FR3064358A1 - EQUIPMENT FOR SEAL AND EARTH ARTICLES COMPRISING A DRAINING GEOCOMPOSITE ASSOCIATED WITH A DEVICE FOR DETECTING LEAKS, INFILTRATION OR FLOW OF A FLUID - Google Patents

Abstract

The invention relates to equipment for sealed structures and earthworks (1) comprising: - a draining geocomposite (2) integrating drains (20) for collecting and draining water, the draining geocomposite being intended to be positioned in contact with a body to protect; - An organ collecting and evacuating (3) drainage water, the drains draining geocomposite being designed to pour into the collection and evacuation member; - A device for detecting leaks, infiltrations or flows of a fluid comprising a sensor array consisting of optical fibers (40) inserted inside the drains.

Description

Holder (s): AFITEX Simplified joint-stock company, NATIONAL INSTITUTE FOR RESEARCH IN SCIENCES AND TECHNOLOGIES FOR THE ENVIRONMENT AND AGRICULTURE Public establishment, CEMENTYS.

Extension request (s)

Agent (s): LEGI LC.

EQUIPMENT FOR SEALED WORKS AND EARTH WORKS COMPRISING A DRAINING GEOCOMPOSITE ASSOCIATED WITH A DEVICE FOR LEAK DETECTION, INFILTRATION OR FLOWS OF A FLUID.

FR 3 064 358 - A1

The invention relates to equipment for sealed structures and earthen structures (1) comprising:

- a draining geocomposite (2) integrating drains (20) intended to collect and drain water, the draining geocomposite being intended to be positioned in contact with a body to be protected;

- a collecting and evacuating member (3) of the drainage water, the draining geocomposite drains being designed to pour into the collecting and evacuating member;

- A device for detecting leaks, infiltrations or flows of a fluid comprising a network of sensors consisting of optical fibers (40) inserted inside the drains.

Equipment for sealed structures and earth structures comprising a draining geocomposite associated with a device for detecting leaks, infiltration or flow of a fluid.

The field of the invention is that of the design and manufacture of equipment for sealed structures and earthen structures.

More specifically, the invention relates to a technique making it possible to detect in real time the presence of a leak, of infiltration or of a flow of a fluid, such as water, in a sealed structure or in a earthen work.

A sealed structure is conventionally associated in essence with water retention basins or canals.

In sealed structures, waterproofing geomembranes are placed at the bottom of these structures so as to establish a seal, and thus to prevent water infiltration and degradation of the structure by soil erosion.

Also, a leak in the waterproofing geomembranes can cause degradation of the structure, and / or contaminate or pollute the soil.

In such works, the detection of leaks is however not easy by the very nature of the works. The prior art thus proposes various solutions making it possible to control the tightness of sealed structures.

According to a first approach, the tightness control devices are known which are implemented during a specific tightness control intervention.

There is thus known a system of the electric brush and a system of the dipole which each implement an electric mesh underlying the sealing geomembrane. These solutions require an intervention in which a tool generating a current and placed near the geomembrane and where, when there is a leak in the geomembrane, an electric arc is created between the tool and the electric mesh.

These techniques have a low cost of implementation but nevertheless require that the sealed structure be put out of operation when carrying out the tightness control. In addition, such techniques are only implemented when a leak in the geomembrane is presumed. Thus, these techniques do not make it possible to carry out a tightness control in real time.

According to a second approach, fixed type tightness control devices are known, which use sensors permanently installed under the waterproofing membrane and which make it possible to carry out a tightness control in real time.

Such a technique indeed makes it possible to check the seal after covering the geomembrane, even when the sealed structure is in operation, directly from an external control box.

This technique of waterproofing sensors has the drawback, however, of requiring a substantial and time-consuming intervention during the production of the waterproofed structure, prior to the break in the sealing geomembrane. Indeed, the different sensors must each be installed in different places under the geomembrane.

According to another drawback, such a technique is particularly expensive to implement.

Finally, the previous techniques all have the defect of not allowing a precise location of any water leaks presented by the sealed structure.

The invention aims to overcome the drawbacks of the prior art.

More specifically, the invention aims to propose a solution aimed at making it possible to control leaks, infiltrations or water flows in real time from a sealed structure or from an earth structure, which is more simple to implement than the sealed sensor technique described in the prior art.

