The present invention concerns a method and device for
putting a drain pipe almost horizontally in the ground,
whereby a plough is moved through the ground so as to
form a ditch, and whereby the drain pipe is put in the
ditch and draining material is pressed in the ditch while
this ditch is being formed by the plough.
Horizontal drain pipes are used in large pipeline works,
whereby the pipeline is put 5 to 6 m deep, in order to
lower the groundwater level.
Such horizontal drain pipes are also used for soil
consolidation.
In order to provide these drain pipes, chain ditch
diggers are often used which dig a ditch of about 30 cm
wide, in which the drain pipe is placed. Immediately
thereafter, the ditch is filled with sand.
The sand in the ditch absorbs large amounts of water from
the environment.
However, with such chain ditch diggers, the drain pipe
cannot be placed at a large depth, in particular not
deeper than 8 m, for example 18 to 20 m deep.
For a ditch which is 8 m deep and at least 30 cm wide,
made with a chain ditch digger, at least 2.4 m3 sand per
running metre are required, which may cause problems to
supply the sand, in particular over the weak clay layers
which need to be consolidated.
Moreover, the same amount of soil per running metre which
is to be removed or spread was excavated by the chain
ditch digger.
Thus, providing a drain pipe with such a device is time-consuming
and, as a consequence, expensive.
However, the ditch to provide the drain pipe in must not
be very wide. A few centimetres will do.
That is why, in order to provide a drain pipe
horizontally in the ground, use is already made of a
plough which makes a very narrow groove in the ground in
which the drain pipe is provided while said groove is
being formed, after which drainage material, usually
sand, is pressed in the groove.
Such a method is described in CH-A-486.607.
Compressed air or water under pressure are supplied to a
closed funnel with powdered material such as sand, which
funnel is connected to a ring-shaped chamber surrounding
the drain pipe at the bottom of the ditch and provided
with a number of mouth pieces directed towards the back
via a flexible pipe.
In this manner, a casing of powdered material is formed
around the drain pipe in the ditch. However, this casing
has a very limited height which is about equal to the
width of the ditch which is significantly wider than the
drain pipe, so that it is relatively difficult to draw
the plough, which has for a result that no deep ditches
can be formed.
When the ditch is further filled afterwards with ordinary
soil, there will be more ordinary soil above the drainage
material than that there is drainage material above the
drain pipe, so that the draining effect is restricted.
Also, this method cannot be used for ditches of very
large depths, for example of 8 m or more.
Moreover, it is not possible to fill the ditch up to a
large height according to the above-described manner, and
certainly not to bring the draining material under
pressure and thus in a relatively compact manner up to
almost the ground surface.
The present invention aims a method for putting a drain
pipe almost horizontally in the ground which excludes the
above-mentioned and other disadvantages and which makes
it possible to provide a drain pipe almost horizontally
at a large depth in a simple and fast manner and
nevertheless obtain a good drainage.
This aim is reached according to the invention as the
ditch is filled with drainage material over a height
which is significantly larger than the width of the
ditch, such that a water guiding screen is formed above
the drain pipe.
The formed ditch can be quite narrow and nevertheless be
filled with sand or other drainage material. The formed
screen of sand or other drainage material serves to
supply water to the drain pipe and to thus obtain the
above-mentioned good drainage.
The drainage material can be pressed in the ditch both
mechanically by means of a push mechanism and
pneumatically or hydraulically by means of fluid under
pressure, whereby drainage material is supplied under
hydraulic or pneumatic pressure in the ditch at different
heights.
Preferably, fluid under pressure is squirted in front of
the plough in order to loosen the soil in front of the
plough and to reduce the forces on the plough.
The present invention also concerns a device which is
suitable for applying the above-mentioned method.
Thus, the present invention concerns a device for putting
a drain pipe horizontally in the ground, which device
contains a plough, means to move this plough in the
ground, means to provide the drain pipe in the ditch
formed by the plough and means to provide drainage
material under pressure above the drain pipe in the ditch
formed by the plough, whereby the latter means contain
means to provide the drainage material under pressure
over a height which is significantly larger than the
width of the ditch.
According to a particular embodiment, the latter means
include a push mechanism which may contain a push element
and means to move this push element back and forth.
According to another embodiment, the above-mentioned
means contain pipes for the drainage material reaching up
to different levels, means to supply drainage material to
these pipes and means to pneumatically or hydraulically
exert pressure on the drainage material in these pipes.
Under the lower end of each pipe can be provided one or
several deflectors directed slantingly backwards.
On its front side, the plough may contain a high-pressure
pipeline directed from top to bottom which is provided
with nozzles directed to the front, and means to supply
fluid under pressure to these nozzles.
