(19)
(11)EP 3 102 937 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
20.05.2020 Bulletin 2020/21

(21)Application number: 15710836.6

(22)Date of filing:  05.02.2015
(51)International Patent Classification (IPC): 
G01N 33/38(2006.01)
E21B 47/00(2012.01)
G01N 21/43(2006.01)
E21B 33/14(2006.01)
E21B 47/12(2012.01)
(86)International application number:
PCT/GB2015/050321
(87)International publication number:
WO 2015/118333 (13.08.2015 Gazette  2015/32)

(54)

METHOD OF MONITORING SUBSURFACE CONCRETE STRUCTURES

VERFAHREN ZUR ÜBERWACHUNG VON UNTERIRDISCHEN BETONSTRUKTUREN

PROCÉDÉ DE SURVEILLANCE DE STRUCTURES SOUTERRAINES EN BÉTON


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 05.02.2014 GB 201401921
21.02.2014 GB 201403124

(43)Date of publication of application:
14.12.2016 Bulletin 2016/50

(73)Proprietors:
  • Cementation Skanska Limited
    Maple Cross Rickmansworth Hertfordshire WD3 9SW (GB)
  • Cambridge Enterprise Limited
    Cambridge CB2 1TN (GB)
  • Ove Arup & Partners International Limited
    London W1T 4BQ (GB)

(72)Inventors:
  • BELL, Andrew
    Doncaster South Yorkshire DN5 9NB (GB)
  • OUYANG, Yue
    Doncaster South Yorkshire DN5 9NB (GB)
  • SOGA, Kenichi
    Department of Engineering (GB)
  • NICHOLSON, Duncan
    13 Fitzroy Street (GB)

(74)Representative: McGeough, Gemma Ann 
Withers & Rogers LLP 4 More London Riverside
London SE1 2 AU
London SE1 2 AU (GB)


(56)References cited: : 
EP-A1- 2 466 063
US-A1- 2012 205 103
  
  • SELLOUNTOU E-A ET AL: "Thermal Integrity Profiling: A Recent Technological Advancement in Integrity Evaluation of Concrete Piles", PROCEEDINGS FROM THE FIRST INTERNATIONAL CONFERENCE, SEMINAR ON DEEP FOUNDATIONS; SANTA CRUZ , BOLIVIA; APRIL 23-26, 2013, , 23 April 2013 (2013-04-23), pages 1-20, XP002743515, Retrieved from the Internet: URL:http://www.pile.com/reference/SeminarO nDeepFoundations2013/ThermalIntegrityProfi ling.pdf
  • Yong Wang: "Monitoring of concrete curing process with embedded fiber Bragg gratings", Proceedings of SPIE, vol. 4204, 1 January 2001 (2001-01-01), pages 23-30, XP055005138, ISSN: 0277-786X, DOI: 10.1117/12.417409
  • Gray Mullins ET AL: "Thermal Integrity Profiling: An Innovative Technique for Drilled Shafts Special Issue: Innovation", DEEP FOUNDATIONS May/June 2012, 2 May 2012 (2012-05-02), pages 51-54, XP055388918, Retrieved from the Internet: URL:http://www.grlengineers.com/wp-content /uploads/2012/05/DFI_MAY_JUN2012_pg51-54.p df [retrieved on 2017-07-07]
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description


[0001] The present invention relates to a method of monitoring subsurface concrete structures, in particular a method of monitoring subsurface concrete structures during hydration of the concrete.

[0002] There is a need to minimise failures within the built environment. In recent years, this has been driven not only by safety considerations, but also by a need to optimise the use of limited natural resources.

[0003] As such, it is necessary to monitor built structures, in order to identify potential failures. A problem arises when the built structure is inaccessible, e.g. if the structure is at a subsurface location.

[0004] Subsurface concrete structures are generally made by pouring fresh concrete into a cavity (such as an underground borehole, or a shuttered structure to contain the concrete). They require non-visual assessment after curing to ensure that the poured concrete is present in the designed quantity at all points in the structure and that there are no voids, bulges or significant anomalies in the concrete.

[0005] In some cases, strain gauges are used to facilitate non-visual assessment of subsurface structures after curing. The non-visual assessment of subsurface structures after curing may also be done using a technique known as cross-hole sonic logging.

