JP4077207B2 - Double impermeable sheet and its laying method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a double water-impervious sheet to be laid at a final disposal site for waste, and after inhaling the air in the double water-impervious sheet and floating on the sea surface or water, water is injected into the double water-impervious sheet. The present invention relates to a method of laying a double water-impervious sheet that is sunk under the sea surface or under the water surface.
[0002]
[Prior art]
In conventional waste final disposal sites, water-blocking work was carried out simply by laying down vinyl chloride sheets, rubber sheets, asphalt coating sheets, polyolefin resin sheets, etc., but the water-blocking effect was maintained over a long period of time. In recent years, double water-impervious sheets in which a filler having a water-impervious effect is filled between these two water-impervious sheets have been widely used.
[0003]
The main filler used in this double water-impervious sheet is a cellulose / acrylonitrile polymer or acrylic acid / vinyl alcohol copolymer that does not deteriorate even if it swells due to infiltrated water and does not adversely affect the environment. In recent years, clay minerals such as bentonite based on montmorillonite, which swells by reacting with water and exhibits water-stopping properties, have been used. Yes.
This bentonite is used alone or in the form of a geosynthetic clay liner in which bentonite is held between an upper cloth made of woven or non-woven cloth and a lower cloth made of non-woven cloth. However, since this bentonite is generally used in a clay state in consideration of adhesion to a water-impervious sheet or upper and lower cloths, when used as a clay, the weight increases, resulting in poor efficiency of transportation, etc. If the water sheet is made relatively small and the weight is kept low, there is a drawback that the laying work efficiency is deteriorated.
[0004]
Therefore, by using bentonite as the particles instead of as clay, there are advantages such as even transport because it is lightweight becomes easy laying work, because there is no adhesion between the water shield sheet or vertical fabric laying When suspended in the course of work or laid on a slope or a vertical surface, bentonite has a disadvantage that it is biased downward between the double water-impervious sheets.
[0005]
In addition, when laying a double impermeable sheet under the sea surface or under the water surface, it is necessary to increase the apparent specific gravity of the double impermeable sheet than seawater or water, especially when laying under the sea surface, Since the specific gravity had to be increased, the conventional resin water-proof sheet could not be used.
[0006]
Furthermore, since the apparent specific gravity cannot be increased with the dry granular bentonite as it is, it is necessary to include water in the bentonite. Since it is lost, it is necessary to adjust the amount of water supplied according to the installation site. However, even if bentonite is pre-cured at the site, it is difficult to adjust such moisture for reasons such as drying before entering the double water-impervious sheet or air entering.
[0007]
[Problems to be solved by the invention]
The present invention solves the disadvantages and problems of the prior art described above, and it is lightweight and easy to carry and lay, but it can be suspended or laid on a slope or a vertical surface in the course of laying. There is no disadvantage that the water-stopping material is biased downward between the double water-impervious sheets and requires leveling work, etc., and the apparent specific gravity suitable for the installation location can be easily obtained, and after the installation, Providing a double water-impervious sheet that is self-repairing when the water sheet breaks, and a method for laying a double water-impervious sheet that lays the double impermeable sheet under the sea surface or under the water surface The task is to do.
[0008]
[Means for Solving the Problems]
As a result of various studies to solve the above-mentioned problems, the present inventors have provided a suction means on the water-impervious sheet, and if the air in the bag-like part is sucked from the suction means to reduce the pressure, Even if the bentonite as the filled water-stopping material is in the form of particles, it can be prevented from being biased in the double water-impervious sheet, and a water-permeable tube is inserted over substantially the entire longitudinal direction of the water-stopping material. If water is injected from the injection means provided on the water-impervious sheet in a reduced pressure state while the nonwoven fabric for water permeability is placed in a reduced pressure state, the double water-impervious sheet is in a reduced pressure state. The double waterproof sheet according to the present invention was completed by investigating that the apparent specific gravity of the double waterproof sheet can be easily changed through the entire top cover of the waterproof material in a short time. .
