In-situ online detection method for curing process parameters of grout used to fill cracks in stone cultural relics

Abstract

This invention discloses an in-situ online detection method for the curing process parameters of grout filling material in stone artifacts. A fiber optic temperature sensor, fiber optic strain sensor, and fiber optic humidity sensor are fabricated using fiber Bragg gratings and integrated into a single package to obtain a grout curing process parameter detection device. Multiple of these devices are vertically placed at different heights within the stone artifact's cracks. Each device is connected to a corresponding signal input terminal of a modem. When the grout is injected into the cracks, the modem collects and demodulates the drift data of the center wavelength corresponding to each sensor in each device. The demodulated data is then transmitted to a computer, which calculates the grout curing process parameters at different heights within the cracks.

Description

Technical Field

[0001] This invention relates to the field of stone cultural relic restoration technology, specifically to an in-situ online detection method for parameters of the curing process of grout used to fill cracks in stone cultural relics. Background Technology

[0002] Among the commonly used methods for restoring stone artifacts, grouting is the most traditional and effective. It can fill large cracks caused by geological movements, depending on their size, and can also finely repair surface cracks. It effectively repairs and reinforces the internal structure of stone artifacts, ensuring their safety and reliability.

[0003] The testing technology for grouting materials used in stone cultural relics is mainly divided into two types: online testing and offline testing.

[0004] Offline testing primarily includes X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). XRD allows for non-destructive analysis of the crystal structure of materials within stone artifacts, assessing the compatibility between the restoration material and the original material, thereby monitoring the restoration effect and material stability. FTIR provides crucial information on the chemical composition and structural characteristics of grouting materials used in stone artifacts, aiding in the evaluation of their applicability, stability, and impact on artifact preservation. SEM can provide vital information on the microstructure and properties of grouting materials used in stone artifacts. However, offline testing techniques require pre-processing of samples and are costly and time-consuming.

[0005] Online inspection primarily includes nuclear magnetic resonance (NMR) testing, infrared thermography, and optical microscopy. NMR testing, in grouting experiments, allows for real-time tracking of the hydration process of the grouting material and observation of the grout's diffusion within rock pores and fissures. Infrared thermography provides a rapid, non-destructive method for inspecting grouting materials in stone artifacts, helping to assess the material's performance and effectiveness, thus guiding restoration and conservation efforts. Optical microscopy acquires magnified visible spectrum images of the grout.

[0006] In general, existing detection technologies are insufficient for online, in-situ, real-time monitoring of key parameters such as temperature, humidity, and micro-strain during the curing process of grouting materials. Therefore, researching a detection method suitable for key parameters during the curing process of grouting materials for stone cultural relics can provide important support for evaluating the effectiveness of rock mass fissure treatment for stone cultural relics and offer significant assistance in improving the efficiency of fissure treatment for stone cultural relics. Summary of the Invention

[0007] The purpose of this invention is to provide an in-situ online detection method for parameters of the curing process of grout filling material for stone cultural relics, so as to solve the technical problem that existing detection technologies are difficult to realize online in-situ real-time detection of key parameters such as temperature, humidity and micro-strain during the curing process of grouting materials in the process of repairing stone cultural relics by grouting.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] This invention discloses an in-situ online detection method for parameters of the curing process of grout used to fill cracks in stone cultural relics, comprising the following steps:

[0010] S1. Fiber optic temperature sensors, fiber optic strain sensors, and fiber optic humidity sensors are fabricated using fiber Bragg gratings, and the fiber optic temperature sensors, fiber optic strain sensors, and fiber optic humidity sensors are calibrated respectively to establish the relationships between temperature and the central resonant wavelength of the fiber Bragg grating in the fiber optic temperature sensor, the relationship between strain and the central resonant wavelength of the fiber Bragg grating in the fiber optic strain sensor, and the relationship between humidity and the central resonant wavelength of the fiber Bragg grating in the fiber optic humidity sensor.

[0011] S2. The fiber optic temperature sensor, fiber optic humidity sensor and fiber optic strain sensor prepared in step S1 are integrated and packaged to obtain a device for detecting parameters of the filling slurry curing process.

[0012] S3. Construct an online detection system for the curing process parameters of the filling grout in the cracks of stone cultural relics. Use multiple filling grout curing process parameter detection devices prepared in step S2, and place them vertically at different heights in the cracks of the stone cultural relics, keeping the placement position constant. Connect each filling grout curing process parameter detection device to the corresponding signal input terminal of the modem, and connect the signal output terminal of the modem to the signal input terminal of the computer.

[0013] S4. Prepare the filling slurry and inject it evenly into the cracks of the stone artifact under constant temperature and humidity conditions.

[0014] S5. The drift data of the center wavelengths of the fiber optic temperature sensor, fiber optic strain sensor, and fiber optic humidity sensor in each filling slurry curing process parameter detection device are collected by a modulator and demodulated to obtain demodulated data information. Then, the demodulated data information is transmitted to a computer. The computer calculates the filling slurry curing process parameters at different height positions of the cracks in the stone cultural relic based on the relationship between temperature and the center resonant wavelength of the fiber Bragg grating in the fiber optic temperature sensor, the relationship between strain and the center resonant wavelength of the fiber Bragg grating in the fiber optic strain sensor, and the relationship between humidity and the center resonant wavelength of the fiber Bragg grating in the fiber optic humidity sensor. The filling slurry curing process parameters include the temperature change, strain change, and humidity change of the filling slurry during the curing process.

[0015] Specifically, the curing process parameters of the filling slurry include the temperature, humidity, and micro-strain of the filling slurry.

[0016] This method discloses an optical fiber detection method for the internal temperature, humidity, and micro-strain of a grout (such as water glass grout) used to fill cracks in stone artifacts during the curing process. The method uses a fiber Bragg grating temperature sensor, a fiber Bragg grating strain sensor, and a fiber Bragg grating humidity sensor to perform online in-situ measurements of temperature, humidity, and micro-strain during the curing process of the grout used to fill cracks in simulated sandstone artifacts.

[0017] During testing, the fiber optic humidity sensor primarily responds to three changes in the slurry's internal temperature, humidity, and micro-strain. The strain sensor primarily responds to two changes in the slurry's internal temperature and strain. The fiber optic temperature sensor only responds to changes in the slurry's temperature. The fiber optic temperature sensor has two functions: first, to measure temperature changes during the slurry's curing process; and second, to act as a temperature compensation unit for the strain sensor and the fiber optic humidity sensor, eliminating the influence of slurry temperature changes on strain and humidity measurement results. The strain sensor also has two functions: first, to measure strain changes within the cured slurry; and second, to act as a strain compensation unit for the fiber optic humidity sensor, eliminating the influence of slurry strain changes on humidity measurement results.

[0018] This invention will provide important support for evaluating the effectiveness of treating rock fissures in stone cultural relics, and has significant scientific and engineering application value.

[0019] Preferably, in step S1, the fiber optic temperature sensor is used to monitor the temperature during the slurry curing process and to eliminate the influence of temperature on humidity and strain detection results. That is, the fiber optic temperature sensor serves as both a temperature compensation unit for the fiber optic humidity sensor and the fiber optic strain sensor. The fiber optic temperature sensor is prepared by the following method: using an untreated bare fiber Bragg grating, and then sealing the grating region of the bare fiber Bragg grating with a stainless steel capillary tube to obtain the fiber optic temperature sensor. Before sealing, the bare fiber Bragg grating is calibrated at temperature to establish the relationship between temperature and the center resonant wavelength of the bare fiber Bragg grating, so as to achieve accurate temperature detection and temperature compensation.

