An airport roadbed settlement monitoring structure and method based on distributed optical fiber embedding

Abstract

The present invention relates to the field of road engineering, and particularly to an airport roadbed settlement monitoring structure and method based on distributed optical fiber embedding. The airport roadbed settlement monitoring structure based on distributed optical fiber embedding provided by the present invention includes an airport road surface, which includes a road surface layer and a roadbed layer. An airport roadbed settlement monitoring system is provided in the roadbed layer. The airport roadbed settlement monitoring system includes a temperature compensation optical cable, a metal-based cable-shaped optical cable, an overall settlement measuring instrument, and a single-point settlement measuring instrument. The extending directions of the temperature compensation optical cable, the metal-based cable-shaped optical cable, and the overall settlement measuring instrument are the same. The single-point settlement measuring instrument is located in the extending direction of the overall settlement measuring instrument. The metal-based cable-shaped optical cable extends linearly, and the temperature compensation optical cable extends non-linearly. The airport roadbed settlement monitoring structure based on distributed optical fiber embedding provided by the present invention realizes long-distance, lossless, anti-interference, continuous, and intelligent monitoring of roadbed settlement.

Description

Technical Field

[0001] The invention relates to the field of road engineering, and in particular to an airport roadbed settlement monitoring structure and method based on distributed optical fiber burial. Background Art

[0002] In airport projects, it is necessary to monitor the settlement of the roadbed to prevent excessive differential settlement from causing damage to the runway structure, endangering the safety and smoothness of aircraft takeoff and landing and the long-term durability of airport facilities. Foundation settlement monitoring is mainly carried out by burying monitoring instruments in each layer of the foundation, obtaining the settlement and deformation of the foundation based on the measured data, and predicting future development trends. At present, the main methods for foundation settlement monitoring include settlement plate method, leveling method, monitoring pile method, etc. Traditional settlement monitoring methods are mostly point monitoring, and there are errors in "using points for surfaces", which makes it difficult to comprehensively and effectively characterize the settlement conditions of the foundation. At the same time, there are problems such as large on-site workload, low level of automation, cumbersome burial plans, and construction that is easily disturbed. It is urgent to develop a large-scale, automated, real-time, and high-precision monitoring method for foundation settlement in the working area.

[0003] As a new type of sensing material, distributed optical fiber is both a sensing medium and a transmission channel. Compared with other traditional sensing materials, it has obvious advantages in working environments with changeable climate conditions and complex geological conditions. It can realize long-distance, lossless, anti-interference, continuous and intelligent monitoring. By monitoring the change in the frequency of Brillouin scattered light in the distributed optical fiber, the strain of the measured part can be determined and the deformation can be calculated, thereby realizing large-scale automatic monitoring of foundation settlement. At present, in the application of foundation settlement monitoring, distributed optical fiber mainly adopts the vertical stretching method (direct burial). Although it can monitor the stratified settlement of the foundation at the buried point more accurately, from the plane dimension of the settlement area to be measured, it still belongs to the category of point monitoring. The lateral burial of distributed optical fiber lacks strain-displacement analysis methods, and there is currently no precedent for its widespread application in engineering. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide an airport roadbed settlement monitoring structure and method based on distributed optical fiber burial, so as to solve the problems in the prior art.

[0005] To achieve the above object and other related objects, on the one hand, the present invention provides an airport roadbed settlement monitoring structure based on distributed optical fiber burial, including an airport road surface, the airport road surface includes a road surface layer and a road base layer, and an airport roadbed settlement monitoring system is provided in the road base layer. The airport roadbed settlement monitoring system includes a temperature compensation optical cable, a metal-based cable-shaped optical cable, an overall settlement measuring instrument, and a single-point settlement measuring instrument. The extending directions of the temperature compensation optical cable, the metal-based cable-shaped optical cable, and the overall settlement measuring instrument are the same. The single-point settlement measuring instrument is located in the extending direction of the overall settlement measuring instrument. The metal-based cable-shaped optical cable extends linearly, and the temperature compensation optical cable extends non-linearly.

[0006] In some embodiments of the present invention, a plurality of airport roadbed settlement monitoring systems are provided in the road base layer.

[0007] In some embodiments of the present invention, along the extending direction of the airport runway, the temperature compensation optical cable, the metal-based cable-shaped optical cable, and the overall settlement measuring instrument are all buried horizontally.

[0008] In some embodiments of the present invention, the airport roadbed settlement monitoring system includes a plurality of single-point settlement measuring instruments, and the single-point settlement measuring instruments are evenly distributed in the extending direction of the overall settlement measuring instrument.

[0009] In some embodiments of the present invention, in the airport road surface with a unit width, the length of the temperature compensation optical cable is 1.05 - 1.20 times the length of the metal-based cable-shaped optical cable.

