Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to sealing screens for
waste dumps, e.g., garbage dumps and the like, consisting of
protectiv0 impermeable layers.
Sealing screens for waste dumps that are to be newly
formed are known in many forms. west German Patent Publication
No. DE-OS 30 44 436 describes a sealing screen that is produced
from water and ash, in particular ash from a power station. west
German Patent Publication No. DE-AS 26 30 345 describes a process
lQ in which a plastic foil, which is embedded in flnely ground bulk
or loose material, is used a a sealing screen. other sealing
screens are also kno~n, these being produced from natural
materials, such as clay.
The requirements placed on the new waste or garbage
dumps are extremely strict. Thus, not only is the highest
quality and safety demanded of the materials and construction
process used for sealing screens demanded; also demanded is a
capability for a rapid, cost effective and realiable repairabil-
ity that must be able to cope with unforeseable damage inflicted
upon the sealing screen. Unforeseable damage to the sealing
- screen can result from chemical conversion processes in a
material that has been dumped, as some of such processes last a
number of years. Further, damage may be caused by physical
forces involved when the waste material is actually being dumped.
The sealing screens in use up to now do not permit the
rapid and localized determination of damage in the screens and
the rapid, cost effective, and reliable repairing of the screens.
The repair of prior art sealing screens is only possi~le by using
expensive and time consuming construction measures.
The present invention overcomes such disadvantages.
According to the present invention, there is provided a seallng
screen with the following construction: (a~ two sealing layers
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tha-t are installed at a predetermlned distance from each other;
(b) a control fil-ter layer b~tween the sealing layers, (c) an
in~ectlon line system that is installed in the control filter
layer, (d) a second system of lines within the control fllter
layer, that initially serves to inspect the ~irst seal layer and
during an in;ection into the control filter layer serves as an
air and water removal system; (e) a grip-like division of the
sealing screen into individual areas, which in each instance are
partioned off from the ad~acent individual areas by means of
sealing connec-tions perpendicular to the sealing layer and are
connected through an accessible inspection and collection shaft
or a walkable tunnel to a water removal line, (f) a drain layer
with a drainage line system to remove drainage water from
material that has been dumpad; and (g) a covering layer for
protecting the drain layer when the material to be dumped is
incorporated.
The incorporation of two sealing layers into the
sealing screen increases security and protection in contrast to
single-layer sealing screens. Any damage to the first sealing
layer can be detected in a timely fashion, since the drainage
water that is present in the material that is dumped immediately
penetrates the control filter layer and moves through the piping
system to the collector pit or the tunnel, which are inspected
one a regular basis.
Damage to the sealing screen is caused by whatever
source is localized and can be located because of the grating-
like and partitioned division of the individual areas of the
sealing layers. Injection of sealing material and thus the
complete sealing of the control filter layer in the damaged areas
can take place very rapidly and accurately by means of the pipes
of the in;ection system, which results in the integrity of the
seal being quickly re-established.
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The invention provides for a testing procedure before
the dump is put into operation in order that damage -to the
sealing layers can be detected in a timely fashion when the
sealing screen is still under construction and can be repaired
directly. It is preferred that this checking is done prior to
the installation of the drainage layer and the covering layer,
and is done section by section corresponding to the dried-like
division of the sealing screen. The following is used in order
to check a sealing screen which forms a base for a dump. Areas
in the sealing screen are sub-divided by means of impermeable
vertical supports. Piping systems in the areas ar~ connected
through air-tight connections to a vacuum pump. The air is
evacuated from the individual area at the sealing screen. The
partial vacuum that results from this between the two sealing
surfaces is maintained for a period of time~ Any resulting
pressure increase once the pumps have been switched off will
indicate improper sealing of the seal for the individual area.
This process allows the base sur~ace of the waste dump to be
checked for seal integrity immediately after installation. A
prassure gauge is used to monitor the pressure during this
process.
The invention also sets out a checking procedure to be
instituted after the waste dump has been put into operation.
After the successful checking of the seal base before dump use
and after the start of filling the dump with waste material, the
control filter layer between the sealing layers, which is filled
with filter gravel, can be filled with water to the point that
all the pores in the gravel are filled with water. Once an
individual area of the sealing system has been filled, any loss
of water can be read from a gauge on a level pipe that is con-
nected to the control filter area. This allows ongoing inspec-
tion of the indlvidual areas of sealing system for seal in-
tegrity. A screw cap installed on the level pipe makes it
possible to carry out the above-described check of the partial
vacuum without any outside air getting into the system.
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The present invention will be fur-ther illustrated by
way of the accompanying drawings in which:-
Fig. 1 shows a cross section of the sealing screen;
Fig. 2a shows an embodiment of the present inventionhaving an inspection and collector shaft;
Fig. 2b shows another embodiment of the present
invention illustrating the inspection system;
Fig. 3 shows a cross section of the seallng screen
integral with an inspection tunnel according to another
embodiment of the present invention; and
Fig. 4 shows a plan view of the grid-like surface
division of the sealing screen with the sealed off and
partitioned connections between the sealing layers.
The invention is directed towards a sealing screen for
waste dumps and the like. The sealing screen ~omprises several
protective impermeable layers. The layers of the sealing screen
combine to protect the environment, i.e., the ground water, etc.,
from waste deposited into the waste dump.
Referring now to Fig. 1, the sealing screen has a
bottom sealing layer (2) installed against the ground. Above the
bottom sealing layer (2) ls a control filter layer (3). The
control filter layer (3~ wlll usually consist of some substance
such as filter gravel, and can be filled with water or some gas.