In order to better explain the characteristics of the
invention, the two following preferred embodiments of a
method and a device according to the invention are
described as an example only without being limitative in
any way, with reference to the accompanying drawings, in
which:
figure 1 schematically represents a side view of a
device for putting a drain pipe almost horizontally
in the ground according to the invention, during the
application of the method according to the
invention; figure 2 represents the part which is indicated by
F2 in figure 1 to a larger scale; figure 3 shows a section according to line III-III
in figure 1, but with a pressure mechanism in
another position; figure 4 shows a section analogous to that in figure
3, but with reference to another position of a push
element; figure 5 schematically represents a part of a side
view analogous to that in figure 1, but with
reference to another embodiment of the device
according to the invention; figure 6 schematically represents the application of
a vacuum consolidation of the soil after a drain
pipe according to the invention has been put in the
ground.
The device represented in figures 1 to 4 contains a
caterpillar tractor 1 upon which a reel 2 is provided on
one end upon which the drain pipe 3 is wound.
On the same end, a plough 4 is provided on the tractor 1
which consists of a vertical pipe 5 upon which two
parallel walls 6 are fixed on the back side and upon
which a high-pressure pipeline 7 provided with nozzles 8
is connected by two sidepieces 9 on the front side.
The width of this plough 4 is only slightly larger than
the diameter of the drain pipe 3, namely only a few
centimetres. The depth of the plough 4 is significantly
larger and amounts to a few metres, even more than 8 m,
and it is for example 18 to 20 m.
This plough 4 can be moved up and down in a guide 10
fixed on the above-mentioned back end of the tractor 1.
Said plough 4 is strutted on top by means of a prop 11
which is fixed to the top end of the plough 4 on the one
hand and to the front side of the tractor 1 on the other
hand.
The bottom side of the plough 4 can be connected to the
front side of the tractor 1 or to a second tractor by
means of a cable 12.
The top end of the pipe 5 is situated at the height of
the shaft of the reel 2. The part of the drain pipe 3
which is wound off the reel 2, extends through this pipe
5 and then backward, under the end of this pipe 5 and
between the walls 6 over the bottom of the ditch 13
formed by the plough 4.
The end of this drain pipe 3 is fixed to the bottom end
of an additional vertical pipe 14 which sticks in the
ground where the ditch 13 begins.
The high-pressure pipeline 7 is a pipe with a smaller
diameter than the pipe 5 which goes somewhat deeper than
this pipe 5. The top end of this high-pressure pipeline
7 is connected to a high-pressure hose 15 which is
connected to a high-pressure pump 16.
The device contains means 17 to provide sand under
pressure in the ditch 13.
These means 17 contain a funnel 18 on the one hand
provided on the back side of the tractor 1, behind the
plough 4 and which opens with its lower end in the space
between the two walls 6, and a push mechanism 19 on the
other hand to mechanically push the freshly supplied sand
backward.
In the example represented in figures 1 to 4, the latter
push mechanism 19 consists of a push element 20 which is
provided such that it can be moved between the walls 6
and means to move this push element 20 back and forth in
relation to the plough 4. These means consist of a
support 21 placed against the pipe 5 and preferably fixed
to it, for example by means of welding, arms 22 which are
hinge-mounted to the support 21 and which are hinge-mounted
to the push element 20, and a push cylinder 23 to
rotate the arms 22.
Since, when the arms 22 are rotated, the push element 20
also moves in the vertical direction, the push cylinder
23 will be provided between the top side of the pipe 5
and the top end of the push element 20. Naturally, the
push cylinder 23 is connected to an oil source under
pressure via a control mechanism.
Providing the drain pipe 3 at a relatively large depth in
the ground is simple and as follows.
Before the plough 4 is provided in the ground, an end of
the drain pipe 3 is provided through the pipe 5 and fixed
to the lower end of the additional pipe 14.
The whole is put in the ground.
In weak layers, this can be done by squirting a hole in
the soil in front of it by means of fluid under pressure.
A manner which is always applicable consists in putting
a rectangular box profile 24 in the ground in which the
additional pipe 14 and the plough 4 fit and of which the
front side 24A can be removed, as is represented in
figures 3 and 4. This box profile is hereby preferably
filled with water.
When this box profile 24 is provided at a sufficiently
large depth, the front side 24A is pulled out of the
ground, and the pipe 14 and the plough 4 are lowered in
it.
The plough 4 is moved forward through the soil by the
tractor 1, but also due to the movement of the push
element 20 which lunges out on the ground or on the
already provided sand during its backward movement. In
weak ground, the back-and-forth movement of the push
element 20 alone may be sufficient to move the plough 4
forward.
Of course, this forward movement is made significantly
easier by squirting fluid under pressure through the
nozzles 8. As a fluid can be used water or air or a
mixture thereof. This squirting can be carried out
intermittently.
The pipe 14 remains in place, i.e. where the ditch 13
begins.
As soon as the plough 14 has moved forward, the remaining
part of the box profile 24 is pulled out of the ground
for possible re-use.
