Optical fiber monitoring device and method for simultaneous measurement of temperature, humidity and total suction

Abstract

The application discloses a fiber monitoring device and method for simultaneous measurement of temperature, humidity and total suction three parameters, which comprises a packaging body, a filter core, a first fiber grating, a second fiber grating, a grating sleeve and an armored lead, the filter core and the grating sleeve are respectively arranged at two ends of the packaging body, the armored lead is arranged outside the grating sleeve, and the first and second fiber gratings are fixed to the outlet terminal after being passed through the filter core, the packaging body and the grating sleeve. In the application, the fiber sensing technology is used for simultaneous monitoring of the temperature, humidity and suction three parameters, without the need for on-site power supply, electromagnetic interference is avoided, the electrical insulation is good, the application range is wide, the quasi-distributed monitoring is realized by using the fiber sensing technology, and the application has the outstanding advantages of simple structure, small size, easy installation, good stability, high safety, high measurement precision, high sensitivity, fast response speed, batch production and the like, and is suitable for fine monitoring of air temperature and humidity on the ground and monitoring of the temperature, humidity and suction of unsaturated soil.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental monitoring, and particularly relates to a fiber-optic monitoring device and method for synchronously measuring temperature, humidity and total suction. BACKGROUND

[0002] Humidity is an important environmental parameter, and its measurement is of great significance in the fields of aerospace, mining, medicine, food, agriculture, petrochemical industry, power and the like. Currently commonly used humidity sensors mainly include electrolyte type humidity sensors, ceramic type humidity sensors and polymer type humidity sensors, which all have certain limitations: the electrolyte type humidity sensor has serious humidity hysteresis, small humidity measurement range, poor pollution resistance and durability; the ceramic type humidity sensor has low precision and is difficult to integrate; and the measurement results of the capacitive or resistive polymer type humidity sensor are easily affected by the ambient temperature.

[0003] Suction is one of the most important parameters in unsaturated soil. Among the current several monitoring methods, the non-contact filter paper method, the cold mirror dew point instrument method and the steam equilibrium method are generally used for indoor tests, and need to prepare compacted soil samples in advance and are affected by temperature, and are not suitable for in-situ measurement and cannot meet the requirements of real-time measurement. The thermocouple humidity meter, the polymer capacitive humidity sensor and the Sol-gel resistive humidity sensor can be used for in-situ measurement of total suction after packaging, but these three methods are based on electrical signal measurement, and the test accuracy and stability will be poor in long-term measurement, and the sensors have high cost, large volume and high sensitivity to electromagnetic interference, and cannot be used in disposal repositories with high temperature, high radioactivity and strong electromagnetic interference.

[0004] The fiber-optic monitoring technology has unique advantages of small volume, low cost, high temperature resistance, anti-electromagnetic interference, good durability, distributed and real-time measurement, and if the above humidity and suction monitoring can be synchronously realized based on the fiber-optic technology, it will have wide application prospects.

[0005] A Chinese invention patent with application number 201810780619.7 discloses a fiber humidity sensor, a manufacturing method, a data processing method, and an acquisition device. The FBG in the patent is coated with a polyimide coating layer and can respond to changes in humidity and temperature. However, the response time required by polyimide is relatively long, the humidity sensitivity coefficient is not high, and the PI manufacturing process is complex. The curing temperature and curing time will affect the humidity-sensitive characteristics of the humidity-sensitive element. A Chinese invention patent with application number 201921507331.9 discloses an all-fiber humidity sensing device based on a polyvinyl alcohol film. The polyvinyl alcohol solution is dropped on the fiber grating, and after drying treatment, a polyvinyl alcohol film is formed. When the humidity of the external environment changes, the polyvinyl alcohol film can quickly absorb and analyze the moisture around it, and reach equilibrium with the external humidity, thereby causing the wavelength of the micro-nano fiber grating to shift. However, the polyvinyl alcohol manufacturing process is complex, the linearity between polyvinyl alcohol and humidity is general, the measurement accuracy is low, the stability is poor, and the humidity is poor, which cannot meet the current measurement requirements. A Chinese invention patent with application number 201320883480.1 discloses a humidity sensing structure based on a fiber Bragg grating. The deposition of silica dioxide is used as a water-absorbing material to realize humidity and temperature measurement. However, it separates temperature and humidity into two independent individuals and realizes humidity sensitivity by filling the water-absorbing material in the tube. However, the packaging structure is complex and not convenient for practical application. SUMMARY

[0006] To solve the technical problems existing in the prior art, the purpose of the present application is to provide a fiber monitoring device and method for simultaneous measurement of temperature and humidity and total suction three parameters.