[0006] However, in the case of subsurface structures made from concrete poured in situ, a potential failure may arise during the construction of the structure. There is therefore a need to identify potential failures as early as possible, particularly in those subsurface structures that are used to support or retain other structures, such as concrete piles or diaphragm walls.

[0007] US 2012/0205103 discloses cement slurry monitoring methods including monitoring one or more parameters of the cement slurry at various positions along a borehole during the curing process.

[0008] According to a first aspect of the invention, there is provided a method in accordance with independent claim 1, of monitoring a subsurface concrete structure, the method comprising the steps of:
providing a reinforcement cage (20) or framework assembly for a subsurface concrete structure; providing a fibre optic array (48) in association with said reinforcement cage (20) or framework assembly, the fibre optic array comprising at least one fibre optic cable sensor, wherein the fibre optic cable sensor comprises a fibre optic cable which acts as a sensing element; providing an interrogator (50) connected to the fibre optic array; installing said reinforcement cage (20) or framework assembly at a desired subsurface location (30); applying concrete medium to surround the reinforcement cage or framework assembly and the at least one fibre optic cable sensor (48) at said subsurface location (30); using said at least one fibre optic cable sensor (48) immediately or shortly after the application of concrete medium to directly sense temperature data along a length of the at least one fibre optic cable sensor during hydration of the subsurface concrete structure; using said interrogator (50) to collect said temperature data during hydration of the subsurface concrete structure; and analysing said temperature data to determine a characteristic of the subsurface concrete structure, wherein the at least one fibre optic cable sensor is folded or doubled upon itself so as to leave an opening between its parts, thereby forming an open loop arrangement having a first section (40) and a second section (42) which are spaced apart from one another and extending along a length of the reinforcement cage or framework assembly.

[0009] The term 'subsurface concrete structure' is intended to mean a concrete structure having at least a significant part of the structure located below ground level, e.g. in a borehole or cavity.

[0010] The invention allows for real time temperature monitoring of the structure during hydration of the concrete, thereby providing a mechanism for identifying potential anomalies and defects (e.g. due to the presence of voids, fissures or non-homogeneous concentrations within the structure) during formation and before the structure is completed.

[0011] It is highly desirable to ensure that a uniform concrete structure has been formed and that there are no anomalies which will render the structure to be weak. Concrete defects could be present due to a congested reinforcement, which is difficult to detect. By means of the method of in accordance with the invention, heat generation and dissipation within the concrete during the curing process may be observed, as a result, potential failures can be detected early.

[0012] In addition, the method in accordance with the invention means that the structure can be instrumented ahead of construction, thus minimising the presence of operators during the placement of the framework or reinforcement assembly and pouring of the concrete medium.

[0013] The collecting/gathering of temperature data may be performed on site or remotely. The remote gathering of data is advantageous as it reduces human capital requirements on site.

[0014] The fibre optic array comprising at least one fibre optic cable sensor is used to collect distributed temperature data, and said distributed temperature data is analysed to determine the integrity of the subsurface concrete structure.

[0015] In accordance with the invention an interrogator is connected to the fibre optic array comprising at least one fibre optic cable sensor, for collecting the temperature data during hydration of the subsurface concrete structure. This facilitates the assessment of the temperature data.

[0016] The interrogator may also be set up for automatic data collection.

[0017] Preferably, the temperature is monitored in real time during hydration of the subsurface concrete structure. Due to the fact that a much more information-rich temperature data set is produced, it enables the assessment of the overall structure thermal condition throughout the curing process, along with clear identification of regions in the structure not exhibiting heat flow - that may be indicative of anomalies within the concrete structure.

[0018] In exemplary embodiments, the fibre optic array comprising at least one fibre optic cable sensor comprises a plurality of fibre optic cable sensors.

[0019] In embodiments comprising a plurality of fibre optic cable sensors, preferably each fibre optic cable sensor extends to a known depth within the reinforcement cage of the subsurface structure.

[0020] In accordance with the present invention the fibre optic array comprises at least one fibre optic cable sensor in an open loop arrangement having a first section and a second section spaced apart from one another and extending along a length of the reinforcement cage or framework assembly.