[0010] In some embodiments of the present invention, the temperature compensation optical cable includes a first optical fiber body and a first optical cable outer sheath for wrapping the first optical fiber body.

[0011] In some embodiments of the present invention, the metal-based cable-shaped optical cable includes a second optical fiber body and a second optical cable outer sheath for wrapping the second optical fiber body.

[0012] In some embodiments of the present invention, the temperature compensation optical cable, the metal-based cable-shaped optical cable, the overall settlement measuring instrument, and the single-point settlement measuring instrument are buried in fine sand.

[0013] In some embodiments of the present invention, the temperature compensation optical cable, the metal-based cable-shaped optical cable, the overall settlement measuring instrument, and the single-point settlement measuring instrument are covered with backfilled original soil.

[0014] In some embodiments of the present invention, bentonite is doped in the backfilled original soil.

[0015] In some embodiments of the present invention, it further includes a BOTDR distributed sensor, and the BOTDR distributed sensor is respectively connected to the optical fibers in the optical cable.

[0016] On the other hand, the present invention provides a method for monitoring the settlement of airport roadbeds based on the embedding of distributed optical fibers. The settlement of the airport roadbed is monitored by the above-mentioned monitoring structure for the settlement of airport roadbeds based on the embedding of distributed optical fibers, including:

[0017] Calculating and obtaining the estimated actual strain according to Equation (1)

[0018]

[0019] where is the average strain;

[0020] ε(x) is the difference between the strain of the metal-based cable optical fiber (22) and the strain of the temperature compensation optical fiber (21), x ∈ [0, l];

[0021] α is the strain reduction coefficient, representing the degree of fiber relaxation;

[0022] β is the standard deviation coefficient, representing the internal strain redistribution of the optical fiber;

[0023] Determining the maximum settlement position according to Equation (2), and the zero point x = x of the function Y(x) 0 is the maximum settlement position:

[0024]

[0025] where

[0026]

[0027] Calculating and obtaining the estimated displacement according to Equation (5)

[0028]

[0029] Thus, the relative settlement distance of the airport roadbed is obtained.

[0030] In some embodiments of the present invention, the strain reduction coefficient α is the ratio of the total elongation Δl of the optical fiber ε to the actual total elongation Δl of the optical fiber, and the strain reduction coefficient α = 0.9 - 1.0.

[0031] In some embodiments of the present invention, the standard deviation coefficient β = 0.2 - 1.0.

[0032] In some embodiments of the present invention, the standard deviation coefficient β is calculated according to Equation (3):

[0033]

[0034] In some embodiments of the present invention, the overall settlement distance of the airport roadbed is obtained according to the sum of the relative settlement distance and the absolute settlement distance, and the absolute settlement distance is measured by an overall settlement measuring instrument (23) and a single-point settlement measuring instrument (24).

[0035] On the other hand, the present invention provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the steps of the above-mentioned airport roadbed settlement monitoring method based on distributed optical fiber embedding are realized.

[0036] On the other hand, the present invention provides a device, including: a processor and a memory, the memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory, so that the device executes the steps of the above-mentioned airport roadbed settlement monitoring method based on distributed optical fiber embedding.

[0037] On the other hand, the present invention provides a device, which may include:

[0038] Estimated actual strain A calculation module, configured to calculate and obtain the estimated actual strain according to Equation (1)

[0039]

[0040] where is the average strain;

[0041] ε(x) is the difference between the strain of the metal-based cable optical cable (22) and the strain of the temperature compensation optical cable (21), x ∈ [0, l];

[0042] α is the strain reduction coefficient, which characterizes the degree of fiber relaxation;

[0043] β is the standard deviation coefficient, which characterizes the internal strain redistribution of the optical fiber;

[0044] A maximum settlement position calculation module, configured to determine the maximum settlement position according to Equation (2), and the zero point x = x of the function Y(x) 0 is the maximum settlement position:

[0045]

[0046] where

[0047]

[0048] Estimated displacement A calculation module, which calculates and obtains the estimated displacement according to Equation (5)

[0049]

[0050] Optionally, it further includes an overall settlement distance calculation module for obtaining the overall settlement distance of the airport roadbed according to the sum of the relative settlement distance and the absolute settlement distance. Description of the Drawings

[0051] Fig. 1(a) shows a schematic diagram of the settlement monitoring structure of the airport roadbed of the present invention under the condition of no settlement.

[0052] Fig. 1(b) shows a schematic diagram of the settlement monitoring structure of the airport roadbed of the present invention under the condition of settlement.

[0053] Figure 2 It shows a schematic diagram of the distributed optical fiber measurement principle of BOTDR.