[0009]
In addition, if the air in the double water-impervious sheet is sucked and floated on the sea surface or the water surface, water is injected into the double water-impervious sheet and submerged under the sea surface or below the water surface. Since there is almost no air in the seat, the apparent specific gravity can be increased with a small amount of water, so that the double water-impervious sheet can be submerged under the sea surface or under the water surface without damaging the self-healing properties of bentonite. The apparent specific gravity can be made, and even when air remains in the double water-impervious sheet, the injection means for injecting water and the suction means for sucking air in the double water-impervious sheet are water-impervious. If a double water-impervious sheet provided near the same edge of the sheet is used, the air in the double water-impervious sheet rises upward when the double water-impervious sheet is submerged under the sea surface or under the water surface. Therefore, the present invention has been studied to find out that it is necessary to suck the air. It was completed the double water barrier sheet laying methods.
[0010]
That is, the present invention provides a bag-shaped portion in which all four edges of a pair of opposed rectangular water-proof sheets are in close contact with each other and sealed, and is made of a woven or non-woven fabric having substantially the same size as the bag-shaped portion. A water-stopping material in which granular bentonite is held by a cloth and a lower cloth made of non-woven cloth, and both cloths are connected by needle punching at a predetermined interval, is over the water-permeable non-woven cloth in which a water-permeable tube is inserted. over substantially the entire longitudinal direction of the fabric is inserted in a state of being heavy wear, inlet from the injection valve to the formation Ri permeability for nonwovens by injecting water through a water permeable non-woven fabric on the water stopping material An injection means for spreading water over the entire cloth is provided in the vicinity of the longitudinal edge of the water-impervious sheet on the upper cloth side and at a position facing the water-permeable nonwoven fabric. Suction means consisting of a suction port for sucking air and a suction valve A double water-impervious sheet, characterized in that provided in the water shield sheets,
In this double water-impervious sheet, the double water-impervious sheet provided near the edge where the suction means is provided with the injection means,
A pair of rectangular water-proof sheets facing each other, the edges of the four circumferences are all in close contact with each other and sealed in a sealed bag-like part and have a size substantially the same as that of the bag-like part. Granular bentonite is held between the cloths, and both cloths are needle punched at predetermined intervals and connected to each other. Watarura over and go water across upper cloth waterproof material through the heavy wear is not the be inserted in a state Note inlet and injection valve and by injecting water into the formation Ri permeability for nonwovens from permeable non-woven fabric A suction port for sucking air in the bag-like portion, and injecting means for causing the air in the bag-like portion to be provided in the vicinity of the longitudinal edge of the water-impervious sheet on the upper cloth side and at the position facing the nonwoven fabric for water permeability A suction means consisting of a suction valve is provided on the waterproof sheet on the upper fabric side. After sucking the air in the bag-like part from the suction means of the double waterproof sheet, the double waterproof sheet is placed in the state where the injection means is located on the shoulder with the upper sheet side waterproof sheet as the upper surface. The amount of water that floats on the sea surface or water surface and at least part of the bentonite of the water-stopping material remains granular is injected from the injection means into the water- permeable nonwoven fabric so that the apparent specific gravity of the double water-impervious sheet is greater than seawater or water. A double impermeable sheet laying method under the sea surface or under the water surface,
In this method of laying a double water-impervious sheet, a double water-impervious sheet in which the injection means and the suction means are provided in the vicinity of the same edge of the water-impervious sheet is used. The present invention relates to a method for laying a double water-impervious sheet that sucks air from the suction means that remains in the bag-like portion that has sunk down and has risen to the shoulder after a predetermined time has elapsed.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the double water-impervious sheet according to the present invention and the laying method thereof will be described in detail with reference to the drawings.
1 is a plan view of an embodiment of a double water-impervious sheet according to the present invention, FIG. 2 is a right side view of FIG. 1, FIG. 3 is a cross-sectional view taken along line AA in FIG. FIG. 5 is a plan view of another embodiment of the double water-impervious sheet, FIG. 5 is a water stop in which bentonite is held between a pair of upper and lower cloths that are needle punched and connected at predetermined intervals. FIG. 6 is an enlarged side view of a water-permeable nonwoven fabric in which a water-permeable tube is inserted, FIG. 7 is an explanatory view showing how air in a double water-impervious sheet is sucked, and FIGS. FIG. 8 is a right side explanatory view showing an embodiment of the double water-impervious sheet laying method according to the present invention for each step, and FIG. 8 shows the upper cloth side after sucking the double water-impervious sheet in FIG. With the double impervious sheet floating on the sea surface or water surface with the injection means positioned on the shoulder with the water impervious sheet as the upper surface Be explanatory right side view and FIG. 9 is an explanatory right side view showing a state in which the apparent specific gravity of the double water shield sheets laid double water barrier sheet is greater than the sea water or water under subsea or surface.