[0021] The first section of said at least one fibre optic cable sensor may be arranged on one side of the reinforcement cage and the second section of said at least one fibre optic cable sensor may be arranged on an opposing side of the reinforcement cage.

[0022] In exemplary embodiments, a first fibre optic cable sensor is arranged to extend in an open loop along a central axis of the reinforcement cage.

[0023] In exemplary embodiments, one or more additional fibre optic cable sensors may be arranged to each define a single or a plurality of open loops at a peripheral location of the reinforcement cage.

[0024] The or each fibre optic cable sensor may be attached to the reinforcement cage prior to location of the reinforcement cage at said subsurface location.

[0025] The or each fibre optic cable sensor may be a single mode fibre optic sensor or a multimode fibre optic sensor.

[0026] The installation of the components for monitoring the integrity of the concrete structure using a method in accordance with the invention is efficient and safe, which are important factors on an active construction site.

[0027] Other aspects and features of the invention will be apparent from the following description, made by way of example, with reference to the following drawings, in which:

FIG.1 is a schematic diagram showing one stage of installation of a subsurface concrete structure;

FIG.2 is a schematic diagram showing a further stage of installation of a subsurface concrete structure;

FIG.3 is a schematic diagram showing an example of the dynamic temperature data sensed and collected by the optical fibre array during hydration of the subsurface concrete structure;

FIG.4 is a schematic diagram showing an exemplary arrangement of an optical fibre array positioned on a reinforcement assembly in a borehole; and

FIG.5 is a cross-sectional view of the borehole along AA' in FIG. 4.



[0028] Referring firstly to Figure 1, a crane or other suitable lifting device 10 is shown lowering a reinforcement or framework assembly 20 into a borehole or cavity 30 in the ground, for the purpose of creating a subsurface concrete structure.

[0029] Once the assembly 20 has been positioned at the desired location, concrete (not shown) is applied to fill the borehole or cavity 30, thereby surrounding the assembly 20.

[0030] As will be understood, the concrete will undergo a period of hydration, during which the concrete will harden to create a subsurface concrete structure having integral reinforcement or framework.

[0031] The reinforcement or framework assembly 20 (hereinafter referred to as 'the assembly') is configured to define a substructure of the subsurface concrete structure to be created. As such, the assembly 20 will typically be constructed as a cage or frame, using metal bar or the like. According to a preferred method of the invention, the assembly 20 is constructed above ground (e.g. on site or at a location remote from the intended installation location).

[0032] In exemplary embodiments, the assembly 20 is configured for creating a concrete pile or panel of a diaphragm wall, for example.

[0033] In general terms, a fibre optic array is used to directly sense and collect temperature data during hydration of the subsurface concrete structure. That is to say, the fibre optic array functions as a temperature sensor array. This is different to known prior art monitoring systems wherein a plurality of discrete sensors are individually positioned at set subsurface locations within the poured concrete.

[0034] In the example of Figure 1, a fibre optic cable sensor 48 is provided in association with the assembly 20. The term "fibre optic cable sensor" is used to indicate a fibre optic cable in which the optical fibre acts as a sensing element. The fibre optic cable sensor 48 is arranged in an open loop (i.e. folded/turned or doubled upon itself so as to leave an opening between its parts) having two sections (a first section and a second section) 40, 42 which are spaced apart from one another, with the first section 40 of the fibre optic cable sensor 48 extending down one side of the assembly 20 and the second section 42 of the fibre optic cable sensor 48 extending up from the opposing side of the assembly 20. A third section 46 of the fibre optic cable sensor 48 connecting the first and second sections extends across an underside of the assembly 20. The fibre optic cable sensor 48 is attached to the assembly 20 (e.g. using an adhesive, clamps, twisted wire, clips or ties or the like), prior to location at said subsurface location. For example, the fibre optic cable sensor is attached above ground, during or after construction of the assembly 20.

[0035] In the illustrated example of Figure 1, rollers 44 are used to guide the fibre optic cable sensor 48 during the lowering of the assembly 20 into the borehole or cavity 30. It would be understood that where rollers 44 are used, the first and second sections 40, 42 of the fibre optic cable sensor 48 are attached to the respective side of the assembly 20 as it is being lowered into the cavity 30.

