An integrated monitoring device and method for dam deformation and seepage based on distributed optical fiber

Abstract

An integrated monitoring device and method for dam deformation and seepage based on distributed optical fiber, belonging to the technical field of geotechnical engineering structure safety monitoring. This monitoring device and method fix weak fiber gratings on the outer surface of PVC pipes to form deformation sensors, wind armored optical fibers around the outer surface of inclinometers and connect them to a heating power supply through wires to form seepage sensors, and the two sensors are fixedly connected through a circular clamp. The device measures the strain data of the measuring point through the deformation sensor, restores the pipe structure deformation by using the inverse finite element method, measures the temperature distribution along the optical fiber through the seepage sensor, and indirectly judges the occurrence and location of seepage by the abnormality of the temperature field, and can monitor the seepage and strain changes of the dam in real time and for a long time. The measurement device has high measurement accuracy, provides a more convenient and effective test means for the development of integrated monitoring of geotechnical structure deformation and seepage, and has good popularization value.

Description

Technical Field

[0001] The present invention belongs to the technical field of geotechnical engineering structure safety monitoring, and relates to an integrated monitoring device for the deformation and seepage of rock and soil masses based on distributed optical fibers, specifically an optical fiber sensor device and method suitable for the settlement and seepage monitoring of dams. Background Art

[0002] Earth-rock dams play a crucial role in the flood control system. They protect the lives and property of people on both sides of the dam and are also the largest barrier against flood disasters. There are numerous existing earth-rock dams, and the vast majority of them have problems such as being built for too long and aging in performance. During their service life, disasters such as leakage and settlement often occur. Real-time monitoring of the performance and changes of dams is beneficial to avoiding major disasters and ensuring the safety of people on both sides of the dam. Therefore, the safety monitoring of dams during their service life has become increasingly important. The seepage and settlement problems of earth-rock dams are particularly prominent. Therefore, the seepage inside the dam and the sliding deformation of the dam body are the top priorities of dam monitoring, and the monitoring results provide data support for the evaluation of the safety and stability of the dam.

[0003] The development of dam seepage into large-scale dam leakage is a slow-changing process. Therefore, long-term real-time monitoring is required to better evaluate the safety performance of the dam. Moreover, the temperature field change of the dam caused by seepage is random. Traditional point-type monitoring cannot meet the monitoring requirements and is prone to disasters due to missed inspections and difficulty in realizing seepage positioning and the inability to implement early intervention measures. Applying distributed optical fiber sensing technology in the monitoring field can perform real-time, long-term, and overall coverage monitoring of the temperature and strain of the dam, effectively avoiding the disadvantages of traditional monitoring methods. Utilizing the unique advantages of distributed optical fiber sensors such as corrosion resistance, electromagnetic interference resistance, and integration of information collection and transmission, and applying it to the research on the seepage and deformation monitoring of earth-rock dams has unique advantages and broad prospects. Therefore, the present invention proposes an integrated monitoring device and method for the deformation and seepage of dams based on distributed optical fibers. Summary of the Invention

[0004] The purpose of the present invention is to provide an integrated monitoring device and method for the deformation and seepage of dams based on distributed optical fibers. The equipment device is simple, and the engineering actual installation and operation are convenient. At the same time, it can monitor the seepage and strain changes of the dam in real time and accurately, solving the problems of integrated measurement of dam deformation and seepage and the difficulty of realizing the overall, real-time, and long-term monitoring of the dam performance.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: An integrated monitoring device for dam deformation and seepage based on distributed optical fiber includes a deformation sensor, a seepage sensor, and a power supply. The deformation sensor includes a PVC pipe and a weak fiber grating provided on the surface of the PVC pipe. The seepage sensor includes an inclinometer tube and an armored optical fiber wound around the inclinometer tube. The PVC pipe is connected to the inclinometer tube by sliding into a groove on the inner wall of the inclinometer tube through an annular clamp; the power supply is electrically connected to both ends of the armored optical fiber.