[0012]
In the drawings, X is a double water-impervious sheet according to the present invention laid at a waste final disposal site or the like, and has a structure in which a water-stop material 2 described later is filled between water-impervious sheets 1 and 1 described later. However, it is not necessarily manufactured at a factory, and may be manufactured directly on site.
[0013]
Reference numeral 1 denotes a rectangular water-impervious sheet, and a pair of water-impervious sheets 1 and 1 are opposed to each other, and the edges 1a of the four circumferences thereof are all in close contact with each other by means of welding or the like, and the bag-like part 1b sealed inside. Is formed. The water shielding sheet 1 may be a synthetic resin sheet such as polyethylene, polypropylene, polyester, polyamide, polyvinyl chloride, and may have a non-woven fabric as its outer layer.
[0014]
2 is a granulated bentonite 2a sandwiched between an upper cloth 2b made of a woven or non-woven cloth and a lower cloth 2c made of a non-woven cloth having a size substantially the same as that of the bag-like portion 1b. Is a water-stopping material 2 that is needle punched and connected to the water, and water is injected when laying the double water-impervious sheet X as will be described later, but at least part of the bentonite 2a remains granular If the water-impervious sheet 1 is damaged or the edge 1a of the water-impervious sheet 1 is poorly adhered, seawater or water enters from the damaged part or the poorly-adhered part. The bentonite 2a swells and has a self-repairing property that closes the damaged part.
[0015]
Reference numeral 3 denotes a water-permeable nonwoven fabric in which a water-permeable tube 3a is inserted and is applied over substantially the entire longitudinal direction of the upper cloth 2b, and the injected water is spread over the entire upper cloth 2b of the water blocking material 2. It is the nonwoven fabric for water flow for making it pass. The water permeable tube 3a has a structure in which a material such as a monofilament is formed in a mesh shape, and does not collapse even when a large load is applied, and water freely enters and exits inside and outside the entire tube. it can. Further, the water permeable nonwoven fabric 3 main body functions as a filter so that the water permeable tube 3a is not clogged by bentonite 2a or the like made of clay by the water permeated through the upper cloth 2b of the water blocking material 2. As the water permeable nonwoven fabric 3 in which the water permeable tube 3a is inserted, an endren filter (manufactured by Maeda Kosen Co., Ltd.) or the like can be preferably used.
Further, the water-permeable nonwoven fabric 3 is not necessarily arranged at the center in the width direction of the double water-impervious sheet X as shown in FIG. 1, and a plurality of water-permeable nonwoven fabrics 3 are arranged at symmetrical positions as shown in FIG. Also good.
[0016]
4 injection means for Watarura go water across upper cloth 2b of water stopping material 2 through the water-permeable nonwoven fabric for 3 to inject water into the water-permeable non-woven fabric 3 made of a injection valve 4b and Inlet 4a , and the the injection means 4 that are provided in the hydrostatically for nonwoven fabric 3 that faces the position in the longitudinal direction of the edge 1a near the water shield sheet 1 of the upper cloth 2b side. Since the injection means 4 is provided in the vicinity of the longitudinal edge 1a of the water-impervious sheet 1, if the laying operation is performed with the injection means 4 positioned on the shoulder, the water injection operation can be easily performed. It is. Moreover, since the injection | pouring means 4 is provided in the position facing the water-permeable nonwoven fabric 3, it distributes the water inject | poured from the injection | pouring means 4 to the whole upper cloth 2b of the water stop material 2 through the water-permeable nonwoven fabric 3. FIG. Is possible.
