Device for sensing pressure of a fluid, such as a liquid or a gas, in particular pore water pressure

Abstract

The disclosure concerns a device (1) for sensing a pressure (Pm) of a fluid (2), comprising: - a first layer (4) having a row (7) of at least two through-holes (8) each having a fluid inlet (9) exposed to the fluid pressure and a fluid outlet (10); - a second layer (11) attached to the first layer, comprising a row (14) of at least two cavities (15), each having a cavity opening (16) at the position (17) of the fluid outlet of the at least two through-holes; - at least one pressure-responsive element (18) arranged in between the first layer and the second layer, wherein the pressure-responsive element is deflected by the fluid pressure into each of the at least two cavities; and - a sensing configuration (19) connected to the at least one pressure-responsive element, for sensing the at least two deflections.

Description

[0001] Title: Device for sensing pressure of a fluid, such as a liquid or a gas, in particular pore water pressure

[0002] FIELD

[0003] The present disclosure relates to a device for sensing pressure of a fluid, such as a liquid or a gas, in particular pore water pressure, a (non-)infrastructural element or tubular element comprising such a device, a method of operating such a device, a method of calibrating such a device and a method of manufacturing such a device.

[0004] BACKGROUND

[0005] E.g. in low-lying countries like the Netherlands, dikes protect land from flooding. One of the main failure mechanisms that can lead to dike breaching and subsequently flooding is slope instability. The construction of a dike is one of the loading conditions to which a slope and subsoil may be subjected, when regarding the safety with respect to slope stability. Raising an embankment leads to excess “pore water pressure” in soft soil foundation layers, resulting in low effective stresses. Due to feasibility and economic reasons, critical levels of stability (low factors of safety) are often accepted during the construction of dikes; all the more because potential damage in terms of loss of life and injuries during construction is usually low, compared to the design conditions.

[0006] “Pore water pressure” (sometimes abbreviated to “pop”) refers to the pressure of groundwater held within a soil or rock, in gaps between particles (pores), in other words “pore water pressure” is the pressure experienced by water trapped in the voids in a saturated soil mass. Pore water pressure is affected by the soil type, water flow conditions and level of the water table. Pore water pressure is important in geotechnical engineering as it influences soil behavior, including its shear strength. In general, the presence of water or pore water pressure reduces the soil resistance and also leads to increase in stimulus loads, resulting in reduction of stability coefficients. Thus, it is of paramount importance to be able to measure pore water pressure to determine the structural integrity of earthworks. CN 201184834 Y discloses a fiber-optical water pressure sensor. The water pressure sensor comprises a pipe body. The periphery of the pipe body is provided with a plurality of micropores. Both ends of the pipe body are provided with end covers. A sensor fixing device is arranged in the pipe body in the longitudinal direction. The sensor fixing device is provided with a plurality of axial notches. Pressure optical fiber grating sensors are arranged inside the axial notches. Temperature sensors are arranged outside the notches. The exterior of the pressure optical grating sensors and the exterior of the temperature optical fiber grating sensors are fixed on the sensor fixing device through protective layers. After a plurality of pressure optical fiber grating sensors are joined, the pressure optical fiber grating sensors are connected with the temperature sensor in series, and are connected with an external photosignal adjusting and processing device. When the optical fiber grating movable pore-water pressure sensor is used, a plurality of the optical fiber grating movable pore-water pressure sensors are buried under bituminous concrete pavement. Void water in the pavement enters the pipe through the micropores on the pipe body, and pressurizes the surface of the sensor fixing device. The pressure is transferred to the photosignal adjusting and processing device through the pressure optical fiber grating sensors for analysis and processing. In this way, corresponding maintenance measures can be taken to the pavement and void water is prevented from greatly damaging the pavement.

[0007] US 11473260 A1 discloses a stress cell for direct measurement of effective stress in saturated soil. The effective stress cell comprises a sensing diaphragm, a porous diaphragm, a connector and a strain sensor. The porous diaphragm allows pore-water to enter the interior space between the sensing diaphragm and the porous diaphragm to provide complete balance of pore-water pressures in the front and back of the sensing diaphragm. Thus, the effective stress cell can directly and accurately measure the effective stress in saturated soil using only one diaphragm at one location without measuring pore-water pressure.

[0008] An object of the present invention is to provide an improved device for sensing pressure of a fluid, such as a liquid or a gas, in particular pore water pressure.

[0009] A further object of the invention is to provide an aforementioned device, wherein pore water pressure can be measured over either very short or very long distances, such as kilometers long. SUMMARY

[0010] Thereto, according to the present invention, a device for sensing a pressure (Pm) of a fluid, such as a liquid or a gas, is provided, comprising: a first layer, with a first main surface and a second, opposing main surface, the first layer having a row of at least two through-holes arranged in a row direction and extending from the first main surface to the second main surface, the at least two through-holes each having a fluid inlet exposed to the fluid pressure at the first main surface and a fluid outlet at the second main surface; a second layer, with a third main surface and a fourth, opposing main surface, wherein the second layer is attached to the second main surface with the third main surface, the second layer comprising a row of at least two cavities arranged in the row direction, each having a cavity opening at the position of the fluid outlet of the at least two through-holes of the first layer; at least one pressure-responsive element, e.g. extending in the row direction, arranged in between the first layer and the second layer, wherein the fluid pressure at the fluid inlet at the first main surface can be transferred to the pressure- responsive element via the fluid outlet at the second main surface, wherein the pressure-responsive element is deflected by the fluid pressure into each of the at least two cavities at the at least two cavity openings; and a sensing configuration connected to the at least one pressure- responsive element, for sensing the at least two deflections of the pressure-responsive element into the at least two cavities.

[0011] Due to its unique design, the above device e.g. allows for highly accurate pore water pressure measurements. Furthermore, the device can be very short or very long, such as kilometers long, because the basic design, i.e. the first layer, the second layer, the pressure-responsive element and the sensing configuration, can basically be “repeated / extrapolated” in the row direction until the desired length is reached. Longer row lengths therein allow the measurement of the distribution of e.g. the pore water pressure, which may vary per through-hole along the length of the row. Additionally, acoustic pressure can also be measured, wherein the row of through-holes may act like a phased array. The pressure-responsive element may concern a “single” element that extends along the at least two through- holes / cavity openings. Alternatively, the pressure-responsive element may concern an individual pressure-responsive element per (combination of) through-hole / cavity opening.

[0012] CN 102183211 A discloses a sensor which calculates excess pore water pressure by detecting temperature and wavelength drift value of a strain optical fiber. The disclosure also relates to a method for measuring excess pore water pressure of a road surface by using such a sensor. However, CN 102183211 A discloses the presence of multiple holes, such as nine holes, per cavity, which makes it difficult to accurately measure “per-hole” pressure and, thus, pressure distribution, with the design according to CN 102183211 A. CN 102183211 A thus (also) does not disclose that each cavity has a cavity opening at the position of the fluid outlet of (each of) the at least two through-holes of the first layer. CN 102183211 A moreover also does not disclose that the pressure-responsive element is deflected (d) by the fluid pressure into each of the at least two cavities at the at least two cavity openings. Instead, the pressure-responsive element according to CN 102183211 A deflects into a single cavity, as a result of the fluid pressure exerted via the multiple holes. Consequently, CN 102183211 A also does not disclose a sensing configuration connected to the at least one pressure-responsive element, for sensing the at least two deflections of the at least one pressure-responsive element into the at least two cavities.

[0013] An embodiment relates to an aforementioned device, wherein the first layer and the pressure-responsive element are formed as an integrated or monolithic layer, which has advantages in terms of ease of manufacturing (and cost) and e.g. when a watertight first layer / pressure-responsive element is sought after. The through- hole then strictly speaking is not a through-hole - because the through-hole and the pressure-responsive element are part of the same (first) layer - but a hole extending up to the pressure-responsive element, i.e. the respective end of the hole is “covered” by the pressure-responsive element.