[0054] Figure 3 It shows a schematic diagram of the calculation of the optical fiber strain and the vertical displacement of the present invention.

[0055] Figure 4 It shows a schematic diagram of the analytical relationship between the optical fiber strain and the vertical displacement based on the calibration test in the embodiment of the present invention.

[0056] Figure 5 It shows a schematic diagram of the settlement back calculation based on the optical fiber strain in the embodiment of the present invention.

[0057] Figure 6 It shows a schematic diagram of the roadbed settlement monitoring cloud map in the embodiment of the present invention.

[0058] Figure 7 It shows the roadbed settlement monitoring data and the correction results in the embodiment of the present invention.

[0059] Description of Component Labels

[0060] 1 Airport pavement

[0061] 11 Road surface layer

[0062] 12 Roadbed layer

[0063] 2 Airport roadbed settlement monitoring system

[0064] 21 Temperature compensation optical cable

[0065] 22 Metal-based cable-like optical cable

[0066] 23 Overall settlement measuring instrument

[0067] 24 Single-point settlement measuring instrument

[0068] 25 Optical fiber demodulator Detailed Implementation Modes

[0069] Through a large amount of practical research, the inventor of the present invention provides an airport roadbed settlement monitoring structure and method based on distributed optical fiber embedding. The monitoring structure and method can achieve large-scale, automated, real-time, and high-precision monitoring of airport roadbed settlement, and timely warn of differential settlement that may damage the pavement structure strength and threaten the safety of aircraft takeoff and landing. Based on this, the present invention is completed.

[0070] In the first aspect of the present invention, an airport roadbed settlement monitoring structure based on distributed optical fiber embedding is provided. As shown in FIGS. 1(a) and 1(b), it includes an airport pavement 1, the airport pavement 1 includes a road surface layer 11 and a roadbed layer 12, and an airport roadbed settlement monitoring system 2 is provided in the roadbed layer 12. The airport roadbed settlement monitoring system 2 includes a temperature compensation optical cable 21, a metal-based cable-shaped optical cable 22, an overall settlement measuring instrument 23, and a single-point settlement measuring instrument 24. The extending directions of the temperature compensation optical cable 21, the metal-based cable-shaped optical cable 22, and the overall settlement measuring instrument 23 are the same. The single-point settlement measuring instrument 24 is located in the extending direction of the overall settlement measuring instrument 23. The metal-based cable-shaped optical cable 22 extends linearly, and the temperature compensation optical cable 21 extends non-linearly. The road surface layer 11 of the airport pavement 1 usually further includes a surface layer, a base layer, and a cushion layer. The airport roadbed settlement monitoring system 2 is usually located in the roadbed layer 12. The linear extension usually means that when the metal-based cable-shaped optical cable 22 is buried, a certain prestress can be applied to both ends of the optical fiber to make it in a straightened state, so that it can extend linearly in the roadbed layer 12 to effectively sense minute vertical deformations (as shown by the arrow direction in FIG. 1(b)). The non-linear extension usually means that the temperature compensation optical cable 21 is in a relaxed and non-straightened state when buried (for example, in the airport pavement 1 with a unit width, the length of the temperature compensation optical cable 21 is 1.05-1.20 times the length of the metal-based cable-shaped optical cable 22). Thus, it can extend non-linearly in the subgrade layer 12. The temperature compensation optical cable 21 in a relaxed state does not sense minute vertical deformations and only measures the strain caused by temperature changes. The measured optical fiber strain can be used to correct the optical fiber strain measured by the linearly extending metal-based cable-shaped optical cable 22, and further calculate the relative settlement distance of the measurement point in the airport roadbed relative to the airport roadbed itself. The single-point settlement measuring instrument 24 is located in the extending direction of the overall settlement measuring instrument 23. The single-point settlement measuring instrument 24 can obtain the settlement distance of the airport roadbed itself at a specific measurement point, and can obtain the relative difference of each part of the airport roadbed relative to the above specific measurement point according to the overall settlement measuring instrument 23, so as to determine the overall settlement distance of each part of the airport roadbed itself, and can learn the settlement distance of the measurement point relative to the original road surface according to the relative settlement distance of the measurement point relative to the airport roadbed itself calculated as above.

