GB1561320A

GB1561320A - Water retaining linings

Info

Publication number: GB1561320A
Application number: GB5027377A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-03-21
Filing date: 1978-03-21
Publication date: 1980-02-20

Description

(54) IMPROVEMENTS IN OR RELATING TO WATER RETAINING LININGS (71) I, LESLIE AUSTIN FISHER, a British subject of 24 Fisher Close, Hythe, Kent, do hereby declare the invention, for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to flexible liquidretaining linings, such as are used in the construction of storage reservoirs, supply channels and other constructions for holding or conveying large volumes of water or other liquids. For simplicity, in the following part of this specification, reference will be made to water, as this is the liquid most likely to be concerned, but it is to be understood that the invention can be used with linings for constructions for holding bodies or other liquids.

A largely effective and inexpensive way to provide a body of water in a storage reservoir, for instance, is to excavate a shallow pit with sloping sides and line it with a water-impervious sheet. A standard technique involves digging a trench completely round the perimeter of the pit which is to serve as the water-storage reservoir and securing the free edges of the lining by folding them into the trench, which is then back-filled. Very large water-storage reservoirs and analogous structures can be made quickly and inexpensively by this technique. A useful lining material is a synthetic rubber sheeting, made for instance of the material marketed by Du Pont under the name HYPALON, and comprising a pair of HYPALON layers and an intermediate reinforcing mesh material of, for instance, NYLON.

Lined ground cavities of this kind can suffer from a disadvantage, if the level of the water stored in the cavity falls below that of ground water in the surrounding terrain. If this occurs, the ground water tends to seep between the cavity and the lining and can lift the latter off the sloping sides.

The present invention is based upon the discovery of an effective way of ensuring that, if this occurs, the ground water seeps into the reservoir via one or more relief valves in the part of the lining against the sides of the cavity.

According to this invention, a flexible liquid-retaining lining is provided for installation in a cavity in the ground to hold a body of water or other liquid, comprising a lining sheet including at least one relief valve in the form of an aperture covered, on the side which in use is contacted by the liquid to be retained, with a flexible valve sheet secured over the aperture in surface-to-surface relationship with the lining sheet, the valve sheet and the lining sheet being free to separate from one another at least at the area which is below tthe valve aperture when the lining is installed.

The present invention also consists in a water reservoir, supply channel or other construction for holding a body of water, comprising a cavity in the ground, having installed therein a liquid-retaining lining according to the preceding paragraph.

In order that the invention may be readily understood, reference is made to the accompanying drawing, wherein: Fig. 1 shows a diagrammatic part section through a water reservoir constructed as a lined cavity in the ground; Fig. 2 shows a cross-section through a seepage relief valve in acordance with a preferred embodiment of this invention; Fig. 3 shows the valve of Fig. 2, in diagrammatic perspective view, partly broken away, when closed; Fig. 4 shows a view similar to Fig. 3, when the valve is open.

In Fig. 1, the profile of the reservoir is indicated by a chain-dotted line and hatching and includes a generally level area 10, which may represent the original ground level, a sloping side surface 11 forming a side of the reservoir cavity 12 and a generally level base area 13. The reservoir is thus a cavity excavated from the ground, in this example. Fig. 1 also illustrates the construction which may be used in a typical supply channel such as a canal, Fig. 1 showing a half-section taken transversely of the channel. The water-retaining lining is a single lining sheet, indicated at 14, which is typically made up on site by searning together a number of smaller sheets. In this way, the lining 14 can conform to the general shape of the cavity 12.The lining 14 covers the base area 13, the sloping sides 11 and the immediate perimeter area of the reservoir, as shown at 15. A trench indicated by cross-shading at 16 is made around the perimeter 15 and the free edges 17 of the lining sheet 14 are anchored in place by being folded into the trench 16, which is then back-filled, e.g. to the original ground level, so as to hold the edges 17 of the sheet 14 in place. The reservoir is then ready for use and is filled with water to a normal level, indicated at A.