[0006] Specifically, one weak fiber grating is provided on each of the upper and lower surfaces of the PVC pipe. An epoxy resin film is sprayed on the surface of the weak fiber grating, and one end of the two weak fiber gratings is connected to each other;

[0007] The armored optical fiber adopts a structure in which a metal body is wrapped around the optical fiber core.

[0008] Specifically, an annular clamp is sleeved on the PVC pipe. The annular clamp includes two split rings. The split ring adopts a structure in which a sector-shaped protrusion is connected to an arc at each end. A fixing bolt is provided on each arc. The PVC pipe is connected to the inclinometer tube by sliding into a groove on the inner wall of the inclinometer tube through the fixing bolt.

[0009] Specifically, a half PVC pipe cut along the neutral axis is used as a casing to cover the optical fiber and is fixed with glue for encapsulation protection. An optical fiber is arranged on each of the upper and lower surfaces, and then the optical fibers on the upper and lower surfaces are fused by an optical fiber fusion splicer, so that the strain results measured on the upper and lower surfaces can be compared and referenced.

[0010] An integrated monitoring method for dam deformation and seepage based on distributed optical fiber uses the above monitoring device, connects the weak fiber grating to a fiber grating demodulator, connects the armored optical fiber to a fiber demodulator and adopts the following steps:

[0011] Deformation monitoring: Monitor the strain data of the weak fiber grating through the fiber grating demodulator, and use the strain stress information to analyze and obtain the structural displacement by the inverse finite element method, and reconstruct the structural deformation shape;

[0012] Seepage monitoring: Heat the armored optical fiber through the power supply. The armored optical fiber transmits the temperature data to the fiber demodulator. Utilize the coupling relationship between the temperature field and the seepage field, and through the distributed continuous measurement data of the spatial temperature field, realize the distributed monitoring of the seepage characteristics of the dam.

[0013] The use process of the above integrated monitoring device for dam deformation and seepage based on distributed optical fiber includes the following steps:

[0014] The first step is to first manufacture and assemble the sensor structure for deformation monitoring:

[0015] The weak fiber Bragg grating is pre-stretched to fit tightly to the outer surface of the PVC pipe and consolidated with high-strength quick-drying glue. After the quick-drying glue is completely solidified, a layer of epoxy resin is applied on it for packaging to protect the optical fiber. An optical fiber is arranged on the upper and lower surfaces and then the optical fibers on the upper and lower surfaces are fused with a fiber optic fusion splicer. In this way, the strain results measured on the upper and lower surfaces can be compared and referenced.

[0016] The second step is to make and assemble the sensor structure for seepage monitoring:

[0017] The armored optical fiber is evenly wrapped around the outer surface of the inclinometer tube at a certain interval, and the optical fiber is fixed with quick-drying glue. The two ends of the optical fiber are connected to the heating power supply through wires. After completing the above two steps, the installation of the main parts of the deformation and seepage sensor is completed.

[0018] The third step is to connect the assembled deformation sensor and seepage sensor:

[0019] Tighten the annular clamp connector on the PVC pipe by rotating the screws, align the raised part of the annular clamp with the optical fiber arrangement position to prevent the connector from pressing on the pipe and affecting the strain measurement result. Then slide the annular clamp connector into the inclinometer tube through the groove inside the inclinometer tube, connect the optical fiber to the optical fiber demodulator, and thus complete the installation of the integrated deformation and seepage monitoring device.

[0020] The beneficial effects of the present invention are as follows: the device of the present invention utilizes the unique advantages of optical fiber sensors, such as corrosion resistance, anti-electromagnetic interference, good durability, high measurement accuracy, and integration of information collection and transmission, to effectively assemble deformation sensors and seepage sensors into an integrated monitoring device through a ring clamp, which can achieve the purpose of integrated monitoring of dam deformation and seepage. This integrated monitoring device for dam deformation and seepage based on distributed optical fiber can achieve overall coverage, real-time and long-term monitoring of vertical settlement and seepage of rock and soil bodies, and is used for long-term, real-time monitoring of vertical displacement and seepage of earth-rock dams. The measuring device has a simple installation method, easy operation, and high measurement accuracy, which provides a more convenient and more effective experimental means for the development of integrated monitoring of rock and soil structure deformation and seepage, and has good promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a structural diagram of the integrated monitoring device for dam deformation and seepage based on distributed optical fiber.