[0017]
5 is a suction means provided on the water-impervious sheet 1 on the upper cloth 2b side, comprising a suction port 5a for sucking air in the bag-like portion 1b between the water-impervious sheets 1 and 1, and a suction valve 5b. The suction valve 5b includes, for example, a mode provided on the water shielding sheet 1 as shown in FIGS. 1 to 4 and a mode provided in the middle of a hose connected to the suction port 5a as shown in FIG. Further, since the suction means 5 is used only for suction and is not used for press-fitting or the like, a valve such as a check valve can be used as the suction valve 5b, but this is not necessarily the case. Furthermore, since the double water-impervious sheet X is laid after sucking the air in the bag-like portion 1b by the suction means 5, the installation position of the suction means 5 is not particularly limited. Since the length is several tens of meters and the width is several meters, if the suction means 5 is provided in the vicinity of the edge 1a in the longitudinal direction of the water-impervious sheet 1, it is easy to work and is put on it. This is preferable because it is difficult to be damaged by the weight of the waste. Further, when the suction means 5 is provided near the edge 1a where the injection means 4 is provided, the double water-impervious sheet X is placed on the sea surface with the suction means 5 and the injection means 4 positioned on the shoulder. Since it can be laid under the water or under the surface of the water, it is more preferable that the air remaining in the bag-like portion 1b rising to the shoulder can be sucked again from the suction means 5.
[0018]
A method for laying a double water-impervious sheet according to the present invention having such a structure will be described with reference to FIGS.
In order to carry out the method of laying the double water-impervious sheet according to the present invention, for example, as shown in FIG. 7, a suction valve 5b is installed in the middle of the hose connected to the suction port 5a of the suction means 5, and the hose First, the vacuum pump is driven with the suction valve 5b opened to suck the air in the bag-like portion 1b, and the bag-like portion 1b is depressurized in the bag-like portion 1b. The suction valve after the inner surface of the water shielding sheet 1 and the upper cloth 2b of the water blocking material 2 and the nonwoven fabric 3 for water permeable are brought into close contact with each other so that the water blocking material 2 and the water permeable nonwoven fabric 3 do not move in the bag-like portion 1b. Close 5b. When the air in the bag-like part 1b is sucked in this way, the bentonite 2b of the water-stopping material 2 filled in the bag-like part 1b is in the form of particles. There is no occurrence of a phenomenon such as bentonite or the like that has a viscosity and is in close contact with the inner surface of the water shielding sheet 1 and cannot suck the air in the bag-like portion 1b. In addition, if the pressure change in the bag-like part 1b is measured after the air in the bag-like part 1b is sucked, it is possible to detect the contact state of the close-contact part of the water-impervious sheet 1 and the presence or absence of breakage of the water-impervious sheet 1. it can.
[0019]
Thus, the air in the bag-like part 1b is sucked to close the suction valve 5b, and the hose on the vacuum pump side is removed from the suction valve 5b while the inside of the double water-impervious sheet X is kept in a reduced pressure state. As described above, the double water-impervious sheet X is floated on the sea surface or the water surface with the suction means 5 and the injection means 4 positioned on the shoulder. At this time, since the inner surface of the water shielding sheet 1, the upper cloth 2b of the water blocking material 2, and the nonwoven fabric 3 for water permeability are in close contact, operations such as hanging can be easily performed.
[0020]
Next, in order to inject water from the injection means 4 into the double impermeable sheet X, although not shown, the injection valve 4b of the injection means 4 and the injection pump, the water storage tank, etc. are sequentially connected via a hose, First, the infusion pump is driven with the infusion valve 4b opened, and the water in the water storage tank is spread from the infusion port 4a to the entire upper cloth 2b of the water blocking material 2 through the water-permeable nonwoven fabric 3. It is injected into the shaped part 1b. In addition, if there is a facility such as water supply at the laying location, tap water may be supplied directly without using a water storage tank or the like, and if the laying location is the sea, seawater pumped from the sea may be injected. .
[0021]
The water thus injected passes through the water permeable tube 3a of the water permeable non-woven fabric 3 which is attached over the entire length of the upper cloth 2b of the water blocking material 2 because the bag-like portion 1b is in a reduced pressure state. It reaches the end of the bag-like portion 1b in a short time, spreads over the entire water-permeable nonwoven fabric 3, and further penetrates into the upper cloth 2b of the water blocking material 2. The apparent specific gravity of the double waterproof sheet X is the seawater. Or it becomes larger than water, and as shown in FIG. 9, the whole double water-impervious sheet X sinks.