During use of water from the reservoir, it is possible for its level to fall considerably, depending upon supply and demand, for example to a point as low as that indicated at B. This may well be below the natural water-table of the ground in which the reservoir is constructed, as indicated by the broken line at C, or it may happen for other reasons that the water level in the reservoir falls below a local or general water level outside- the reservoir. This outside water therefore tends to find- its way into the reservoir cavity, as already indicated, and it then exerts a pressure, indicated by the arows 18, against the outside of the lining sheet 14.When the reservoir is filled to the normal level indicated at A, this pressure 18 is opposed by the static pressure of the reservoir water and either no seepage occurs or it has no undesirable effect, as in either case there is no appreciable disturbance of the lining sheet 14. At times of low water level, as indicated at B, however9 the pressure 18 can cause the lining sheet 14 to shift. This occurs if ground water indicated at 18 seeps between the sloping sides 11 and the base 13 of the cavity, on the one hand, and the lining sheet 14, on the other hand. It is found that in severe cases of seepage, the sheet 14 falls into folds. Moreover, it does not recover its normal location against the sloping sides 11 or the base 13 of the reservoir, and especially the former, when the water level rises again.Although such reservoirs are extremely useful, this kind of effect can be very disadvantageous, as it can only be avoided by generally maintaining a normal water level, which may well be imposible in practice, and it creates a very difficult and costly maintenance problem.

The present invention therefore provides a solution to this problem in the form of one or more seepage relief valves disposed in the lining or like liquid-retaining sheet material. The relief essentially comprises an aperture located in the lining sheet so as to be positioned in use betwen the highest and lowest water levels. This aperture has to be closed, in normal operation, so as to prevent the stored water from escaping from the reservoir and so the aperture is covered with a flexible material forming a valve sheet, which is secured to the lining sheet around the aperture so as to overlie the latter and to be in surface-to-surface relationship with the lining sheet, the lining sheet and the flexible valve sheet being free to separate from one another at least in that region which is below the aperture when the lining is installed.This location of the area of free separation between the two mutually superposed sheets ensures that if leakage or sepage occurs, so that ground water passes through the aperture in the lining sheet and so into the pocket-like structure formed by it and the overlying valve sheet, the water can drain out of the pocketlike structure and leak harmlessly into the body of water still present in the reservoir, without disturbing the lining. Preferably, the flexible valve sheet material is large in area in relation to the aperture. A convenient arrangement is given if the aperture is circular, for example 15-25 cms, most suitably 18-22 cms in diameter, and if the flexible valve sheet is the preferred shape, being namely square or rectangular and ranging in size from 30-50 cms per side.

The valve sheet is desirably seamed ta the lining sheet over wide areas adjacent two of its opposed sides and over short lengths of its other two sides, so as to leave the valve sheet free to separate from the lining sheet along the central parts of the latter two sides both above and below the aperture in use and over a length ranging from 1522 cms and, most preferably, a length approximately the same as the diameter of the aperture.

An especially desirable and preferable feature of the invention is the provision of means in the form of a protective material to prevent solid material, e.g. stones, from passing through the aperture, without preventing the passage of water or other liquid material as desired. Such protective material is, essentially, impervious to solids at least of the coarser kind likely to cause the valve to malfunction if allowed in, while still being pervious to liquid and can conveniently be provided in the form of a guard of wire mesh, expanded metal or similar open-mesh material, the material preferably being rigid, light in weight and, most importantly, non-corrodable and otherwise resistant to attack by water.Such a stone-retaining grille or similar protective mesh material prevents seepage water from washing solid bodies through the aperture which,if allowed to occur, could leave the valve in an open condition after the reservoir water had resumed a level above the seepage relief valve. Where the valve is formed by attaching the flexible sheet material over the aperture in the form of a rectangular or square piece seamed along each of two opposed sides and, possibly and preferably, also along the terminal parts of each of the other two opposed sides, it is convenient to locate the solid-retaining guard grille or protective material in place by disposing it in the flat envelope or pocket formed over the aperture in the lining sheet and between the latter and the piece of flexible valve sheet secured to it to form the seepage relief valve.

In a reservoir, canal or other body of liquid held in a lining having in it one or more seepage relief valves or structures according to this invention, if the liquid level fails sufficiently to expose the valves (which would be provided nominally at the same level, if more than one), water or other liquid in the surrounding ground will exert pressure as described, but instead of lifting the lining off the pit sides this water will open the valves by raising the pieces of flexible valve sheet so as to allow such water or other liquid to flow through the apertures and also through the openings formed between the lining sheet and valve sheet, as they freely separate. Stones and other solid materials are held back by the wire mesh or other guard screens, however.