[0022] Figure 2 This is the right view of the integrated monitoring device for dam deformation and seepage based on distributed optical fiber.

[0023] Figure 3 This is the front view of the seepage sensor.

[0024] Figure 4 Isometric view of the deformation sensor.

[0025] Figure 5 Left view of the deformation sensor.

[0026] Figure 6 Left view of the inclinometer tube.

[0027] Figure 7 Side view of the ring fixture.

[0028] Figure 8 Isometric view of the ring fixture.

[0029] Figure 9 Schematic diagram of the working principle of the integrated monitoring device for dam deformation and seepage based on distributed optical fiber.

[0030] Figure 10 Schematic diagram of the two-node inverse beam element structure iBeam3.

[0031] Figure 11 Comparison diagram of the dial indicator and the inverse finite element measurement values in the inverse finite element method to restore the deformation verification test of the beam element structure.

[0032] Figure 12 Linear fitting curve diagram of the temperature characteristic value and the flow velocity in the verification test of the relationship between the seepage rate and the temperature rise of the heating optical fiber.

[0033] In the figure: 101, inclinometer tube; 102, armored optical fiber; 201, PVC pipe; 202, weak fiber grating; 300, ring fixture; 301a, sector protrusion; 301b, arc; 302, fixing bolt. Detailed implementation manners

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in detail and clearly below with reference to the accompanying drawings in the embodiments of the present invention. The specific embodiments described are only a part of the numerous embodiments of the present invention and do not represent all embodiments. Generally, the components of the embodiments of the present invention shown in the drawings can be installed and implemented in different positions or assembly manners. Based on the specific embodiments described in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0035] Figure 1The figure shows a structural diagram of an integrated monitoring device for dam deformation and seepage based on distributed optical fiber. In the figure, this integrated monitoring device for dam deformation and seepage based on distributed optical fiber includes a deformation sensor, a seepage sensor, and a power supply. The deformation sensor includes a PVC pipe 201 and weak fiber Bragg gratings 202 provided on the upper and lower surfaces of the PVC pipe 201. The seepage sensor includes an inclinometer tube 101 and armored optical fiber 102 wound around the inclinometer tube 101. The power supply is electrically connected to both ends of the armored optical fiber 102 through wires (as Figures 2 - 6 shown).

[0036] A circular clamp 300 is sleeved on the PVC pipe 201. The circular clamp 300 includes two split rings. The split ring adopts a structure in which two arcs 301b are connected to both ends of a sector-shaped protrusion 301a. A fixing bolt 302 is provided on each arc 301b. The PVC pipe 201 is connected to the inclinometer tube 101 by sliding into a groove on the inner wall of the inclinometer tube 101 through the fixing bolt 302 (as Figure 7 and 8 shown).

[0037] The armored optical fiber 102 is evenly wound around the inclinometer tube 101, and the armored optical fiber is fixed with quick-drying glue. Both ends of the armored optical fiber are connected to a heating power supply through wires. Due to the metal body wrapped around the optical fiber core of the armored optical fiber, it can be heated by connecting to a heating power supply through wires to achieve the purpose of providing a linear heat source for the entire length of the optical fiber. At the same time, the outer metal "armor" can protect the optical fiber core and can also be bent naturally, having the advantages of high voltage resistance and strong tensile resistance, and can provide excellent optical cable protection and safety.

[0038] Weak fiber Bragg gratings 202 are arranged on the upper and lower outer surfaces of the PVC pipe 201. The optical fiber is pre-stretched and closely attached to the upper and lower outer surfaces of the PVC pipe, and fixed with high-strength quick-drying glue. After the quick-drying glue is completely solidified, a layer of epoxy resin is applied on it for encapsulation to protect the optical fiber.

[0039] The circular clamp 300 is fixed on the PVC pipe by tightening screws. The deformation sensor is slid into the groove inside the inclinometer tube through the fixing bolt 302, so as to assemble the deformation sensor and the seepage sensor into an integrated monitoring device for deformation and seepage.