[0020] The grating region of the bare fiber Bragg grating is encapsulated with a stainless steel capillary to eliminate the influence of stress on the detection results during the detection process; at the same time, the two ends are sealed with epoxy resin to prevent the filling slurry from entering the stainless steel capillary during the detection process.

[0021] Preferably, in step S2, the fiber optic strain sensor is used to monitor the strain during the curing process of the filling slurry and to eliminate the influence of strain on the humidity detection results. That is, the fiber optic strain sensor is used as a strain compensation unit of the fiber optic humidity sensor while also serving as a fiber optic strain sensor. The fiber optic strain sensor uses an untreated bare fiber Bragg grating.

[0022] Preferably, in step S3, the fiber optic humidity sensor is prepared using the following method:

[0023] A1. A bare fiber Bragg grating is used, and the bare fiber Bragg grating is pre-processed. The bare fiber Bragg grating includes a fiber core, a grating region on the fiber core, a cladding covering the outer periphery of the fiber core, and a coating covering the outer periphery of the cladding. The cladding and coating structures corresponding to the grating region are removed.

[0024] A2. The pretreated fiber Bragg grating is treated with silane to enhance the adhesion strength of the fiber Bragg grating surface.

[0025] A3. Prepare chitosan-polyvinyl alcohol humidity-sensitive material to obtain chitosan-polyvinyl alcohol hydrogel;

[0026] A4. Chitosan-polyvinyl alcohol hydrogel is uniformly coated onto the outer peripheral surface of the fiber Bragg grating corresponding to the grating area after silane treatment, and then dried to form a humidity-sensitive film on the outer peripheral surface of the fiber Bragg grating corresponding to the grating area, thereby obtaining a fiber optic humidity sensor.

[0027] As a preferred embodiment, in step A3, the chitosan-polyvinyl alcohol moisture-sensitive material is prepared using the following method:

[0028] A3.1 Add chitosan powder to glacial acetic acid solution and stir evenly at room temperature to obtain chitosan solution;

[0029] A3.2 Add polyvinyl alcohol powder to deionized water and stir evenly in a water bath to obtain a polyvinyl alcohol solution;

[0030] A3.3. After adding the polyvinyl alcohol solution to the prepared chitosan solution and stirring evenly at room temperature, chitosan-polyvinyl alcohol hydrogel is obtained.

[0031] Preferably, in step A3, the mass ratio of chitosan to polyvinyl alcohol is in the range of 4.5:1 to 7.2:1.

[0032] Preferably, in step A3.1, the mass fraction of the glacial acetic acid solution is in the range of 2% to 5%.

[0033] Preferably, in step A3.2, the mass fraction of the polyvinyl alcohol solution is in the range of 10% to 11%.

[0034] Preferably, in step S2, the integrated packaging of the fiber optic temperature sensor, fiber optic humidity sensor, and fiber optic strain sensor is carried out using the following method: a porous stainless steel tube is used to wrap the corresponding grating area of ​​each of the fiber optic temperature sensor, fiber optic humidity sensor, and fiber optic strain sensor. At the same time, the corresponding fiber optic pigtails of each of the fiber optic temperature sensor, fiber optic humidity sensor, and fiber optic strain sensor extend from the same end of the porous stainless steel tube. The wall of the porous stainless steel tube is uniformly provided with multiple through holes; and the end of each fiber optic pigtail extending out of the porous stainless steel tube is sealed.

[0035] The porous stainless steel tube effectively protects the various sensors during measurement. Sealing one end of the porous stainless steel tube secures the individual fiber optic pigtails, ensuring their relative positions remain constant. During measurement, the filling slurry enters the porous stainless steel tube from the other end and contacts the sensors, enabling simultaneous measurement of temperature, humidity, and micro-strain at the same location.

[0036] Preferably, in step S5, when the computer calculates the curing process parameters of the filling grout at different heights of the cracks in the stone artifact, the fiber optic temperature sensor and fiber optic strain sensor are used as the temperature compensation unit and strain compensation unit of the fiber optic humidity sensor, respectively. The curing process parameters of the filling grout are obtained by processing a pre-constructed matrix model. The matrix model is as follows:

[0037]

[0038] In the formula, ΔλB_1 Δλ is the total wavelength shift of the fiber Bragg grating in the fiber optic temperature sensor. B_2 Δλ is the total wavelength shift of the fiber Bragg grating in the fiber strain sensor. B_3 ΔT represents the total wavelength shift of the fiber Bragg grating in the fiber optic humidity sensor; Δε represents the temperature change; ΔRH represents the strain change; and ΔRH represents the humidity change.

[0039] K T_1 The temperature sensitivity coefficient of the fiber Bragg grating in the fiber optic temperature sensor is expressed as:

[0040]

[0041] K ε_1 K T_2 The fiber Bragg grating strain sensitivity coefficient and temperature sensitivity coefficient of the fiber optic strain sensor are respectively expressed as:

[0042] K ε_1 =λ B-2 (1-P ε );

[0043]

[0044] K RH K ε_2 and K T_3 The sensitivity coefficients of the fiber Bragg grating for humidity, strain, and temperature in the fiber optic humidity sensor are respectively expressed as:

[0045]

[0046] K ε_2 =λ B_3 (1-P ε );

[0047]

[0048] In the above formula, λ B 1. λ B 2, λ B 3 represents the resonant center wavelength of the fiber Bragg grating in the fiber optic temperature sensor, fiber optic strain sensor, and fiber optic humidity sensor, respectively; α is the thermal expansion coefficient of the fiber optic material. P is the thermo-optic coefficient; ε r is the effective elastic coefficient of the optical fiber Bragg grating. f Where is the fiber radius; t is the thickness of the humidity-sensitive film; C0 is the surface bonding coefficient between the fiber grating and the humidity-sensitive film; E M and E f The Young's modulus, α, of the humidity-sensitive thin film and the optical fiber, respectively.M(RH) Let A be the coefficient of hygroscopic expansion of the moisture-sensitive film. M and A f These are the cross-sectional areas of the humidity-sensitive thin film and the optical fiber, respectively; α M(T) and α f(T) These are the coefficients of thermal expansion of the humidity-sensitive thin film and the optical fiber, respectively.

[0049] The present invention has the following beneficial effects:

[0050] This invention solves the technical problem that existing detection technologies are unable to achieve online, in-situ, real-time monitoring of key parameters such as temperature, humidity, and micro-strain during the curing process of grouting materials in the restoration of stone cultural relics using grouting methods. The technical solution of this invention can simultaneously monitor multiple key parameters such as the temperature, humidity, and strain of the filling grout, providing comprehensive monitoring data for the restoration and protection of stone cultural relics. The fiber Bragg grating sensor is highly sensitive to changes in temperature, humidity, and strain, and can detect minute changes, exhibiting high sensitivity. Furthermore, the fiber optic sensor is unaffected by electromagnetic interference, can operate stably in complex electromagnetic environments, has strong anti-interference capabilities, and possesses good long-term stability. Attached Figure Description

[0051] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will now be described in further detail with reference to the accompanying drawings, wherein:

[0052] Figure 1 This is a schematic diagram of the fiber optic temperature sensor structure of the present invention.

