Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02229758 1998-02-17
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DRAINAGE METHOD AND STRAP
DRAINING MATERIALS THEREFOR
BACKGROUND OF THE INVENTION
The present invention relates to a novel drainage method and the strap
draining
materials therefor and, in particular, to a draining method adapted for use in
drainage
system in the soil conservation on mountain slopes, agricultural industry and
in civil
engineering work and to flexible thin sheet like draining straps having a high
resistance to
pressure and a high efficiency of drain absorption.
Conventionally, the most frequent use of water permeable and draining
materials
in drainage in the soil conservation on mountain slopes, underground
irrigation and
drainage on farms, and the civil engineering work on tunnel road bases and
retaining walls
are of a tubular type, that is, the so-called permeability pipes or drain
pipes. The basic
structure of a drain pipe is all that the circumference of at least of more
than a half of the
upper half portion of the circular tubular pipe is opened up with numerous
tiny cracks
densely distributed like meshes of a net for collecting infiltration water
from the soil cover
into the non-porous water collecting part of the lower half portion in the
pipe and from
there again water to flow out along the longitudinal direction of the pipe.
However,
because the infiltration water moves water to flow downwardly into the lower
half
portion of the pipe by the water head and the water gravity, it must also
carry along the
tiny sandy particles into the meshes. Certainly, the sandy particles after
collecting for
some time gradually seal the meshes resulting thus in a blockade. Even though
a part of
the sandy particles entering the pipe can be discharged together with the
water that has
infiltrated into the pipe, because the amount of water collecting in the pipe
is small and
the speed of drain flow is low, a majority of sandy particles will settle on
the lower half
portion of the pipe. When collecting over a long period, it also results in
disadvantages
that there is blockade in the pipe and reduction in the amount of drain.
Sometimes, to
prevent blocking of the meshes, there is covered on the outside of the drain
pipe with a
non-woven coating or a synthetic fiber gauze as the filtering layer thereby
forming a
multiple-layer permeability pipe or drain pipe.
However, since after use over a period of such a filtering layer blockade can
still
occur, its use would merely accomplish the effect of prolonging the life only.
Furthermore,
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as drain pipes of the kind are mostly made of a hard plastics, this makes the
construction
process on embedding relatively inconvenient. Again, as the total area of the
meshes
provided on the unit area of the circumference of the drain pipe to act as the
water inlet
hole differs greatly from the pipe diameter sectional area (water service
sectional area)
and the actual amount of drainage in the drain pipes is less than one third of
its sectional
area, no siphonic action will thus be created. On the other hand, if the
circumference of
the pipe is formed densely with meshes, there will be a great reduction in
theresistanee to
pressure in the drain pipe and the pipe can hardly be resistant to the soil
pressure and the
heavy pressure from vehicles, the drain pipe will get distorted easily and
will even break
by pressure leading to a blockade in the meshes or the pipe.
In order that the drain pipe be flexible and bendable to facilitate
construction, a
soft flexible permeable pipe made of various materials of PVC coated screw-
type spring
steel wire, non-woven fabric tube and nylon yarn has also been disclosed.
However,
even with such a flexible permeable pipe the problems of the aforesaid
blockade in the
meshes and the resistance to pressure still remain.
Others also include disclosure of forming a screw ditch on the outer
circumference
of a hard plastic drain pipe and in which the meshes are provided inside the
ditch whereby
it enhances the strength of the pipe body and improves the absorption
efficiency
There is disclosed also another type of a non-tubular type of drain sheet.
This type
of drain strap is formed by coating on the surface of a hard plastics formed
concavo-
convex support body with a layer of felt non-woven fabric. The support body
also has the
two sides formed in ditches, however, the opening of the ditches is broader
than the ditch
bottom.
It is a purpose of the present invention to provide a new draining material
which
differs in construction, shape and principle from the foregoing various drain
pipes and
sheets, and which provides a large drainage of high absorption rate, a
resistance to
pressure, resists blockage and is adapted for use in most kinds of drainage
systems.
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SUMMARY OF THE INVENTION
In accordance with this invention liquid is absorbed from soil, by capillary
action,
into a plurality of drain-collecting slots provided on at least one surface of
a strap-like
drain material embedded in the soil. The slots include a plurality of notches
in the surface
of the drain material which are. smaller than and extend to the slots and are
sufficiently
small to create a capillary effect, and the slots extend along a longitudinal
direction of the
drain material.