The invention also aims to propose such a solution which is economical to implement.

The invention also aims to propose such a solution which makes it possible to obtain a precise location of leaks, infiltrations or water flows.

These objectives, as well as others which will appear subsequently, are achieved thanks to the invention which relates to equipment for sealed works and earthen works comprising:

- a draining geocomposite integrating drains intended to collect and drain water, the draining geocomposite being intended to be positioned in contact with a body to be protected;

- a body for collecting and evacuating drainage water, the drains of the draining geocomposite being designed to pour into the collecting and evacuating body;

- a device for detecting leaks, infiltrations or flow of a fluid comprising a network of sensors, characterized in that the network of sensors consists of optical fibers inserted inside the drains, and in that the device for detecting leaks, infiltrations or flow of a fluid comprises:

- means for emitting light pulses in the optical fibers;

- means for acquiring and analyzing pulses of light backscattered in the optical fibers, intended to detect temperature variations caused by the presence of a fluid along the optical fibers.

The equipment for sealed structure and earthen structure according to the invention makes it possible to have a technique for detecting leaks, infiltration or flow of a fluid, such as water, which operates in real time.

In fact, thanks to the network of sensors formed by the optical fibers inserted inside the drains, the presence of a leak, of infiltration or of a flow of a fluid is immediately detected by the detection device, without the need to put the sealed work or the earthwork out of operation. For example, if the structure is a basin, there is no need to empty it.

More specifically, in the context of a sealed structure, it has been found that the temperature of the soil underlying a geomembrane of the structure has a constant average temperature. When there is a water leak, this average temperature tends to vary depending on the water temperature of the structure. A temperature variation detected below the membrane is thus analyzed as corresponding to a water leak at the geomembrane.

The equipment according to the invention also has a lower cost than the waterproof sensor system presented by the prior art.

Indeed, due to the geocomposite design, the sensor network made up of optical fibers is installed directly during the installation of the draining geocomposite which is intended to be located in contact with the body to be protected.

In addition, thanks to the draining function of the draining geocomposite, as well as to the presence of the drains inside the geocomposite, a leak, an infiltration and / or a flow of water are directly drained towards the drains where they will be detected by optical fiber.

These drains, thanks to their resistance to large deformations, also make it possible to protect the optical fiber against mechanical attack, for example in the event of ground movement.

The fluid preferably corresponds to a liquid, in particular to water, but also, for example, to hydrocarbons. The fluid can also correspond to a gas or air. This fluid is detected in particular when it is in motion and when it causes a variation in temperature near the sensor network.

Advantageously, the draining geocomposite comprises two geotextile layers, the drains being located between the geotextile layers, the draining geocomposite having functions of water drainage and filtration of solid particles.

These functions are added to the intrinsic function of the geocomposite in terms of protecting the body to be protected, which may be located in contact with the geocomposite.

In the case where the equipment is used in a sealed structure with a sealing geomembrane, the draining geocomposite is intended to be located below the sealing geomembrane, this sealing geomembrane forming the body to be protected.

This draining geocomposite makes it possible to provide mechanical support to the sealing geomembrane, to protect it against irregularities in the soil on which the draining geocomposite is located, and to avoid the creation of pockets following soil erosion.

Preferably, the geotextile sheets are each formed by needling from a non-woven material.

Such geotextile layers are particularly advantageous for producing the draining geocomposite.

Even more preferably, the geotextile sheets are formed from plastic fibers.

These plastic fibers can for example be made of polypropylene or PET (poly (ethylene terephthalate)).

The geotextile thus formed is particularly suitable for draining runoff water, filtering solid particles and protecting a geomembrane located above.

According to an advantageous characteristic, the geotextile sheets are needled together.

Thanks to the needling of the geotextile sheets together, the drains are held in position between the two sheets.

According to a preferred embodiment, the drains are formed from tubular sheaths having perforations permeable to fluids.

Such drains make it possible to ensure that the optical fibers will only be in contact with drainage water during a leak.

Advantageously, the perforations are regularly distributed along the tubular sheaths.

Preferably, the sheaths are corrugated and have a regular succession of grooves, and the perforations are located inside the grooves. The perforations are notably carried out according to the following repetition:

- first diametrically opposite in a first groove along a first axis;

- then along a second axis perpendicular to the first axis in the next groove.