[0053] Figure 2 This is a schematic diagram of the fiber optic humidity sensor structure of the present invention.

[0054] Figure 3 This is a schematic diagram of the filling slurry curing process parameter detection device of the present invention.

[0055] Figure 4 This is a schematic diagram of the online detection system for the curing process parameters of the stone artifact crack filling grout of the present invention.

[0056] Figure 5 The figures show the internal temperature variation curves of water glass slurry at different heights measured in an embodiment of the present invention.

[0057] Figure 6 The curves showing the changes in internal humidity of water glass slurry at different heights are shown in the embodiments of the present invention.

[0058] Figure 7 The figures show the internal stress variation curves of water glass slurry at different heights measured in an embodiment of the present invention.

[0059] Explanation of reference numerals in the attached figures: 101, fiber optic temperature sensor; 102, fiber optic strain sensor; 103, fiber optic humidity sensor; 200, bare fiber Bragg grating; 201, fiber core; 202, grating area; 203, cladding; 204, coating layer; 205, stainless steel capillary; 206, humidity-sensitive film; 300, device for detecting parameters during the curing process of filling slurry; 301, porous stainless steel tube; 302, stone artifact; 303, crack in stone artifact; 304, filling slurry; 305, modem; 306, computer; 308, through hole; 400, epoxy resin. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0061] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship commonly used when the product is in use. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. In addition, the terms "horizontal," "vertical," etc., do not indicate that the component is required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0062] This invention can be applied to the repair of cracks in stone cultural relics, and solves the technical problem that existing detection technologies are unable to achieve online in-situ real-time detection of key parameters such as temperature, humidity and micro-strain during the curing process of grouting materials in the process of repairing stone cultural relics 302 using grouting.

[0063] See also Figures 1 to 4 Based on the above-mentioned technical problems, this invention discloses an in-situ online detection method for parameters of the curing process of grout filling material for stone cultural relics, comprising the following steps:

[0064] S1. Fiber optic temperature sensor 101, fiber optic strain sensor 102, and fiber optic humidity sensor 103 are fabricated using fiber Bragg gratings, and the fiber optic temperature sensor, fiber optic strain sensor, and fiber optic humidity sensor are calibrated respectively to establish the relationship between temperature and the central resonant wavelength of the fiber Bragg grating in the fiber optic temperature sensor, the relationship between strain and the central resonant wavelength of the fiber Bragg grating in the fiber optic strain sensor, and the relationship between humidity and the central resonant wavelength of the fiber Bragg grating in the fiber optic humidity sensor.

[0065] S2. The fiber optic temperature sensor 101, fiber optic humidity sensor 103 and fiber optic strain sensor 102 prepared in step S1 are integrated and packaged to obtain the filling slurry curing process parameter detection device 300.

[0066] S3. Construct an online detection system for the curing process parameters of the filling grout in the cracks of stone cultural relics. Use multiple filling grout curing process parameter detection devices 300 prepared in step S2, and place them vertically at different heights in the cracks 303 of the stone cultural relics, keeping the placement position constant. Connect each filling grout curing process parameter detection device 300 to the corresponding signal input terminal of the modem 305, and connect the signal output terminal of the modem 305 to the signal input terminal of the computer 306.

[0067] S4. Prepare filling slurry 304 and inject the filling slurry 304 evenly into the cracks 303 of the stone cultural relic under constant temperature and humidity conditions.

[0068] S5. The modulator 305 collects the drift data of the center wavelengths of the fiber optic temperature sensor 101, fiber optic strain sensor 102, and fiber optic humidity sensor 103 in the parameter detection device 300 for each filling slurry curing process, and demodulates the data to obtain the demodulated data information. Then, the demodulated data information is transmitted to the computer 306. The computer 306 calculates the filling slurry curing process parameters at different height positions of the crack 303 of the stone cultural relic based on the relationship between temperature and the central resonant wavelength of the fiber Bragg grating in the fiber optic temperature sensor, the relationship between strain and the central resonant wavelength of the fiber Bragg grating in the fiber optic strain sensor, and the relationship between humidity and the central resonant wavelength of the fiber Bragg grating in the fiber optic humidity sensor. The filling slurry curing process parameters include the temperature change, strain change, and humidity change of the filling slurry during the curing process.

[0069] This solution discloses an optical fiber detection method for the internal temperature, humidity, and micro-strain of the filling slurry 304 (e.g., water glass slurry) during the curing process of the fissure 303 of a stone artifact 302. The method uses a fiber Bragg grating temperature sensor 101, a fiber Bragg grating strain sensor 102, and a fiber Bragg grating humidity sensor 103 to perform online in-situ measurements of the temperature, humidity, and micro-strain during the curing process of the filling slurry 304 in the fissure 303 of a simulated sandstone artifact.

[0070] During detection, the fiber optic humidity sensor 103 primarily responds to three changes in the slurry's internal temperature, humidity, and micro-strain. The strain sensor 102 primarily responds to two changes in the slurry's internal temperature and strain. The fiber optic temperature sensor 101 only responds to changes in the slurry's temperature. The fiber optic temperature sensor 101 has two functions: first, to measure temperature changes during the slurry's curing process; and second, to act as a temperature compensation unit for the strain sensor 102 and the fiber optic humidity sensor 103, eliminating the influence of slurry temperature changes on strain and humidity measurement results. The strain sensor 102 has two functions: first, to measure strain changes within the cured slurry; and second, to act as a strain compensation unit for the fiber optic humidity sensor 103, eliminating the influence of slurry strain changes on humidity measurement results.

[0071] This invention will provide important support for evaluating the effectiveness of treating rock fissures in stone cultural relics, and has significant scientific and engineering application value.

[0072] Specifically, the curing process parameters of the filling slurry 304 include the temperature, humidity, and micro-strain of the filling slurry 304.

[0073] Specifically, for the structure of the fiber optic temperature sensor 101 fabricated in step S1, please refer to [link / reference needed]. Figure 1The fiber grating 200 includes an untreated bare fiber Bragg grating 200, which includes a fiber core 201, a grating region 202 on the fiber core 201, a cladding 203 covering the outer periphery of the fiber core 201, a coating layer 204 covering the outer periphery of the cladding 203, and a stainless steel capillary 205 sleeved on the outer periphery of the coating layer corresponding to the grating region 202, with both ends of the stainless steel capillary 205 sealed.

[0074] Preferably, in step S1, the fiber optic temperature sensor 101 is used to monitor the temperature during the slurry curing process and to eliminate the influence of temperature on humidity and strain detection results. That is, the fiber optic temperature sensor 101 serves as both a fiber optic temperature sensor and a temperature compensation unit for the fiber optic humidity sensor 103 and the fiber optic strain sensor 102. The fiber optic temperature sensor 101 is prepared by the following method: using an untreated bare fiber Bragg grating 200, and then sealing the grating region 202 of the bare fiber Bragg grating 200 with a stainless steel capillary tube 205 to obtain the fiber optic temperature sensor 101. Before sealing, the bare fiber Bragg grating 200 is calibrated at temperature to establish the relationship between temperature and the center resonant wavelength of the bare fiber Bragg grating 200, so as to achieve accurate temperature detection and temperature compensation.