[0014] An embodiment relates to an aforementioned device, wherein the sensing configuration is arranged at a neutral axis of the device. This may be the neutral axis / line from a “bending strain” perspective, but also the neutral axis / line from a geometrical perspective. The position of the neutral line can be chosen by engineering the thickness, material properties, and geometry of the device materials as well as the fixation methods chosen. Thus, relatively little variation in response is thus obtained. However, in some embodiments the sensing configuration may be arranged away from the neutral line to measure out-of-plane bending.

[0015] An embodiment relates to an aforementioned device, wherein the sensing configuration comprises an optical sensing configuration, which allows for accurate sensing of fluid pressure, in particular distributed sensing of fluid pressure.

[0016] An embodiment relates to an aforementioned device, wherein the optical sensing configuration comprises at least one optical fiber extending in the row direction. Optical fiber technology is highly advantageous for measuring the deflection of the pressure-responsive element, which translates to local strain on the optical fiber. One or more light transmission properties of the optical fiber can be advantageously measured when the pressure-responsive element and thus the optical fiber are deflected into the at least two cavities.

[0017] An embodiment relates to an aforementioned device, wherein a diameter of at least one of the fluid outlets at the second main surface is 10 - 50 times an outer diameter of the at least one optical fiber, to prevent clogging of the respective through-hole in situations where small contaminants can be present in the fluid of which the pressure is to be measured.

[0018] An embodiment relates to an aforementioned device, wherein a diameter of at least one of the cavity openings at the third main surface is larger than a diameter of the corresponding fluid outlet at the second main surface, which allows the pressure-responsive element to have sufficient room for deflecting into the respective cavity.

[0019] An embodiment relates to an aforementioned device, wherein the pressure-responsive element comprises a membrane. Such a membrane, in particular a membrane foil, is relatively sensitive to pressure variations, causing minimal membrane deformations to be transferred to the sensing configuration, thus leading to accurate, high-resolution measurements.

[0020] An embodiment thus relates to an aforementioned device, wherein the membrane comprises a membrane foil.

[0021] An embodiment relates to an aforementioned device, wherein the membrane is flat at at least one of the at least two fluid outlets and / or cavity openings, which allows for a relatively predictable and linear deflection of the membrane. However, the deflection in practice may not be fully linear, due to sticking of the membrane, et cetera. This should of course be taken into account when calibrating the device.

[0022] An embodiment relates to an aforementioned device, wherein the membrane is rippled at at least one of the at least two fluid outlets and / or cavity openings, wherein the ripples are preferably concentrically arranged around a center of the at least one of the at least two fluid outlets and / or cavity openings, wherein the optical sensing configuration is preferably connected to concentric ripples at the center of the concentric ripples to allow for specific interactions with the sensing configuration.

[0023] An embodiment relates to an aforementioned device, wherein the at least two through-holes and the at least two cavities are spaced-apart in the row direction, wherein at least one of the at least two through-holes, at least one corresponding cavity, at least one corresponding portion of the pressure-responsive element and at least one corresponding portion of the sensing configuration together form an individual pressure sensor. Such an individual pressure sensor can e.g. be individually read out or calibrated.

[0024] An embodiment relates to an aforementioned device, wherein at least one of the at least two cavity openings is circular, oval, elliptical or rectangular, preferably with rounded corners, to allow for even pressure transfer to, and even deflection of, the underlying pressure-responsive element. Furthermore, it is furthermore prevented that relatively sharp edges of the cavity opening damage the pressure-responsive element and / or sensing configuration when the pressure- responsive element and / or sensing configuration is repeatedly deflected / relaxed.

[0025] An embodiment relates to an aforementioned device, wherein the sensing configuration is arranged at a side of the pressure-responsive element turned away from the first layer. Thus, the sensing configuration itself does not interfere with pressure application to the surface of the pressure-responsive element turned towards the through-hole. The sensing configuration therein may advantageously run through / along, or be accommodated in, the cavity openings.

[0026] An embodiment relates to an aforementioned device, wherein at least one of the at least two cavities is in fluid contact with a pressure response calibration space, such as a pressure calibration channel running along the at least two cavities, via the cavity opening and / or via a further cavity opening separate from the cavity opening to calibrate the pressure response of the pressure-responsive element and / or sensing configuration, improving the accuracy thereof. Preferably, the pressure calibration channel can be opened up, such as at the distal ends thereof, such that the pressure calibration channel can be cleaned (e.g. by blowing), for instance when condensation has taken place. When using the device for acoustic measurements, the distal ends of the pressure calibration channel can be either closed or open(ed) depending on the frequency range to be measured (low / mid / high).

[0027] An embodiment relates to an aforementioned device, wherein the second layer is attached to the first layer and / or the sensing configuration is attached to the pressure-responsive element with a bonding layer to allow for a relatively strong and durable connection. Preferably the bonding layer comprises glue, resin or the like. More preferably the bonding layer at the same time is relatively flexible, allowing for bending of the device in a direction perpendicular to the first and / or second layer, without damaging the device.

[0028] An embodiment relates to an aforementioned device, wherein: at the position of the cavity, the bonding layer comprises at least one protrusion, such as a V-shaped protrusion, when seen in cross-section in a direction perpendicular to the row direction, for holding and bonding the at least one optical fiber to the pressure-responsive element and / or at a position between cavities, the second layer comprises at least one groove, such as a V-shaped groove, when seen in cross-section in a direction perpendicular to the row direction, for holding the at least one optical fiber.

[0029] An embodiment relates to an aforementioned device, wherein at least one of the at least two fluid inlets is covered by a fluid-permeable filter, such as a grid or gauze, to prevent debris, such as soil, from entering the fluid inlet and clogging up the through-holes.

[0030] An embodiment relates to an aforementioned device, wherein, when the sensing configuration comprises an optical fiber, at least one optical fiber comprises a Fiber Bragg Grating (FBG), which can be used at discrete positions to be used as an inline optical filter to block / reflect certain wavelengths, which is particular useful for sensing applications. In principle, any other means for optically establishing the deflection of the pressure-responsive element and the optical fiber can also be used. An embodiment relates to an aforementioned device, wherein, when the sensing configuration comprises an optical fiber, at least one optical fiber is a continuous fiber, allowing for distributed sensing applications.

[0031] An embodiment relates to an aforementioned device, wherein, when the sensing configuration comprises an optical fiber, the sensing configuration comprises at least two, preferably at least three, parallel optical fibers extending in the row direction and arranged at the position of the at least two cavity openings. This allows for increased accuracy in pressure sensing through the measurement of differences of the strain in the at least two optical fibers, thereby cancelling out the (common to all optical fibers) effects of temperature, i.e. thermal expansion of the pressure-responsive element and changes in refractive index of the optical fiber as well as environment-induced strain on the pressure-responsive element resulting from e.g. excessive bending of the pressure-responsive element.

[0032] An embodiment relates to an aforementioned device, wherein, when the sensing configuration comprises an optical fiber, the sensing configuration comprises at least one calibration optical fiber, extending in the row direction, parallel to the at least one optical fiber, the at least one calibration optical fiber not being arranged at the position of the at least two cavity openings. This allows for further calibration of the device, and any read-out instrument used therewith, in particular when regions of strongly elevated optical fiber strain are present. Furthermore, this allows for additional pressure measurements, bending measurements, as well as temperature measurements (between the cavities).

[0033] The calibration optical fibers may be used for measuring in-plane bending, e.g. by discriminating between strain in the calibration optical fibers being induced by temperature from strain in calibration optical fibers induced by in-plane curvature of the device. The same principles may apply when e.g. three parallel optical fibers extending along the cavity openings are used.