[0007] To achieve the above-mentioned purposes and achieve the above-mentioned technical effects, the technical solution adopted by the present application is as follows:

[0008] The fiber monitoring device for simultaneous measurement of temperature and humidity and total suction three parameters comprises a packaging main body, a filter core, a first fiber grating, a second fiber grating, a grating sleeve, and an armored lead. One end of the packaging main body is provided with a filter core, and the other end of the packaging main body opposite to the one end is provided with a grating sleeve. The grating sleeve is externally provided with an armored lead. The first fiber grating and the second fiber grating are both sequentially passed out of the filter core, the packaging main body, and the grating sleeve and then fixed to the outlet terminal.

[0009] Further, one end of the packaging main body is detachably provided with a connecting sleeve head. The end of the connecting sleeve head away from the packaging main body is fixed to the filter core.

[0010] Further, the packaging body comprises a hollow sleeve, a threaded connecting column, a grating fixing plate and a fiber outlet hole, the hollow sleeve, the threaded connecting column and the grating fixing plate are coaxially arranged, one end of the hollow sleeve is provided with the threaded connecting column, the threaded connecting column is provided with external threads, the connecting sleeve head is provided with internal threads matched with the external threads, one end of the grating fixing plate penetrates through the threaded connecting column and extends into the hollow sleeve, the other end of the grating fixing plate opposite to the one end is provided with a filter core, the first fiber grating and the second fiber grating are fixed on two sides of the grating fixing plate respectively, the first fiber grating and the second fiber grating are both fixed by one end through an adhesive, and the threaded connecting column is provided with a plurality of fiber outlet holes which are distributed on different sides of the grating fixing plate.

[0011] Further, the threaded connecting column is provided with two fiber outlet holes which are symmetrically distributed on two opposite sides of the grating fixing plate, the diameter of the fiber outlet hole is 0.3-0.5 mm, and the tail fiber of the first fiber grating and the second fiber grating respectively penetrates through one fiber outlet hole and then extends into the hollow sleeve and then penetrates out from the center of the grating sleeve.

[0012] Further, the filter core is a porous structure of sintered stainless steel at high temperature, the pore size is 1-65 mu m, the diameter is 10-12 mm, and the height is 20-50 mm, the filter core is fixed with the connecting sleeve head through an adhesive, and the diameter of the filter core is the same as that of the hollow sleeve of the packaging body.

[0013] Further, the first fiber grating is a humidity and suction measuring grating which can respond to changes in humidity and suction, the grating area length of the first fiber grating is 10±4 mm, the humidity sensitive material coated on the grating area is , the coating thickness is 30±5 mu m, and the coating length is 15±5 mm; the second fiber grating is a temperature measuring grating, the grating area length of the second fiber grating is 10±4 mm, the material coated on the grating area is acrylate, and the second fiber grating can only respond to changes in temperature.

[0014] Further, the diameter of the grating sleeve is 0.9-1.2 mm, the armored lead wire penetrates through the center of the grating sleeve, and the diameter of the armored lead wire is 3-5 mm.

[0015] The application also discloses application of the fiber monitoring device for synchronously measuring three parameters of temperature, humidity and total suction as described above in fine monitoring of air temperature and humidity on the ground surface and monitoring of temperature, humidity and suction of unsaturated soil.

[0016] The application discloses an application method of the fiber monitoring device for synchronously measuring three parameters of temperature, humidity and total suction in fine monitoring of air temperature and humidity on the ground surface, and the application method comprises the following steps:

[0017] (1) Hammer the support pole into the soil to a depth of more than 30 cm to ensure stability;

[0018] (2) Insert the fiber optic monitoring device for simultaneous measurement of temperature, humidity and total suction into the holes reserved for the support poles according to the designed spacing and fasten them with screws;

[0019] (3) 3-6 optical fiber monitoring devices for synchronously measuring the three parameters of temperature, humidity and total suction can be connected in parallel through a splitter and connected to an optical fiber demodulation device to obtain monitoring wavelength data.

[0020] (4) Calculate the near-surface air temperature and humidity using formulas (1) and (2):

[0021]

[0022]

[0023] Where RH is the relative humidity of the air near the surface, %; t is the air temperature near the surface, °C; K t1 , K t2 are the temperature sensitivity coefficients of the first fiber Bragg grating 14 and the second fiber Bragg grating 15, pm / °C; K RH is the humidity sensitivity coefficient of the first fiber Bragg grating 14, pm / %; Δλ1 and Δλ2 are the wavelength changes of the first fiber Bragg grating 14 and the second fiber Bragg grating 15, pm; t0 and RH0 are the initial temperature (°C) and the initial relative humidity (%), respectively.