[0036] The fibre optic cable sensor 48 may be a conventional single mode optical fibre sensor e.g. of a kind known in the art or a multimode optical fibre sensor.

[0037] As can be seen in Figure 2, an interrogator 50 is connected to each section 40, 42 of the fibre optic cable sensor 48, preferably before the assembly 20 is immersed in concrete. The fibre optic cable sensor 48 also functions as a communication link to the interrogator 50. The interrogator 50 is configured to collect the measured temperature data from the first and second sections 40, 42 of the fibre optic cable sensor 48 during hydration of the subsurface concrete structure.

[0038] In exemplary embodiments, the collected temperature data is used for determining one or more characteristics of the subsurface concrete structure. More particularly, the data is monitored to determine the integrity of the subsurface concrete structure, thus identifying potential anomalies within the subsurface concrete structure. For example, during hydration, a pattern of changes in the spatially distributed temperature may be anticipated along the structure, and if the collected data varies significantly from the anticipated pattern, this will indicate an anomaly within the structure (e.g. a void, fissure or non-homogeneous concentration of material). The spatially distributed temperature data can then be interrogated to identify the location of the anomaly.

[0039] In exemplary methods of the invention, a single fibre optic cable sensor is used to collect the temperature data. In the embodiment of Figure 2, the first and second sections 40, 42 of the fibre optic cable sensor 48 are used for detecting undesired temperature differentials across the hydrating structure (e.g. by comparing the temperature at one side with the temperature at the other side, for any given depth below ground level). In other embodiments, any number of fibre optic cable sensors could be used.

[0040] In exemplary methods of the invention, a first fibre optic cable sensor may be arranged to extend in an open loop along a central axis of the assembly 20, and one or more additional fibre optic cable sensors may be arranged to each define a single or a plurality of open loops at peripheral locations of the assembly 20 (e.g. spaced circumferentially with respect to the periphery of the structure).

[0041] With particular reference to Figure 3, an exemplary method of directly sensing and collecting temperature data during hydration of the subsurface concrete structure will be described.

[0042] As mentioned above, the concrete will undergo a period of hydration, during which the concrete will harden to create a subsurface concrete structure having integral reinforcement or framework.

[0043] At the start of the hydration period and throughout the hydration period, a light signal 60 is transmitted down the fibre optic cable sensor 48.

[0044] As the light signal 60 is transmitted down the fibre optic cable sensor 48, temperature data in the form of back-scatter signals 70 are collected by the interrogator 50 along the length of the fibre optic cable sensor 48. In exemplary methods, the light signal 60 is in the form of a laser signal.

[0045] The collected back-scatter signals 70 are reconstructed into visual form, for example in the form of a graph as shown in Figure 3, in order to determine one or more characteristics of the subsurface concrete structure.

[0046] The temperature data is averaged over a prescribed length and sampled at a prescribed rate. For example, the temperature data may be averaged over a length of 0.5m every 0.05m along the length of the fibre optic cable sensor 48. This provides a distributed measurement of the temperature data by the fibre optic cable sensor 48 across the length of the hydrating concrete, rather than discrete spaced apart measurements at different positions in the hydrating concrete as currently obtained by methods known in the art. Accordingly, the risk of bypassing or not identifying a location of potential failure, as may be the case in the prior art methods if the location occurs between two discrete sensors positions, is significantly reduced.

[0047] A region 80 with poor heat flow, which is indicative of an anomaly, will be indicated by a change in the spatially distributed temperature profile.

[0048] In exemplary embodiments, the temperature data is monitored in real time during hydration of the subsurface concrete structure. The real time monitoring of temperature data for the structure during hydration of the concrete, thereby provides a mechanism for identifying potential failures (e.g. due to the presence of voids, fissures or non-homogeneous concentrations within the structure) before the structure is completed.

[0049] Although described with reference to concrete piles and diaphragm walls, the method is also applicable to other subsurface concrete structures, such as raft foundations etc.

[0050] While the fibre optic cable sensor is shown in Figure 2 as having a single open loop, it would be understood that the sensor may be arranged to define a plurality of open loops with each open loop having a downward extending section and an upward extending section. An example, of such an arrangement is shown in Figures 4 and 5.