[0034] An embodiment relates to an aforementioned device, wherein the at least two parallel optical fibers and / or the at least one calibration optical fiber are arranged at the neutral axis and / or are not arranged at the neutral axis of the device.

[0035] An embodiment relates to an aforementioned device, wherein the through-holes in the first layer and the one or more corresponding cavities in the second layer are spaced-apart at regular intervals, to allow for pressure sensing along the device at regular intervals. An embodiment relates to an aforementioned device, wherein the through-holes in the first layer and the one or more corresponding cavities in the second layer are spaced-apart at irregular intervals, to allow for pressure sensing along the device at irregular intervals. Of course, irregular intervals may alternate with regular intervals and any combinations thereof are in principle conceivable.

[0036] An embodiment relates to an aforementioned device, wherein the through-holes in the first layer and the one or more corresponding cavities in the second layer are arranged in a group-wise manner. Thus, pressure distribution can be more accurately measured at the position of the group of through-holes / cavities.

[0037] An embodiment relates to an aforementioned device, wherein the first layer and / or second layer and / or the pressure-responsive element are in the form of a strip extending in the row direction. The use of such strips, when properly sized and applied, allows for bending of the device in a direction perpendicular to the device.

[0038] An embodiment relates to an aforementioned device, wherein the device has a rectangular or square shape when viewed in a direction perpendicular to the first and / or second layer. The device may for instance be plate-shaped, in particular when the first layer and / or second layer and / or the pressure-responsive element are in the form of a strip extending in the row direction.

[0039] An embodiment relates to an aforementioned device, wherein the device is more than 10 m, such as more than 50 m, such as more than 100 m, such as more than 500 m, such as more than 1000 m in length, such that the device can be conveniently inserted or embedded in relatively long infrastructural elements, such as a dike.

[0040] An embodiment relates to an aforementioned device, wherein: the first layer comprises multiple rows of through-holes extending in multiple row directions; the second layer comprises multiple rows of corresponding cavities extending in the multiple row directions; one or more corresponding pressure-responsive elements are arranged in between the first layer and the second layer, extending in the multiple row directions; and a sensing configuration is connected to the one or more corresponding pressure-responsive elements, for sensing the corresponding deflections of the one or more pressure-responsive elements into the corresponding cavities in the multiple row directions.

[0041] Such a device advantageously allows for specific 2D measurements to be made with the device, wherein in principle any configuration of rows is conceivable:

[0042] An embodiment relates to an aforementioned device, wherein the multiple row directions are parallel.

[0043] Therein, the through-holes and corresponding cavities of one row may alternate with the through-holes and corresponding cavities of another row.

[0044] An embodiment relates to an aforementioned device, wherein the multiple rows are arranged at an angle with respect to each other. Analogously, the same may hold for groups of rows, clusters, et cetera.

[0045] Another aspect of the invention concerns an infrastructural element, comprising soil with water as the fluid and an aforementioned device embedded in the soil for measuring pore water pressure in the soil.

[0046] An embodiment relates to an aforementioned infrastructural element, wherein the infrastructural element is a dike. Other infrastructural elements are of course also conceivable, such as a road, canal, et cetera.

[0047] An embodiment relates to an aforementioned infrastructural element, wherein the infrastructural element is more than 10 m, such as more than 50 m, such as more than 100 m, such as more than 500 m, such as more than 1000 m in length. Again, the device according to the invention can be conveniently inserted or embedded in such relatively long infrastructural elements.

[0048] An embodiment relates to an aforementioned infrastructural element, wherein the device has a length of at least 80%, such as at least 90%, such as at least 95% of a length of the infrastructural element, such that pressure sensing can take place along a substantial portion of the infrastructural element.

[0049] An embodiment relates to an aforementioned infrastructural element, wherein the device is arranged at a hotspot, such as near a curve in a river. Thus, the device may be advantageously used at critical locations, such as dike portions near a curve in the river.

[0050] An embodiment relates to an aforementioned infrastructural element wherein the device is arranged in a body of water (or, for that matter, another fluid), at least at a surface of the water body, in a direction at least partially parallel to a wave direction of waves present at the surface of the water body. E.g. near a river, the device may be arranged against a dike, i.e. extending at least partially in a height direction. With a non-infrastructural element, such as a storage tank, the device may be arranged against a tank wall. Thus, the dynamics of a (surface) wave system may be studied. The through-holes / cavity openings may be advantageously placed relatively close to each other (e.g. in a group) at the water surface, to allow for relatively detailed measurements of the waves (and the effects thereof on the dike) at the water surface. Away from the water surface, the through-holes / cavity openings may be spaced further apart from each other. E.g. when an optical sensing configuration is used, a Fourier spectrum analysis can be performed, such that the waves and the impact thereof on (non-)infrastructural elements, such as the dike, can be characterized in terms of their combined frequencies / wave lengths.

[0051] Another aspect of the invention concerns a tubular element, comprising an aforementioned device, wherein the device is helically wound around an outer surface of the tubular element. Thus, an additional angular sensitivity can be added to e.g. detect inflow directions of a / the fluid, in addition to the measurements of temperature, fluid pressure around, and deformations of, the tubular object.

[0052] Another aspect of the invention concerns a method of operating an aforementioned device, for sensing a pressure of a fluid, comprising the steps of: exposing the fluid inlets of the at least two through-holes to the fluid pressure at the first main surface; deflecting the pressure-responsive element into the at least two cavities at the at least two cavity openings by transferring the fluid pressure to the pressure-responsive element via the fluid outlets; and sensing the at least two deflections of the pressure-responsive element into the at least two cavities with the sensing configuration connected to the pressure-responsive element.

[0053] Sensing may be achieved by various means, such as by strain measurements, optical means, such as wave length measurements, polarization measurements, et cetera.

[0054] An embodiment relates to an aforementioned method, comprising the step of, when the sensing configuration comprises an optical fiber: measuring one or more light transmission properties of the optical fiber when the pressure-responsive element and the optical fiber are deflected into the at least two cavities. The actual measurement of light transmission properties may vary, based on design variables of the device, the chosen / desired read-out equipment, and / or the chosen measurement principle, such as wave length, polarization, et cetera.

[0055] Another aspect of the invention relates to a method of calibrating an aforementioned device, when at least one of the at least two cavities is in fluid contact with a pressure response calibration space via the cavity opening and / or a further cavity opening separate from the cavity opening to calibrate the pressure response of the pressure-responsive element and / or sensing configuration, comprising the step of: calibrating the pressure response of the pressure-responsive element and / or sensing configuration with the pressure response calibration space via the cavity opening and / or the further cavity opening.

[0056] The calibration method mentioned in the foregoing paragraph may further comprise the steps of the method of operating an aforementioned device (and the other way around).

[0057] Another aspect of the invention relates to a method of manufacturing an aforementioned device, when the first layer and / or second layer and / or the pressure-responsive element are in the form of a strip extending in the row direction, wherein the first layer, the second layer, the pressure-responsive element and the sensing configuration are attached to each other by simultaneously guiding the first layer, the second layer, the pressure-responsive element and the sensing configuration between two rotating roller presses, preferably in the row direction, such that the first layer, the second layer, the pressure-responsive element and the sensing configuration are pressed together. Such a manufacturing technique in principle allows for the tailor-made manufacturing of kilometers of length of “device”.

[0058] An embodiment relates to an aforementioned method, wherein, when a pressure calibration space is present and the pressure response calibration space is arranged in a pressure response calibration space strip, the first layer, the second layer, the pressure-responsive element, the sensing configuration and the pressure response calibration space strip are attached to each other by simultaneously guiding the first layer, the second layer, the pressure-responsive element, the sensing configuration and the pressure response calibration space strip between two rotating roller presses, preferably in the row direction, such that the first layer, the second layer, the pressure-responsive element, the sensing configuration and the pressure response calibration space strip are pressed together. LIST OF DEFINITIONS

[0059] In the context of the present patent application:

[0060] “Strip” means: an elongated, relatively flat element.