[0024] The present invention discloses an optical fiber monitoring device for synchronously measuring three parameters of temperature, humidity and total suction, and a method for using the device in monitoring the temperature, humidity and suction of unsaturated soil, comprising the following steps:

[0025] (1) Drill holes according to the designed depth and clean the residue in the holes;

[0026] (2) Fixing the optical fiber monitoring device for synchronously measuring the three parameters of temperature, humidity and total suction on a corresponding connecting rod, placing the connecting rod and the optical fiber monitoring device for synchronously measuring the three parameters of temperature, humidity and total suction in an outer cylindrical frame, and straightening and fixing the pigtails of the first fiber Bragg grating and the second fiber Bragg grating;

[0027] (3) Insert the connecting rod, the optical fiber monitoring device for synchronous measurement of temperature, humidity and total suction, and the outer cylindrical frame into the hole as a whole. Fit the outer cylindrical frame to the inner wall of the hole and backfill with screened undisturbed soil to a backfill height of 5 to 10 cm.

[0028] (4) Install the compaction mass block, with a hole in the center of the compaction mass block slightly larger than the diameter of the connecting rod;

[0029] (5) compacting the undisturbed soil by the compacting mass, pulling the compacting mass and the peripheral cylindrical frame to the surface of the undisturbed soil, and continuing to backfill the undisturbed soil according to the above steps, and compacting in layers until the aperture;

[0030] (6) the three-parameter synchronous measurement optical fiber monitoring device of temperature, humidity and total suction is connected in parallel through a shunt and connected to an optical fiber demodulation equipment to obtain monitoring wavelength data;

[0031] (7) the temperature and relative humidity of the unsaturated soil body are calculated through formulas (1) and (2), and the total suction is calculated through formula (3):

[0032]

[0033] wherein s t is the total suction of the unsaturated soil body, kPa; R is a general gas constant, R = 8.31432 J / (mol K); T is an absolute temperature (K), T = 273.16 + t; t is the temperature in ℃; ρ W is the density of water, ρ W = 998 kg / m 3 when t = 20 ℃; υ0 is the reciprocal of the density of water, υ0 = 1 / ρ W , m 3 / kg; ω V is the gram molecular weight of water vapor, ω V = 18.016 kg / kmol; and RH is the humidity of the pore gas of the soil body, %RH.

[0034] Compared with the prior art, the beneficial effects of the present application are:

[0035] 1) The optical fiber sensing technology is used for simultaneous monitoring of temperature, humidity and suction, without the need for on-site power supply, avoiding electromagnetic interference, good electrical insulation, wide application range, and compared with the traditional point monitoring method, the quasi-distributed monitoring is realized by using the optical fiber sensing technology.

[0036] 2) The humidity-sensitive material coated on the grating area of the first fiber grating is The material coated on the grating area of the second fiber grating is acrylate, which can realize synchronous monitoring of the three parameters of temperature, humidity and suction, has the outstanding advantages of simple structure, small size, easy installation, good stability, high safety, high measurement accuracy, high sensitivity, fast response speed, batch production, etc., and is suitable for fine monitoring of surface air temperature and humidity and monitoring of temperature, humidity and suction of unsaturated soil body, and can be used in complex and harsh environments such as oil and gas industry, nuclear power industry and weapon explosive warehouse. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram of the overall three-dimensional structure of the present application;

[0038] Figure 2 is an exploded view of the present application;

[0039] Figure 3 is an internal cross-sectional view of the present application;

[0040] Figure 4 is a perspective view of the package body of the present application;

[0041] Figure 5 is a right view of the package body of the present application;

[0042] Figure 6 is a schematic view of the optical fiber monitoring device for simultaneous measurement of temperature, humidity and total suction three parameters in the fine monitoring of surface air temperature and humidity of the present application;

[0043] Figure 7 is a schematic view of the optical fiber monitoring device for simultaneous measurement of temperature, humidity and total suction three parameters in the monitoring of temperature, humidity and suction of unsaturated soil of the present application;

[0044] Figure 8 is a schematic view of the limiting device of the present application;

[0045] Figure 9 is a calibration graph of temperature and humidity of the present application; wherein, figure a is the wavelength and temperature relationship of the first and second fiber gratings under the condition of humidity 11.3%, temperature 10-60℃, and figure b is the wavelength and humidity relationship of the first fiber grating under the condition of temperature 25℃, humidity 11.3-97.8%RH;

[0046] Figure 10 is a humidity and total suction curve of unsaturated soil of the present application; wherein, figure a is the relative humidity and total suction curve of unsaturated soil pore air at 25℃, and figure b is the wavelength curve of the first fiber grating and total suction in unsaturated soil at 25℃. DETAILED DESCRIPTION

[0047] The present application will be described in detail below so that the advantages and features of the present application can be more easily understood by those skilled in the art, and the scope of protection of the present application can be more clearly defined.