[0022]
If the injection valve 4b is closed and the water injection is stopped when the double water-impervious sheet X sinks in this way, the bentonite 2a of the water-stopping material 2 remains self-healing without injecting too much water. The double water-impervious sheet X is laid in the state. Also, if the suction work before laying is not enough and air remains in the bag-like portion 1b, the air rises upward, so that the suction means 5 located on the shoulder is sucked. You can do it. When the double water-impervious sheet X is laid in the sea, a sandbag or the like may be placed on the double water-impervious sheet X in order to prevent floating and turn-up by waves.
[0023]
【The invention's effect】
The double water-impervious sheet according to the present invention as described in detail above is a double water-impervious sheet in which a waterproof material is simply filled between the double water-impervious sheets like the conventional double water-impervious sheet. Unlike the water-impervious sheet, the water-impervious sheet is provided with suction means, so that the double water-impervious sheet is depressurized by using the suction means and the inner surface of the water-impervious sheet and the water-permeable material are filled. Since the shape of the double water-impervious sheet can be maintained by keeping the nonwoven fabric in close contact, it is filled even when suspended or laid on a slope or vertical surface in the process of laying Since there is no disadvantage that the water-stopping material is biased downward between the double water-impervious sheets, large work processes such as leveling work can be reduced, and there is almost air in the double water-impervious sheet. You can increase the apparent specific gravity with a small amount of water. In addition, it is possible to easily make the double water-impervious sheet have an apparent specific gravity suitable for the place where it is laid, and in the longitudinal direction on the upper fabric of the water-stopping material in which granular bentonite is held between the upper fabric and the lower fabric Since the water-permeable nonwoven fabric into which the water-permeable tube is inserted is overlaid, the water injected from the injection means is injected into the entire upper fabric of the water-stopping material through the water-permeable nonwoven fabric. Therefore, it is a double water-impervious sheet that is particularly useful when laying under the sea or water.
[0024]
And the laying method of the double water-impervious sheet according to the present invention is that the air in the double water-impervious sheet is sucked and floated on the sea surface or the water surface, and then water is injected into the double water-impervious sheet to below the sea surface or the water surface. It is a laying method that sinks underneath, and since it does not contain water when it floats on the sea surface or water surface, it is lightweight and because it is in a decompressed state, the waterproof material in the double water-impervious sheet will not be biased Work such as hanging when the double impermeable sheet floats on the sea surface or the water surface can be easily performed, and when water is injected and submerged under the sea surface or under the water surface, a non-woven fabric for water permeability is provided as a water passage Since the double impermeable sheet is also in a reduced pressure state, water can be spread over at least the entire upper surface of the double impermeable sheet in a short time, so that the laying operation can be performed efficiently. Furthermore, since it is difficult to change the apparent specific gravity of the ready-made double water-impervious sheet, it was necessary to place a sandbag or the like in order to sink the double water-impervious sheet under the sea surface or the water surface. By using the double impermeable sheet laying method according to the present invention, it is easy to make the apparent specific gravity suitable for the laying place just by injecting water until the double impermeable sheet sinks below the sea surface or below the water surface. It can be done.
In addition, even when air remains in the double water-impervious sheet, since the suction means is provided, the air that has risen upward in the bag-like portion after laying can be sucked, Not only can a part of the sheet be lifted but also a phenomenon in which an uneven load acts on a portion where the water-impervious sheet is deformed due to the presence of air and breaks does not occur.
[0025]
The industrial value of the double water-impervious sheet and its laying method according to the present invention that exhibits such various effects is very large.
[Brief description of the drawings]
FIG. 1 is a plan view of one embodiment of a double water-impervious sheet according to the present invention.
FIG. 2 is a right side view of FIG.
FIG. 3 is a cross-sectional view taken along line AA in FIG.
FIG. 4 is a plan view of another embodiment of the double water-impervious sheet according to the present invention.
FIG. 5 is an explanatory cross-sectional view of a water stop material in which bentonite is held between a pair of opposed upper and lower cloths that are needle punched and connected at predetermined intervals.
FIG. 6 is an enlarged side view of a water permeable nonwoven fabric in which a water permeable tube is inserted.
FIG. 7 is an explanatory view showing a state of sucking air in the double water-impervious sheet.
FIG. 8 After the double water-impervious sheet in FIG. 1 is sucked, place the double water-impervious sheet on the sea surface or water surface with the upper cloth-side water-impervious sheet on the upper surface and the injection means positioned on the shoulder. It is right side explanatory drawing which shows the state which floated.