[0061] “Pressure” may e.g. mean: static fluid pressure, dynamic fluid pressure or acoustic pressure.

[0062] BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The disclosure will be explained in more detail below, with reference to illustrative embodiments shown in the drawings. Therein:

[0064] Figure 1a shows an example embodiment of an infrastructural element comprising a device according to the present disclosure, wherein the device is arranged at a hotspot, in this case near a curve in a river;

[0065] Figure 1b shows an example embodiment of an infrastructural element comprising a device according to the present disclosure, wherein the device is arranged at a delimitation between an infrastructural element and an adjacent body of water;

[0066] Figure 1c shows an example embodiment of a non-infrastructural element in the form of a tubular element, comprising a device according to the present disclosure helically wound around an outer surface of the tubular element;

[0067] Figure 2 shows an example embodiment of a device according to the present disclosure, along a longitudinal section thereof;

[0068] Figure 3 shows an example embodiment of a device according to the present disclosure, wherein, respectively, the first layer, the pressure-responsive element comprising the sensing configuration, the second layer and the pressure calibration channel are shown in a direction perpendicular to the respective layer / element / channel;

[0069] Figure 4 shows an example embodiment of a cross-section of the device according to the present disclosure at the position of the through-hole / cavity opening;

[0070] Figures 5a - 5c shows several example embodiments of a pressure- responsive element for use with a device according to the present disclosure; Figure 6 shows a cross-sectional view of the example embodiment of the pressure-responsive element of Figure 5b;

[0071] Figure 7 shows an example embodiment of a device according to the present disclosure, along a longitudinal section thereof, comprising a pressure calibration channel provided with a reference pressure Pref;

[0072] Figure 8 shows an example embodiment of a longitudinal section of the device according to the present disclosure at the position of a through-hole / cavity opening, wherein the pressure-responsive element is deflected into the cavity opening (with the lower side of Figure 8 showing the strain distribution measured by the sensing configuration for the respective row of cavity openings);

[0073] Figure 9a shows an example embodiment of a cross-section of the device according to the present disclosure at the position of a through-hole / cavity opening, wherein the pressure-responsive element is deflected into the cavity opening by a fluid pressure Pm, while at the same time a reference pressure Pref is applied via the pressure calibration channel;

[0074] Figure 9b shows an example embodiment of a longitudinal section of the device according to the present disclosure at the position of a through-hole / cavity opening, wherein the pressure-responsive element is deflected into the cavity opening by a fluid pressure Pm, while at the same time a reference pressure Pref is applied via the pressure calibration channel;

[0075] Figure 9c shows an example embodiment of a longitudinal section of the device according to the present disclosure at the position of a through-hole / cavity opening, wherein the pressure-responsive element is deflected into the cavity opening by a fluid pressure Pm, while at the same time a reference pressure Pref is applied via the pressure calibration channel, wherein a porous material is arranged in the through- hole;

[0076] Figure 9d shows an example embodiment of a longitudinal section of the device according to the present disclosure at the position of a through-hole / cavity opening, wherein the pressure-responsive element is deflected into the cavity opening by a fluid pressure Pm, while at the same time a reference pressure Pref is applied via the pressure calibration channel, wherein a calibration ring is arranged in the through- hole;

[0077] Figure 10 shows an example embodiment of a device according to the present disclosure, wherein a sensing configuration, with three parallel optical fibers, and the second layer are shown in a direction perpendicular to the sensing configuration and the second layer;

[0078] Figure 11a shows an example embodiment of a device according to the present disclosure, wherein a sensing configuration with three parallel optical fibers and two parallel calibration optical fibers, and the second layer are shown in a direction perpendicular to the sensing configuration and the second layer;

[0079] Figure 11 b shows an example readout of the strain of a device according to the present disclosure connected to a long-pulse distributed strain sensing instrument;

[0080] Figure 12 shows an example method of manufacturing a device according to the present disclosure, wherein the first layer, the second layer, the pressure-responsive element and the sensing configuration are attached to each other by simultaneously guiding the first layer, the second layer, the pressure-responsive element and the sensing configuration between two rotating roller presses in the row direction, such that the first layer, the second layer, the pressure-responsive element and the sensing configuration are pressed together;

[0081] Figure 13 shows an example embodiment of a device according to the present disclosure, wherein the first layer comprises multiple rows of through-holes extending in parallel row directions; and

[0082] Figure 14 shows an example embodiment of a device according to the present disclosure, wherein the first layer comprises multiple rows of through-holes arranged at an angle (a) with respect to each other.

[0083] DETAILED DESCRIPTION

[0084] Figures 1a - 14 will be discussed in conjunction. As mentioned in the foregoing, Figure 1a shows an example embodiment of an infrastructural element 37, for instance in the form of a dike 40 (as shown), comprising a device 1 according to the present disclosure (of which an example embodiment is shown in Figure 2), wherein the device 1 is arranged at a hotspot 41 , in this case near a curve in a river 43. The infrastructural element 37, such as the dike 40, comprises soil 38 with water 39 as the fluid 2. The device 1 is embedded in the soil 38 for measuring pore water pressure in the soil 38. The infrastructural element 37 may be more than 10 m, such as more than 50 m, such as more than 100 m, such as more than 500 m, such as more than 1000 m in length. The device 1 may have a length of at least 80%, such as at least 90%, such as at least 95% of a length of the infrastructural element 37, such that pore water pressure distribution in the infrastructural element 37 can be accurately measured. The device 1 may thus also be more than 10 m, such as more than 50 m, such as more than 100 m, such as more than 500 m, such as more than 1000 m in length.

[0085] As shown in Figure 1 b, the device 1 may be arranged at a delimitation between the infrastructural element 37. e.g. in the form of a dike 40, and an adjacent body of water 51 , such as a river 43. The device 1 extends through a surface 52 of the water body 51 , such that waves 53 present at the surface 52 of the water body 51 impinge at least part of the device 1. Thus, measurement of wave height, wave roll- on / roll of 54 and the position thereof on the river 43 bank (or alternatively a sea wall or similar object) can be measured or reconstructed. Also, the wave character can be analyzed, e.g. by analyzing the pressure signals of the (individual) pressure sensors 26 with Fourier analysis. Signals in the lower frequency range may indicate laminar roll-on / roll-off of the waves 53 over the individual pressure sensors 26, signals in the higher frequency range may indicate turbulent roll-on / roll-off of the waves 53 over the individual pressure sensors 26.

[0086] With a non-infrastructural element, such as a storage tank (not shown), the device 1 may be arranged against a tank wall. Thus, the dynamics of a (surface) wave system in a tank may be studied. The through-holes 8 / cavity openings 16 may be advantageously placed relatively close to each other (e.g. in a group) at the water surface 52, to allow for relatively detailed measurements of the waves 53 (and the effects thereof on the dike 40) at the water surface 52. Away from the water surface 52, the through-holes 8 / cavity openings 16 may be spaced further apart from each other. E.g. when an optical sensing configuration 20 is used, a Fourier spectrum analysis can be performed, such that the waves 53 and the impact thereof on (non- )infrastructural elements, such as the dike 40, can be characterized in terms of their combined frequencies / wave lengths. The lower part of Figure 1 b shows the pressure response, along with the reconstructed wave height and wave roll-on / roll-off position, of several individual pressure sensors 26 at various points in time, i.e. at t = ti, t = t2 and t = ts, respectively.

[0087] Figure 1c shows an example embodiment of a non-infrastructural element 57 in the form of a tubular element 56, such as a pipe, pillar, cable, hose, duct, or the like, comprising a device 1 according to the present disclosure helically wound around an outer surface 58 of the tubular element 56. To wind the device 1 around the outer surface 58, the device 1 is shaped like a strip 36. The device 1 needs to be sufficiently flexible to do so. Helical winding of the device 1 over the outer surface 58 offers (additional) angular sensitivity, e.g. to detect a main direction of a fluid flow, by analysis of the fluid-induced thrust exposed to individual pressure sensors, such as shown in the cross-section A-A’ in the lower part of Figure 1c.