[0075] Specifically, the method for sealing and encapsulating the grating region 202 of the bare fiber Bragg grating 200 using a stainless steel capillary tube 205 is as follows: first, the stainless steel capillary tube 205 is sleeved on the outer periphery of the grating region 202 of the bare fiber Bragg grating 200, and then epoxy resin 400 glue is used to seal the two ends of the stainless steel capillary tube 205 corresponding to the two ends of the grating region 202.

[0076] The grating region 202 of the bare fiber Bragg grating 200 is encapsulated with a stainless steel capillary tube 205 to eliminate the influence of stress on the detection results during the detection process; at the same time, the two ends are sealed with epoxy resin 400 to prevent the filling slurry 304 from entering the stainless steel capillary tube 205 during the detection process.

[0077] Specifically, in one embodiment of the stainless steel capillary 205, a stainless steel capillary 205 with an inner diameter of 400-600 μm and a length of 1.5-2.5 cm is used to encapsulate the fiber grating region 202.

[0078] Preferably, in step S2, the fiber optic strain sensor 102 is used to monitor the strain during the curing process of the filling slurry 304 and to eliminate the influence of strain on the humidity detection results. That is, the fiber optic strain sensor 102 serves as both a fiber optic strain sensor 102 and a temperature compensation unit for the fiber optic humidity sensor 103. The fiber optic strain sensor 102 directly uses an untreated bare fiber Bragg grating 200 without any further processing.

[0079] Specifically, for the structure of the fiber optic humidity sensor 103 obtained in step S3, please refer to [link / reference needed]. Figure 2 .

[0080] Preferably, in step S3, the fiber optic humidity sensor 103 is prepared using the following method:

[0081] A1. A bare fiber Bragg grating 200 is used, and the bare fiber Bragg grating 200 is pre-processed. The bare fiber Bragg grating 200 includes a fiber core 201, a grating region 202 on the fiber core 201, a cladding 203 covering the outer periphery of the fiber core 201, and a coating layer 204 covering the outer periphery of the cladding 203. The cladding 203 and the coating layer structure 204 corresponding to the grating region 202 are removed.

[0082] A2. The pretreated fiber Bragg grating is treated with silane to enhance the adhesion strength of the fiber Bragg grating surface.

[0083] A3. Prepare chitosan-polyvinyl alcohol humidity-sensitive material to obtain chitosan-polyvinyl alcohol hydrogel;

[0084] A4. Chitosan-polyvinyl alcohol hydrogel is uniformly coated on the outer peripheral surface of the fiber Bragg grating corresponding to the grating region 202 after silane treatment, and then dried to form a humidity-sensitive film 206 on the outer peripheral surface of the fiber Bragg grating corresponding to the grating region 202, thereby obtaining the fiber optic humidity sensor 103.

[0085] Specifically, in step A1, the fiber Bragg grating is preprocessed using the following method:

[0086] Immerse the fiber Bragg grating in 95-98% concentrated sulfuric acid for 60-70 minutes to remove all polyacrylate coating; immerse the fiber Bragg grating area in anhydrous ethanol and deionized water and shake to clean for 8-10 minutes, then air dry at room temperature for later use.

[0087] Specifically, in step A2, the pre-processed fiber Bragg grating is treated with silane using the following method:

[0088] To improve the adhesion strength of the humidity-sensitive film on the fiber surface, the fiber grating is placed in 10%–12% silane coupling agent for 20–30 minutes, then the fiber is removed and cleaned with deionized water. Finally, it is placed in a vacuum drying oven and dried at 90–100°C for 10–15 minutes before being taken out for use.

[0089] As a preferred embodiment, in step A3, the chitosan-polyvinyl alcohol moisture-sensitive material is prepared using the following method:

[0090] A3.1 Add chitosan powder to glacial acetic acid solution and stir evenly at room temperature to obtain chitosan solution;

[0091] A3.2 Add polyvinyl alcohol powder to deionized water and stir evenly in a water bath to obtain a polyvinyl alcohol solution;

[0092] A3.3. After adding the polyvinyl alcohol solution to the prepared chitosan solution and stirring evenly at room temperature, chitosan-polyvinyl alcohol hydrogel is obtained.

[0093] Preferably, in step A3, the mass ratio of chitosan to polyvinyl alcohol is in the range of 4.5:1 to 7.2:1, preferably 4.5:1.

[0094] Preferably, in step A3.1, the mass fraction of the glacial acetic acid solution is in the range of 2% to 5%.

[0095] Preferably, in step A3.2, the mass fraction of the polyvinyl alcohol solution is in the range of 10% to 11%.

[0096] In one embodiment of preparing chitosan-polyvinyl alcohol (PVA) humidity-sensitive material, 1-2 g of chitosan powder was added to 20-25 ml of 2%-5% glacial acetic acid solution and stirred at room temperature for 4-5 h; then 1.2-1.5 g of PVA powder was weighed and added to 10-12 ml of deionized water and stirred in a 90-100°C water bath for 2-3 h; finally, 2-2.5 ml of PVA solution was added dropwise to the prepared chitosan solution and stirred at room temperature for 5-6 h to obtain chitosan-PVA hydrogel; in this embodiment, the mass ratio of chitosan to PVA ranged from 4.67:1 to 7.2:1.

[0097] Specifically, in step A4, the chitosan-polyvinyl alcohol moisture-sensitive material is coated using a dip-coating method. Specifically, 0.1–0.2 g of hydrogel is picked up with tweezers, and the tweezers tip is slowly pulled along the outer peripheral surface of the fiber Bragg grating region after silane treatment. Then, it is placed in a drying oven at 60–70°C for 20–30 minutes. This process is repeated 5–6 times to ultimately form a thin film around the fiber Bragg grating region. Figure 2 As shown.

[0098] The working principles of the fiber optic temperature sensor and fiber optic strain sensor are analyzed as follows.

[0099] The resonant center wavelength (λ) of a fiber Bragg grating B ) and the effective refractive index (n) of optical fiber eff The relationship between the grating period (Λ) and the grating period (Λ) is linear, and its expression is:

[0100] λ B =2n eff Λ (1)

[0101] When the external temperature changes, the effective refractive index of the grating will change; at the same time, thermal expansion can also change the grating period. Therefore, temperature changes will cause the center wavelength of the fiber Bragg grating to drift.

[0102] The fiber Bragg grating in the fiber optic temperature sensor is only affected by temperature. Therefore, when only temperature is involved, the total wavelength shift (Δλ) of the fiber Bragg grating is... B_1 )for:

[0103]

[0104] In equation (3), α is the coefficient of thermal expansion of the optical fiber material. The thermo-optic coefficient is given by K, where ΔT is the temperature change. T_1 Let K be the temperature sensitivity coefficient of the fiber Bragg grating in the fiber optic temperature sensor. T_1 Represented as:

[0105]

[0106] In equation (3), λ B_1 The wavelength α represents the resonant center wavelength of the fiber Bragg grating in the fiber optic temperature sensor, where α is the coefficient of thermal expansion of the fiber material. The thermo-optic coefficient is denoted as .

[0107] However, optical fibers exhibit photoelasticity, and strain can cause λ to... B A drift occurs; therefore, when an optical fiber is subjected to external stress, it is sensitive to both strain and temperature. The drift (Δλ) of the center wavelength of the fiber Bragg grating in the fiber strain sensor is significant. B-2 ) is defined as:

[0108]

[0109] In equation (4), P ε K is the effective elastic-optical coefficient of the optical fiber, Δε is the strain change experienced by the optical fiber, and K is the effective elastic-optical coefficient of the optical fiber. ε_1K is the strain sensitivity coefficient of the fiber Bragg grating in the fiber optic strain sensor. T_2 is the temperature sensitivity coefficient of the fiber Bragg grating in the fiber strain sensor.