[0071] In the airport roadbed settlement monitoring structure based on distributed optical fiber burial provided by the present invention, the distance between the temperature compensating optical cable 21, the metal-based rope-like optical cable 22, the overall settlement measuring instrument 23 and the single-point settlement measuring instrument 24 is usually not too large. For example, the maximum spacing between the temperature compensating optical cable 21, the metal-based rope-like optical cable 22 and the overall settlement measuring instrument 23, the single-point settlement measuring instrument 24 is usually not more than 60 cm, preferably not more than 30 cm, specifically 5-30 cm, 5-10 cm, 10-15 cm, 15-20 cm, 20-25 cm, or 25-30 cm, and the distance between the temperature compensating optical cable 21 and the metal-based rope-like optical cable 22 can usually be ≤5 cm, ≤1 cm, 1-2 cm, 2-3 cm, 3-4 cm, or 4-5 cm, so that they can cooperate with each other as a whole. Under the premise of consistent extension direction, the corresponding parts can perform data measurement for the same measurement area to ensure the reliability of the data. In the entire airport pavement 1, multiple airport pavement subsidence monitoring systems 2 can be provided in the pavement base layer 12, so as to quickly measure various parts of the airport pavement 1. According to the extension direction of the airport runway, the spacing between the airport pavement subsidence monitoring systems 2 can be 4m-20m, 4m-8m, 8m-12m, 12m-16m, or 16m-20m. According to the extension direction of the airport runway, the temperature compensation optical cable 21, the metal-based rope-shaped optical cable 22 and the overall subsidence measuring instrument 23 are usually buried horizontally to facilitate data acquisition.

[0072] In the airport roadbed settlement monitoring structure based on distributed optical fiber burial provided by the present invention, the number of single-point settlement measuring instruments 24 in the airport roadbed settlement monitoring system 2 can be one or more, and its main function is to provide one or more bases for the overall settlement measuring instrument 23. The overall settlement measuring instrument 23 and the single-point settlement measuring instrument 24 usually cooperate with each other, and the extension direction of the overall settlement measuring instrument 23 and the single-point settlement measuring instrument 24 is usually consistent with the temperature compensation optical cable 21 and the metal-based rope-shaped optical cable 22. The spacing between the settlement measuring instruments can usually be 20-40m, 20-25m, 25-30m, 30-35m, or 35-40m, so that the overall settlement distance of the airport roadbed itself can be determined according to the measurement results of the single-point settlement measuring instrument 24 and the overall settlement measuring instrument 23.

[0073] In the airport roadbed settlement monitoring structure based on distributed optical fiber embedding provided by the present invention, those skilled in the art can select appropriate optical cables as the temperature compensation optical cable 21 and the metal-based cable-shaped optical cable 22. For example, the temperature compensation optical cable 21 includes a first optical fiber body and a first optical cable outer sheath for wrapping the first optical fiber body. The diameter of the first optical fiber body can be 0.25 mm to 0.90 mm, 0.25 mm to 0.30 mm, 0.30 mm to 0.40 mm, 0.40 mm to 0.50 mm, 0.50 mm to 0.60 mm, 0.60 mm to 0.70 mm, 0.70 mm to 0.80 mm, or 0.80 mm to 0.90 mm. The thickness of the first optical cable outer sheath can be 1 mm to 3 mm, 1 mm to 1.5 mm, 1.5 mm to 2 mm, 2 mm to 2.5 mm, or 2.5 mm to 3 mm. The metal-based cable-shaped optical cable 22 includes a second optical fiber body and a second optical cable outer sheath for wrapping the second optical fiber body. The diameter of the second optical fiber body can be 0.25 mm to 0.90 mm, 0.25 mm to 0.30 mm, 0.30 mm to 0.40 mm, 0.40 mm to 0.50 mm, 0.50 mm to 0.60 mm, 0.60 mm to 0.70 mm, 0.70 mm to 0.80 mm, or 0.80 mm to 0.90 mm. The thickness of the second optical cable outer sheath can be 1 mm to 3 mm, 1 mm to 1.5 mm, 1.5 mm to 2 mm, 2 mm to 2.5 mm, or 2.5 mm to 3 mm.

[0074] In the airport roadbed settlement monitoring structure based on distributed optical fiber embedding provided by the present invention, the temperature compensation optical cable 21, the metal-based cable-shaped optical cable 22, the overall settlement measuring instrument 23, and the single-point settlement measuring instrument 24 can usually be buried in fine sand. Thereby, the service life of the optical fiber can be improved, and the cutting damage to it under the action of soil pressure and aircraft dynamic load can be avoided. In addition to installing a sheath outside the optical fiber, the thickness of the fine sand layer can usually be 5 cm to 0.5 m, 5 cm to 10 cm, 10 cm to 20 cm, 20 cm to 40 cm, 40 cm to 60 cm, 60 cm to 80 cm, or 80 cm to 100 cm. The temperature compensation optical cable 21, the metal-based cable-shaped optical cable 22, the overall settlement measuring instrument 23, and the single-point settlement measuring instrument 24 can also be covered with backfilled original soil. If the above components are buried in fine sand, the backfilled original soil can be laid on the fine sand, thereby ensuring the monitoring accuracy of the optical fiber. The backfill soil can usually be in-situ soil, and a small amount of bentonite can be added thereto, thereby improving the coupling effect between the distributed optical fiber and the soil base.