[0088] Figure 2 shows an example embodiment of a device 1 according to the present disclosure, along a longitudinal section thereof. The device 1 is configured for sensing a pressure Pmof a fluid 2, such as a liquid 3 or a gas. The device 1 comprises a first layer 4, with a first main surface 5 and a second, opposing main surface 6. The first layer 4 has a row 7 of at least two through-holes 8 arranged in a row direction R and extending from the first main surface 5 to the second main surface 6. The at least two through-holes 8 each have a fluid inlet 9 exposed to the fluid pressure Pmat the first main surface 5 and a fluid outlet 10 at the second main surface 6. the device 1 also has a second layer 11 , with a third main surface 12 and a fourth, opposing main surface 13. The second layer 11 is attached to the second main surface 6 with the third main surface 12. The second layer 11 comprises a row 14 of at least two cavities 15 arranged in the row direction R. Each cavity 15 has a cavity opening 16 at the position 17 of the fluid outlet 10 of the at least two through-holes 8 of the first layer 4. At least one pressure-responsive element 18 extends in the row direction R being arranged in between the first layer 4 and the second layer 11 . The fluid pressure Pmat the fluid inlet 9 at the first main surface 5 can be transferred to the pressure- responsive element 18 via the fluid outlet 10 at the second main surface 6. The pressure-responsive element 18 is deflected (d) by the fluid pressure Pminto the at least two cavities 15 at the at least two cavity openings 16. A sensing configuration 19 is connected to the pressure-responsive element 18, for sensing the at least two deflections (d) of the pressure-responsive element 18 into the at least two cavities 15.

[0089] The sensing configuration 19 may be arranged at a neutral axis 59 of the device 1 , although in some embodiments the sensing configuration 19 may be arranged away from the neutral axis 59. The sensing configuration 19 comprises an optical sensing configuration 20, which may comprise at least one optical fiber 21 extending in the row direction R. The pressure-responsive element 18 comprises a membrane 22. The membrane 22 preferably comprises a membrane foil 23. The membrane 22 is preferably flat at at least one of the at least two fluid outlets 10 and / or cavity openings 16. The at least two through-holes 8 and the at least two cavities 15 may be spaced-apart in the row direction R, wherein at least one of the at least two through-holes 8, at least one corresponding cavity 15, at least one corresponding portion of the pressure-responsive element 18 and at least one corresponding portion of the sensing configuration 19 together form an individual pressure sensor 26.

[0090] At least one of the at least two fluid inlets 9 may be covered by a fluid- permeable filter 32, such as a grid or gauze, to prevent debris, such as soil, from entering the fluid inlet 9.

[0091] The first layer 4 and / or second layer 11 and / or the pressure- responsive element 18 may be in the form of a strip 36 extending in the row direction R. The device 1 / strip 36 may have a thickness of e.g. 1 - 5 mm.

[0092] Figure 3 shows an example embodiment of a device 1 according to the present disclosure, such as the example embodiment of the device 1 as shown in Figure 2, wherein, respectively, the first layer 4, the pressure-responsive element 18 comprising the sensing configuration 19, the second layer 11 and the pressure calibration channel 60 are viewed in a direction perpendicular to the respective layer 4, 11 , element 18 and channel 60. At least one of the at least two cavity openings 16 may be circular, oval, elliptical or rectangular, preferably with rounded corners, such as shown in Figure 3.

[0093] At least one optical fiber 21 may comprise a Fiber Bragg Grating (FBG) 33. The at least one optical fiber 21 may be a continuous optical fiber 34.

[0094] Pref may relate to a vacuum being applied, or a pressure lower than the pressure to be measured (Pm) at the top (fluid) side of the pressure-responsive element 18.

[0095] Figure 4 shows an example embodiment of a cross-section of the device 1 according to the present disclosure, such as the example embodiment of the device 1 as shown in Figures 2 and 3, at the position of the through-hole 8 / cavity opening 16. A diameter D1 of at least one of the fluid outlets 10 at the second main surface 6 may be 10 - 50 times an outer diameter D2 of the at least one optical fiber 21. The sensing configuration 19 is preferably arranged at a side of the pressure- responsive element 18 turned away from the first layer 4. At least one of the at least two cavities 15 may be in fluid contact with a pressure response calibration space 27 via the cavity opening 16 and / or a further cavity opening 28 separate from the cavity opening 16 to calibrate the pressure response of the pressure-responsive element 18 and / or sensing configuration 19. The calibration space 27 may be formed in a cover element 46, e.g. a detachable cover element, as shown in Figure 4, which covers the lower end of the cavity 15. The second layer 11 may be attached to the first layer 4 and / or the sensing configuration 19 may be attached to the pressure-responsive element 18 with a bonding layer 29. Therein:

[0096] At the position of the cavity 16, the bonding layer 29 comprises at least one protrusion 30, such as a V-shaped protrusion 31a, when seen in crosssection in a direction perpendicular to the row direction R, for holding and bonding the at least one optical fiber 21 to the pressure-responsive element 18. In addition thereto, at a position between cavities 16, the second layer 11 may comprise at least one groove 30, such as a V-shaped groove 31 b, when seen in cross-section in a direction perpendicular to the row direction R, for holding the at least one optical fiber 21 . Other shapes than a V-groove may also be conceivable, such as a blob shape. The shape as such is in principle not essential and is the result of the bonding material used. Instead of a bonding layer 29, other attachment means are conceivable. It should be noted that at all times strain of the pressure-responsive element should directly result in strain of the sensing configuration 19 / optical fiber 21 , i.e. the bonding layer 29 or material should not interfere with the foregoing.

[0097] The pressure-responsive element 18 / membrane 2 must be fixed between the first layer 4 and the second layer 11 in an “immovable” manner (i.e. the pressure-responsive element 18 may not come loose) e.g. by “clicking” the pressure- responsive element 18 into place, by clamping and / or welding.

[0098] A diameter D3 of at least one of the cavity openings 16 at the third main surface 12 may larger than a diameter D1 of the corresponding fluid outlet 10 at the second main surface 6. The diameters D1 and D3 may also be roughly the same.

[0099] Figures 5a - 5c shows several example embodiments of a pressure- responsive element 18 for use with a device 1 according to the present disclosure. The pressure-responsive elements 18 as shown are to be provided per through-hole 8 / cavity 15 pair, i.e. the pressure-responsive elements 18 are single / individual pressure-responsive elements. The pressure-responsive elements 18 thus does not extend past multiple pairs of through-holes 8 / cavity openings 16.

[0100] Figure 6 shows a cross-sectional view of the example embodiment of the pressure-responsive element 18 of Figure 5b. The membrane 22 may be rippled 24 at at least one of the at least two fluid outlets 10 and / or cavity openings 16. The ripples 24 are preferably concentrically arranged around a center 25 of the at least one of the at least two fluid outlets 10 and / or cavity openings 16. The optical sensing configuration 20 is preferably connected to the concentric ripples 24 at the center of the concentric ripples 24, such as via a spacer element 47, as shown in Figure 6.

[0101] Figure 7 shows an example embodiment of a device 1 according to the present disclosure, along a longitudinal section thereof, comprising a pressure calibration channel 60 provided with a reference pressure Pref. The device 1 may be calibrated as explained with reference to Figures 9a and 9b. For acoustic applications, a variable reference pressure Pref may be provided to the pressure calibration channel 60 such that the pressure-responsive element(s) 18 may function as an array of speakers.