[0048] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0049] On the one hand, the present invention discloses an optical fiber monitoring device for synchronously measuring temperature, humidity and total suction, such as Figures 1-5 As shown, the device includes a packaging body 11, a filter element 12, a connecting sleeve 13, a first fiber Bragg grating 14, a second fiber Bragg grating 15, a grating sleeve 16, an armored lead 17 and an outlet terminal 18. A connecting sleeve 13 is provided at one end of the packaging body 11, and the connecting sleeve 13 is fixedly connected to the filter element 12. A grating sleeve 16 is provided at the other opposite end of the packaging body 11. An armored lead 17 is provided on the outside of the grating sleeve 16. The center of the grating sleeve 16 passes through the armored lead 17. The pigtails of the first fiber Bragg grating 14 and the second fiber Bragg grating 15, the grating sleeve 16 and the armored lead 17 pass through the outlet terminal 18 and are fixed to the outlet terminal 18 by an adhesive.

[0050] The packaging body 11 includes a hollow sleeve 21, a threaded connecting column 22, a grating fixing plate 23 and a fiber outlet hole 24. The hollow sleeve 21, the threaded connecting column 22 and the grating fixing plate 23 are a whole and the three are coaxially arranged. A threaded connecting column 22 is provided at one end of the hollow sleeve 21. The threaded connecting column 22 is provided with an external thread that is compatible with the connecting sleeve 13. One end of the grating fixing plate 23 passes through the threaded connecting column 22 and extends into the hollow sleeve 21. The other end opposite to the grating fixing plate 23 is provided with a filter element 12. The hollow sleeve 21 has the same diameter as the filter element 12. Two fiber outlet holes 24 are provided on the threaded connecting column 22. The two fiber outlet holes 24 are symmetrically distributed on both sides of the grating fixing plate 23. The diameter of the fiber outlet hole 24 is 0.3~0.5mm.

[0051] One end of the connecting sleeve 13 is fixed to the filter element 12, and the other end thereof is an open-hole structure, in which an internal thread matching the external thread is arranged. The connecting sleeve 13 is fixed to the threaded connecting column 22 by the cooperation between the internal thread and the external thread. The filter element 12 is a porous structure of stainless steel sintered by powder at high temperature, with a pore size of 1 to 65 μm, a diameter of 10 to 12 mm, and a height of 20 to 50 mm. The filter element 12 is fixed to the connecting sleeve 13 by an adhesive.

[0052] The first fiber Bragg grating 14 is a humidity and suction measurement grating. The grating area length of the first fiber Bragg grating 14 is 10±4 mm, and the humidity sensitive material coated on the grating area is The coating thickness is 30±5 μm and the coating length is 15±5 mm.

[0053] The second fiber Bragg grating 15 is a temperature measurement grating. The grating region length of the second fiber Bragg grating 15 is 10±4 mm. The material coated on the grating region is acrylic ester and can only respond to temperature changes.

[0054] The first fiber grating 14 and the second fiber grating 15 are fixed on both sides of the grating fixing plate 23, and the first fiber grating 14 and the second fiber grating 15 are both fixed by a single end through an adhesive, the tail fibers of the first fiber grating 14 and the second fiber grating 15 respectively pass into one fiber outlet hole 24 and then pass out, the tail fibers of the first fiber grating 14 and the second fiber grating 15 pass through the fiber outlet hole 24 and extend into the hollow sleeve 21, and then pass through the center of the grating sleeve 16, the diameter of the grating sleeve 16 is 0.9-1.2mm, the center of the grating sleeve 16 passes through the armored lead 17, and the diameter of the armored lead 17 is 3-5mm.

[0055] In addition, the application further discloses an application of the fiber monitoring device for simultaneously measuring three parameters of temperature, humidity and total suction in fine monitoring of air temperature and humidity on the ground and monitoring of temperature, humidity and suction of unsaturated soil.

[0056] The application method of the fiber monitoring device for simultaneously measuring three parameters of temperature, humidity and total suction in fine monitoring of air temperature and humidity on the ground is as shown in the figure and comprises the following steps: Figure 6

[0057] (1) hammer the supporting vertical rod 31 into the soil 32, and the depth of the soil is greater than 30cm to ensure stability;

[0058] (2) insert the fiber monitoring device 33 for simultaneously measuring three parameters of temperature, humidity and total suction into the hole reserved in the supporting vertical rod 31 according to the designed interval, and fasten through the screw 34;

[0059] (3) 3-6 fiber monitoring devices 33 for simultaneously measuring three parameters of temperature, humidity and total suction are connected in parallel through a shunt and connected to a fiber demodulation device to obtain monitoring wavelength data.