According to a preferred characteristic, the tubular sheaths are made of chemically inert plastic.

According to this characteristic, the drains are then particularly resistant to hydrocarbons and to all chemical and thermal stresses.

According to a preferred solution, the geocomposite is in the form of rectangular strips, each strip comprising at least one drain, the drain or drains extending parallel to the length of the strip.

The rectangular strips can be wrapped around mandrels during their production. In this way, the installation of the geocomposite is particularly easy, the installers then having only to unroll the geocomposite on the body to be protected from the sealed structure or from the earth structure.

According to a preferred characteristic, the strips comprise one or more drains regularly spaced in width.

According to this characteristic, the device for detecting the equipment according to the invention can be adapted to have a particularly precise detection of leaks, flows or infiltration of water while allowing effective drainage of this water.

Preferably, the acquisition and analysis means are designed to use Raman backscattering.

Thanks to Raman backscattering, the measurement made is dependent only on the temperature near the optical fiber.

According to a preferred embodiment of the invention, the acquisition and analysis means are designed to:

- measure the time elapsed between the light pulse in the fiber and the backscattered light pulse, the elapsed time corresponding to a long localization datum of the optical fiber;

- measure the amplitude of a Raman peak of a backscattered light spectrum, the amplitude measured corresponding to a variation or not of temperature.

Preferably, the acquisition and analysis means are designed to measure the amplitude of a Rayleigh peak of a backscattered light spectrum, the amplitude measured corresponding to an acoustic emission, the optical fibers being intended to detect vibrations. resulting from leakage, infiltration or flow of a fluid.

According to an advantageous solution, the device for detecting leaks, infiltrations or flows of a fluid comprises means for depressurizing or injecting air into the drains.

These means of vacuum or air injection improve the accuracy of detection by the detection device.

In fact, for example when a sealed basin type structure is in operation, the temperature of the soil may be at the same temperature as that of water. In the event of a water leak, the temperature variation recorded by the detection device may be extremely small.

The injection of air into the drains then makes it possible to disturb the system to increase the discriminating aspect of the measurement by increasing the thermal gradient.

Similarly, a seal defect is highlighted following a vacuum created in a drain using vacuum or air injection means.

Preferably, the means for placing under vacuum or for injecting air are configured to inject air at a temperature different from that of the water in the sealed structure.

Thanks to air injection, the presence of water following a leak is more easily detected due to the more marked temperature variations between the sections of optical fibers which are in contact with water and those which are not in contact with water.

According to another advantageous solution, the device for detecting leaks, infiltrations or flows of a fluid comprises means for injecting water into the drains.

These water injection means can be used as part of an operation to simulate a water leak. In this way, the detection capacity of the device for detecting leaks, infiltrations or flows of a fluid can be tested and / or calibrated.

The water injection means can also make it possible to detect clogging of the draining geocomposite (calcification, biofilms, etc.).

Indeed, by putting a drain under water pressure, the excess water must normally spread quickly to the adjacent drains. In the event of clogging, the excess water fails or takes longer to reach the adjacent drains.

Consequently, when a drain is pressurized with water, the detection device makes it possible to determine whether the draining geocomposite is clogged.

For pressurizing a drain, pneumatic plugs can be inserted inside the drains to circumscribe a section of the drain in which the overpressure of water is created.

Other characteristics and advantages of the invention will appear more clearly on reading the following description of preferred embodiments of the invention, given by way of illustrative and nonlimiting examples, and of the appended drawings among which:

- Figure 1a is a schematic representation according to a top view of a water retention basin provided with the equipment according to the invention;

- Figure 1b is a schematic representation according to a top view of a channel provided with the equipment according to the invention;

- Figure 2 is a schematic illustration of the draining geocomposite incorporating drains into which optical fibers are inserted;

- Figure 3 is a schematic representation of a section of a sealed structure with the draining geocomposite and the organ for collecting and discharging drainage water;

- Figure 4 is a schematic representation of the installation and connections of the geocomposite at the edge of a structure;

- Figures 5a and 5b are representations of a draining geocomposite strip;

- Figure 6 is a schematic representation of the establishment of several strips of draining geocomposite;

- Figure 7 is a schematic representation of a drain and the optical fiber inserted inside the drain.