[0102] Figure 8 shows an example embodiment of a longitudinal section of the device 1 according to the present disclosure at the position of a through-hole 8 / cavity opening 16, wherein the pressure-responsive element 18 is deflected into the cavity opening 16 (with the lower side of Figure 8 showing the strain distribution measured by the sensing configuration 19 for the respective row of cavity openings 16). The device 1 may be operated for sensing a pressure of a fluid 2 by: exposing the fluid inlets 9 of the at least two through-holes 8 to the fluid pressure P(m) at the first main surface 5; deflecting (d) the pressure-responsive element 18 into the at least two cavities 15 at the at least two cavity openings 16 by transferring the fluid pressure P to the pressure-responsive element 18 via the fluid outlets 10; and sensing the at least two deflections (d) of the pressure-responsive element 18 into the at least two cavities 15 with the sensing configuration 19 connected to the pressure-responsive element 18.

[0103] One or more light transmission properties of the optical fiber 21 may be measured when the pressure-responsive element 18 and the optical fiber 21 are deflected into the at least two cavities 15 with appropriate readout means 55.

[0104] Figure 9a shows an example embodiment of a cross-section of the device 1 according to the present disclosure at the position of a through-hole 8 / cavity opening 16, wherein the pressure-responsive element 18 is deflected into the cavity opening 16 by a fluid pressure Pm, while at the same time a reference pressure Pref is applied via the pressure calibration channel 60. Figure 9b shows an example embodiment of a longitudinal section of the device 1 according to the present disclosure at the position of a through-hole 8 / cavity opening 16, wherein the pressure-responsive element 18 is deflected into the cavity opening 16 by a fluid pressure Pm, while at the same time a reference pressure Pref is applied via the pressure calibration channel 60.

[0105] Figure 9c shows an example embodiment of a longitudinal section of the device 1 according to the present disclosure at the position of a through-hole 8 / cavity opening 16, wherein the pressure-responsive element 18 is deflected into the cavity opening 16 by a fluid pressure Pm, while at the same time a reference pressure Pref is applied via the pressure calibration channel 60, wherein a porous material 65 is arranged in the through-hole 8. The porous material 65 may be in the form of a disc or ring. The porous material 65 may be engineered to be selectively permeable to specific fluids as to measure the partial pressure of the specific fluid or family of fluids in a mixture of fluids.

[0106] Figure 9d shows an example embodiment of a longitudinal section of the device 1 according to the present disclosure at the position of a through-hole 8 / cavity opening 16, wherein the pressure-responsive element 18 is deflected into the cavity opening 16 by a fluid pressure Pm, while at the same time a reference pressure Pref is applied via the pressure calibration channel 60, wherein a (“zero”) calibration ring 64 is arranged in the through-hole 8. However, the calibration ring 64 may also be omitted to simplify construction of the device 1 and to improve the accuracy of the sensor calibration, because the direction of deflection is not altered during calibration.

[0107] The device 1 may be calibrated by: calibrating the pressure response of the pressure-responsive element 18 and / or sensing configuration 19 with the pressure response calibration space 27 via the cavity opening 15 and / or the further cavity opening 28.

[0108] Figure 10 shows an example embodiment of a device 1 according to the present disclosure, wherein a sensing configuration 19, with three parallel optical fibers 21 , and the second layer 11 are shown in a direction perpendicular to the sensing configuration 19 and the second layer 11 , i.e. the sensing configuration 19 comprises at least two, preferably at least three (as shown), parallel optical fibers 21 extending in the row direction R and arranged at the position 17 of the at least two cavity openings 16. It is also conceivable that the optical fiber 21 “zigzags” along the cavities 15, i.e. runs perpendicular to the row direction R at the position of the cavities 15 (indicated with reference numeral 21’).

[0109] Figure 11a shows an example embodiment of a device 1 according to the present disclosure, wherein a sensing configuration 19 with three parallel optical fibers 21 and two parallel calibration optical fibers 35, and the second layer 11 are shown in a direction perpendicular to the sensing configuration 19 and the second layer 11. The sensing configuration 19 comprises at least one calibration optical fiber 35, such as two (as shown) extending in the row direction R, parallel to the at least one optical fiber 21 , the at least one calibration optical fiber 35 not being arranged at the position 17 of the at least two cavity openings 16. The at least two parallel optical fibers 21 and / or the at least one calibration optical fiber 35 may be arranged at the neutral axis 59 (see e.g. Figure 2) and / or are not arranged at the neutral axis 59 of the device 1.

[0110] Figure 11b shows an example read-out of the strain of a device 1 according to the present disclosure connected to read-out equipment 55 in the form of a long-pulse distributed strain sensing instrument 55, i.e. a distributed strain sensing instrument 55 with a pulse width larger than the periodicity of the cavities 15 / cavity openings 16. The distributed strain read-out instrument 55 produces a forward-moving optical pulse 69. The graph 66 in the middle of Figure 11 b shows optical fiber 21 strain. The graph 67 in the lower part of Figure 11 b shows the distributed strain sensing instrument response. The strain 68 in the calibration optical fibers 35 is shown with some offset for clarity. In the lower graph, uniform strain induced in the calibration optical fibers 35 is recorded by the readout instrument 55. Therein, the read-out instrument 55 averages the strain induced in the optical fiber 21. It should be noted that the square wave as shown is an “ideal” signal shape - in reality the wave shape will be (slightly) different from a square wave. Furthermore, depending on the design variables chosen, many signal shapes are possible. An important aspect of the invention, is that read-out equipment with a lower spatial resolution (measurement points per unit of distance), can still perform accurate measurements by taking averages over portions of the device 1 as a whole. For example, to move over the square wave I periodic wave with a moving average is to measure the pressure over a range equal to the window of the moving average which translates to the spatial resolution of the read-out equipment 55. Thus, it is not intended to take a single average over an entire kilometers long device 1. Figure 12 shows an example method of manufacturing a device 1 according to the present disclosure, wherein the first layer 4, the second layer 11 , the pressure-responsive element 18 and the sensing configuration 19 are attached to each other by simultaneously guiding the first layer 4, the second layer 11 , the pressure- responsive element 18 and the sensing configuration 19 between two rotating roller presses 44 in the row direction R, such that the first layer 4, the second layer 11 , the pressure-responsive element 18 and the sensing configuration 19 are pressed together. The pressure response calibration space 27 may be arranged in a pressure response calibration space strip 61 , wherein the first layer 4, the second layer 11 , the pressure-responsive element 18, the sensing configuration 19 and the pressure response calibration space strip 61 are attached to each other by simultaneously guiding the first layer 4, the second layer 11 , the pressure-responsive element 18, the sensing configuration 19 and the pressure response calibration space strip 61 between the two rotating roller presses 44, in the row direction R, such that the first layer 4, the second layer 11 , the pressure-responsive element 18, the sensing configuration 19 and the pressure response calibration space strip 61 are pressed together.

[0111] Figure 13 shows an example embodiment of a device 1 according to the present disclosure, wherein the first layer 4 comprises multiple rows 7 of through- holes 8 extending in parallel row directions R1 , R2. The second layer 11 analogously may comprise multiple rows 14 of corresponding cavities 15 extending in the multiple row directions R1 , R2. One or more corresponding pressure-responsive elements 18 are arranged in between the first layer 4 and the second layer 11 , extending in (or spanning) the multiple row directions R1 , R2. A sensing configuration 19 may again be connected to the one or more corresponding pressure-responsive elements 18, for sensing the corresponding deflections (d) of the one or more pressure-responsive elements 18 into the corresponding cavities 15 in the multiple row directions R1 , R2. The through-holes 8 in the first layer 4 and the one or more corresponding cavities 15 in the second layer 11 may be spaced-apart at regular intervals I. The through-holes 8 in the first layer 4 and the one or more corresponding cavities 15 in the second layer 11 may also be spaced-apart at irregular intervals I. The through-holes 8 in the first layer 4 and the one or more corresponding cavities 15 in the second layer 11 may also be arranged in a group-wise manner 62, wherein the through-holes 8 / cavities 15 are spaced relatively closer together than at other positions in the row 7. The through- holes 8 and corresponding cavities 15 of one row 7, 14 may alternate with the through- holes 8 and corresponding cavities 15 of another row 14, 7.