[0060] (4) calculate the air temperature and humidity near the ground through formulas (1) and (2):

[0061]

[0062]

[0063] Wherein, RH is the relative humidity of the air near the ground, %, t is the air temperature near the ground, ℃, K t1 , K t2 are the temperature sensitivity coefficients of the first fiber grating 14 and the second fiber grating 15, pm / ℃, respectively, K RH is the humidity sensitivity coefficient of the first fiber grating 14, pm / %, and Δλ1 and Δλ2 are the wavelength change amounts of the first fiber grating 14 and the second fiber grating 15, pm, t0 and RH0 are the initial temperature (℃) and the initial relative humidity (%), respectively.

[0064] ​The application method of the temperature, humidity and total suction three-parameter synchronous measurement optical fiber monitoring device of the application in the monitoring of the temperature, humidity and suction of the unsaturated soil body is as shown in the accompanying drawings and comprises the following steps: Figures 7-8

[0065] (1) Drill a hole 41 with a diameter of 5-10 cm according to the designed depth, and clean the residual materials in the hole;

[0066] (2) Fix the temperature, humidity and total suction three-parameter synchronous measurement optical fiber monitoring device 33 on the connecting rod 42, the connecting rod 42 is a hollow structure with an outer diameter consistent with that of the temperature, humidity and total suction three-parameter synchronous measurement optical fiber monitoring device 33, straighten the tail fiber 43 of the first fiber grating 14 and the second fiber grating 15, and fix the tail fiber 43 through the wire locker 44 on the upper part of the connecting rod 42;

[0067] (3) Put the connecting rod 42, the temperature, humidity and total suction three-parameter synchronous measurement optical fiber monitoring device 33 and the peripheral cylindrical frame 46 into the hole 41 as a whole, fix the connecting rod 42 and the peripheral cylindrical frame 46 in the hole 41 through the limiting device 45, and make the peripheral cylindrical frame 46 fit the inner wall of the hole 41; backfill the original soil 48 after screening, and the backfill height is 5-10 cm; the limiting device 45 is provided with a fixing hole 51 and a limiting hole 52, a fixing screw is passed through the fixing hole 51 to fix the limiting device 45 and the peripheral cylindrical frame 46, and a limiting screw is passed through the limiting hole 52 to fix the limiting device 45 and the connecting rod 42, as shown in a; Figure 7

[0068] (4) Remove the limiting device 45, and install the tamping mass 47, the tamping mass 47 is provided with a central hole with a diameter slightly larger than that of the connecting rod 42, as shown in b; Figure 7

[0069] (5) Tamp the original soil 48 through the tamping mass 47, and lift the tamping mass 47 and the peripheral cylindrical frame 46 to the surface layer of the original soil 48, continue to backfill the drilled hole according to the above steps, and tamp layer by layer until the hole mouth, as shown in c; Figure 7

[0070] (6) Connect 3-6 temperature, humidity and total suction three-parameter synchronous measurement optical fiber monitoring devices 33 in parallel through a shunt, and connect the devices to an optical fiber demodulation device to obtain monitoring wavelength data;

[0071] (7) Calculate the temperature and relative humidity of the unsaturated soil body through formulas (1) and (2), and calculate the total suction through formula (3):

[0072]

[0073] Wherein, s t ​​​​is the total suction of the unsaturated soil, kPa; R is the universal gas constant, R = 8.31432 J / (mol K); T is the absolute temperature (K), T = 273.16 + t; t is the temperature in °C; ρ w is the density of water. When t = 20℃, ρ W =998kg / m 3 ;υ0 is the reciprocal of the density of water, υ0=1 / ρ W , m 3 / kg;ω v is the gram molecular weight of water vapor, ω v =18.016kg / kmol; RH is the pore gas humidity of the soil, %RH.

[0074] Example 1

[0075] like Figures 1-6 and Figure 9 As shown, the optical fiber monitoring device for synchronous measurement of temperature, humidity and total suction three parameters includes a packaging body 11, a filter element 12, a connecting sleeve 13, a first optical fiber Bragg grating 14, a second optical fiber Bragg grating 15, a grating sleeve 16, an armored lead 17 and an outlet terminal 18. A connecting sleeve 13 is provided at one end of the packaging body 11, and the connecting sleeve 13 is fixedly connected to the filter element 12. A grating sleeve 16 is provided at the other opposite end of the packaging body 11. An armored lead 17 is provided on the outside of the grating sleeve 16. The center of the grating sleeve 16 passes through the armored lead 17. The pigtails of the first optical fiber Bragg grating 14 and the second optical fiber Bragg grating 15, the grating sleeve 16 and the armored lead 17 pass through the outlet terminal 18 and are fixed to the outlet terminal 18 by an adhesive.