On return of the water to a higher level so that the valves are covered again, the water pressure in the reservoir or the like structure closes the valves so that the flexible valve sheet materials again seal the apertures in the lining sheet and the reservoir water or other stored liquid does not escape by flowing through the seepage relief valves to the outside.

In order that the invention may be more readily understood, a preferred form of it is described below in conjunction with Figs.

2 to 4 of the accompanying drawing.

A portion of the lining sheet shown at 14 in Fig. 1 is indicated on a larger scale in Fig. 2, at 24; this is made for instance of reinforced HYPALON sheeting. In this, a circular aperture 25 is formed. Over the aperture, a rectangle of flexible material forming a valve sheet 26 is secured so as normally to cover the aperture 25 and so keep it closed to the passage of water. The valve sheet 26 overlies a substantial area of the lining sheet around the aperture 25.

However, outside the central region of the valve sheet 26 which actually overlies the aperture 25, there is an annular or other intermediate region of the valve sheet 26, which is normally disposed in surface-to-surface relationship with the lining sheet 24 (save for the intervening protective material described below), so that the two sheets are unsecured in this intermediate region.

In the remaining peripheral region of the valve sheet 26, it is secured to the lining sheet 24, again being in surface-to-surface relationship and in this instance is held by seaming or otherwise attaching together, except where the respective sheet materials are left free of one another, at 28 and 29, as seen best in Figs. 3 and 4, described below. An expanded metal grille 30 is located in the pocket formed by the lining sheet 24 and the valve sheet 26 so as to overlie the aperture 25 and the surrounding part of the lining sheet 24 corresponding to the intermediate region of the valve sheet 26.

Fig. 3 shows the valve in perspective view in the closed condition, while Fig. 4 shows it open, i.e. when ground water is seeping into the reservoir, as a result of the water level falling below the level where the valve or valves are located in the side of the lining. The intermediate region of the valve has the grille 30 overlying it and, outside this, at 27 are the parts of the peripheral region extending along two opposed sides of the valve sheet 26 and over the terminal parts of the other two opposed sides, i.e.

except for the free areas 28 and 29, where the valve sheet 26 is affixed to the lining sheet 24.

WHAT I CLAIM IS: 1. A flexible liquid-retaining lining for installation in a cavity in the ground to hold a body of water or other liquid, comprising a lining sheet including at least one relief valve in the form of an aperture covered, on the side which in use is contacted by the liquid to be retained, with a flexible valve sheet secured over the aperture in surface-to-surface relationship with the lining sheet, the valve sheet and the lining sheet being free to separate from one another at least at the area which is below the valve aperture when the lining is installed.

2. A lining according to claim 1, in which the valve sheet and the lining sheet are free to separate both in the area below the valve aperture and in the opposite area above the valve aperture.

3. A lining according to claim 1 or 2, in which a central region of the valve sheet overlies the aperture and is surrounded by an intermediate region of the valve sheet in an unsecured surface-to-surface relationship

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

guard of wire mesh, expanded metal or similar open-mesh material, the material preferably being rigid, light in weight and, most importantly, non-corrodable and otherwise resistant to attack by water. Such a stone-retaining grille or similar protective mesh material prevents seepage water from washing solid bodies through the aperture which,if allowed to occur, could leave the valve in an open condition after the reservoir water had resumed a level above the seepage relief valve.Where the valve is formed by attaching the flexible sheet material over the aperture in the form of a rectangular or square piece seamed along each of two opposed sides and, possibly and preferably, also along the terminal parts of each of the other two opposed sides, it is convenient to locate the solid-retaining guard grille or protective material in place by disposing it in the flat envelope or pocket formed over the aperture in the lining sheet and between the latter and the piece of flexible valve sheet secured to it to form the seepage relief valve.

In a reservoir, canal or other body of liquid held in a lining having in it one or more seepage relief valves or structures according to this invention, if the liquid level fails sufficiently to expose the valves (which would be provided nominally at the same level, if more than one), water or other liquid in the surrounding ground will exert pressure as described, but instead of lifting the lining off the pit sides this water will open the valves by raising the pieces of flexible valve sheet so as to allow such water or other liquid to flow through the apertures and also through the openings formed between the lining sheet and valve sheet, as they freely separate. Stones and other solid materials are held back by the wire mesh or other guard screens, however.

On return of the water to a higher level so that the valves are covered again, the water pressure in the reservoir or the like structure closes the valves so that the flexible valve sheet materials again seal the apertures in the lining sheet and the reservoir water or other stored liquid does not escape by flowing through the seepage relief valves to the outside.

