
FIGS. 3 and 4 show cross sections of two different drains according
to the invention.
In FIG. 1 a clay layer 1 is spread out on a suitably prepared
surface 2, whereupon a layer of drains 3 is arranged on the clay
layer 1. If the drain consists of paper, the direction of the
fibres in the paper should be oriented across the embankment. The
first clay layer is given a relatively limited length, but it
extends over the whole width of the embankment. Thereafter a new
clay layer is spread out upon the drain and then comes one more
layer of drains etc. When the embankment has reached the intended
level, the process is repeated with a new clay layer direct on the
earth surface immediately in front of the just finished embankment,
so that the embankment grows in short pieces.
From the cross section in FIG. 2 it appears how a finished
embankment according to the invention consists of a plurality of
clay layers separated from each other by means of drains.
In FIG. 3 the core material 11 of the drain consists of a thin,
wave-shaped strip of plastics. On both sides of the strip, paper
sheets 12 are anchored. Due to the wave-shape of the strip,
longitudinal channels 13 are formed on each side of the core. When
the drain is put into the soil, water will penetrate through the
paper, into the channels and along these to the open earth surface.
It is important that the paper acts as a filter.
If not, the channels will be filled with soil and thus become
impermeable. It is of course possible to use other materials than
plastics and paper in the present combination, but as these
materials not only give the drain the desired stiffness and
elasticity, but also are cheap, the combination is especially
suitable. In some cases, however, it can be advantageous to have a
core of metal having the same profile instead of a core of
plastics.
FIG. 4 shows another embodiment of the invention, which differs
from the embodiment according to FIG. 3 only in the way that the
core 11 has been made even more robust. The waves on the both sides
are mirror images of each other. This embodiment is preferred for
production reasons when the core material consists of plastics, but
otherwise it has the same effect as the embodiment according to
FIG. 3.
When embankment fillings are to be horizontally drained, the drain
according to the invention can also by reason of its strength take
up horizontal shearing tensions in the filling, which has a
stabilizing effect thereon. (The stabilizing effect of the drain is
in this case -- besides occurring through dewatering of the clay --
the same as for the stabilizing pile construction for embankment
fillings as is described in Vag- och Vattenbyggaren, No. 8, August
1968, Oleg Wager, Stability improving pile construction for
embankment fillings.) By this means a heavier load may often be put
on the embankment. An important difference between the paper drain
of FIG. 2 and the drain according to FIGS. 3 and 4 is that the
paper in the former acts as a drain having high resistance to water
flow, while in the latter case the paper only acts as a filter. As
the paper is stretched by means of the channeled core, it may also
be thinner than the paper in the drain consisting only (as in FIG.
2) of cardboard. The capacity and hence the efficiency of the drain
is increased hereby. The new drain of FIGS. 3 and 4 has two channel
systems separated from each other, which makes it more
reliable.
The drains according to the present invention may be manufactured
in convenient widths adapted for the actual draining problem. The
channel depth in the core may also be adapted to the dewatering
demand. The distance between the drains is dependent on i.a. the
character of the soil. For horizontal drainage the c/c distance is
generally between 0.5 and 1.5 m.
Besides draining embankments for roads and the like, the drains are
also suitable for draining around buildings and for draining of
fields. On account of the high capacity and shape of the drain the
advantage is obtained that the ditch, in which the drain is placed,
may be made appreciably narrower than when using conventional
drains. The filter layer makes it also unnecessary to have the same
high requirements on the grain distribution of the material
surrounding the drain as is the fact in connection with
conventional drain pipes. The drain is practically not at all
influenced by possible uneven settlements in the earth.
The invention is not limited to the embodiments shown but can be
modified in different ways within the scope of the invention.
* * * * *