[0075] In the airport roadbed settlement monitoring structure based on distributed optical fiber embedding provided by the present invention, a BOTDR distributed sensor may further be included. The BOTDR distributed sensors are generally respectively connected to the optical fibers in the optical cable. For example, the BOTDR distributed sensors may be respectively connected to the first optical fiber body and the second optical fiber body, so as to obtain the strain amounts of the first optical fiber body and the second optical fiber body. The BOTDR distributed sensors, the overall settlement measuring instrument 23, and the single-point settlement measuring instrument 24 may be further connected to a computer, so as to transmit the measured information to the computer and further perform subsequent processing on the relevant data.

[0076] In the airport roadbed settlement monitoring structure based on distributed optical fiber embedding provided by the present invention, the monitoring principle is specifically as follows: The uneven settlement of the roadbed drives the embedded distributed optical fiber to deform synergistically, that is, lateral tension is generated. The strain change generated axially in the optical fiber at the differential settlement causes a frequency drift in the Brillouin scattering spectrum of the sampling points in this section. The relationship between the Brillouin frequency shift change amount and the optical fiber temperature and strain is shown in Equation (6). After the Brillouin frequency shift signal is analyzed by the demodulator, according to the results of the previous calibration test, the differential settlement amount of the roadbed can be deduced and calculated inversely. Figure 2 The figure shows a schematic diagram of the distributed optical fiber measurement principle based on Brillouin scattering optical time domain reflectometry (BOTDR).

[0077]

[0078] In the formula, v B (ε,T) is the Brillouin frequency shift amount of the distributed optical fiber when the temperature is T and the strain is ε; v B (0,T 0 ) is the Brillouin frequency shift amount of the distributed optical fiber when the temperature is T 0 and the strain is 0; respectively represent the proportionality coefficients of strain and temperature, which are related to the optical fiber type and are calibrated by the manufacturer. The settlement of the roadbed is characterized by the axial tensile strain of the distributed optical fiber, that is, the vertical displacement. The key technology is to analyze the correlation between the optical fiber strain and the displacement amount and displacement position, so as to provide a basis for the analysis of the axial strain of the optical fiber buried in the soil medium - the settlement of the roadbed soil. To achieve the above purpose, the optical fiber strain under known vertical displacements of different positions and magnitudes can be obtained through calibration tests, and the corresponding relationship between the two can be established.

[0079] The second aspect of the present invention provides an airport roadbed settlement monitoring method based on distributed optical fiber embedding. The settlement of the airport roadbed is monitored by the airport roadbed settlement monitoring structure provided in the first aspect of the present invention, including:

[0080] Calculating and obtaining the estimated actual strain according to Equation (1)

[0081]

[0082] Among them, is the average strain, that is, the average value of each ε(x);

[0083] ε(x) is the difference between the strain of the metal-based cable optical cable and the strain of the temperature compensation optical cable. ε(x) is the actual strain measurement result of the optical fiber, in which the strain of the optical fiber caused by temperature change is removed, x ∈ [0, l], and l is the optical fiber length of the test section;

[0084] α is the strain reduction coefficient, which characterizes the degree of fiber relaxation;

[0085] β is the standard deviation coefficient, which characterizes the internal strain redistribution of the optical fiber;

[0086] Determine the maximum settlement position according to Equation (2). The zero point x = x of the function Y(x) 0 is the maximum settlement position, because for the maximum settlement position x 0 the values obtained by integrating the strain in the two sections of 0~x 0 and x 0 ~l should be basically the same:

[0087]

[0088] Among them,

[0089]

[0090] If a vertical displacement occurs at a certain point on the optical fiber, as Figure 3 shown, let the position coordinate of point A be x, take the microelement dx on the optical fiber, and the original optical fiber AB section becomes A'B' section after deformation. Therefore, according to the Pythagorean theorem and the strain definition, the vertical displacement y(x) of each point is the integral of y′(x) from the end point to this point. According to the most unfavorable settlement, Equations (3) and (4) can be obtained in the one-way deformation region;

[0091] Calculate the estimated displacement according to Equation (5)

[0092]

[0093] Estimated displacement can represent the relative settlement of each point on the airport subgrade in the extension direction of the airport subgrade settlement monitoring system.