[0076] The packaging body 11 includes a hollow sleeve 21, a threaded connecting column 22, a grating fixing plate 23 and a fiber outlet hole 24. The hollow sleeve 21, the threaded connecting column 22 and the grating fixing plate 23 are a whole and the three are coaxially arranged. A threaded connecting column 22 is provided at one end of the hollow sleeve 21. The threaded connecting column 22 is provided with an external thread that is compatible with the connecting sleeve 13. One end of the grating fixing plate 23 passes through the threaded connecting column 22 and extends into the hollow sleeve 21. The other end opposite to the grating fixing plate 23 is provided with a filter element 12. The hollow sleeve 21 has the same diameter as the filter element 12. Two fiber outlet holes 24 are provided on the threaded connecting column 22. The two fiber outlet holes 24 are symmetrically distributed on both sides of the grating fixing plate 23. The diameter of the fiber outlet hole 24 is 0.5 mm.

[0077] The connecting sleeve head 13 is fixed at one end with the filter core 12, and the other end is an open hole structure, and an internal thread matched with an external thread is arranged in the hole. The connecting sleeve head 13 is fixed on the threaded connecting column 22 through the cooperation of the internal thread and the external thread. The filter core 12 is a high-temperature powder sintered stainless steel porous structure, with a pore diameter of 1-65 μm, a diameter of 12 mm, and a height of 30 mm. The filter core 12 is fixed with the connecting sleeve head 13 through an adhesive.

[0078] The first fiber grating 14 is a humidity and suction measuring grating. The grating area of the first fiber grating 14 is 10 mm long, and the humidity-sensitive material coated on the grating area is with a coating thickness of 30 μm and a coating length of 15 mm.

[0079] The second fiber grating 15 is a temperature measuring grating. The grating area of the second fiber grating 15 is 10 mm long, and the material coated on the grating area is acrylate, which can only respond to temperature changes.

[0080] The first fiber grating 14 and the second fiber grating 15 are fixed on both sides of the grating fixing plate 23. Both the first fiber grating 14 and the second fiber grating 15 are fixed by one end through an adhesive. The tail fibers of the first fiber grating 14 and the second fiber grating 15 respectively pass through one fiber outlet hole 24 and then out. The tail fibers of the first fiber grating 14 and the second fiber grating 15 pass through the fiber outlet hole 24 and extend into the hollow sleeve 21, and then pass through the center of the grating sleeve 16. The diameter of the grating sleeve 16 is 0.9 mm. The grating sleeve 16 passes through the armored lead 17, and the diameter of the armored lead 17 is 3 mm.

[0081] The application method of the fiber monitoring device for simultaneous measurement of temperature, humidity, and total suction three parameters in the fine monitoring of surface air temperature and humidity of the embodiment is as shown in Figure 6 , which includes the following steps:

[0082] (1) Hammer the support stand 31 into the soil 32 to a depth of more than 30 cm to ensure stability.

[0083] (2) Insert the fiber monitoring device 33 for simultaneous measurement of temperature, humidity, and total suction three parameters into the hole reserved in the support stand 31 according to the designed spacing, and fasten it through the screw 34.

[0084] (3) The three fiber monitoring devices 33 for simultaneous measurement of temperature, humidity, and total suction three parameters can be connected in parallel through a shunt and connected to a fiber demodulation device to obtain monitoring wavelength data.

[0085] (4) Calculate the near-surface air temperature and humidity through formulas (1) and (2):

[0086]

[0087]

[0088] Wherein, RH is the relative humidity of the near-surface air, %; t is the near-surface air temperature, ℃; K t1 , K t2 are the temperature sensitivity coefficients of the first fiber grating 14 and the second fiber grating 15, pm / ℃, respectively; K RH is the humidity sensitivity coefficient of the first fiber grating 14, pm / %; Δλ1 and Δλ2 are the wavelength change amounts of the first fiber grating 14 and the second fiber grating 15, pm; t0 and RH0 are the initial temperature (℃) and the initial relative humidity (%), respectively.

[0089] Figure 9 is the calibration graph of temperature and humidity, Fig. a is the relationship between the wavelength and the temperature of the first fiber grating 14 and the second fiber grating 15 under the conditions of humidity 11.3% and temperature 10-60℃, and Fig. b is the relationship between the wavelength and the humidity of the first fiber grating 14 under the conditions of temperature 25℃ and humidity 11.3-97.8% RH.