[0051] In the embodiment shown in Figures 4 and 5, the fibre optic cable sensor 148 is arranged to define two open loops. The first loop is defined by a first section 140 of the fibre optic cable sensor 148 extending down one side of the assembly 20, a second section 142 of the fibre optic cable sensor 148 extending up from a diametrically opposite side of the assembly 20, and a third section 146 of the fibre optic cable sensor 148 connecting the first and second sections 140, 142. In the embodiment shown, the third section 146 extends along an outer perimeter of the assembly (see Figure 5), although it would be understood that it may extend across an underside of the assembly 20 as in the previously described embodiment.

[0052] The second loop is defined by a fourth section 141 of the fibre optic cable sensor 148 extending down a third side of the assembly 20, a fifth section 143 of the fibre optic cable sensor 148 extending up from a fourth side of the reinforcement assembly 20 diametrically opposite the third side, and a sixth section 147 of the fibre optic cable sensor 148 connecting the fourth and fifth sections 141, 143. A seventh section 149 of the fibre optic cable sensor 148 connects the second section 142 to the fourth section 141.

[0053] The number of loops and hence the number of sections of the fibre optic cable extending along the sides of the assembly and their relative spacing is decided by the desired spatial resolution of temperature measurement. The temporal and spatial temperature profile evaluated from the fibre optic cable sensor readings will be used for data interpretation.

[0054] For example, for a circular cross-sectional concrete column of diameter 0.6m, and perimeter 3.77m, having four vertical fibre optic cable sections along its length would allow a peripheral spatial resolution of less than 1m.

[0055] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.


Claims

1. A method of monitoring a subsurface concrete structure, the method comprising the steps of:

providing a reinforcement cage (20) or framework assembly for a subsurface concrete structure;

providing a fibre optic array (48) in association with said reinforcement cage (20) or framework assembly, the fibre optic array comprising at least one fibre optic cable sensor, wherein the fibre optic cable sensor comprises a fibre optic cable which acts as a sensing element;

providing an interrogator (50) connected to the fibre optic array;

installing said reinforcement cage (20) or framework assembly at a desired subsurface location (30);

applying concrete medium to surround the reinforcement cage or framework assembly and the at least one fibre optic cable sensor (48) at said subsurface location (30);

using said at least one fibre optic cable sensor (48) immediately or shortly after the application of concrete medium to directly sense temperature data along a length of the at least one fibre optic cable sensor during hydration of the subsurface concrete structure;

using said interrogator (50) to collect said temperature data during hydration of the subsurface concrete structure; and

analysing said temperature data to determine a characteristic of the subsurface concrete structure,

wherein the at least one fibre optic cable sensor is folded or doubled upon itself so as to leave an opening between its parts, thereby forming an open loop arrangement having a first section (40) and a second section (42) which are spaced apart from one another and extending along a length of the reinforcement cage or framework assembly.


 
2. A method according to claim 1, wherein the temperature data is monitored in real time during hydration of the subsurface concrete structure.
 
3. A method according to any preceding claim, wherein the fibre optic array (48) comprises a plurality of fibre optic cable sensors (48).
 
4. A method according to claim 3, wherein each fibre optic cable sensor (48) extends to a known depth within the reinforcement cage (20) or framework assembly of the subsurface structure.
 
5. A method according to any preceding claim, wherein the first section (40) of said at least one fibre optic cable sensor (48) is arranged on one side of the reinforcement cage (20) or framework assembly and the second section (42) of said at least one fibre optic cable sensor (48) is arranged on an opposing side of the reinforcement cage (20) or framework assembly.
 
6. A method according to any preceding claim, wherein a first fibre optic cable sensor (48) is arranged to extend in an open loop along a central axis of the reinforcement cage (20) or framework assembly.
 
7. A method according to any preceding claim, wherein one or more additional fibre optic cable sensors (48) are arranged to each define a single or a plurality of open loops at a peripheral location of the reinforcement cage (20) or framework assembly.
 
8. A method according to any preceding claim, wherein the or each fibre optic cable sensor (48) is attached to the reinforcement cage (20) or framework assembly prior to location of the reinforcement cage (20) or framework assembly at said subsurface location.
 
9. A method according to any preceding claim, wherein the or each fibre optic cable sensor (48) is a single mode fibre optic sensor or a multimode fibre optic sensor.
 