[0040] One end of the two weak fiber Bragg gratings 202 arranged on the upper and lower outer surfaces of the PVC pipe 201 is fused with an optical fiber fusion splicer, and then the weak fiber Bragg grating demodulator is connected to the weak fiber Bragg grating 202, and the optical fiber demodulator is connected to the armored optical fiber 102. The device is buried in the earth-rock dam through drilling, and real-time monitoring can be carried out.

[0041] As attached Figure 9As shown in the working schematic diagram of the integrated monitoring device for dam deformation and seepage based on distributed optical fiber, the device is buried in the earth-rock dam through drilling. When seepage occurs in the dam, the temperature anomaly of the heated optical fiber at the seepage location can be clearly seen through the optical fiber demodulator, so as to indirectly achieve the precise positioning of the seepage location through the anomaly of the temperature field. When the dam undergoes settlement and other deformations under the action of external load and so on, by checking the strain distribution along the optical fiber through the optical fiber demodulator, the strain value of the optical fiber at that location can be obtained, and the deformation value can be calculated using the following formula:

[0042] δ = εd

[0043] In the formula: ε is the optical fiber strain value, d is the length of the optical fiber strain section, and δ is the deformation amount of the section to be measured.

[0044] The usage process of this integrated monitoring device for dam deformation and seepage based on distributed optical fiber is as follows:

[0045] The first step is to first manufacture and assemble the sensor structure for deformation monitoring:

[0046] Pre-stretch the optical fiber and closely attach it to the outer surface of the PVC pipe, and consolidate it with high-strength quick-drying glue. After the quick-drying glue is completely solidified, apply a layer of epoxy resin on it for encapsulation to protect the optical fiber. A half PVC pipe cut along the central axis can also be used as the outer shell to cover the weak fiber grating and fix it with glue for encapsulation protection. A weak fiber grating is arranged on both the upper and lower surfaces, and then the weak fiber gratings on the upper and lower surfaces are fused by an optical fiber fusion splicer, so that the strain measurement results of the upper and lower surfaces can be compared and referenced.

[0047] The second step is to manufacture and assemble the sensor structure for seepage monitoring:

[0048] Wind the optical fiber evenly around the outer surface of the inclinometer tube at regular intervals, and fix the optical fiber with quick-drying glue. Connect the two ends of the optical fiber to the heating power supply through wires. After completing the above two steps, the installation of the main parts of the deformation and seepage sensors is completed.

[0049] The third step is to connect the assembled deformation sensor and seepage sensor:

[0050] Tighten and fix the annular fixture connector on the PVC pipe by rotating the screw. Align the fan-shaped protrusion of the annular fixture with the arrangement position of the weak fiber grating to prevent the connector from pressing on the weak fiber grating on the pipe and affecting the strain measurement result. Then slide the annular fixture into the inside of the inclinometer tube through the groove inside the inclinometer tube, so that the installation of the integrated monitoring device for deformation and seepage is completed. Then connect the weak fiber grating to the optical fiber grating demodulator, and connect the armored optical fiber to the optical fiber demodulator to start monitoring.

[0051] The spacing of the temperature-sensitive optical fiber wound on the inclinometer tube, the installation quantity of the device, the selection of the measuring range, etc. shall be determined according to actual requirements.

[0052] The integrated monitoring principle of dam deformation and seepage based on distributed optical fiber is as follows:

[0053] Inverse finite element method is adopted for deformation monitoring. The inverse finite element method is an intelligent algorithm that uses a small amount of local discrete strain data as input and outputs the displacement field of the structure. By analyzing the inverse problem of finite elements, the structural changes are deduced, that is, the structural displacement is obtained by solving the strain-stress information. There are thousands of gratings arranged on a single optical fiber for weak fiber Bragg gratings, and the interval between adjacent gratings can be as small as 10 mm. Therefore, in actual engineering, it can be considered as a fully distributed optical fiber arrangement. The fiber Bragg grating demodulator obtains several strain data of the measured weak fiber Bragg grating points, and the discrete strain data is used to estimate the structural deformation in real time. Each sensing unit of the shape restoration sensing array adopts a new type of two-node inverse beam element iBeam3 that is simple and effective for two-dimensional deformation monitoring of beam structures. As shown in the appendix Figure 10 As shown, the iBeam3 element is a uniaxial element that can withstand tension, compression, and bending. Each element has 2 nodes, and each node has 3 degrees of freedom, namely the linear displacements along the x and y directions and the angular displacement around the z axis. The length of the element is L. Taking the beam element cross-section width × height = b × 2h as an example, the local coordinate system (x, y, z) and the global coordinate system (X, Y, Z) are established, and the local coordinate system is at a unit node. The analysis steps are as follows:

[0054] Based on the classical beam theory, the two Cartesian components of the displacement vector in two-dimensional deformation can be expressed as:

[0055]

[0056] u y (x,y,z) = v(x)

[0057] In the formula, u x and u y are the displacements of each point along the x and y directions respectively; u and v are the translational momenta along the x and y directions, is the rotational momentum along the z direction.

[0058] According to the small deformation assumption in elasticity mechanics, the linear strain-displacement relationship is:

[0059]

[0060] In the formula, ε is the strain value in the x direction, that is, the axial strain.

[0061] The displacement function inside the element is expressed by using the element shape function and the displacement parameters of the element end nodes:

[0062]

[0063]

[0064]

[0065] Among them,

[0066] N1 = 1 - ξ

[0067] N2 = ξ

[0068] Q1 = 2ξ 3 -3ξ 2 +1

[0069] Q2 = 3ξ 2 -2ξ 3

[0070] M1 = L(ξ 3 -2ξ 2 +ξ)

[0071] M2 = L(ξ 3 -ξ 2 )

[0072] In the formula, N i , Q i and M i are unit shape functions, i = 1, 2; u i , v i and respectively represent the displacement amounts of the node in the x, y, and z directions; ξ = x / L ∈ [0, 1], which is a dimensionless local coordinate.

[0073] According to the small deformation assumption in elasticity theory, combined with the derivation of the linear strain-displacement relationship and the unit shape function, the axial strain ε and the curvature k are expressed as:

[0074]

[0075]

[0076] Among them,

[0077]

[0078]

[0079]

[0080] In the formula, ε is the strain value in the x direction, that is, the axial strain; k is the curvature; ε(u e ) and k(u eare the axial strain and bending curvature caused by stretching respectively; u e is the nodal displacement vector; the matrix B b and B m are the derivatives of the shape functions, N i，x is the shape function N i the first derivative of N with respect to x, Q i,xx is the shape function Q i the second derivative of Q with respect to x, M i,xx is the shape function M i the second derivative of M with respect to x, i = 1, 2.

[0081] A crucial step in actual measurement is the measurement and processing of the discrete deformation data on the surface of the structure. The fiber Bragg grating sensors are attached to the upper and lower surfaces of the element, and the total number of measurement points is denoted as n. The strain value on the upper surface of the i-th measurement point obtained from the measurement and processing is ε i + and the strain value on the lower surface is ε i － . Thus, the axial strain ε i and curvature k i of the measured element are respectively:[[]]

[0082]

[0083]

[0084] where i corresponds to a certain measurement point in the inverse finite element, i = 1, …, n; n is the number of measurement points of the element; εi and ki are respectively the axial strain and curvature of the i-th measurement point in the element; 2h is the thickness of the element

[0085] For the iBeam3 inverse element, considering axial tension and bending deformation, the weighted least squares functional Φ e (u e ) related to axial tension and bending deformation is used to regenerate the deformed shape of the discretized structure by minimizing over all the discretized nodal degrees of freedom. Φ e (u e ) can be expressed as:[[]]

[0086]

[0087] where L e is the element length, 2h is the thickness of the element, n is the number of measurement points of the element; ω b and ω m are the weighting coefficients, ω bi and ω mi are the weighting coefficients of the i-th measurement point in the element and are related to the strain of each individual cross-section. When there are experimental values for the strain of each analysis cross-section, take ω bi = ωmi = 1.