[0110] Among them, the fiber Bragg grating strain sensitivity coefficient K of the fiber strain sensor ε_1 and temperature sensitivity coefficient K T_2 They are represented as follows:

[0111] K ε_1 =λ B-2 (1-P ε (5)

[0112]

[0113] In equations (5) and (6), λ B-2 P represents the resonant center wavelength of the fiber Bragg grating in the fiber optic strain sensor. ε α is the effective elastic-optical coefficient of the optical fiber, and α is the thermal expansion coefficient of the optical fiber material. The thermo-optic coefficient is denoted as .

[0114] The working principle of the fiber optic humidity sensor is analyzed as follows.

[0115] The fiber optic humidity sensor utilizes the strain-sensitive properties of humidity-sensitive materials and fiber Bragg gratings to detect humidity. The chitosan-polyvinyl alcohol hydrogel absorbs moisture and expands, dehydrates and contracts according to changes in external humidity, thereby generating axial stress of stretching or contraction and transmitting it to the fiber Bragg grating, thus causing a shift in the center wavelength.

[0116] Therefore, the total wavelength shift (Δλ) of the fiber Bragg grating in the fiber humidity sensor B_3 It can be defined as:

[0117]

[0118] In equation (7), λ B-3 ε represents the resonant center wavelength of the fiber Bragg grating in the fiber optic humidity sensor. RH ε T Δε and Δε represent the coefficient of hygroscopic expansion, coefficient of thermal expansion, and stress change of the fiber optic grating itself after coating with chitosan-polyvinyl alcohol hydrogel, respectively. Where:

[0119]

[0120] In equations (8) and (9) above, A M and A f These are the cross-sectional areas of the humidity-sensitive material thin film and the optical fiber, respectively; E M and E fThese are the Young's moduli of the humidity-sensitive thin film and the optical fiber, respectively; α M(RH) and α M(T) These are the coefficients of humid expansion and thermal expansion of the humidity-sensitive film, respectively; α f(RH) and α f(T) These are the wet expansion coefficient and thermal expansion coefficient of the optical fiber, respectively.

[0121] Because bare FBG is insensitive to humidity, i.e., its coefficient of hygroscopic expansion α f(RH) If the value is 0, then according to equation (7):

[0122] Δλ B_3 =λ B_3 (K RH ΔRH+K ε_2 Δε+K T_3 ΔT) (10)

[0123] In equation (10), λ B-3 K represents the resonant center wavelength of the fiber Bragg grating in the fiber optic humidity sensor, where ΔRH is the change in humidity; RH K ε_2 and K T_3 K represents the sensitivity coefficients of the fiber Bragg grating of the fiber optic humidity sensor for humidity, strain, and temperature, respectively. RH K ε_2 and K T_3 They can be represented as:

[0124]

[0125] K ε_2 =λ B_3 (1-P ε (12)

[0126]

[0127] In equations (11)-(13), P ε r is the effective elastic coefficient of the fiber Bragg grating; f t is the fiber radius; t is the thickness of the humidity-sensitive film; C0 is the surface bonding coefficient between the fiber grating and the humidity-sensitive film; E M and E f These are the Young's moduli of the humidity-sensitive thin film and the optical fiber, respectively; α M(RH) A is the coefficient of hygroscopic expansion of the moisture-sensitive film; M and A f These are the cross-sectional areas of the humidity-sensitive material thin film and the optical fiber, respectively; α M(T) and α f(T) These are the coefficients of thermal expansion of the humidity-sensitive thin film and the optical fiber, respectively. The thermo-optic coefficient is denoted as .

[0128] For preference, please refer to Figure 3 In step S2, the integrated packaging of the fiber optic temperature sensor 101, fiber optic humidity sensor 103, and fiber optic strain sensor 102 is carried out using the following method: a porous stainless steel tube 301 is used to wrap the corresponding grating area 202 of each of the fiber optic temperature sensor 101, fiber optic humidity sensor 103, and fiber optic strain sensor 102. At the same time, the corresponding fiber optic pigtails of each of the fiber optic temperature sensor 101, fiber optic humidity sensor 103, and fiber optic strain sensor 102 extend from the same end of the porous stainless steel tube 301. The wall of the porous stainless steel tube 301 is uniformly provided with multiple through holes 308. The end of each fiber optic pigtail extending out of the porous stainless steel tube 301 is sealed.

[0129] The porous stainless steel tube 301 effectively protects each sensor during measurement. Sealing one end of the porous stainless steel tube 301 is to fix each optical fiber pigtail, keeping their relative positions constant. Additionally, during measurement, the filling slurry 304 enters the porous stainless steel tube 301 from the other end and contacts each sensor, enabling simultaneous measurement of temperature, humidity, and micro-strain at the same location.

[0130] Specifically, the specifications of the porous stainless steel tube 301 used are an inner diameter of 3-4 mm and a length of 2-3 cm.

[0131] Preferably, in step S5, the vertical distance between two adjacent filling slurry curing process parameter detection devices 300 is 10-30 mm.

[0132] Preferably, in step S5, the vertical distance between two adjacent filling slurry curing process parameter detection devices 300 is 25-30 mm.

[0133] For details, please refer to Figure 4 The filling slurry 304 is uniformly injected into the cracks 303 of the stone cultural relic under constant temperature and humidity conditions.

[0134] Preferably, in step S6, the filling slurry 304 is a water glass slurry, which is prepared by the following method: first, dissolve sodium silicate powder in deionized water and stir evenly at room temperature to obtain a sodium silicate solution; then, treat the sodium silicate solution with ultrasound to remove bubbles, and let it stand after ultrasound treatment; finally, add ethylene glycol diacetate to the sodium silicate solution and stir evenly in a water bath to obtain the water glass slurry.

[0135] Specifically, as one embodiment of the water glass slurry, 8-9g of sodium silicate powder is dissolved in 20-25ml of deionized water, stirred at room temperature for 60-70 minutes, and ultrasonically treated for 50-60 minutes to achieve degassing. It is then allowed to stand for 10-20 minutes for later use. 15-20ml of deionized water and 3.5-4ml of 98-99% ethylene glycol diacetate are added to the sodium silicate solution, and the mixture is stirred in a water bath at 35-40°C for 3-5 minutes.

[0136] Preferably, in step S5, when the computer calculates the curing process parameters of the filling grout at different height positions of the cracks in the stone artifact, the fiber optic temperature sensor and fiber optic strain sensor are used as the temperature compensation unit and strain compensation unit of the fiber optic humidity sensor, respectively, and the curing process parameters of the filling grout are obtained by performing a pre-constructed matrix model; the matrix model can be established as follows from equations (2), (4) and (10):

[0137]

[0138] In equation (14), Δλ B_1 Δλ is the total wavelength shift of the fiber Bragg grating in the fiber optic temperature sensor. B_2 Δλ is the total wavelength shift of the fiber Bragg grating in the fiber strain sensor. B_3 ΔT represents the total wavelength shift of the fiber Bragg grating in the fiber optic humidity sensor; Δε represents the temperature change; ΔRH represents the strain change; and K represents the humidity change. T_1 The temperature sensitivity coefficient of the fiber Bragg grating in the fiber optic temperature sensor is given by reference equation (3), K. ε_1 K T_2 These are the fiber Bragg grating strain sensitivity coefficient and temperature sensitivity coefficient of the fiber optic strain sensor, respectively, expressed in equations (5) and (6), K. RH K ε_2 and K T_3 The coefficients representing the humidity, strain, and temperature sensitivity of the fiber Bragg grating of the fiber optic humidity sensor are respectively expressed by Equations (11), (12), and (13).