Ansprüche

1. Verfahren zur Überwachung von unterirdischen Betonstrukturen, wobei das Verfahren die folgenden Schritte umfasst:

- Bereitstellung eines Armierungskäfigs (20) bzw. einer Rahmenanordnung für eine unterirdische Betonstruktur;

- Bereitstellung einer Glasfaseranordnung (48) in Verbindung mit dem Armierungskäfig (20) bzw. der Rahmenanordnung, wobei die Glasfaseranordnung mindestens einen Glasfaserkabel-Sensor aufweist und wobei der Glasfaserkabel-Sensor mit einem Glasfaserkabel versehen ist, dass als Sensorelement wirkt;

- Bereitstellung eines Abfragegeräts (50), das mit der Glasfaseranordnung verbunden ist;

- Installierung des Armierungskäfigs (20) oder der Rahmenanordnung an einer gewünschten unterirdischen Stelle (30);

- Einbringen von Beton-Material, um den Armierungskäfig (20) bzw. die Rahmenanordnung zu umschließen, und Einbringen von mindestens einem Glasfaserkabel-Sensor 48 zu der unterirdischen Stelle (30);

- Verwendung des mindestens einen Glasfaserkabel-Sensors (48) sofort oder kurz nach dem Einbringen des Betonmaterials zum direkten Messen von Temperaturdaten entlang der Länge von dem mindestens einen Glasfaserkabel-Sensor während der Hydration der unterirdischen Betonstruktur;

- Verwendung des Abfragegeräts (50) zur Erfassung der Temperaturdaten während der Hydration der unterirdischen Betonstruktur; und

- Analysieren der Temperaturdaten, um eine Charakteristik der unterirdischen Betonstruktur zu bestimmen,

- wobei der mindestens eine Glasfaserkabel-Sensor (48) gefaltet oder auf sich selbst gedoppelt wird, um so eine Öffnung zwischen seinen Teilen zu lassen, wodurch eine offene Schleifenanordnung mit einem ersten Abschnitt (40) und einem zweiten Abschnitt (42) gebildet wird, die voneinander getrennt sind und sich entlang einer Länge des Armierungskäfigs bzw. der Rahmenanordnung erstrecken.


 
2. Verfahren nach Anspruch 1, wobei die Temperaturdaten während der Hydration der unterirdischen Betonstruktur in Echtzeit überwacht werden.
 
3. Verfahren nach einem der vorhergehenden Ansprüche, wobei die Glasfaseranordnung eine Mehrzahl von Glasfaserkabel-Sensoren (48) aufweist.
 
4. Verfahren nach Anspruch 3, wobei jeder Glasfaserkabel-Sensor (48) sich bis hinab zu einer bekannten Tiefe innerhalb des Armierungskäfigs (20) bzw. der Rahmenanordnung der unterirdischen Struktur erstreckt.
 
5. Verfahren nach einem der vorhergehenden Ansprüche, wobei der erste Abschnitt (40) des mindestens einen Glasfaserkabel-Sensors (48) auf einer Seite des Armierungskäfigs (20) bzw. der Rahmenanordnung und der zweite Abschnitt (42) des mindestens einen Glasfaserkabel-Sensors (48) auf der gegenüberliegenden Seite des Armierungskäfigs (20) bzw. der Rahmenanordnung angeordnet ist.
 
6. Verfahren nach einem der vorhergehenden Ansprüche, wobei ein erster Glasfaserkabel-Sensor (48) derart angeordnet ist, dass er sich in einer offenen Schleife entlang einer Zentralachse des Armierungskäfigs (20) bzw. der Rahmenanordnung erstreckt.
 
7. Verfahren nach einem der vorhergehenden Ansprüche, wobei einer oder mehrere zusätzliche Glasfaserkabel-Sensoren (48) vorgesehen sind, von denen jeder eine einzige oder eine Mehrzahl von offenen Schleifen in einem peripheren Bereich des Armierungskäfigs (20) bzw. der Rahmenanordnung bildet.
 