[0112] Figure 14 shows an example embodiment of a device 1 according to the present disclosure, wherein the first layer 4 comprises multiple rows 7 of through- holes 8 arranged at an angle a with respect to each other, such as an angle a of 0 - 90 degrees, e.g. 15 - 75 degrees, such as 30 - 60 degrees. As shown in Figure 14, the device 1 may have a rectangular or square shape when viewed in a direction perpendicular to the first 4 and / or second layer 11.

[0113] Although the disclosure has been described above with reference to example embodiments, variants within the scope of the present disclosure will readily occur to those skilled in the art after reading the above description. Such variants are within the scope of the independent claims and the dependent claims. In addition, it is to be understood that express rights are requested for variants as described in the dependent claims. It should also be noted that the example embodiments shown in the Figures, or features thereof, may be combined to yield embodiments not explicitly shown in the Figures.

[0114] LIST OF REFERENCE NUMERALS

[0115] 1. Device for sensing a pressure of a fluid

[0116] 2. Fluid

[0117] 3. Liquid

[0118] 4. First layer

[0119] 5. First main surface

[0120] 6. Second main surface

[0121] 7. Row of through-holes

[0122] 8. Through-hole

[0123] 9. Fluid inlet

[0124] 10. Fluid outlet

[0125] 11. Second layer

[0126] 12. Third main surface

[0127] 13. Fourth main surface

[0128] 14. Row of cavities

[0129] 15. Cavity

[0130] 16. Cavity opening

[0131] 17. Position of fluid outlet of through-hole / cavity opening

[0132] 18. Pressure-responsive element

[0133] 19. Sensing configuration

[0134] 20. Optical sensing configuration

[0135] 21. Optical fiber

[0136] 22. Membrane

[0137] 23. Membrane foil

[0138] 24. Rippled membrane

[0139] 25. Center of fluid outlet and / or cavity opening.

[0140] 26. Individual pressure sensor

[0141] 27. Pressure response calibration space

[0142] 28. Further cavity opening

[0143] 29. Bonding layer

[0144] 30. Protrusion

[0145] 31. V-shaped protrusion (31a) / V-shaped groove (31 b)

[0146] 32. Fluid-permeable filter 33. Fiber Bragg Grating

[0147] 34. Continuous optical fiber

[0148] 35. Calibration optical fiber

[0149] 36. Strip

[0150] 37. Infrastructural element

[0151] 38. Soil

[0152] 39. Water

[0153] 40. Dike

[0154] 41. Hotspot

[0155] 42. Curve

[0156] 43. River

[0157] 44. Roller press

[0158] 45. V-shaped groove

[0159] 46. Cover element

[0160] 47. Spacer element

[0161] 48. Inlet of pressure response calibration space

[0162] 49. Outlet of pressure response calibration space

[0163] 50. Storage roll

[0164] 51. Water body

[0165] 52. Surface of water body

[0166] 53. Wave

[0167] 54. Roll-on / roll-off

[0168] 55. Readout equipment

[0169] 56. Tubular element

[0170] 57. Non-infrastructural element

[0171] 58. Outer surface of tubular element

[0172] 59. Neutral axis

[0173] 60. Pressure response calibration channel

[0174] 61. Pressure response calibration space strip

[0175] 62. Group of through-holes

[0176] 63. Acoustic signal

[0177] 64. Calibration ring

[0178] 65. Porous material

[0179] 66. Optical fiber strain 67. Distributed strain sensing instrument response

[0180] 68. Calibration fiber strain

[0181] 69. Forward-moving optical pulse of strain readout equipment Pm= Pressure to be measured

[0182] Pref = Reference pressure

[0183] R = Row direction (R1 , R2) d = Deflection of pressure-responsive element

[0184] D1 = Diameter of fluid outlet D2 = Diameter of optical fiber

[0185] D3 = Diameter of cavity opening

[0186] I = Interval between adjacent through-holes / cavities a = Angle between rows R1 , R2

Claims

CLAIMS1. Device (1) for sensing a pressure (Pm) of a fluid (2), such as a liquid (3) or a gas, comprising: a first layer (4), with a first main surface (5) and a second, opposing main surface (6), the first layer having a row (7) of at least two through-holes (8) arranged in a row direction (R) and extending from the first main surface to the second main surface, the at least two through-holes each having a fluid inlet (9) exposed to the fluid pressure at the first main surface and a fluid outlet (10) at the second main surface; a second layer (11), with a third main surface (12) and a fourth, opposing main surface (13), wherein the second layer is attached to the second main surface with the third main surface, the second layer comprising a row (14) of at least two cavities (15) arranged in the row direction (R), each having a cavity opening (16) at the position (17) of the fluid outlet of the at least two through-holes of the first layer; at least one pressure-responsive element (18) arranged in between the first layer and the second layer, wherein the fluid pressure at the fluid inlet at the first main surface can be transferred to the pressure-responsive element via the fluid outlet at the second main surface, wherein the pressure-responsive element is deflected (d) by the fluid pressure into each of the at least two cavities at the at least two cavity openings; and a sensing configuration (19) connected to the at least one pressure- responsive element, for sensing the at least two deflections of the at least one pressure-responsive element into the at least two cavities.

2. Device (1) according to claim 1 , wherein the first layer (4) and the pressure-responsive element (18) are formed as an integrated or monolithic layer (4).

3. Device (1) according to claim 1 or 2, wherein the sensing configuration (19) is arranged at a neutral axis (59) of the device.

4. Device (1) according to any one of the claims 1 - 3, wherein the sensing configuration (19) comprises an optical sensing configuration (20).

5. Device (1) according to claim 4, wherein the optical sensing configuration (20) comprises at least one optical fiber (21) extending in the row direction (R).

6. Device (1) according to claim 5, wherein a diameter (D1) of at least one of the fluid outlets (10) at the second main surface (6) is 10 - 50 times an outer diameter (D2) of the at least one optical fiber (21).

7. Device (1) according to any one of the preceding claims, wherein a diameter (D3) of at least one of the cavity openings (16) at the third main surface (12) is larger than a diameter (D1) of the corresponding fluid outlet (10) at the second main surface (6).

8. Device (1) according to any one of the preceding claims, wherein the pressure-responsive element (18) comprises a membrane (22).

9. Device (1) according to claim 7, wherein the membrane (22) comprises a membrane foil (23).

10. Device (1) according to claim 8 or 9, wherein the membrane (22) is flat at at least one of the at least two fluid outlets (10) and / or cavity openings (16).

11. Device (1) according to claim 8 or 9, wherein the membrane (22) is rippled (24) at at least one of the at least two fluid outlets (10) and / or cavity openings (16), wherein the ripples are preferably concentrically arranged around a center (25) of the at least one of the at least two fluid outlets and / or cavity openings, wherein the optical sensing configuration (20) is preferably connected to concentric ripples at the center of the concentric ripples.

12. Device (1) according to any one of the preceding claims, wherein the at least two through-holes (8) and the at least two cavities (15) are spaced-apart in the row direction (R), wherein at least one of the at least two through-holes, at least one corresponding cavity, at least one corresponding portion of the pressure-responsiveelement (18) and at least one corresponding portion of the sensing configuration (19) together form an individual pressure sensor (26).

13. Device (1) according to any one of the preceding claims, wherein at least one of the at least two cavity openings (16) is circular, oval, elliptical or rectangular, preferably with rounded corners.

14. Device (1) according to any one of the preceding claims, wherein the sensing configuration (19) is arranged at a side of the pressure-responsive element turned away from the first layer (4).