FIG. 9 is an explanatory diagram on the right side view showing a state in which the apparent density of the double water-impervious sheet is made larger than seawater or water and the double impermeable sheet is laid under the sea surface or under the water surface.
[Explanation of symbols]
X Double impervious sheet 1 Impermeable sheet
1a Edge
1b Bag-like part 2 Water stop material
2a Bentonite
2b Top cloth
2c Lower cloth 3 Non-woven fabric for water permeability
3a Permeable tube 4 Injection means
4a Inlet
4b Injection valve 5 Suction means
5a Suction port
5b Suction valve

Claims (4)

In the bag-like part (1b) in which the four edges (1a) of the pair of rectangular water-proof sheets (1, 1) facing each other are in close contact with each other, the bag-like part (1b) is approximately the same size. A granular bentonite (2a) is held between an upper cloth (2b) made of woven or non-woven cloth and a lower cloth (2c) made of non-woven cloth, and both cloth (2b, 2c) are needled at predetermined intervals. The water blocking material (2) punched and connected causes the water permeable non-woven fabric (3) inserted with the water permeable tube (3a) to overlap the entire length of the upper cloth (2b). was in a state being inserted in, inlet (4a) and the injection valve (4b) formed Ri translucent water for nonwovens from the (3) to be injected with water 該止water through a translucent water for nonwoven (3) An injection means (4) for spreading water over the entire upper cloth (2b ) of the material ( 2 ) is in the vicinity of the longitudinal edge (1a) of the water shielding sheet (1) on the upper cloth (2b) side And provided at a position facing the water-permeable nonwoven fabric (3). The suction means (5) comprising a suction port (5a) and a suction valve (5b) for sucking the air in the bag-like part (1b) is provided with a water shielding sheet (1) on the upper cloth (2b) side. ) Is provided in the double water-impervious sheet (X).   The double water-impervious sheet (X) according to claim 1, wherein the suction means (5) is provided in the vicinity of the edge (1a) where the injection means (4) is provided. The same size as the bag-like part (1b) in the bag-like part (1b) in which the four edges (1a) of the pair of opposing rectangular water-impervious sheets (1, 1) are all closely attached and sealed. A granular bentonite (2a) is held between an upper cloth (2b) made of woven or non-woven cloth and a lower cloth (2c) made of non-woven cloth so that both cloth (2b, 2c) are needle punched at predetermined intervals. The water-stopping nonwoven fabric (3) into which the water-permeable tube (3a) is inserted is overlapped over the entire length of the upper cloth (2b). in inlet (4a) and injection valve is inserted (4b) and formed SQLDESC_BASE_TABLE_NAME This injection of water into the transparent water for nonwoven (3) through the translucent water for nonwoven (3) 該止waterstops (2 and wherein in the longitudinal direction of the edge (1a) near the upper fabric (2b) injection means for entire go water Watarura (4) of the upper fabric (2b) side of the water barrier sheet (1)) of The bag is provided at a position facing the nonwoven fabric for water permeability (3) A suction means (5) comprising a suction port (5a) and a suction valve (5b) for sucking the air in the shaped part (1b) is placed on the water shielding sheet (1) on the upper cloth (2b) side. After sucking the air in the bag-like part (1b) from the suction means (5) of the double waterproof sheet (X) provided, the waterproof sheet (1) on the upper cloth (2b) side is removed. The double water-impervious sheet (X) is floated on the sea surface or water surface with the injection means (4) positioned on the shoulder on the upper surface, and at least one of the bentonite (2a) of the water blocking material (2). parts by is greater than leave remaining amount of water to the infusion means (4) is injected into the transparent water for nonwoven (3) sea water or water the apparent specific gravity of said double water shield sheets (X) of the particulate, A method for laying a double water-impervious sheet, characterized in that the double water-impervious sheet (X) is laid under the sea surface or under the water surface.   The double water-impervious sheet (X) in which the injection means (4) and the suction means (5) are provided near the same edge (1a) of the water-impervious sheet (1) The air remaining in the bag-like portion (1b) that has risen to the shoulder after a predetermined time has elapsed after (X) is submerged under the sea surface or water surface is sucked from the suction means (5). The laying method of the double waterproof sheet as described in 2.

Images