During the forward movement of the plough 4, the push
element 20 is successively pushed backward by means of
the pressure cylinder 23, as is represented in figure 3,
and quickly moved forward. Figure 4 represents this push
element 20 in its foremost position against the support
21.
Each time the push element 20 is moved into this foremost
position, a space 25 is created on its back side between
the walls 6, between this push element 20 and the already
compressed sand, in which space 25 the lower end of the
funnel 18 opens. This funnel 18 is filled with dry dune
sand which falls in said space 25 due to the
gravitational force and which is compressed during the
next backward movement of the push element 20.
In this way, sand is pressed in the ditch 13 so that a
water guiding screen, namely a sand screen, is formed
above the drain pipe 3 which, as the plough 4 moves
forward, is wound off the reel 2 and always ends up with
a longer part on the bottom of the ditch 13, preferably
at a small distance from the ground surface.
Afterwards, the ditch 13 can be further filled with soil,
preferably soil which is not permeable to air, in
particular clay or bentonite.
Water caught in the drain pipe 3 can be removed via the
additional pipe 14. To this end, a pump 26 can be
provided at the bottom in this pipe 14 with a pressure
pipe 27 extending through the pipe 14 to the top of the
ground surface.
According to a variant of the above-mentioned embodiment,
the arms 22 can be replaced by pressure cylinders or even
the entire system consisting of the push element 20,
support 21 and arms 22 can be replaced by inflatable
bellows and means to blow up these bellows and make them
deflate again.
In order to facilitate the movement of the plough 4,
instead of or apart from a high-pressure pipeline 7 with
nozzles 8, means can be provided to make the plough 4
vibrate, so that a fluidization of the soil in front of
the plough 4 can be obtained thanks to this vibration.
The embodiment of the device represented in figure 5
differs from the above-described device in that the means
17 to provide sand under pressure in the formed ditch 13
do not contain a push mechanism 19, but pneumatic means.
These means 17, depending on the depth, contain two or
several, for example three vertical sand pipes or pipes
28 erected between the walls 6 of the plough 4 and
reaching up to different depths in the ground.
To the bottom end of each of these sand pipes 28 are
fixed one or several deflectors 29 directed slantingly to
the bottom and to the back into which said sand pipes 28
open. The deflectors 29 thus extend between the walls 6
up to almost the back end of these walls 6. Between the
bottom edge of a deflector 29 and the accompanying sand
pipe 29 is provided a horizontal partition 30.
The top ends of these sand pipes 28 open in a chamber 31
above the guide 10.
Onto this chamber 31 are connected a screw pump 32 on the
one hand and a compressed air line 33 on the other hand.
The compressed air line 33 is connected to an air
receiver which is not represented in figure 5, whereas
the screw pump 32 is connected to a funnel 34 erected on
top of a moveable storage tank 35 mounted on
caterpillars.
During the forward movement of the plough 4, sand is
pumped in the chamber 31 by the screw pump 32. This sand
is squirted under pressure through the sand pipes 28 in
the ground behind the pipe 5, by means of the compressed
air which is blown in the chamber 31 via the compressed
air line 33, and pushed backward by the deflectors 29.
Thus, also in this embodiment is formed a sand screen
with compressed sand behind the plough 4 and above the
drain pipe 3 provided on the bottom of the ditch 13.
The above-described device and method are particularly
suitable for the vacuum consolidation of soil, which is
known as such.
To this end, an air-tight layer 36 of for example one
metre thick must be provided above the sand screen in the
ditch 13, and the top ends of the pipe 14 and of the
drain pipe 3 must be sealed by means of seals 37 and 38
as represented in figure 6.
The pressure pipe 27 is connected to the bottom side of
a vacuum tank 39 in which is created an underpressure by
a vacuum pump 40 erected on top.
A suction pipe 41 connected to the top side of the vacuum
tank 39 opens in the additional pipe 14 on the one hand
and in the end of the drain pipe 3 protruding above the
ground on the other hand.
In the bottom of the vacuum tank 39 is erected a water
pump 42 with a non-return valve onto which a delivery
hose 43 is connected.
The medium, in particular water which is collected in the
drain pipe 3, is pumped through the pump 26 to the vacuum
tank 39, whereby the vacuum helps to collect this medium
in the vacuum tank 39. Thus, the water level in the
ditch 13 is kept low, for example at a depth of 15 m.
Via the suction pipe 41 is created an underpressure in
the sand in the ditch 13. Water situated in the
surrounding soil will quickly flow towards this ditch 13
and be pumped up, so that the soil is quickly
consolidated.
With the above-described devices, it is possible to put
a drain pipe almost horizontally in the ground in a fast
and simple manner and to simultaneously provide a sand
screen over it.
Instead of sand, another drainage material can be
provided in the ditch 13.
The present invention is by no means limited to the
above-described embodiments represented in the
accompanying drawings; on the contrary, such a method and
device for putting a drain pipe almost horizontally in
the ground can be made in all sorts of variants while
still remaining within the scope of the invention.