[0094] In the method for monitoring the settlement of airport roadbed based on distributed optical fiber embedding provided by the present invention, α is related to the properties and the state of the optical fiber itself, and usually the value of α of the used optical fiber can be obtained through pre-experimental measurement. The strain reduction coefficient α can be measured by the ratio of the total elongation Δl of the optical fiber calculated based on the measured data ε to the actual total elongation Δl of the optical fiber, so as to characterize the degree of optical fiber relaxation. In a specific embodiment of the present invention, the two ends of the optical cable used in the monitoring system can be fixed in the laboratory in advance, the middle is suspended, and a known deformation is applied thereto. The strain of the optical fiber is measured by the BOTDR distributed sensor connected to the optical fiber, and the total elongation Δl of the optical fiber is calculated according to the strain ε . At the same time, the actual total elongation Δl of the optical fiber is monitored, so as to calculate the strain reduction coefficient α of this kind of optical fiber. Then, in the calculation of specific engineering monitoring, the value of the strain reduction coefficient α can be used. The value of the strain reduction coefficient α can usually be 0.9 - 1.0, 0.9 - 0.92, 0.92 - 0.94, 0.94 - 0.96, 0.96 - 0.98, or 0.98 - 1.0.

[0095] In the method for monitoring the settlement of airport roadbed based on distributed optical fiber embedding provided by the present invention, β is related to the properties and the state of the optical fiber itself, and usually the value of β of the used optical fiber can be obtained through pre-experimental measurement. The standard deviation coefficient β is calculated by the formula (3): (3). In a specific embodiment of the present invention, the two ends of the optical cable used in the monitoring system can be fixed in the laboratory in advance, the middle is suspended, and a known deformation is applied thereto. The strain of the optical fiber is measured by the BOTDR distributed sensor connected to the optical fiber. According to the formula (3), the β that makes the calculated deformation error the smallest is selected as the β value of this kind of optical fiber. Then, in the calculation of specific engineering monitoring, the value of β can be used. The value of the standard deviation coefficient β can usually be 0.2 - 1.0, 0.2 - 0.4, 0.4 - 0.6, 0.6 - 0.8, or 0.8 - 1.0.

[0096] In the method for monitoring the settlement of airport roadbed based on distributed optical fiber embedding provided by the present invention, the overall settlement distance of the airport roadbed can be obtained according to the sum of the relative settlement distance and the absolute settlement distance. The relative settlement distance is the relative settlement distance of the measurement point in the airport roadbed relative to the airport roadbed itself. The relative settlement distance can be based on the estimated displacement as described above It is calculated that, based on the relative settlement distance of the obtained measurement points with respect to the airport roadbed itself, and adding the overall settlement distance of each part of the airport roadbed itself, the settlement distance of the measurement points with respect to the original road surface can be calculated. The overall settlement distance of each part of the airport roadbed itself can be measured by a single-point settlement measuring instrument and an overall settlement measuring instrument. For example, the settlement distance of the airport roadbed itself at a specific measurement point can be obtained by a single-point settlement measuring instrument, and the relative difference of each part of the airport roadbed with respect to the above specific measurement point can be obtained according to the overall settlement measuring instrument, so as to determine the overall settlement distance of each part of the airport roadbed itself.

[0097] The third aspect of the present invention provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the steps of the airport roadbed settlement monitoring method based on distributed optical fiber embedding provided in the second aspect of the present invention are implemented.

[0098] The fourth aspect of the present invention provides a device, including: a processor and a memory, the memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory, so that the device executes the steps of the airport roadbed settlement monitoring method based on distributed optical fiber embedding provided in the second aspect of the present invention.

[0099] The fifth aspect of the present invention provides a device, which may include:

[0100] Estimated actual strain A calculation module, configured to calculate and obtain the estimated actual strain according to formula (1)

[0101]

[0102] wherein, is the average strain;

[0103] ε(x) is the difference between the strain of the metal-based cable optical cable (22) and the strain of the temperature compensation optical cable (21), x ∈ [0, l];

[0104] α is the strain reduction coefficient, which characterizes the degree of fiber relaxation;

[0105] β is the standard deviation coefficient, which characterizes the internal strain redistribution of the optical fiber;

[0106] A maximum settlement position calculation module, configured to determine the maximum settlement position according to formula (2), and the zero point x = x of the function Y(x) 0 is the maximum settlement position:

[0107]

[0108] wherein,

[0109]

[0110] Estimated displacement Calculation module, which calculates and obtains the estimated displacement according to Equation (5)

[0111]

[0112] Optionally, it further includes an overall settlement distance calculation module, which is used to obtain the overall settlement distance of the airport roadbed according to the sum of the relative settlement distance and the absolute settlement distance.

[0113] In the present invention, the operating principles of the various modules in the above device can refer to the airport roadbed settlement monitoring method based on distributed optical fiber embedding as described above, and will not be elaborated here.