[0139] The detection principle of this invention is as follows: This invention employs three types of fiber optic sensors, including a strain sensor composed of an untreated fiber Bragg grating, a fiber optic temperature sensor 101 encapsulated with an untreated bare fiber Bragg grating 200 and a stainless steel capillary tube 205, and a fiber optic humidity sensor 103 composed of a fiber Bragg grating with the coating removed and a humidity-sensitive material chitosan / polyvinyl alcohol. These sensors are encapsulated in a porous stainless steel tube 301, forming a device capable of online in-situ detection of parameters related to the curing process of slurry filling cracks in stone artifacts.

[0140] In use, the detection device is placed inside the crack 303 and filled with slurry 304. During the detection process, the sensor remains in continuous contact with the slurry 304. When the temperature or humidity of the slurry 304 changes, or when expansion or contraction stress occurs, these changes cause a corresponding change in the center wavelength of the fiber optic grating. Specifically, the fiber optic temperature sensor 101, encapsulated in a stainless steel capillary tube 205, is primarily affected by temperature. The strain sensor is affected by both temperature and strain, but temperature compensation can be achieved using the detection value of the fiber optic temperature sensor 101 at the same location. The fiber optic humidity sensor 103 is affected by temperature, humidity, and strain simultaneously, and temperature and strain compensation can be achieved using the detection values ​​of the fiber optic temperature sensor 101 and the fiber optic strain sensor 102 at the same height. The center wavelength drift is acquired by a fiber optic grating demodulator, and the demodulated data is transmitted to a computer 306, allowing for the calculation of changes in various parameters during the curing process.

[0141] The in-situ online detection method for the curing process parameters of the grout used to fill cracks in stone cultural relics, as disclosed in this invention, has the following technical advantages:

[0142] 1. It can simultaneously monitor multiple key parameters such as temperature, humidity, and strain of the filling grout, providing comprehensive monitoring data for the restoration and protection of stone cultural relics. The fiber Bragg grating sensor is very sensitive to changes in temperature, humidity, and strain, and can detect minute changes. It has high sensitivity, and the fiber optic sensor is not affected by electromagnetic interference. It can work stably in complex electromagnetic environments, has strong anti-interference ability, and has good long-term stability.

[0143] 2. Each sensor is encapsulated in a porous stainless steel tube, enabling its use in harsh environments, such as high humidity or corrosive environments. It has strong environmental adaptability. The strain sensor can achieve temperature compensation by using the detection value of the fiber optic temperature sensor at the same location. In addition, the fiber optic humidity sensor can achieve temperature and strain compensation by using the detection values ​​of the fiber optic temperature sensor and the fiber optic strain sensor at the same height, further improving the accuracy of the measurement.

[0144] 3. In-situ detection can be carried out simply by placing the device for the curing process parameters of the filling slurry inside the crack, without damaging the structure of the cultural relic. Data is collected in real time through a fiber optic demodulator, which is easy to process and analyze by computer, facilitating data management and decision support. It can also achieve continuous monitoring of the curing process and realize in-situ online detection.

[0145] 4. The devices for each filling slurry curing process parameter can be adjusted in position and quantity as needed to adapt to different monitoring requirements. They can also be integrated with other monitoring systems or automated control systems to achieve more advanced monitoring and control functions.

[0146] 5. Compared with traditional monitoring methods, the fiber optic sensor of this invention provides a more cost-effective solution.

[0147] To further illustrate the method of the present invention, the following application examples are disclosed.

[0148] The in-situ online detection method for the curing process parameters of the grout used to fill cracks in stone cultural relics disclosed in this embodiment includes the following steps:

[0149] Step A: Prepare an optical fiber temperature sensor 101 to monitor the temperature during the slurry curing process and eliminate the influence of temperature on humidity and strain detection results. Specifically, the optical fiber temperature sensor 101 serves as both an optical fiber temperature sensor and a temperature compensation unit for the optical fiber humidity sensor 103 and the optical fiber strain sensor 102. The optical fiber temperature sensor 101 is prepared using the following method:

[0150] An untreated bare fiber Bragg grating 200 is used, and then the grating region 202 of the bare fiber Bragg grating 200 is sealed and encapsulated using a stainless steel capillary tube 205 with an inner diameter of 0.5 mm and a length of 20 mm to obtain a fiber optic temperature sensor 101. Before encapsulation, the bare fiber Bragg grating 200 is calibrated at temperature to establish the relationship between temperature and the center resonant wavelength of the bare fiber Bragg grating 200. Specifically, the operation method of sealing and encapsulating the grating region 202 of the bare fiber Bragg grating 200 using a stainless steel capillary tube 205 is as follows: first, the stainless steel capillary tube 205 is sleeved on the outer periphery of the grating region 202 of the bare fiber Bragg grating 200, and then the two ends of the stainless steel capillary tube 205 corresponding to the two ends of the grating region 202 are sealed with epoxy resin 400 glue. The grating region 202 of the bare fiber Bragg grating 200 is encapsulated with a stainless steel capillary tube 205 to eliminate the influence of stress on the detection results during the detection process; at the same time, the two ends are sealed with epoxy resin 400 to prevent the filling slurry 304 from entering the stainless steel capillary tube 205 during the detection process.

[0151] Step B: Prepare an optical fiber strain sensor 102 to monitor the strain during the curing process of the filling slurry 304 and to eliminate the influence of strain on the humidity detection results. That is, the optical fiber strain sensor 102 serves as both an optical fiber strain sensor and a strain compensation unit for the optical fiber humidity sensor 103. The optical fiber strain sensor 102 uses an untreated bare fiber Bragg grating 200. Perform strain calibration on the optical fiber strain sensor 102 to establish the relationship between strain and the central resonant wavelength of the fiber Bragg grating in the optical fiber strain sensor 102.

[0152] Step C: Fabricate an optical fiber humidity sensor 103 to respond to temperature change information, humidity change information, and micro-strain change information; establish the relationship between humidity and the central resonant wavelength of the fiber Bragg grating in the optical fiber humidity sensor 103, specifically including the following steps:

[0153] C1. A bare fiber Bragg grating 200 is used, and the bare fiber Bragg grating 200 is pretreated. The bare fiber Bragg grating 200 includes a fiber core 201, a grating region 202 on the fiber core 201, a cladding 203 covering the outer periphery of the fiber core 201, and a coating layer 204 covering the outer periphery of the cladding 203. The cladding 203 and the coating layer structure corresponding to the grating region 202 are removed. Specifically, the fiber Bragg grating is immersed in 98% concentrated sulfuric acid for 60 minutes to remove all polyacrylate coating layers. Then, the fiber grating region 202 is immersed in anhydrous ethanol and deionized water and shaken for 10 minutes before being air-dried at room temperature for later use.