[0090] Example 2

[0091] The application method of the fiber monitoring device for simultaneous measurement of temperature, humidity and total suction three parameters in the monitoring of temperature, humidity and suction of unsaturated soil body is as shown in Fig. Figures 7-8 , which comprises the following steps:

[0092] (1) Drill a hole 41 with a diameter of 5 cm according to the designed depth, and clean the residues in the hole;

[0093] (2) Fix the fiber monitoring device 33 for simultaneous measurement of temperature, humidity and total suction three parameters on the connecting rod 42, which is a hollow structure with an outer diameter consistent with that of the fiber monitoring device 33 for simultaneous measurement of temperature, humidity and total suction three parameters (both are 12 mm), straighten the tail fibers 43 of the first fiber grating 14 and the second fiber grating 15, and fix them through the wire locker 44 on the upper part of the connecting rod 42;

[0094] (3) Put the connecting rod 42, the fiber monitoring device 33 for simultaneous measurement of temperature, humidity and total suction three parameters, and the peripheral cylindrical frame 46 into the hole 41 as a whole, fix the connecting rod 42 and the peripheral cylindrical frame 46 in the hole 41 through the limiting device 45, and make the peripheral cylindrical frame 46 fit the inner wall of the hole 41; backfill the undisturbed soil 48 after screening, and the backfilling height is 5 cm; the limiting device 45 is provided with a fixing hole 51 and a limiting hole 52, a fixing screw passes through the fixing hole 51 to fix the limiting device 45 and the peripheral cylindrical frame 46, and a limiting screw passes through the limiting hole 52 to fix the limiting device 45 and the connecting rod 42, as shown in Fig. Figure 7 a;

[0095] (4) Remove the limiting device 45, install the compaction mass 47, the compaction mass 47 has a center hole with a diameter of 12.4mm, which is slightly larger than the diameter of the connecting rod 42, as shown in Figure 7 b;

[0096] (5) Compaction of the undisturbed soil 48 by the compaction mass 47, lifting the compaction mass 47 and the peripheral cylindrical frame 46 to the surface of the undisturbed soil 48, and continuing to backfill the drilled hole according to the above steps, layer-by-layer compaction, until the hole is filled, as shown in Figure 7 c;

[0097] (6) Parallel connection of the three-parameter simultaneous measurement optical fiber monitoring device 33 through the shunt, and access to the optical fiber demodulation equipment to obtain the monitoring wavelength data;

[0098] (7) Calculation of the temperature and relative humidity of the unsaturated soil body by formulas (1) and (2), and calculation of the total suction by formula (3):

[0099]

[0100] wherein, s t is the total suction of the unsaturated soil body, kPa; R is the universal gas constant, R = 8.31432 J / (mol K); T is the absolute temperature (K), T = 273.16 + t; t is the temperature in ℃; ρ w is the density of water, ρ W = 998 kg / m 3 when t = 20℃; υ0 is the reciprocal of the density of water, υ0 = 1 / ρ W , m 3 / kg; ω v is the molar mass of water vapor, ω v = 18.016 kg / kmol; RH is the humidity of the soil body, %RH.

[0101] Figure 10 Fig. a is a curve diagram of the relative humidity of the unsaturated soil pore air and the total suction at 25℃, and Fig. b is a curve diagram of the total suction in the unsaturated soil and the wavelength of the first fiber grating 14 at 25℃.

[0102] The remaining parts or structures not specifically described in the present application can adopt the prior art or existing products, which will not be described here.

[0103] The parts or structures not specifically described in the present application can adopt the prior art or existing products, which will not be described here.

[0104] The above merely illustrates the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. The application method of the optical fiber monitoring device for simultaneous measurement of temperature, humidity and total suction three parameters in the monitoring of temperature, humidity and suction of unsaturated soil body, characterized in that, The temperature and humidity and total suction three-parameter synchronous measurement optical fiber monitoring device includes a packaging body, a filter core, a first fiber grating, a second fiber grating, a grating sleeve and an armored lead, one end of the packaging body is provided with the filter core, the other end of the packaging body opposite to the one end is provided with the grating sleeve, the grating sleeve is externally provided with the armored lead, the first fiber grating and the second fiber grating are both sequentially out of the filter core, the packaging body and the grating sleeve and then fixed to the wire outlet terminal; The application method comprises the following steps: (1) drilling according to the designed depth, cleaning the residual in the hole; (2) fixing the temperature and humidity and total suction three-parameter synchronous measurement optical fiber monitoring device on the matching connecting rod, placing the connecting rod and the temperature and humidity and total suction three-parameter synchronous measurement optical fiber monitoring device in the peripheral cylindrical frame, straightening and fixing the tail fibers of the first fiber grating and the second fiber grating; (3) putting the connecting rod, the temperature and humidity and total suction three-parameter synchronous measurement optical fiber monitoring device and the peripheral cylindrical frame into the hole as a whole, making the peripheral cylindrical frame adhere to the inner wall of the hole, backfilling the screened undisturbed soil with a height of 5-10 cm; (4) installing the compaction mass block, the compaction mass block is provided with a central hole slightly larger than the diameter of the connecting rod; (5) compacting the undisturbed soil through the compaction mass block, lifting the compaction mass block and the peripheral cylindrical frame to the surface layer of the undisturbed soil, continuously backfilling the undisturbed soil according to the above steps, and compacting layer by layer until the hole mouth; (6) connecting 3-6 temperature and humidity and total suction three-parameter synchronous measurement optical fiber monitoring devices in parallel through a shunt, connecting the optical fiber demodulation equipment, and obtaining the monitoring wavelength data; (7) calculating the temperature and relative humidity of the unsaturated soil body through formulas (1) and (2), and calculating the total suction through formula (3): （1）； （2）； （3）； wherein, RH is the relative humidity of the unsaturated soil body; t is the temperature of the unsaturated soil body, °C; are the temperature sensitivity coefficients of the first and second fiber Bragg gratings, respectively, pm / °C; is the humidity sensitivity coefficient of the first fiber Bragg grating, pm / %; is the wavelength variation of the first and second fiber Bragg gratings, pm; are the initial temperature and the initial relative humidity, respectively; is the total suction of the unsaturated soil body, kPa; R is the universal gas constant, R= 8.31432 J / (mol K); T is the absolute temperature, T = 273.16 t ; t is the temperature in °C; is the inverse of the density of water, = 1 / , m 3 / kg; is the density of water, when t = 20 °C, = 998 kg / m 3 ; is the molar mass of water vapor, = 18.016 kg / kmol.

