GB2085949A - Composite lining for protecting earth surfaces and method for making same - Google Patents

Abstract

The present invention relates to improvements in lining and protecting earth surfaces intended for liquid holding. A reinforcing layer of woven fabric (12) having at least one textured side (13) is provided with a substrate layer (15) of liquid-impermeable material bonded to the other side of the fabric. The fabric is preferably woven of chemically resistant yarn such as nylon. The liquid-impermeable material is preferably elastomeric sheeting. The fabric is installed on the earth surface with the substrate layer adjacent to the earth surface. A layer (20) of cementitious material is applied to the textured side of the fabric, preferably in the form of shotcrete. The lining is resistant to damage by animals and mechanical equipment and to attack by chemicals or organic solvents and will remain impermeable in spite of accidental cracking due to mechanical damage or subsidence of earth beneath the lining. <IMAGE>

Description

SPECIFICATION Composite lining for protecting earth surfaces and method for making same This invention relates to the lining of earth surfaces such as are used in the beds of ponds, canals, and the like.

Several methods have been used to line the bottoms and sides of canals, irrigation ditches, ponds, and holding basins to render them impermeable to the passage of water and to protect the soil from erosion.

In accordance with one of these methods, the soil in situ was mixed with Portland cement or other binding material to convert the soil to structural material. This method was useful only when the granulometry of the soil was satisfactory within rather narrow limits. It was suitable for horizontal surfaces or relatively flat slopes, but it lacked the structural strength to be used on steep slopes or vertical surfaces. The most serious disadvantage of this method was that it created a rigid mate rial which was subject to cracking as a result of drying shrinkage or soil settlement, and the cracks rendered the lining unacceptable since the water or other liquid could seep through the cracks.

Another prior method involved the application of asphaltic concrete to the soil surfaces.

This method was suitable for horizontal or flatly sloped surfaces, but it also lacked the structural strength for steeply sloped or vertical surfaces. An advantage of asphaltic concrete was that it was more plastic than other materials such as Portland cement, but this material also tended to crack as a result of soil subsidence. Moreover, asphaltic concretes were not suitable for the containment of fluid wastes containing organic solvents, since such solvents tended to dissolve the asphaltic concrete.

Rather than mixing the cement directly into the soil, other methods have been used in which a sand and cement mortar was sprayed directly onto the surface to be protected. This process is known as "shotcreting". Two types of shotcreting processes have been known. If the sand and cement were premixed with the required amount of water, it was known as a "wet" process. If the sand and cement were delivered pneumatically to a nozzle, at which point water was added to the mix, it was known as a "dry" process. A reinforcing mesh was sometimes incorporated in the shotcrete lining. Linings produced by shotcreting were normally of a thickness of about 10 centimeters. Shotcreting had certain advantages in that it could be applied to horizontal, vertical, or even overhead surfaces.However, the extremely rigid high quality lining resulting from the use of this process was relatively expensive. While it was not subject to catastrophic cracking, fine cracks did develop, permitting loss of soil from behind the lining and passage of water through the lining.

Since all of the prior methods using cement or concrete have been subject to cracking, other types of linings have been used which avoided the use of cementitious material, and in which a lining was provided with sheets of an elastomeric material. This elastomeric sheeting was usually relatively thin and lacked strength, so that it was often reinforced with a fabric woven of synthetic yarn. These linings were relatively economical, but even with the most heavily reinforced sheeting, it was susceptible to puncture damage from equipment or cattle hooves. In addition, some of the linings were toxic when ingested by cattle.

Chemical waste-holding ponds lined with such material could not be cleaned by mechanical equipment. Moreover, the very light weight of such linings made them susceptible to floating even when a small amount of gas from the earth accumulated beneath the lining.

According to one aspect of the present invention there is provided a method for lining and protecting an earth surface intended for liquid holding which comprises the steps of providing a reinforcing layer of woven fabric having substantial tensile strength and having at least one side which is textured, bonding a sealing layer of liquid-impermeable material to the other side of the fabric, installing the fabric over the earth surface with the sealing layer adjacent the earth surface, and applying a layer of cementitious material to the textured side of the fabric to provide a tough protective covering.