[0154] C2. The pretreated fiber Bragg grating is treated with silane to enhance the adhesion strength of the fiber Bragg grating surface. Specifically, the fiber Bragg grating is placed in 10% silane coupling agent for 30 minutes, then the fiber is taken out and cleaned with deionized water. Finally, it is placed in a vacuum drying oven and dried at 90°C for 15 minutes before being taken out for use.

[0155] C3. Prepare chitosan-polyvinyl alcohol humidity-sensitive material to obtain chitosan-polyvinyl alcohol hydrogel;

[0156] Specifically, 1g of chitosan powder was added to 20ml of a 4% (w / w) glacial acetic acid solution and stirred at room temperature for 4 hours. 1.5g of polyvinyl alcohol powder was weighed and added to 12ml of deionized water and stirred in a 95℃ water bath for 3 hours. Finally, 2ml of the polyvinyl alcohol solution was added dropwise to the prepared chitosan solution and stirred at room temperature for 6 hours to obtain a chitosan-polyvinyl alcohol hydrogel. In this example, the mass ratio of chitosan to polyvinyl alcohol in the prepared chitosan-polyvinyl alcohol hydrogel was 4.5:1.

[0157] C4. Chitosan-polyvinyl alcohol hydrogel is uniformly coated onto the outer peripheral surface of the fiber Bragg grating region 202 after silane treatment, and then dried to form a humidity-sensitive film 206 on the outer peripheral surface of the fiber Bragg grating region 202, thereby obtaining the fiber optic humidity sensor 103. Specifically, the humidity-sensitive material is coated using a pull-up method. The tip of tweezers is slowly pulled up along the outer peripheral surface of the fiber Bragg grating region 202 after silane treatment, and then placed in a 60°C drying oven for 20 minutes. The above operation is repeated 5 times to finally form a thin film around the fiber Bragg grating region 202.

[0158] Step D: The fiber optic temperature sensor 101, fiber optic humidity sensor 103 and fiber optic strain sensor 102 prepared in steps A to C are integrated and packaged to obtain the filling slurry curing process parameter detection device 300.

[0159] Specifically, a porous stainless steel tube 301 with an inner diameter of 3mm and a length of 25mm is used to wrap the fiber optic grating area 202 of the fiber optic temperature sensor 101, the fiber optic humidity sensor 103, and the fiber optic strain sensor 102, and one end of the fiber is fixed with epoxy resin 400.

[0160] Step E: Use three filling slurry curing process parameter detection devices 300 prepared in step D, and place them vertically at different heights in the cracks 303 of the stone artifact, keeping the placement position unchanged. The vertical distance between two adjacent filling slurry curing process parameter detection devices 300 is 30mm. Connect each filling slurry curing process parameter detection device 300 to the corresponding signal input terminal of the modem 305, and connect the signal output terminal of the modem 305 to the signal input terminal of the computer 306.

[0161] Step F: Prepare water glass slurry as filling slurry 304 for the cracks 303 of the stone cultural relic, and inject the filling slurry 304 evenly into the cracks 303 of the stone cultural relic under constant temperature and humidity conditions.

[0162] Specifically, the preparation process of the water glass slurry is as follows: Dissolve 8.5g of sodium silicate powder in 20ml of deionized water, stir at room temperature for 60min, sonicate for 50min to achieve degassing, and let stand for 10min for later use. Add 15ml of deionized water and 3.5ml of 98% ethylene glycol diacetate to the sodium silicate solution, and stir in a 35℃ water bath for 3min.

[0163] Step G: The center wavelength drift data of the fiber optic temperature sensor 101, fiber optic strain sensor 102 and fiber optic humidity sensor 103 in the parameter detection device 300 for each filling slurry curing process are collected by the modulator 305 and demodulated to obtain the demodulated data information; then the demodulated data information is transmitted to the computer 306, and the computer 306 calculates the curing process parameters of the filling slurry 304 at different height positions of the crack 303 of the stone cultural relic.

[0164] The analysis of the detection results in this embodiment is as follows: Figures 5 to 7 As shown.

[0165] Figure 5This indicates the temperature distribution within the water glass slurry during the curing process. The results show that the temperature initially increases and then decreases at different heights, with the most significant temperature change occurring at 2 cm. This is because the silica formed from the water glass slurry and acetic acid has a high density and is unstable, decomposing into silicon dioxide. This causes the slurry at the bottom to cure first, resulting in the earliest temperature increase. Furthermore, the bottom portion has the least contact with air and is least affected by external temperature. Conversely, the slurry at the top has more contact with the outside environment and continuously releases heat during curing, thus exhibiting the lowest temperature.

[0166] Figure 6 This indicates the humidity distribution within the slurry during the water glass curing process. The results show that from the start to the end of curing, the humidity inside the slurry gradually decreases at a slower rate. This is because as the temperature first increases and then decreases, the hydrolysis reaction rate within the slurry gradually decreases, and the evaporation rate of water caused by temperature also decreases. The humidity at 2 cm depth begins to decrease first, but as curing progresses, the humidity at 8 cm depth decreases the most rapidly.

[0167] The reasons are: (1) The silica formed by water glass slurry and acetic acid has a large density and is unstable. It decomposes into silicon dioxide, which makes the slurry at the bottom solidify first, so the humidity decreases first; (2) The slurry at the top has the largest contact area with the external environment and reacts with carbon dioxide continuously, so the moisture loss rate at the top is the fastest.

[0168] Figure 7 This indicates the stress distribution within the slurry during the solidification process of water glass in sandstone samples with different pore sizes. The results show that the shrinkage stress is greatest at 2 cm. As mentioned earlier, the solidification of the slurry occurs "from bottom to top." Initially, the increase in temperature causes some of the slurry to "thermally expand," thus generating tensile stress on the stress sensors. When the material at the bottom solidifies, the bottom volume shrinks, causing the unsolidified slurry above to shift downwards. Because water glass slurry has a certain viscosity, the stress sensors at 5 cm and 8 cm receive a downward tensile stress, thus offsetting some of the shrinkage stress generated by the material. The tensile stress is greater closer to the top of the sensor.