2. The application method of the temperature, humidity and total suction three-parameter simultaneous measurement optical fiber monitoring device according to claim 1 in the monitoring of the temperature, humidity and suction of the unsaturated soil body, characterized in that, The one end of the packaging body is detachably provided with a connecting sleeve head, and the end of the connecting sleeve head away from the packaging body is fixed with the filter core.

3. The application method of the temperature, humidity and total suction three-parameter simultaneous measurement optical fiber monitoring device in the monitoring of the temperature, humidity and suction of the unsaturated soil body according to claim 2, characterized in that, The packaging body comprises a hollow sleeve, a threaded connecting column, a grating fixing plate and a fiber wire outlet hole, the hollow sleeve, the threaded connecting column and the grating fixing plate are coaxially arranged, one end of the hollow sleeve is provided with the threaded connecting column, the threaded connecting column is provided with external threads, the connecting sleeve head is provided with internal threads matched with the external threads, one end of the grating fixing plate passes through the threaded connecting column and extends into the hollow sleeve, the other end of the grating fixing plate opposite to the one end is provided with the filter core, the first fiber grating and the second fiber grating are respectively fixed to two sides of the grating fixing plate, the first fiber grating and the second fiber grating are both single-endedly fixed through an adhesive, the threaded connecting column is provided with a plurality of fiber wire outlet holes, and the fiber wire outlet holes are distributed on different sides of the grating fixing plate.

4. The application method of the temperature, humidity and total suction three-parameter simultaneous measurement optical fiber monitoring device according to claim 3 in the monitoring of the temperature, humidity and suction of the unsaturated soil body, characterized in that, The threaded connecting column is provided with two fiber wire outlet holes, the two fiber wire outlet holes are symmetrically distributed on the opposite sides of the grating fixing plate, the diameter of the fiber wire outlet hole is 0.3-0.5 mm, and the tail fibers of the first fiber grating and the second fiber grating respectively pass through one fiber wire outlet hole and then extend into the hollow sleeve and then out of the center of the grating sleeve.

5. The application method of the temperature, humidity and total suction three-parameter simultaneous measurement optical fiber monitoring device according to claim 2 in the monitoring of the temperature, humidity and suction of the unsaturated soil body, characterized in that, The filter core is a sintered stainless steel porous structure at high temperature, with a pore size of 1-65 microns, a diameter of 10-12 mm, and a height of 20-50 mm, and is fixed with the connecting sleeve head through an adhesive.

6. The application method of the temperature, humidity and total suction three-parameter simultaneous measurement optical fiber monitoring device according to claim 1 in the monitoring of the temperature, humidity and suction of the unsaturated soil body, characterized in that, The first fiber grating is a humidity and suction measuring grating, which can respond to changes in humidity and suction, the grating length of the first fiber grating is 10±4 mm, the humidity sensitive material coated on the grating area is ORMOCER, the coating thickness is 30±5 microns, and the coating length is 15±5 mm; the second fiber grating is a temperature measuring grating, the grating length of the second fiber grating is 10±4 mm, and the material coated on the grating area is acrylate, which can only respond to changes in temperature.

7. The application method of the temperature, humidity and total suction three-parameter simultaneous measurement optical fiber monitoring device according to claim 1 in the monitoring of the temperature, humidity and suction of the unsaturated soil body, characterized in that, The diameter of the grating sleeve is 0.9-1.2 mm, the armored lead passes through the center of the grating sleeve, and the diameter of the armored lead is 3-5 mm.

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