With reference to FIGS. 1a and 1b, the equipment according to the invention is designed for sealed structures and various earth structures 1. As illustrated in Figure 1a, the equipment can be installed in a water retention basin (sealed structure) or, as illustrated in Figure 1b, the equipment can be installed in a channel (sealed structure) ). According to an embodiment not illustrated, the equipment can be installed in a dike (earthen structure) or on any other type of sealed or earthen structure having a body to be protected from leaks, infiltrations or spills of water. 'a fluid, such as water.

In a manner known per se, the equipment according to the invention comprises a draining geocomposite. This draining geocomposite is intended to be located in contact with a body to be protected.

According to Figures 1a and 1b, in the context of a sealed structure, a sealing geomembrane forms the body to be protected. In this case, the draining geocomposite 2 is intended to be positioned directly on the ground of the structure, and to be covered by a sealing geomembrane (geomembrane not shown).

Referring to Figure 2, this draining geocomposite 2 incorporates drains 20 which are intended to capture and drain runoff water.

As illustrated in FIGS. 1a and 1b, the equipment according to the invention also comprises a member 3 for collecting and discharging drainage water. This collection and evacuation member 3 is positioned at the bottom of the slopes formed by the floor of the structure (slopes represented by the arrows F in FIGS. 1a and 1b).

The drains 20 of the draining composite are designed to pour into the collecting and evacuating member.

As illustrated in Figure 3 and as mentioned above, the draining geocomposite 2 is positioned as a function of the slopes of the structure. Indeed, the drains extend in the geocomposite by being aligned with the direction of the slope, to the lowest point of the structure where the organ for collecting and discharging drainage water 3 is located. In this case, the collection and evacuation member 3 corresponds to a trench integrating a main drainage tube covered with particles (generally aggregates).

The equipment according to the invention also comprises a device for detecting leaks, infiltrations or flows of a fluid. This fluid preferably corresponds generically to liquids, in particular to water, but also to hydrocarbons. The fluid can also correspond to gases or even to air.

This device for detecting leaks, infiltrations or flows of a fluid comprises a network of sensors 4 (network partially shown in FIGS. 1 a and 1 b).

According to the principle of the invention and with reference to FIG. 2, the sensor network consists of optical fibers 40 which are inserted inside the drains 20 of the draining geocomposite 2.

With reference to FIGS. 1a and 1b, the device for detecting leaks, infiltrations or flows of a fluid comprises a housing 5 which integrates means for emitting light pulses 50 into the optical fibers, and means of acquisition and analysis 51 of pulses of light backscattered in the optical fibers. The acquisition and analysis means are intended to detect temperature variations caused by the presence of a fluid, for example water, along the optical fibers.

For this, the means of acquisition and analysis are designed to use Raman scattering. This temporal reflectometry technology allows, by sending a very short pulse of light (about 10 nanoseconds) into the optical fiber, to have a return by backscattering of the light at all times along the fiber.

More specifically, the acquisition and analysis means are designed to measure the time elapsed between the light pulse emitted in the fiber and the backscattered light pulse. The time between the light pulse in the fiber and the backscattered light pulse corresponds to a location datum along the optical fiber. Indeed, knowing the speed of light in a fiber, by timing the return of the pulse, the acquisition and analysis means make it possible to determine the origin of the backscattered light pulse.

The means of acquisition and analysis also measure the amplitude of the Raman peak of the spectrum of backscattered light. This amplitude measured corresponds to a variation or not of temperature.

Raman backscatter is a phenomenon of inelastic interaction between light and silica. The detection of the temperature variation by Raman effect makes it possible to locate the areas of the structure where there is water, by observing the temperature variations over time.

Indeed, during a leak, the presence of water increases or decreases the average temperature of the soil.

The means of acquisition and analysis are programmed with a detection algorithm which makes it possible to interpret the variations in temperature in the soil.

As previously explained, this technology allows backlight scattering of the light along the fiber at all times.

The backscattered pulse then presents a particular light spectrum which can be analyzed by the device.