[0169] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Under the teachings of the present invention, modifications can be made to these features and embodiments to adapt to specific situations and materials without departing from the spirit and scope of the invention. The embodiments described in this invention are only a part of the embodiments of the invention, not all of them. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. Therefore, the invention is not limited to the specific embodiments disclosed herein, and all other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for in-situ online detection of parameters during the curing process of grout filling material for stone cultural relics, characterized in that, Includes the following steps: S1. Fiber optic temperature sensors, fiber optic strain sensors, and fiber optic humidity sensors are fabricated using fiber Bragg gratings, and the fiber optic temperature sensors, fiber optic strain sensors, and fiber optic humidity sensors are calibrated respectively to establish the relationships between temperature and the central resonant wavelength of the fiber Bragg grating in the fiber optic temperature sensor, the relationship between strain and the central resonant wavelength of the fiber Bragg grating in the fiber optic strain sensor, and the relationship between humidity and the central resonant wavelength of the fiber Bragg grating in the fiber optic humidity sensor. S2. The fiber optic temperature sensor, fiber optic humidity sensor and fiber optic strain sensor prepared in step S1 are integrated and packaged to obtain a device for detecting parameters of the filling slurry curing process. S3. Construct an online detection system for the curing process parameters of the filling grout in the cracks of stone cultural relics. Use multiple filling grout curing process parameter detection devices prepared in step S2, and place them vertically at different heights in the cracks of the stone cultural relics, keeping the placement position constant. Connect each filling grout curing process parameter detection device to the corresponding signal input terminal of the modem, and connect the signal output terminal of the modem to the signal input terminal of the computer. S4. Prepare the filling slurry and inject it evenly into the cracks of the stone artifact under constant temperature and humidity conditions. S5. The drift data of the center wavelengths of the fiber optic temperature sensor, fiber optic strain sensor, and fiber optic humidity sensor in each filling slurry curing process parameter detection device are collected by a modulator and demodulated to obtain demodulated data information. Then, the demodulated data information is transmitted to a computer. The computer calculates the filling slurry curing process parameters at different height positions of the cracks in the stone cultural relic based on the relationship between temperature and the center resonant wavelength of the fiber Bragg grating in the fiber optic temperature sensor, the relationship between strain and the center resonant wavelength of the fiber Bragg grating in the fiber optic strain sensor, and the relationship between humidity and the center resonant wavelength of the fiber Bragg grating in the fiber optic humidity sensor. The filling slurry curing process parameters include the temperature change, strain change, and humidity change of the filling slurry during the curing process. In step S5, when the computer calculates the curing process parameters of the filling grout at different heights of the cracks in the stone artifact, the fiber optic temperature sensor and fiber optic strain sensor are used as the temperature compensation unit and strain compensation unit of the fiber optic humidity sensor, respectively. The curing process parameters of the filling grout are obtained by processing a pre-constructed matrix model. The matrix model is as follows: ； Where, This represents the total wavelength shift of the fiber Bragg grating in the fiber optic temperature sensor. This represents the total wavelength shift of the fiber Bragg grating in the fiber strain sensor. This represents the total wavelength shift of the fiber Bragg grating in the fiber optic humidity sensor. This refers to the change in temperature. The change in strain This represents the change in humidity. The temperature sensitivity coefficient of the fiber Bragg grating in the fiber optic temperature sensor is expressed as: ； , The fiber Bragg grating strain sensitivity coefficient and temperature sensitivity coefficient of the fiber optic strain sensor are respectively expressed as: ； ； , and The sensitivity coefficients of the fiber Bragg grating for humidity, strain, and temperature in the fiber optic humidity sensor are respectively expressed as: ； ； ； In the above formula, , , These represent the resonant center wavelengths of the fiber Bragg gratings in fiber optic temperature sensors, fiber optic strain sensors, and fiber optic humidity sensors, respectively. The coefficient of thermal expansion of the optical fiber material. Thermo-optic coefficient; The effective elastic coefficient of the fiber Bragg grating. The radius of the optical fiber; The thickness of the humidity-sensitive film. The surface bonding coefficient between the fiber grating and the humidity-sensitive film. and These are the Young's moduli of humidity-sensitive thin films and optical fibers, respectively. The coefficient of moisture expansion of the moisture-sensitive film; and These are the cross-sectional areas of the humidity-sensitive material thin film and the optical fiber, respectively. and These are the coefficients of thermal expansion of the humidity-sensitive thin film and the optical fiber, respectively.

2. The in-situ online detection method for the curing process parameters of the stone artifact fissure filling grout according to claim 1, characterized in that, In step S1, the fiber optic temperature sensor serves not only as a fiber optic temperature sensor but also as a temperature compensation unit for the fiber optic humidity sensor and fiber optic strain sensor. The fiber optic temperature sensor is fabricated using the following method: an untreated bare fiber Bragg grating is used, and then the grating region of the bare fiber Bragg grating is sealed and encapsulated using a stainless steel capillary tube to obtain the fiber optic temperature sensor. Before encapsulation, the bare fiber Bragg grating is temperature-calibrated to establish the relationship between temperature and the center resonant wavelength of the bare fiber Bragg grating.

3. The in-situ online detection method for the curing process parameters of the stone artifact fissure filling grout according to claim 1, characterized in that, In step S1, the fiber optic strain sensor serves as both a fiber optic strain sensor and a strain compensation unit for the fiber optic humidity sensor; the fiber optic strain sensor employs an untreated bare fiber Bragg grating.

4. The in-situ online detection method for the curing process parameters of the stone artifact fissure filling grout according to claim 1, characterized in that, In step S1, the fiber optic humidity sensor is prepared using the following method: A1. A bare fiber Bragg grating is used, and the bare fiber Bragg grating is pre-processed. The bare fiber Bragg grating includes a fiber core, a grating region on the fiber core, a cladding covering the outer periphery of the fiber core, and a coating covering the outer periphery of the cladding. The cladding and coating structures corresponding to the grating region are removed. A2. The pretreated fiber Bragg grating is treated with silane to enhance the adhesion strength of the fiber Bragg grating surface. A3. Prepare chitosan-polyvinyl alcohol humidity-sensitive material to obtain chitosan-polyvinyl alcohol hydrogel; A4. Chitosan-polyvinyl alcohol hydrogel is uniformly coated onto the outer peripheral surface of the fiber Bragg grating corresponding to the grating area after silane treatment, and then dried to form a humidity-sensitive film on the outer peripheral surface of the fiber Bragg grating corresponding to the grating area, thereby obtaining a fiber optic humidity sensor.

5. The in-situ online detection method for the curing process parameters of the stone artifact fissure filling grout according to claim 4, characterized in that, In step A3, the chitosan-polyvinyl alcohol humidity-sensitive material is prepared using the following method: A3.1 Add chitosan powder to glacial acetic acid solution and stir evenly at room temperature to obtain chitosan solution; A3.2 Add polyvinyl alcohol powder to deionized water and stir evenly in a water bath to obtain a polyvinyl alcohol solution; A3.

3. After adding the polyvinyl alcohol solution to the prepared chitosan solution and stirring evenly at room temperature, chitosan-polyvinyl alcohol hydrogel is obtained.

6. The in-situ online detection method for parameters of the curing process of the stone artifact fissure filling grout according to claim 4 or 5, characterized in that, In step A3, the mass ratio of chitosan to polyvinyl alcohol is in the range of 4.5:1 to 7.2:

1.

7. The in-situ online detection method for parameters of the curing process of the grout filling material for stone cultural relics according to claim 5, characterized in that, In step A3.1, the mass fraction of the glacial acetic acid solution is in the range of 2% to 5%.

8. The in-situ online detection method for parameters of the curing process of the grout filling material for stone cultural relics according to claim 5, characterized in that, In step A3.2, the mass fraction of the polyvinyl alcohol solution is in the range of 10% to 11%.

9. The in-situ online detection method for the curing process parameters of the stone artifact fissure filling grout according to claim 1, characterized in that, In step S2, the integrated packaging of the fiber optic temperature sensor, fiber optic humidity sensor, and fiber optic strain sensor is carried out using the following method: a porous stainless steel tube is used to wrap the corresponding grating area of ​​each fiber optic temperature sensor, fiber optic humidity sensor, and fiber optic strain sensor. At the same time, the corresponding fiber optic pigtails of each fiber optic temperature sensor, fiber optic humidity sensor, and fiber optic strain sensor extend from the same end of the porous stainless steel tube. The wall of the porous stainless steel tube is uniformly provided with multiple through holes. The end of each fiber optic pigtail extending out of the porous stainless steel tube is then sealed.

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