[0088] Based on the variational method, find the extremum of the functional Φ e (u e ), and through minimization, we get:

[0089]

[0090]

[0091]

[0092] In the formula, k e is the element coefficient matrix, which is only related to the element length L, the thickness 2h, and the weighting coefficients ω b and ω m ; f e is the element strain vector, which is related to the strain data measured in reality; u e is the nodal displacement vector of the element.

[0093] After obtaining k e and f e in the local coordinate system, use the coordinate transformation matrix T e to integrate the discrete element matrix equation into the overall system equations:

[0094]

[0095]

[0096]

[0097] KU = F

[0098] Among them,

[0099]

[0100] In the formula, K is the overall system coefficient matrix, F is the overall strain vector, U is the overall nodal displacement vector, T e is the coordinate transformation matrix; θ is the angle between the x-axis of the local coordinate system and the X-axis of the overall coordinate system.

[0101] As can be seen from the above steps, the derivation of the inverse finite element formula is based on the least squares variational principle considering cross-sectional strain in the Euler - Bernoulli beam bending and stretching theory. Since only the strain - displacement relationship is used in the formula and no equilibrium equation is required, the iBeam3 element can reconstruct the structural deformation shape without any material or load information.

[0102] Distributed fiber optic seepage monitoring utilizes the dual functions of sensing and transmission of optical fiber. By measuring the temperature distribution along the optical fiber, it realizes the distributed continuous measurement of the spatial temperature field and the acquisition of the spatial position of the measured temperature field. By utilizing the coupling relationship between the temperature field and the seepage field, the purpose of seepage monitoring is indirectly achieved. Seepage can cause local irregularities in the temperature field. The temperature monitoring method of dam seepage is to indirectly locate and monitor the seepage of the dam by using the abnormal temperature field. The introduction of distributed fiber optic temperature sensing technology utilizes the conversion relationship between the optical signal and the temperature signal in the distributed optical fiber and the correlation characteristics between the temperature field and the seepage field inside the dam to realize the distributed monitoring of the seepage characteristics of the dam. There are two main methods of distributed fiber optic seepage monitoring: the gradient method and the heating method. Since the heating method is less restricted by temperature than the gradient method, it is more sensitive and has a wider application, so the heating method is more effective. The conductor wrapped in the outer layer of the armored optical fiber is heated to increase the temperature around the optical fiber, and then the temperature field distribution along the optical fiber is measured. When seepage occurs in the dam body, the temperature rise of the optical fiber at the seepage location will be significantly smaller than the temperature rise of the surrounding optical fibers. This is because the water flow at the seepage location will participate in the heat transfer process of the optical fiber, taking away part of the heat, making the temperature rise of the optical fiber smaller than the temperature rise of the optical fiber at other locations. When the temperature of the optical fiber is heated to a certain value, the difference with the water flow temperature becomes larger, and the gradient also increases, so the seepage point can be accurately located.

[0103] Taking the inverse finite element method to restore the deformation of the beam unit structure and the verification test of the relationship between the seepage rate and the temperature rise of the heated optical fiber as an example, how to use the device of the present invention to accurately measure the displacement of the dam and indirectly monitor the seepage through the temperature field anomaly is specifically explained, and the test principle of the present invention is further specifically explained:

[0104] The inverse finite element method is used to restore the deformation of the beam unit structure. The purpose is to verify the accuracy of the inverse finite element method in restoring the pipeline deformation. Figure 3 The deformation sensor shown uses a pipe to simulate a beam unit. A PVC pipe with a length of 1m and an outer diameter of 32mm is used. Both ends of the pipe are hinged to divide the pipe into 4 units. A micrometer is arranged at every 25mm interval on the pipe, and a 100g weight is arranged at every 20cm interval on the pipe. Gradual loading is performed, and a total of 5 loadings are recorded as moments t1 to t5. The recorded displacement measurement comparison diagram is from moments t1 to t5. After the loading is completed, the force deformation of the pipe is stable and the micrometer reading is stable. The reading of each micrometer is recorded and the displacement value obtained by converting the optical fiber strain value measured by the demodulator is obtained. The displacement value is specifically obtained by converting the measured strain value through the deformation value calculation formula described in the specific implementation method, and finally the comparison of the micrometer and the inverse finite element method measurement value is obtained as shown in the attached figure. Figure 11 As shown, the maximum error is only 0.456mm, which meets the requirements.