According to another aspect of the invention, there is provided a composite lining for protecting an earth surface intended for liquid holding comprising a reinforcing layer of woven fabric having substantial tensile strength and having at least one side which is textured, a substrate layer of liquid-impermeable material bonded to the other side of the fabric, the substrate layer being adapted to be installed adjacent the earth surface, and a layer of cementitious material bonded to the textile on the textured side of the fabric.

Embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an embodiment of a lining according to the present invention produced in accordance with an embodiment of a method according to the present invention, with layers of the lining partially removed; Figure 2 is a side sectional view of the lining of Fig. 1 Figure 3 is a side sectional view similar to Fig. 2 showing a modified version of the lining; and Figure 4 is a side sectional view similar to Figs. 2 and 3, showing another modified version of the lining.

Referring more particularly to the drawings, Figs. 1 and 2 show a lining 10 installed on an earth surface E.

The lining 10 includes a layer comprising a reinforcing textile or woven fabric 12. At least the upper surface of the fabric 1 2 is provided with a textured effect 1 3 to interlock with the upper layers of the lining as hereinafter described. The textured effect 1 3 may be in the form of tufts, loops, yarn floats, slubs, or protruding fibers which provide the textured effect to the upper surface. Materials having such a textured effect include frise, terry, tufted and other woven pile fabric having yarns or fibers extending above the plane of the ground weave. In addition or alternatively, the yarns of which the fabric is formed may be textured to provide the textured effect 1 3 which interlocks with the upper layers.For example, an irregularly spun very coarse fiber could be woven with another fiber or fibers to produce the textured effect. As another alternative, the protruding fibers forming the textured effect 1 3 could be attached to the fabric. For example, an air-laid web of fine yarn could be punched with a single action needle through a heavy single yarn scrim to produce the textured effect 1 3.

The fabric 1 2 is woven of synthetic yarns or fibers which should provide substantial tensile strength and which should provide maximum resistance to chemical agents or biological organisms so that chemicals or organic solvents which may be contained in the pond or basin for which the lining is used will not attack the fabric. Suitable yarns include nylon, Dacron, or other polyester, Kevlar, polypropylene, acrylic, or other synthetic materials. Preferably, the fabric is formed of nylon, at least 50% of which by weight is producer bulk textured multifilament nylon, such as that sold by E.I. duPont de Nemours s Co. under the trademark ' "Cordura A substrate sealing layer of a liquid-impermeable material, such as elastomeric sheeting 15, is bonded to the fabric 1 2 on the side of the fabric opposite that having the textured effect 1 3. The sheeting may be formed of any suitable elastomeric material such as polyvinyl chloride, chlorinated polyethylene, butyl rubber, Hypalon (chlorosulfonated polyethylene), or other similar material. The elastomeric sheeting 1 5 should be capable of maintaining a liquid-impermeable seal for the lining even if the other layers of the lining become cracked or permeable due to mechanical damage or subsidence of the earth beneath the lining.

The elastomeric sheeting 1 5 would have a typical thickness of about 10 to 30 mils, and is bonded to the bottom surface of the fabric 1 2 by conventional methods such as conventional coating, extruding, laminating, spread coating or casting in place.

The fabric 1 2 is typically produced in mil widths of about 1'5 to 1 8 meters. Before the fabric is shipped to the installation site, the elastomeric sheeting 1 5 is bonded to the surface of the fabric opposite the tufts 1 3.

The fabric sheeting lamination is then shipped to the site and installed on the earth surface E. Adjacent edges of the fabric 1 2 may be joined at 1 7 (Fig. 2) by any conventional means, such as conventional sewing, high frequency sewing, hot melt gluing, joining by any other known mechanical device, or laseractivated chemical fusion. The elastomeric sheeting 1 5 on the back of the fabric 1 2 may be joined at 1 8 by conventional means such as sewing, heat-bonding or cold cementing.