15. Device (1) according to any one of the preceding claims, wherein at least one of the at least two cavities (15) is in fluid contact with a pressure response calibration space (27) via the cavity opening (16) and / or a further cavity opening (28) separate from the cavity opening (16) to calibrate the pressure response of the pressure-responsive element (18) and / or sensing configuration (19).

16. Device (1) according to any one of the preceding claims, wherein the second layer (11) is attached to the first layer (4) and / or the sensing configuration (19) is attached to the pressure-responsive element (18) with a bonding layer (29).

17. Device (1) according to claims 5 and 16, wherein: at the position of the cavity (16), the bonding layer (29) comprises at least one protrusion (30), such as a V-shaped protrusion (31a), when seen in crosssection in a direction perpendicular to the row direction (R), for holding and bonding the at least one optical fiber (21) to the pressure-responsive element (18) and / or at a position between cavities (16), the second layer (11) comprises at least one groove (30), such as a V-shaped groove (31 b), when seen in cross-section in a direction perpendicular to the row direction (R), for holding the at least one optical fiber (21).

18. Device (1) according to any one of the preceding claims, wherein at least one of the at least two fluid inlets (9) is covered by a fluid-permeable filter (32), such as a grid or gauze, to prevent debris, such as soil, from entering the fluid inlet.

19. Device (1) according to any one of the preceding claims, wherein, when dependent on claim 5, at least one optical fiber (21) comprises a Fiber Bragg Grating (FBG) (33).

20. Device (1) according to any one of the preceding claims, wherein, when dependent on claim 5, at least one optical fiber (21) is a continuous fiber (34).

21. Device (1) according to any one of the preceding claims, wherein, when dependent on claim 5, the sensing configuration (19) comprises at least two, preferably at least three, parallel optical fibers (21) extending in the row direction (R) and arranged at the position (17) of the at least two cavity openings (16).

22. Device (1) according to any one of the preceding claims, wherein, when dependent on claim 5, the sensing configuration (19) comprises at least one calibration optical fiber (35), extending in the row direction (R), parallel to the at least one optical fiber (21), the at least one calibration optical fiber not being arranged at the position (17) of the at least two cavity openings (16).

23. Device (1) according to claim 21 or 22, wherein the at least two parallel optical fibers (21) and / or the at least one calibration optical fiber (35) are arranged at the neutral axis (59) and / or are not arranged at the neutral axis of the device.

24. Device (1) according to any one of the preceding claims, wherein the through-holes (8) in the first layer (4) and the one or more corresponding cavities (15) in the second layer (11) are spaced-apart at regular intervals (I).

25. Device (1) according to any one of the claims 1 - 23, wherein the through-holes (8) in the first layer (4) and the one or more corresponding cavities (15) in the second layer (11) are spaced-apart at irregular intervals (I).

26. Device (1) according to any one of the preceding claims, wherein the through-holes (8) in the first layer (4) and the one or more corresponding cavities (15) in the second layer (11) are arranged in a group-wise manner (62).

27. Device (1) according to any one of the preceding claims, wherein the first layer (4) and / or second layer (11) and / or the pressure-responsive element (18) are in the form of a strip (36) extending in the row direction (R).

28. Device (1) according to any one of the preceding claims, wherein the device has a rectangular or square shape when viewed in a direction perpendicular to the first (4) and / or second layer (11).

29. Device (1) according to any one of the preceding claims, wherein the device is more than 10 m, such as more than 50 m, such as more than 100 m, such as more than 500 m, such as more than 1000 m in length.

30. Device (1) according to any one of the preceding claims, wherein: the first layer (4) comprises multiple rows (7) of through-holes (8) extending in multiple row directions (R1 , R2); the second layer (11) comprises multiple rows (14) of corresponding cavities (15) extending in the multiple row directions; one or more corresponding pressure-responsive elements (18) are arranged in between the first layer and the second layer, extending in the multiple row directions; and a sensing configuration (19) is connected to the one or more corresponding pressure-responsive elements, for sensing the corresponding deflections (d) of the one or more pressure-responsive elements into the corresponding cavities in the multiple row directions.

31. Device (1) according to claim 30, wherein the multiple row directions (R1 , R2) are parallel.

32. Device (1) according to claim 31 , wherein the through-holes (8) and corresponding cavities (15) of one row (7; 14) alternate with the through-holes and corresponding cavities of another row (14; 7).

33. Device (1) according to claim 30, wherein the multiple rows (7, 14) are arranged at an angle (a) with respect to each other.

34. Infrastructural element (37), comprising soil (38) with water (39) as the fluid (2) and a device (1) according to any one of the preceding claims embedded in the soil for measuring pore water pressure in the soil.

35. Infrastructural element (37) according to claim 34, wherein the infrastructural element is a dike (40).

36. Infrastructural element (37) according to claim 34 or 35, wherein the infrastructural element is more than 10 m, such as more than 50 m, such as more than 100 m, such as more than 500 m, such as more than 1000 m in length.

37. Infrastructural element (37) according to claim 34, 35 or 36, wherein the device (1) has a length of at least 80%, such as at least 90%, such as at least 95% of a length of the infrastructural element.

38. Infrastructural element (37) according to any one of the claims 34 -37, wherein the device (1) is arranged at a hotspot (41), such as near a curve (42) in a river (43).

39. Infrastructural element (37) according to any one of the claims 34 -38, wherein the device (1) is arranged at a delimitation between the infrastructural element and an adjacent body of water (51), such as a river (43), the device extending through a surface (52) of the water body, such that waves (53) present at the surface of the water body impinge at least part of the device.

40. Tubular element (56), comprising a device (1) according to any one of the claims 1 - 33, wherein the device is helically wound around an outer surface (58) of the tubular element.

41. Method of operating a device (1) according to any one of the claims 1 - 33, for sensing a pressure of a fluid (2), comprising the steps of: exposing the fluid inlets (9) of the at least two through-holes (8) to the fluid pressure at the first main surface (5);deflecting (d) the pressure-responsive element (18) into the at least two cavities (15) at the at least two cavity openings (16) by transferring the fluid pressure to the pressure-responsive element via the fluid outlets (10); and sensing the at least two deflections of the pressure-responsive element into the at least two cavities with the sensing configuration (19) connected to the pressure-responsive element.

42. Method according to claim 41 , comprising the step of, when dependent on claim 5: measuring one or more light transmission properties of the optical fiber (21) when the pressure-responsive element (18) and the optical fiber are deflected into the at least two cavities (15).

43. Method of calibrating a device (1) according to any one of the claims 1 - 33, when dependent on claim 15, comprising the step of: calibrating the pressure response of the pressure-responsive element (18) and / or sensing configuration (19) with the pressure response calibration space (27) via the cavity opening and / or the further cavity opening (28).

44. Method according to claim 41 , further comprising the steps of the method according to claim 43.

45. Method of manufacturing a device (1) according to any one of the claims 1 - 33, when dependent on claim 27, wherein the first layer (4), the second layer (11), the pressure-responsive element (18) and the sensing configuration (19) are attached to each other by simultaneously guiding the first layer, the second layer, the pressure-responsive element and the sensing configuration between two rotating roller presses (44), preferably in the row direction (R), such that the first layer, the second layer, the pressure-responsive element and the sensing configuration are pressed together.

46. Method according to claim 45, wherein, when dependent on claim 15, the pressure response calibration space (27) is arranged in a pressure response calibration space strip, wherein the first layer (4), the second layer (11), the pressure-responsive element (18), the sensing configuration (19) and the pressure response calibration space strip are attached to each other by simultaneously guiding the first layer, the second layer, the pressure-responsive element, the sensing configuration and the pressure response calibration space strip between two rotating roller presses (44), preferably in the row direction (R), such that the first layer, the second layer, the pressure-responsive element, the sensing configuration and the pressure response calibration space strip are pressed together.

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