[0114] In the prior art, the application prospect of distributed optical fiber in foundation settlement monitoring is broad, but currently it is mainly in the direct burial type, which cannot meet the requirements of large-scale monitoring in engineering.

[0115] The airport roadbed settlement monitoring structure and method based on distributed optical fiber embedding provided by the present invention are different from the traditional point-type monitoring method. By using distributed optical fiber as the sensing medium and transmission channel, it realizes long-distance, lossless, anti-interference, continuous and intelligent monitoring of roadbed settlement. In addition, based on the calibration test, the present invention proposes the fiber strain-vertical displacement analysis and roadbed settlement back-calculation methods, and at the same time proposes the construction method of horizontal embedding of distributed optical fiber. Overall, it can timely warn of the differential settlement of the roadbed that may damage the pavement structure strength and threaten the safety of aircraft takeoff and landing, ensuring the smoothness and durability of the runway and the operation safety of the airport. Its monitoring principle and implementation plan are also applicable to the large-scale monitoring of foundation settlement in technical fields such as road engineering, geotechnical engineering, water conservancy engineering, and tunnel engineering.

[0116] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0117] Example 1

[0118] This embodiment relies on the Chengdu Tianfu International Airport intelligent runway project, and adopts metal-based cable (supplied by Suzhou Nanzhi, model NZS-DTS-C08) to monitor the settlement distribution of the roadbed soil, and adopts high-strength steel wire armored cable (supplied by Suzhou Nanzhi, model NZS-DTS-C08) to compensate for temperature changes, and is assisted by high-precision intelligent settlement meters to assist in monitoring and verifying data. The single-point settlement measuring instrument is supplied by Suzhou Nanzhi, model NZS-FBG-DS(1), and the overall settlement measuring instrument is supplied by Suzhou Nanzhi, model NZS-FBG-HD.

[0119] First, a calibration test was carried out to analyze the correlation between the optical fiber strain and the vertical displacement and the vertical displacement position using the FTB 2505 distributed optical fiber demodulator: (1) fix the deformation application position and adjust the deformation amount; (2) fix the deformation amount and adjust the deformation application position. Figure 4 (a) shows the fiber strain after different deformations are applied to the midpoint. Figure 4 (b) and (c) show the strain of the optical fiber under the same deformation at different positions on the left and right of the midpoint, respectively. By intuitively analyzing the results, it can be seen that the greater the total deformation length of the optical fiber, the greater the strain of the optical fiber, which is consistent with engineering experience. Substituting the test results ε(x) and the calibration parameters According to the operator The back-calculated settlement is as follows: Figure 5 As shown in (a) to (c), the relative error between the analytical value of the deformation and the optical fiber length is less than 0.5%, and the engineering feasibility and applicability are good.

[0120] When burying distributed optical fibers in trenches on site, first fill the roadbed to the specified elevation, level and clean the site, and remove hard objects such as lumps of gravel, plant roots, etc. A layer of fine sand about 5 cm thick is laid at the bottom of the trench, the distributed optical fiber is straightened and tightened, and a corrugated tube is placed on the outer cover for protection. Then, 40 cm of fine sand is backfilled, and the original soil with the gravel removed is backfilled on top to detect the optical fiber path and analysis. The length of the distributed optical fiber is determined according to actual needs, and generally covers the entire airport runway. The length of a distributed optical fiber ranges from 2000 to 6000 m, and the specific length in the embodiment is 5000 m. Taking into account both calibration accuracy and engineering cost, a single-point settlement meter or an overall settlement meter is generally deployed every 20 to 40 meters. The laying plan in the embodiment is to deploy single-point settlement meters or overall settlement meters at intervals of 15 meters. The distance between the above-mentioned single-point settlement meter or overall settlement meter and the distributed optical fiber at the corresponding point is not more than 30 cm, and the distance between the temperature compensation optical cable and the metal-based rope-like optical cable is not more than 5 cm. The ends of the above-mentioned temperature compensation optical cable and the metal-based rope-like optical cable are connected to the optical fiber demodulator.