Strength and outer protection are provided to the fabric 1 2 and sheeting 1 5 by an outer layer of cementitious material 20 applied to the upper surface of the fabric 1 2 having the textured effect 1 3. As previously discussed, the upper surface of the fabric 1 2 is textured in order to interlock the cementitious material 20 with the fabric and, preferably, the fabric is also formed of a textured yarn to increase this interlocking effect. The material of the fabric 1 2 and the textured effect 1 3 are such that they are susceptible to wetting by the fluid cementitious material 20.The cementitious material 20 is preferably Portland cement mortar which is sprayed onto the fabric 1 2 in accordance with a process known as "shotcreting". The shotcrete may be applied using either a wet or dry process. The cementitious material 20 is hardenable and applied in a fluid or plastic state.

In applications in which the lining 10 is used to contain harsh chemicals and in which the lining must be resistant to severe attack by chemically contaminated water, the cementitious material 20 may be a product other than Portland cement mortar, such as sulfur or a mixture of sand and sulfur applied in molten state and allowed to cool. As previously mentioned, the fabric 1 2 is woven of synthetic yarns which provide maximum resistance to chemical agents or biological organisms, so that aggressive chemicals released from the mortar or cementitious material 20 will not attack the fabric, and so that chemicals or organic solvents which may be contained in the pond or basin for which the lining is used will not attack the fabric if cracks develop in the layer of cementitious material.

Because of the reinforcing effect of the fabric 1 2 and the impermeability of the underlying elastomeric sheeting 15, only a relatively thin layer of cementitious material 20 need be applied in order to protect the fabric against mechanical damage or abrasion. The thickness of the layer 20 can range from one centimeter to several centimeters. If desired, a steel reinforcing mesh 22 may be interposed in the cementitious material 20 during application. In place of the mesh 22, a fabric reinforcing layer in the form of woven synthetic yarns may be used.

Various modifications of the lining 10 may be used. For example, Fig. 3 shows two layers of the fabric 32, each of which is similar to the fabric 12, bonded back-to-back with a layer of the elastomeric sheeting 35 similar to the sheeting 1 5 between the layers of fabric 32, and the textured surfaces of the fabric facing outwardly. Mortar or other cementitious material 40 is applied to the earth surface E, and lamination comprising the two layers of fabric 33 and elastomeric material 35 is then trowelled or pressed into the fresh mortar, and a top layer of cementitious material 41 is sprayed or placed on top of the fabric. The fabric 32 would then be located at or near the point of zero bending stress, so that it would be subjected to the minimum tensile stresses if the mortar were cracked by ground subsidence or mechanical damage.

As a further modification, Fig. 4 shows a version of the lining used to protect earth slopes under water. Using this method, a thin layer of mortar or other cementitious material 50 would be sprayed on top of the textured side of a bonded lamination of fabric 52 and elastomeric sheeting material 55 which is similar to the fabric 1 2 and bonded elastomeric sheeting 1 5. The upper surface of the mortar would be protected by trowelling a layer 57 of plain fabric or of the fabric and elastomeric sheeting lamination with the textured side down. The resulting assembly would then be lowered under water while the mortar remained in its plastic state.

While the present invention has been shown as applied to a lining for earth surfaces such as are used on the bottom of canals or ponds, it is possible that the bonding of mortar to a textured fabric over elastomeric substrates could be applied in other construction applications.

There is thus provided a lining which overcomes the problems of prior art linings and provides advantages heretofore not obtainable. The above described lining may be used for protecting earth surfaces and is suitable for use in applications such as canals, irrigation ditches, ponds and holding basins. The lining is relatively economical and has an outer protective covering of cementitious material, such as Portland cement mortar, to provide the outer surface of the lining with a material which is resistant to attack by chemicals or organic solvents and can be cleaned by mechanical equipment. The protective covering of cementitious material also provides substantial rigidity and strength to the lining so that it will not be damaged by animals or mechanical equipment, and the substantial weight of the lining prevents it from floating.

The lining is also provided with a sealing substrate so that it will remain impermeable to liquids despite accidental cracking of the cementitious material due to mechanical damage or subsidence of the earth beneath the lining. The lining has reinforcement which reduces the amount of cementitious material required, so that cost is reduced.