The strap-like drain material of the invention comprises a strap having a
plurality
of slots arranged in a spaced-apart fashion across a width of the strap and
extending
along a length of the strap, and a plurality of notches. Each one of the
plurality of
notches corresponds to one of the plurality of slots, the notches extending
from the slots
to a surface of the strap; each notch being sized such that the notch is
capable of creating
a capillary action and drawing liquid from outside the strap and into the slot
corresponding to that notch.
Thus, an aspect of the invention provides a drainage method whereby the
capillary action produced at the narrow crack notches of the small diameter
drain-
collecting slots, extending longitudinally and provided densely on the surface
of the thin
strap-draining materials embedded within the soil, is used to absorb water
contained in
the soil into the slots, and whereby the siphonic force produced by the drop
of water level
is used to enhance absorption and collect and discharge water from one end of
the slots.
An embodiment of the invention provides a drainage method wherein notches of
the drain-collecting slots of the draining materials face downwardly, and
water not only
enters the slots by the capillary action on the one hand, but the surface
tension of water
produced at the narrow notches is used to support water pressure in the slots
not to leak
back on the other hand. At the same time the siphoning force produced at the
section of
drop is used to collect and discharge water, and because of the notches facing
downwardly, it is possible to effectively prevent the drawback that sand
particles sink
because of gravity and collect at and block the slots.
Another embodiment of the invention provides a drainage method in which a
strap-draining material, having on one side densely provided with small hole
diameter
drain-collecting slots extending whole length along the longitudinal direction
and having
the notches capable of producing capillary action, is embedded between soil
cover or
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stratum and the wall of a permeable structure such that the side with the
drain-collecting
slots is in contact with the soil cover or stratum while the side which is
without drain-
collecting slots is adjacent the wall of the structure. The water content from
the soil is
suctioned through the notches into the slots by capillary action, and water
inside the slots
is collected and discharged by the siphoning force created by the drop of
water level at
the two ends of the slots while at the same time, on the side which is without
drain-
collecting slots water from the soil is blocked from permeating into the wall
of the
structure.
Another aspect of the invention is the provision of a strap-like draining
material
capable of effectively implementing the draining method, in which the draining
material
is formed of a weather-resistant, thermoplastic synthetic resin into a thin
sheet elongated
strap body, at least one side thereof having a plurality of tiny drain-
collecting slots
densely arranged spaced-apart along the direction of the breadth of the strap
and
extending the whole length of the strap in the direction of the strap length.
Notches
thereof form cracks narrow enough to create a capillary action, and inside the
slots there
are ditches in section of expanded small round holes to facilitate collection
and discharge
of the water that is absorbed into the slots.
In another aspect the invention can provide a strap-draining material which
can be
used as a waterproof membrane as well as a draining material in basement and
tunnel
constructions. Also, the side that is without drain-collecting slots can have
an even and
smooth surface or a plain surface having a plurality of reinforced ribs.
Alternatively, the
plain surface can have a reinforcement member for enhancing resistance to soil
pressure.
If preferred the side which has slots can be provided with a non-woven filter
material.
Therefore, the drainage method of the invention is adapted for use in a system
of
soil conservation on mountain slopes, underground drainage in fruit ranges and
farmlands, and drainage in road bases. It utilizes a draining strap with at
least one side
having a plurality of parallel-arranged small diameter drain-collecting slots
extending
along the length of the band and with notches in the shape of capillary
cracks, which is
buried in any form, preferably laid flat, within the soil layer to be drained.
By capillary
action at the notches of the slots, water content in the soil is absorbed into
the drain-
collecting slots, and water is drawn, collected and drained through the
siphoning force
created by the drop of water level at the two ends or at any one section of
the slot.
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For draining materials, flexible plastic materials of PVC, PE or PP are used
in
forming thin sheet-like elongated strap bodies. At least one surface of the
strap bodies is
formed with a plurality of narrow drain-collecting ditches densely arranged
spaced-apart
in the direction of breadth of the strap and extending the length of the band.
An opening
of the ditch is formed into capillary cracks, while the ditch portion is
formed in an
expanded small hole, in section. In draining materials of another form, the
surface where
there is no formation of drain-collecting ditches is formed in a flat and even
surface, and
to enhance resistance to pressure and the form protecting the draining
materials, this flat
surface can be provided with a U-shaped reinforcing material. Having also the
function
of a water-resistant membrane, the draining strap may be used in an
infiltration
prevention and drainage system in basement and tunnel constructions.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the invention will be apparent from
the .