[0105] The verification test of the relationship between seepage rate and the temperature rise of the heating optical fiber aims to verify whether there is a linear relationship between the seepage rate and the temperature rise of the heating optical fiber. As attached Figure 2 shows the seepage sensor. The sensor is arranged in the water flow at different flow rates. When the water flow is stable, the flow rate of the water flow is measured with a flow meter. The armored optical fiber is connected to the heating power supply for heating for 15 minutes while recording the temperature change of the optical fiber. Then the power supply is disconnected to stop heating, and the temperature drop data is recorded. After the temperature of the optical fiber returns to the initial temperature, the next set of tests is carried out, and the operation is repeated. It is set at 6 different flow rates, and the temperature rise and temperature drop data of the optical fiber under 6 different heating powers are recorded. Since the temperature of the heating optical fiber will eventually stabilize and fluctuate within a certain range as the heating time prolongs, the difference between the average temperature in the time interval of 10 min - 15 min of the heating period and the initial temperature is taken as the temperature characteristic value at each flow rate. As attached Figure 12 shows the linear fitting curve of the temperature characteristic value and the flow rate when one of the heating powers is 10.06 W / s. The correlation coefficient R 2 is greater than 0.9, indicating a high linear fitting accuracy, which shows that the seepage rate is approximately linearly related to the temperature rise of the heating optical fiber. Therefore, the magnitude of the seepage volume can be judged by the temperature change amount.

[0106] The above embodiments only represent the implementation modes of the present invention, but should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those skilled in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. An integrated monitoring device for dam deformation and seepage based on distributed optical fiber, which comprises a deformation sensor, a seepage sensor and a power supply, and is characterized in that, The deformation sensor includes a PVC pipe (201) and a weak fiber grating (202) provided on the surface of the PVC pipe (201). The seepage sensor includes an inclinometer tube (101) and an armored optical fiber (102) wound around the inclinometer tube (101). The PVC pipe (201) is connected to the inclinometer tube (101) by sliding into a groove on the inner wall of the inclinometer tube (101) through an annular clamp; the power supply is connected to both ends of the armored optical fiber (102) through wires. One weak fiber grating (202) is provided on each of the upper and lower surfaces of the PVC pipe (201). An epoxy resin film is sprayed on the surface of the weak fiber grating (202). One end of the two weak fiber gratings (202) is connected; the armored optical fiber (102) has a structure in which a metal body is wrapped around the optical fiber core. An annular clamp (300) is sleeved on the PVC pipe (201). The annular clamp (300) includes two split rings. The split ring has a structure in which a sector-shaped protrusion (301a) is connected to an arc (301b) at each end. A fixing bolt (302) is provided on each arc (301b). The PVC pipe (201) is connected to the inclinometer tube (101) by sliding into a groove on the inner wall of the inclinometer tube (101) through the fixing bolt (302).

2. A monitoring method for the integration of dam deformation and seepage based on distributed optical fiber, characterized in that, For the monitoring device described in claim 1, connect the weak fiber grating to a fiber grating demodulator and the armored optical fiber to an optical fiber demodulator, and adopt the following steps: Deformation Monitoring: Monitor the strain data of the weak fiber grating through the fiber grating demodulator, and use the strain-stress information to analyze and obtain the structural displacement by the inverse finite element method, and reconstruct the structural deformation shape. Seepage monitoring: Heat the armored optical fiber through the power supply. The armored optical fiber transmits the temperature data to the optical fiber demodulator. Utilize the coupling relationship between the temperature field and the seepage field, and through the distributed continuous measurement data of the spatial temperature field, realize the distributed monitoring of the seepage characteristics of the dam.

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