Claims (23)

1. A method for lining and protecting an earth surface intended for liquid holding which comprises the steps of providing a reinforcing layer of woven fabric having substantial tensile strength and having at least one side which is textured, bonding a sealing layer of liquid-impermeable material to the other side of the fabric, installing the fabric over the earth surface with the sealing layer adjacent the earth surface with the sealing layer adjacent the earth surface, and applying a layer of cementitious material to the textured side of the fabric to provide a tough protective covering.

2. A method as claimed in claim 1, wherein the layer of cementitious material is applied by providing a layer of Portland cement mortar on the textured side of the fabric.

3. A method as claimed in claim 1, wherein the cementitious material is sprayed onto the textured side of the fabric.

4. A method as claimed in any one of the preceding claims, comprising the additional step of interposing a layer of reinforcing mesh in the cementitious material while the cementitious material is being applied.

5. A method as claimed in any one of the preceding claims, wherein elastomeric sheeting is bonded to the fabric to provide the layer of liquid-impermeable material.

6. A method as claimed in any one of the preceding claims, wherein the fabric is provided with tufts projecting from the side of the fabric to which the cementitious material is applied.

7. A method as claimed in any one of the preceding claims, wherein the fabric is provided in the form of a frise type material.

8. A method as claimed in any one of the preceding claims, wherein the fabric is provided by providing a woven synthetic chemical-resistant material.

9. A method as claimed in any one of the preceding claims, wherein the fabric provided is made of nylon.

1 0. A method as claimed in any one of the preceding claims, comprising the additional steps of providing a second layer of woven fabric having at least one side which is textured, bonding the sealing layer of liquidimpermeable material to the other side of the second layer of fabric to form a laminated structure having two layers of fabric with liquid-impermeable material therebetween and the textured surfaces of the fabric layers facing outwardly, and applying a second layer of cementitious material to the earth surface before installing the fabric layers thereon.

11. A method as claimed in any one of the preceding claims, comprising the additional step of placing another layer of textile on the layer of cementitious material to protect the cementitious layer prior to installing the lining on the earth surface.

1 2. A composite lining for protecting an earth surface intended for liquid holding comprising a reinforcing layer of woven fabric having substantial tensile strength and having at least one side which is textured, a substrate layer of liquid-impermeable material bonded to the other side of the fabric, the substrate layer being adapted to be installed adjacent the earth surface, and a layer of cementitious material bonded to the textile on the textured side of the fabric.

1 3. A composite lining as claimed in claim 12, wherein the liquid-impermeable material is elastomeric sheeting.

14. A composite lining as claimed in either claim 1 2 or claim 13, wherein the cementitious material is Portland cement mortar.

1 5. A composite lining as claimed in any one of claims 1 2 to 14, wherein the fabric has tufts projecting from the side to which the cementitious material is applied.

1 6. A composite lining as claimed in any one of claims 1 2 to 15, wherein the fabric is a frise type material.

1 7. A composite lining as claimed in any one of claims 1 2 to 16, wherein the woven fabric is made of synthetic chemical-resistant material.

1 8. A composite lining as claimed in any one of claims 1 2 to 17, wherein the woven fabric is made of nylon.

1 9. A composite lining as claimed in any one of claims 12 to 1 8, comprising in addition a reinforcing mesh interposed in the cementitious material.

20. A composite lining as claimed in any one of claims 1 2 to 19, comprising in addition a second layer of woven fabric having at least one side which is textured, the second layer of fabric being bonded on the other side to the substrate layer to form a laminated structure having two layers of fabric with liquid-impermeable material therebetween and the textured sides of the fabric layers facing outwardly, and a second layer of cementitious material to be applied to the earth surface and bonded to the second layer of fabric on the textured side of the fabric.

21. A composite lining as claimed in any one of claims 1 2 to 20, comprising in addition another layer of fabric on top of the layer of cementitious material to protect the cementitious layer before the lining is installed.

22. A method of lining and protecting an earth surface substantially as herein described with reference to the accompanying drawings.

23. A composite lining for protecting an earth surface substantially as herein described with reference to the accompanying drawings.