following more particular description of a preferred embodiment of the
invention, as
illustrated in the accompanying drawings:
FIG. 1 is a perspective view showing a first embodiment of the draining
material
of the present invention;
FIG. 2 is a perspective view showing a second embodiment of the draining
material of the present invention;
FIG. 3 is a perspective view showing a third embodiment of the draining
material
of the present invention;
FIG. 4(A), (B) and (C) are front views showing the deformation examples of the
draining material attached with a reinforcement material;
FIG. 5 is a front view showing a fourth embodiment of the draining material of
the
present invention;
FIG. 6 is a schematic view showing the apparatus of Examples 1 and 2 of the
draining material of the present invention;
FIG. 7 is a schematic view showing the apparatus of Example 3 of the draining
material of the present invention; and
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FIG. 8(A) and (B) sow respectively the partial enlarged views of the draining
material with slot portions facing upwardly and downwardly illustrating the
principle of
drain absorption.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a perspective view of one embodiment of the draining material of the
present invention, with a section cut off along the direction of its length,
in which the
numeral 1 represents the elongated strap draining material with a flat shape
in section.
This draining material 1 is a flexible strap body made by forming of a weather-
resistant
thermoplastic synthetic resin, one side of which is provided with a plurality
of tiny drain
collecting slots 2 densely arranged spaced-apart along the direction of
breadth and
parallel extending whole length along the longitudinal direction. Notches 21
of the slots
2 are formed in narrow cracks sufficient to create a capillary action and are
communicated inwardly with small round hole slots 22 with an expanded section.
The
other side of the strap body is formed in a flat and smooth surface 3. In this
manner, the
entire strap body is formed in a strap of reel band having the two sides both
actually of a
plain surface capable of being rolled up like a bolt of cloth and cut in
appropriate length
for use according to need. The notches 21 are formed in inlet portions to
absorb water
by capillary phenomenon while the slots 22 are formed in channels for
collecting and
draining water, the action and principle of which will be described
hereinbelow.
FIG. 2 is a second embodiment of the draining material of the present
invention, in
which a draining material lA is basically same as the first embodiment of a
flat elongated
strap body made by forming of a thermoplastic synthetic resin. However, both
the upper
and lower sides of the strap body are formed with drain collecting slots 2 of
same
construction as the first embodiment. In the present embodiment, the drain
collecting
slots 2 on the two sides of the draining strap lA are maintained on the same
pitch and
opposite to each other vertically. However, it is also possible if a
vertically staggered
arrangement is followed.
FIG. 3 is a third embodiment of the draining material of the present
invention,
where in order to enable the soft flexible draining material to have a high
strength of
resistance to soil pressure, there is attached to the flat and smooth surface
3 of the
draining material 1 shown in FIG. 1 a reinforcement material 4 formed of a
hard plastic
material. In the present embodiment, the form material 4 uses simply a U-
shaped
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ri~aterial, however, it is also possible to use, for example, a U-shaped
material 4A containing inside the
slot numerous ribs, or reinforcement in the form of a rectangularly shaped
pipe-like member 4B or
other suitable form 4C, as shown in FTGS. 4(A), (B) and (C).
FIG. 5 is a furtheF embodiment of the draining material of the present
invention,
whereas in the third embodiment one side of the draining material 1 is
attached with a
hard plastics made reinforcement form material 4 in the present embodiment,
however,
the reinforcement portion is formed directly integrally with the draining
material 1. The
reinforcement portion shown in the drawings includes several high and low ribs
41, 42
extending along the longitudinal length, it is apparent however that various
modifications
can be made. Next, on the one side of the foregoing draining strap I having
drain
collecting slots 2, if necessary, there may be coated also with a non-woven
and nylon yarn
as filter material.
EXAMPLE 1
A strip of the draining strap 1 of the first embodiment having length 35cm x
breadth Scm x thickness 0.3cm with a pitch of holes l.2mm on one side thereof
and a
total of 40 lanes of drain collecting slots 2 with notches 21 of a breadth 0.1
Smm and slots
22 of a diameter 0.9mm was obtained. With the ode with slots facing upwardly
and the
inner end higher than the outer end for about 1 cm, the draining strap 1 after
the inner end
was sealed, was embedded on the bottom inside an acryl transparent plastics
made
container 5 of breadth 30cm x length 30cm x height 20cm such that the outer
end of the
draining strap was exposed to the outside for about Gcm as shown in FIG. 6.
Sandy soil
of mud and river sand mixed in a ratio of 2 : 1 and slightly pressed to be
flat and smooth
was filled into the container 5 to a height of l5cm with a remaining height of
Scm on the
soil surface. This remaining height of Scm on the soil surface was fylled with
water 30 x
30 x 5 = 4500cc and after two minutes ( depending upon the rate of water
permeation in
the mud), water flowed out from the outlet end of the draining strap.