With reference to FIGS. 1 a and 1 b, it is thus understood that, in the presence of a water leak, the water flowing through a defect in the sealing geomembrane is distributed over a surface of the geocomposite until reaching a drain into which it pours. The water from the leak is thus captured and drained by the drains 20 of the draining geocomposite. As a result, the presence of optical fiber inside the drains will make it possible to immediately and precisely detect the position of the water leak thanks to the detection device.

The acquisition and analysis means 51 are also designed to measure the amplitude of a Rayleigh peak of a spectrum of backscattered light. The amplitude of the Rayleigh peak measured corresponds to an acoustic emission. The optical fibers can then detect vibrations resulting from leaks, infiltrations or flow of a fluid close to these optical fibers.

Referring to Figure 4, the draining geocomposite 2 is anchored at the top of the slopes of the structure. The draining geocomposite is inserted inside a trench 60 and then is covered with a ballast material 600, thus making it possible to anchor. At the end of the draining geocomposite which extends beyond the trench, the optical fibers are connected to the housing 5 of the detection device. As can be seen, a protection system 70 is positioned above the end of the draining geocomposite 2.

As mentioned above and with reference to FIG. 2, the drains 20 are inserted into the draining geocomposite 2. This draining geocomposite more precisely comprises two layers of geotextile, the drains being located between the layers of geotextile.

This draining geocomposite has functions of water drainage, filtration of solid particles, and protection of a body to be protected, for example to protect a sealing geomembrane which may be located above the geocomposite draining.

The geotextile layers are in particular formed by needling from a nonwoven material. This nonwoven material is more precisely made up of short plastic fibers, and in particular polypropylene and / or PET fibers.

Thus, according to the present embodiment, the draining geocomposite 2 comprises two layers of geotextile which are more precisely:

- A needle-punched nonwoven upper ply 21 composed of plastic fibers;

- A needled nonwoven filtering lower sheet 22 also composed of plastic fibers.

The two geotextile layers are themselves needled together. In this way the drains are kept in position inside the draining geocomposite.

As illustrated in Figures 5a and 5b, the draining geocomposite 2 is in the form of rectangular strips. These rectangular strips can be wound around mandrels 8 during their manufacture in the factory.

Each strip has drains that extend parallel to the length of the strip. With reference to FIG. 5a, it can be seen that the draining geocomposite strip 2 comprises four optical fibers (F1, F2, F3 and F4) inserted inside drains 20.

Preferably, the strips essentially comprise a drain every meter in width. As an indication, the strips measure 3.90 m in width and include four drains provided with optical fiber.

During their manufacture in the factory, the optical fibers 20 are connected to each other at the end of the strips. More specifically, primary connections 90 make it possible to connect the fibers together so that they extend and that they no longer form a single optical fiber. Thanks to this connection, a primary network of optical fibers is formed.

Advantageously, the primary connections are made in the factory, thus avoiding additional interventions on the site of realization of the structure. Protective sheaths 900 (visible in FIG. 5b) are coupled to the end of the strips overlapping the primary connections. These protective sheaths are thermally retractable and can be armed.

Referring to Figure 6, we observe three strips placed next to each other during installation of the geocomposite on the site of a structure. During this on-site installation step, the primary fiber optic networks of the strips are connected together, using secondary connections 91, so that they form a more extensive network.

With reference to FIG. 7, the optical fibers 40 consist of a fiber 400 and a sheath 401.

The optical fiber 40 is inserted inside a drain 20, this drain being in particular formed from a tubular sheath which has perforations permeable to fluids. The perforations are regularly distributed along the tubular sheaths.

Of course, the drains have a sufficient diameter to accommodate the optical fibers and to be able to let drained water circulate.

As an indication, the drains are made of polypropylene (chemically inert plastic). These drains can advantageously have corrugations so that they can more easily be held in place in the draining geocomposite.

According to the preferred embodiment illustrated in FIG. 3, the device for detecting leaks, infiltrations or flows of a fluid comprises:

- means for placing under vacuum or injecting air 71 into the drains 20;

- means 72 for injecting water into the drains.

The means for depressurizing or injecting air 71 comprise a compressor 710 and suction or air injection nozzles 711 coupled to the ends of the drains 20 located next to the sealed structure work and earth 1.

The compressor is designed to vacuum a drain, or to inject air into a drain.