In order that the invention may be more readily understood, a preferred form of it is described below in conjunction with Figs.

2 to 4 of the accompanying drawing.

A portion of the lining sheet shown at 14 in Fig. 1 is indicated on a larger scale in Fig. 2, at 24; this is made for instance of reinforced HYPALON sheeting. In this, a circular aperture 25 is formed. Over the aperture, a rectangle of flexible material forming a valve sheet 26 is secured so as normally to cover the aperture 25 and so keep it closed to the passage of water. The valve sheet 26 overlies a substantial area of the lining sheet around the aperture 25.

However, outside the central region of the valve sheet 26 which actually overlies the aperture 25, there is an annular or other intermediate region of the valve sheet 26, which is normally disposed in surface-to-surface relationship with the lining sheet 24 (save for the intervening protective material described below), so that the two sheets are unsecured in this intermediate region.

In the remaining peripheral region of the valve sheet 26, it is secured to the lining sheet 24, again being in surface-to-surface relationship and in this instance is held by seaming or otherwise attaching together, except where the respective sheet materials are left free of one another, at 28 and 29, as seen best in Figs. 3 and 4, described below. An expanded metal grille 30 is located in the pocket formed by the lining sheet 24 and the valve sheet 26 so as to overlie the aperture 25 and the surrounding part of the lining sheet 24 corresponding to the intermediate region of the valve sheet 26.

Fig. 3 shows the valve in perspective view in the closed condition, while Fig. 4 shows it open, i.e. when ground water is seeping into the reservoir, as a result of the water level falling below the level where the valve or valves are located in the side of the lining. The intermediate region of the valve has the grille 30 overlying it and, outside this, at 27 are the parts of the peripheral region extending along two opposed sides of the valve sheet 26 and over the terminal parts of the other two opposed sides, i.e.

except for the free areas 28 and 29, where the valve sheet 26 is affixed to the lining sheet 24.

WHAT I CLAIM IS: 1. A flexible liquid-retaining lining for installation in a cavity in the ground to hold a body of water or other liquid, comprising a lining sheet including at least one relief valve in the form of an aperture covered, on the side which in use is contacted by the liquid to be retained, with a flexible valve sheet secured over the aperture in surface-to-surface relationship with the lining sheet, the valve sheet and the lining sheet being free to separate from one another at least at the area which is below the valve aperture when the lining is installed.
2. A lining according to claim 1, in which the valve sheet and the lining sheet are free to separate both in the area below the valve aperture and in the opposite area above the valve aperture.
3. A lining according to claim 1 or 2, in which a central region of the valve sheet overlies the aperture and is surrounded by an intermediate region of the valve sheet in an unsecured surface-to-surface relationship

with the lining sheet, the intermediate region being surrounded by a peripheral region of the valve sheet which is in a secured surface-to-surface relationship with the lining sheet except where they are free to separate.
4. A lining according to claim 3, in which the valve sheet is square or rectangular and is secured to the underlying areas of the lining sheet in the parts of its peripheral region which extend along two opposed sides and in the terminal parts of the other two opposed sides, whereby the valve sheet and the lining sheet are free to separate at the central parts of the other two opposed sides.
5. A lining according to any preceding claim, in which the aperture is circular.
6. A lining according to any preceding claim, in which a protective material is provided, for preventing solid material from obstructing the relief valve, while permitting liquid to pass through.
7. A lining according to claim 6, in which the protective material comprises a guard of open-mesh material located over the aperture between the lining sheet and the valve sheet.
8. A lining according to any preceding claim, which comprises synthetic rubber sheeting.
9. A lining according to claim 8, which comprises a plurality of synthetic rubber sheets seamed together and having one or more of the relief valves located so as to be positioned between the highest and lowest liquid levels in the liquid storage cavity provided with the lining.
10. A flexible liquid-retaining lining according to claim 1, substantially as herein described.
11. A water reservoir, supply channel or other contruction for holding a body of water, comprising a cavity in the ground having installed therein a liquid-retaining lining according to any preceding claim.
12. A water reservoir, supply channel or other construction according to claim 11, wherein the cavity has sloping sides, where the one or more relief valves are provided in the lining, and wherein the edge of the lining is secured in the ground around the periphery of the cavity.