Based on observation of the outflow of water, it has been found that water
flows
out from about 2/3 of the slots and the state of water flow appears to be in a
continuous
or intermittent water column of full slots. This indicates that owing to
differences in
density and rate of water permeation among various parts in the nature of the
soil, water
absorbed through the notches by the capillary phenomenon enters the sbts one
after the
other and partially to be collected to form a segment of water column for
discharge. At
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this time when water column flows towards the outlet end via a drop in the
water head, a
vacuum suction effect is created in the rear part thereof which again brings
another
segment of water column of the collected water at the rear part to move
forward so that a
siphonic action is produced. By means of this siphonic action, water that
enters the slots
is continuously sucked out thereby improving further the capillary action to
accomplish a
high rate of water absorption and rate of drainage. That about 1/3 of the
slots where
there is only a small amount that flows out and the flow stops or there is no
water to flow
out, it is because the force of infiltration from the upper layer of the soil
into the lower
layer is not sufficient for absorption and drainage in all of the slot ways of
the present
draining strap. In other words, because the draining strap has an excellent
rate of water
absorption, use of only those draining straps having 25 to 30 lanes of drain
collecting
slots proves to be more than enough with respect to the sandy soil and the
amount of
water use in the present experiment.
EXAMPLE 2
The draining strap 1 of Example 1 was embedded with the reverse side thereof,
that is, the side having slots 2, facing downwardly in the similar position of
the container
5, and the other conditions were same as in Example 1. The container was
filled with
water 4500 cc and then after approximately 2 minutes and 5 seconds had passed,
water
flowed out from the outlet end of the draining strap. Same as in Example 1,
the flow
was still in the form of continuous or intermittent water column flowing out
from about
2/3 of the slots 2 on the straps. To observe that the state of outflow of
water is more
continuous than the state in Example 1 and the rate of flow is more fast, this
can be seen
from the fact that when outflow of water started till the container was filled
to the
capacity of SOOcc and 1000cc respectively, the time t2 needed in Example 2 was
shorter
by a little of several of ten seconds to a few minutes than the time t 1
needed in Example 1.
It can be deduced that when the reverse side of the draining strap is used, as
the upper
part of the slots is closed, there is thus no communication with the air from
the clearances
of the sandy soil to acquire a better effect of siphonic action.
EXAMPLE 3
Two strips la, lb and a section of conventional drain pipe lc (diameter 2cm x
length 32cm) were prepared from the draining strap 1 of Example 1. 2/3
circumferential
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surface of the drain pipe was provided with numerous small holes and the area
of water
infiltration was 70 cm=./m. Both strips of the draining strap and the drain
pipe were
embedded by the same inclination (1/30) in the aforesaid container 5, as shown
in FIG. 7,
with the draining strap 1 a facing downwardly, the draining strap 1 b facing
upwardly and
the drain pipe lc with the non-porous part lying below. About 2 minutes after
addition
of water to the full, water flowed out respectively from the draining straps
la, lb and the
drain pipe 1 c. Rate of flow was observed, it flows more rapidly in the
draining straps 1 a,
lb than the drain pipe lc. When 2 minutes after the outflow of water started,
the
outflow of water in the drain pipe lc decreases gradually to 3 1/2 minutes the
flow of
water stops. While the same outflow ofwater is still maintained in the
draining straps la,
lb, however, after 3 1/2 minutes the amount of outflow of water also decreases
gradually
form the draining strap lb till 4 1/2 minutes the outflow of water stops.
Outflow of
water continues in the draining strap la till after about 30 minutes when it
stops. At this
time, the sandy soil was substantially saturated with water content and the
water level
was no longer there on the upper part of the soil.
From the foregoing result of experiments it can be seen that the draining
strap of
the present invention possesses a strong rate of water absorption and a
drainage effect.
Accordingly, when water head pressure drops gradually there is a tendency that
Infiltration water from the sandy soil infiltrates and flows gradually towards
the
draining straps la, lb, especially towards the side of the draining strap la
that faces
downwardly. It can be deduced that because the rate of water absorption in the
conventional drain pipe is relatively low, the infiltration water infiltrates
and flows
naturally towards the draining straps where the rate of water absorption is
high because
of the capillary and siphonic actions, and thus causes the particle clearances
in soil for
infiltration and flow of the water to gradually form into waterways for the
infiltration
water to be readily led to the draining straps. Once such waterways are
formed, most of
the infiltration water will flow towards the ways thereby reducing the water
head pressure,
the drain pipe 1 c where absorption effect is low will stop draining, and
following this will
then be the draining strap lb and the draining strap la will be the last only.