For air injection, the compressor is configured to inject air at a temperature different from that of the water in the structure. The injected air preferably comes from a capture point next to the sealed structure and earthen structure. In fact, the injection of air into the drains at a temperature different from that of the ground makes it possible to increase the temperature difference measured by the detection device in the event of water leakage.

The water injection means 72, for their part, include one or more water injection pipes 721 inserted inside the drains, next to the optical fibers. Of course, these water injection pipes have a diameter adapted to that of the drains so as not to block the drains due to the presence of the optical fiber and the water injection pipe.

As illustrated in FIG. 3, each water injection pipe 721 is inserted up to a predefined length inside a drain 20 so as to be able to precisely determine the location of a leak of simulated water 722 using said injection pipe.

These water injection means can also be used to determine clogging or fouling (fine particles, calcification, biofilms, ...) of the draining geocomposite. According to an example of implementation of this determination, a section of the drain into which water is injected can be isolated by means of inflatable obturators. The adjacent drains are then supposed to collect and drain the water from the blocked drain.

In the event that the draining geocomposite is not clogged, the water diffuses quickly and the detection device will quickly detect the presence of water in the adjacent drains thanks to the inherent temperature variation.

On the contrary, in the case where the draining geocomposite is clogged, the diffusion of water through the geocomposite is difficult and there will then be a significant period of time between the injection of water into the drain and the detection of a temperature variation in adjacent drains.

Claims (2)

Equipment for watertight work and earthen work (1) comprising: - a draining geocomposite (2) integrating drains (20) intended to collect and drain water, the draining geocomposite being intended to be positioned in contact with a body to be protected; - an organ for collecting and evacuating (3) the drainage water, the drains of the draining geocomposite being designed to pour into the organ for collecting and evacuating; - a device for detecting leaks, infiltrations or flow of a fluid comprising a network of sensors (4), characterized in that the network of sensors consists of optical fibers (40) inserted inside the drains, and in that the device for detecting leaks, infiltrations or flow of a fluid comprises: - means for emitting light pulses (50) in the optical fibers; - Acquisition and analysis means (51) of pulses of light backscattered in the optical fibers, intended to detect temperature variations caused by the presence of a fluid along the optical fibers. Equipment according to claim 1, characterized in that the draining geocomposite (2) comprises two geotextile sheets (21,22), the drains (20) being located between the geotextile sheets, the draining geocomposite having drainage functions of the and filtration of solid particles. Equipment according to the preceding claim, characterized in that the geotextile sheets (21, 22) are each formed by needling from a non-woven material. 4. Equipment according to the preceding claim, characterized in that the geotextile sheets (21,22) are needled together. 5. Equipment according to any one of the preceding claims, characterized in that the drains (20) are formed from tubular sheaths having perforations permeable to fluids. 6. Equipment according to any one of the preceding claims, characterized in that the draining geocomposite (2) is in the form of rectangular strips, each strip comprising at least one drain (20), the drain or drains extending parallel to the length of the strip. 7. Equipment according to the preceding claim, characterized in that the strips comprise one or more drains (20) regularly spaced in width. 8. Equipment according to any one of the preceding claims, characterized in that the acquisition and analysis means (51) are designed to use Raman backscattering. 9. Equipment according to the preceding claim, characterized in that the acquisition and analysis means (51) are designed for: - measure the time elapsed between the light pulse in the fiber and the backscattered light pulse, the elapsed time corresponding to a long localization datum of the optical fiber; - measure the amplitude of a Raman peak of a backscattered light spectrum, the amplitude measured corresponding to a variation or not of temperature. 10. Equipment according to any one of the preceding claims, characterized in that the acquisition and analysis means (51) are designed to measure the amplitude of a Rayleigh peak of a backscattered light spectrum, the measured amplitude corresponding to an acoustic emission, the optical fibers being intended to detect vibrations resulting from leaks, infiltrations or flow of a fluid. 11. Equipment according to any one of the preceding claims, characterized in that the device for detecting leaks, infiltrations or flow of a fluid comprises means for placing under vacuum or injecting air (71 ) in the drains (20). 12. Equipment according to any one of the preceding claims, characterized in that the device for detecting leaks, infiltrations or flow of a fluid comprises means for injecting water (72) into the drains ( 20). 2/4