8. Verfahren nach einem der vorhergehenden Ansprüche, wobei der oder jeder Glasfaserkabel-Sensor (48) an dem Armierungskäfig (20) bzw. der Rahmenanordnung angebracht ist, bevor der Armierungskäfig (20) bzw. die Rahmenanordnung an ihren unterirdischen Standort hinabgelassen wird.
 
9. Verfahren nach einem der vorhergehenden Ansprüche, wobei der oder jeder Glasfaserkabel-Sensor (48) ein Single-Mode-Glasfaser-Sensor oder ein Multi-Mode-Glasfaser-Sensor ist.
 


Revendications

1. Procédé de surveillance d'une structure souterraine en béton, procédé comprenant les étapes consistant à :

- fournir une cage de renforcement (20) ou un assemblage de châssis pour une structure souterraine en béton

- fournir un réseau de fibre optique (48) en combinaison avec la cage de renforcement (20) ou l'assemblage de châssis, le réseau de fibre optique comprenant au moins un capteur de câble à fibre optique dans lequel, ce capteur de câble à fibre optique comprend un câble à fibre optique qui fonctionne comme élément de détection

- fournir un dispositif d'interrogation (50) relié au réseau de fibre optique,

- installer la cage de renforcement (20) ou l'assemblage de châssis à un emplacement souterrain (30) déterminé,

- appliquer un milieu en béton pour entourer la cage de renforcement ou l'assemblage de châssis et au moins ce capteur à câble à fibre optique (48) à l'emplacement souterrain (30)

- utiliser au moins ce capteur à câble à fibre optique (48) immédiatement ou peu de temps après l'application du milieu en béton pour détecter directement la température selon la longueur de ce capteur à câble à fibre optique pendant l'hydratation de la structure souterraine en béton

- utiliser le dispositif d'interrogation (50) pour collecter la donnée de température pendant l'hydratation de la structure souterraine en béton et

- analyser cette donnée de température pour déterminer une caractéristique de la structure souterraine en béton,

- procédé dans lequel le capteur à câble à fibre optique est plié ou doublé sur lui-même de façon à laisser une ouverture entre les éléments et former ainsi une boucle ouverte ayant une première section (40) et une seconde section (42) espacées l'une de l'autre et s'étendant selon la longueur de la cage de renforcement ou de l'assemblage de châssis.


 
2. Procédé selon la revendication 1
selon lequel la donnée de température est contrôlée en temps réel pendant l'hydratation de la structure souterraine en béton.
 
3. Procédé selon l'une quelconque des revendications précédentes
selon lequel le réseau de fibre optique (48) comporte un ensemble de capteurs à câble à fibre optique (48).
 
4. Procédé selon la revendication 3
selon lequel chaque capteur (48) de câble à fibre optique s'étends jusqu'à une profondeur déterminée dans la cage de renforcement (30) ou d'assemblage de châssis de la structure souterraine.
 
5. Procédé selon l'une quelconque des revendications précédentes
selon lequel la première section (40) du capteur à câble à fibre optique (48) prévu sur un côté de la cage de renforcement (20) ou de l'assemblage de châssis et la seconde section (42) d'au moins un capteur (48) à câble à fibre optique est prévue sur le côté opposé de cage de renforcement (20) ou de l'assemblage de châssis.
 
6. Procédé selon l'une des revendications précédentes
selon lequel
un capteur à câble à fibre optique (48) est disposé pour former une boucle ouverte de long de l'axe central de la cage de renforcement (20) ou de l'assemblage de châssis.
 
7. Procédé selon une quelconque des revendications précédentes
selon lequel un ou plusieurs capteurs à câble à fibre optique supplémentaires sont disposés de façon à définir un angle ou un ensemble de boucles ouvertes à un endroit périphérique de la cage de renforcement (20) ou de l'assemble de châssis.
 
8. Procédé selon une quelconque des revendications précédentes
selon lequel le ou chaque capteur à câble à fibre optique (48) est fixé à la cage de renforcement (20) ou à l'assemblage de châssis avant de placer la cage de renforcement (20) ou l'assemblage de châssis à l'emplacement souterrain.
 
9. Procédé selon l'une quelconque des revendications précédentes
selon lequel
le ou chaque capteur à fibre optique (48) est un capteur à fibre optique en monomode ou un capteur à fibre optique multimode.
 




Drawing

















Cited references

REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description