It has been surprisingly found that the draining straps la, lb of the present
invention are better in the water absorption effect than the conventional
drain pipes, and
then of the same draining straps la, lb those facing downwardly contrarily are
better in
CA 02229758 1998-02-17
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the rate of water absorption then those which face upwardly. This will be
described in
more detail in the following by means of partially enlarged drawings of FIGS.
8(A) and
8(B). As shown in FIG. 8(A), because the notches 21 of the drain collecting
slots 2 face
upwardly, inevitably the sandy loam P 1 of larger particle size gradually
collects on the
upper part of the notches 21 causing a partial blockade in the notches.
However, since
the notches extend longitudinally, unlike the general drain pipes which have
individual
meshes of a considerable pitch and can be easily blocked, here there are still
intercommunicating notches of a considerable length or number that can absorb
infiltration water by the capillary action and at: the same time encourage
drainage by the
siphonic action created inside the slots. The result is a much better drain
absorption
effect than is in a drain pipe that relies merely on the water head and the
gravity of water
for water flowing in and drainage. Moreover, the sandy loam P2 that enter the
slots 22
from the narrow notches 21 will not block either because there the space
increases
abruptly and also because of the siphonic action created in the notches the
sandy loam
easily flows out with water.
FIG. 8(B) shows the notches 21 facing downwardly and in the condition, water
flows in by the water-head pressure and the capillary effect. Since the
draining strap 1 is
closed on the above and also the notches 21 face downwardly, both large and
small size
sandy loam particles P1, P2 settle down because of the gravity and will not
collect and
enter the notches and block in. Only the dissolved matter enters the slots 22
and this
matter dissolves in and flows out with water. Next, because the notches are
very narrow,
it is su~cient to support water pressure inside the slots by means of the
surface tension in
the stationary state and there is no back leakage. Also, as it is closed on
the top surface
and air can hardly come in, a vacuum state is more readily produced, which
resulted in the
interior of the slots by the siphonic action, the eff ciencies of water
absorption and
drainage, to the contrary, are better than those whose notches face upwardly.
In
addition, because of the dissolved matter which is drained away
uninterruptedly along
with the water, it results in the crevices between the sandy loam particles to
become
larger thereby increasing further the rate of water infiltration in the sandy
loam and also
results in water mark defects or infiltration routes for water to be collected
readily
towards the draining straps thereby further raising the efficiency of
drainage. Same
experiments were performed under different conditions of soil and water
volume, and at
conditions with different known drain pipes, and similar results were
obtained, which
CA 02229758 1998-02-17
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indicates that the draining straps or bands of the present invention is
superior over the
conventional drain pipes and that the straps with notches facing downwardly
are better
than those with notches facing upwardly or facing any of other directions.
Furthermore, when water content in the sandy loam has reached saturation and
the
draining strap has stopped draining, water drains away again when pressure is
exerted on
the sandy loam and whereby the humidity in the sandy loam drops and the
hardness
increases. If instead vibration is exerted, the conditions will also be the
same.
Frorn the foregoing, it is clear that the drain materials of the present
invention not
only use the capillary action plus siphonic action in achieving a high
effectiveness of water
absorption and drainage, but because also the straps are formed in a flexible
flat band-like
structure to facilitate transportation and construction and resistance to
pressure, permit
gravity rolling at the condition of only a thin soil cover or without a soil
cover thus
making it possible a saving in the cost of construction. Also, in the above
condition
where the soil is saturated with water content, this soil will become
liquefied and form
mire if subject to gravitational pressure or rolling pressure ( such as: by
vehicles, etc.).
However, using the present drain materials it is still possible to continue
draining and to
allow the soil to become hardened at once. The materials are therefore
advantageous to
construction. Besides, since the drain materials are formed of an totally
impermeable
plastics, they can be used as a waterproof membrane as well as a draining
strap to achieve
the dual purposes of preventing water from infiltrating into the inner sides
of the walls of
the construction while simultaneously draining away water from the soil, if
the materials
are attached by the flat and smooth side thereof to the side of the walls of
the basement or
tunnel construction which are in contact with the soil by an adhesive.
The materials are thus a novel and extensively useful drain material for use
in the
drainage system of the agricultural and industrial constructions.
While preferred embodiments of the invention have been shown and described, it
will be apparent to those skilled in the art that changes can be made in this
embodiment
without departing from the principles and spirit of the invention, the scope
of which is
defined in the appended claims.