Checking of the water level in the control *ilter level (3)
allows for checking the integrity of the sealing screen, which
will be described below. An in~ection line system (4), conslst-
ing of perforatecl piping, is installed in the control filter
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layer (3). The in~ection line system (4~, which is accesslble
via an inspection and collection shaft (6) or an access tunnel
(7), can be used to inject sealing compounds into selected areas
of the sealing screen in the event a leak is discovered. ~lso in
the filter control layer (3) is a piping system (5), which is
also accessible v~a the inspection and collection shaft (6) or
the access tunnel (7) and car. be used for inspecting the seal
screen and, during injection of sealing material through the
in;ection line system (4) can be used to remove air and water
from the control filter layer (3). This construction permits
effective sealing of the sealing screen for a portion in which
damage is discovered.
A second sealing layer (1) is formed on the far side of
the control filter layer (3) from the bottom sealing layer (2).
The first and second sealing layers (2~, (1) are installed at a
predetermined distance from each other. This portion of the
sealing screen is partitioned into individual areas by means of
vertical sealing connections (11). As illustrated in Fig. 4,
sealing connections (11) abut to form small sealed regions or
areas in the of sealing screen. In Fig. 4, two alternative
embodiments are illustrated. The first shows an inspection and
collection shafts (6) centered in the small region of the sealing
screen. Access can be had to the in~ection system ~4) and the
piping system (5) from within the inspection and collection shaft
(6). The inspection and collection shaft (6) is large enough so
that a human inspector can enter the shaft and check conditions
of the surrounding area using the pipes. Alternatively, access
tunnel (7) is illustrated in cross hatching. Inst~ad of the
inspection and collectlon shaft (6), which is vertical, a
horizontal access tunnel (7) can be used for access to a series
of small sealed regions of the sealing screen for inspecting the
piping system (5) and the injection system (4) to determine seal
integrity.
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Referring once again to Flg. 1, a draln layer ~9)
having a drainage line system for removing water which drains
from material that has been dumped is provided on top of the
second sealing layer tl)- On top of the drain layer ~9), a
covering layer (10) is provided for protecting the drain layer
(9) from the waste material while it is deposited lnto the dump
area.
One embodiment of the present invention provides for
the vertical inspection and collection shaft (6) to be provided
for each subdivided region of the sealing screen. As illustrated
in Fig. 2a, the shaft ~6) allows access to the injection system
(4) and the piping system (5) for a person who can descend the
shaft (6) from above.
Referring now to Fig. 2b, elements of the present
invention pertaining to checking of the seal are illustrated.
Basically, as each subdivided area of the sealing screen should
be airtight, connecting a vacuum pump to the piping system l5)
and pumping out the air in the sealed area should result in a
partial vacuum being formed in the area between the two sealing
layers (1) and (2). A pressure gauge (12), installed on an end
of a piping system (5), will indicate any pressure increase after
the vacuum pump has been switched off. Any pressure increase
would indicate that lmproper sealing has developed. This method
of inspecting the seal should be used before the drain layer (9)
and the covering layer (10) are installed, so that any damage to
the sealing layers ~1) and (2) can be repaired directly.
Another test procedure allows the seal of each area to
be inspected after the waste dump has been made operational.
Upon making the waste dump operational, the filter control layer
(3) is filled with water or gas at a predetermined pressureO Any
loss of water from the filter control layer (3) can be read from
a level gauge (13) provlded in the shaft (6) or the access tunnel
(7). The level gauge ~13) is usually connected to a pipe from
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the piping system (5). During the vacuum check operation of the
sealing system, the level gauge (13) can be made airtight using a
screw cap ~ n *he event that it has been discovered that
the integrity o~ the sealing screen has been breached, seallng
material can be injected into the area between sealing system
layers (1) and (2) using the pipes of the in~ection system (4).
At the same time, air and water are removed from the area between
the sealing layers (1), (2) via the piping system (5). As
illustrated in Fig. 2b for the embodiment utilizing the shaft (6)
and in Fig. 3 for an embodiment using the access tunnel (7), the
piping system (5) can connect to a water removal line (8) which
will remove the water from the access tunnel (7) or the shaft
(6).
The in;ection line system (4) is composed of collar
pipes. The injection line system (4) comprises numerous
individual pipes which converge on the vertical shaft (6) or the
access tunnel (7). Each individual pipe has an end valve for
producing an airtight seal.
The sealing layers (1) and (2) can be composed of a
mineral material, or composed of some kind of plastic foil.
Alternatively, one layer can be composed of the plast~c foil, and
the other mineral material. The material is selected on the
basis of the waste material for which the dump is to be used to
store.
Previously, the sealing screen has been descrlbed as a
horizontal construction having a bottom sealing layer (2) and a
top sealing layer (1). In practice, the sealing screen can have
almost any orientation from the horizontal to the vertical.
~ lso, the method for checking the sealing layers (1),
(2) before the dump i5 made operational is described in relation
to creating a vacuum in the individual section. Alternatively,
the individual area of seal can be pressurized, and the integrity
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of the seal can be checked by a pressure gauge, from which
detected in pressure would indicate a leak in the seal.
Similarly, in testing the sealing screen after the dump
has been made operational, any gas or liquid could be in~ected
under pressure into the filter control layer (3). Once again, a
decrease ~n pressure would indicate a leak. Alternatively, gas
or liquid having a pressure lower than the atmospheric pressure
can be used in the seal. Detection of an increase of pressure in
the sealing screen would -then denote a lack of integrity in the
sealing screen.
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