[0121] Subtract the strain data of the metal-based cable optical cable 22 from the strain data of the high-strength steel wire armored optical cable 21 at the same position to obtain the roadbed settlement monitoring data after temperature compensation, as follows Figure 6 shown. According to the strain conditions of the distributed optical fiber at each monitoring point shown by the monitoring data, and using the above-mentioned airport roadbed settlement monitoring method based on the buried distributed optical fiber, the vertical deformation (i.e., settlement) of the soil subgrade at the monitoring point can be calculated from the lateral strain of the distributed optical fiber. The roadbed soil settlement distribution obtained thereby is the relative settlement between the monitoring points of the distributed optical fiber, as follows Figure 7 shown by the black line in. The interval between the measuring points on the black line is 0.04 m. According to the measurement data of the high-precision overall settlement measuring instrument 23 and the single-point settlement measuring instrument 24, as follows Figure 7 shown by the blue dots in, the absolute settlements are 29.2312 mm, 23.0720 mm, 16.6855 mm, and 10.4307 mm from left to right respectively, and calibrate the monitoring data of the distributed optical fiber at the corresponding positions; then according to the relative settlement between the monitoring points of the distributed optical fiber, the true settlement conditions of all roadbed soils within the coverage of the distributed optical fiber can be obtained, as follows Figure 7 shown by the red line in, and calculate the differential settlement between different areas of the runway. Taking the monitoring data on October 26, 2018 in as an example, the relative settlement calculated from the distributed optical fiber strain data and the true settlement corrected by the single-point / overall settlement measuring instrument data are as follows Figure 6 shown in. Figure 7 shown.

[0122] In summary, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0123] The above embodiments are only illustrative of the principles and effects of the present invention and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An airport roadbed settlement monitoring method based on distributed optical fiber embedding, characterized in that: An airport roadbed settlement monitoring structure based on distributed optical fiber embedding is used to monitor the settlement of the airport roadbed. Among them, the airport roadbed settlement monitoring structure includes an airport road surface (1), the airport road surface (1) includes a road surface layer (11) and a road base layer (12), and an airport roadbed settlement monitoring system (2) is provided in the road base layer (12). The airport roadbed settlement monitoring system (2) includes a temperature compensation optical cable (21), a metal-based cable optical cable (22), an overall settlement measuring instrument (23) and a single-point settlement measuring instrument (24). The extending directions of the temperature compensation optical cable (21), the metal-based cable optical cable (22) and the overall settlement measuring instrument (23) are the same. The single-point settlement measuring instrument (24) is located in the extending direction of the overall settlement measuring instrument (23). The metal-based cable optical cable (22) extends linearly, and the temperature compensation optical cable (21) extends non-linearly; The estimated actual strain is calculated according to Equation (1). Among them, is the average strain; ε(x) is the difference between the strain of the metal-based cable optical cable (22) and the strain of the temperature compensation optical cable (21), where x ∈ [0, l]; α is the strain reduction coefficient, which characterizes the degree of fiber relaxation; β is the standard deviation coefficient, which characterizes the internal strain redistribution of the optical fiber; Determine the maximum settlement position according to Equation (2), and the zero point x = x of the function Y(x) 0 is the maximum settlement position: Among them, The predicted displacement is calculated according to Equation (5). Thereby, the relative settlement distance of the airport roadbed is obtained.

2. The airport roadbed settlement monitoring method based on distributed optical fiber embedding according to claim 1, characterized in that, A plurality of airport roadbed settlement monitoring systems (2) are provided in the road base layer (12); And / or, along the extending direction of the airport runway, the temperature compensation optical cable (21), the metal-based cable optical cable (22) and the overall settlement measuring instrument (23) are all buried horizontally; And / or, the airport roadbed settlement monitoring system (2) includes a plurality of single-point settlement measuring instruments (24), and the single-point settlement measuring instruments (24) are evenly distributed in the extending direction of the overall settlement measuring instrument (23).

3. The airport roadbed settlement monitoring method based on distributed optical fiber embedding according to claim 1, characterized in that, In the airport road surface (1) with a unit width, the length of the temperature compensation optical cable (21) is 1.05 to 1.20 times the length of the metal-based cable optical cable (22).

4. The airport roadbed settlement monitoring method based on distributed optical fiber embedding according to claim 1, characterized in that, The temperature compensation optical cable (21) includes a first optical fiber body and a first optical cable outer sheath for wrapping the first optical fiber body; And / or, the metal-based cable optical cable (22) includes a second optical fiber body and a second optical cable outer sheath for wrapping the second optical fiber body; And / or, the temperature compensation optical cable (21), the metal-based cable optical cable (22), the overall settlement measuring instrument (23) and the single-point settlement measuring instrument (24) are buried in fine sand; And / or, the temperature compensation optical cable (21), the metal-based cable optical cable (22), the overall settlement measuring instrument (23) and the single-point settlement measuring instrument (24) are covered with backfilled original soil; And / or, bentonite is doped in the backfilled original soil.

5. The airport roadbed settlement monitoring method based on distributed optical fiber embedding according to claim 1, It is characterized in that it further includes a BOTDR distributed sensor, and the BOTDR distributed sensor is respectively connected to the optical fibers in the optical cable.

6. The method for monitoring the settlement of airport roadbed based on distributed optical fiber embedding according to any one of claims 1 to 5, it is characterized in that The strain reduction coefficient α is the ratio of the total elongation Δl of the optical fiber ε to the actual total elongation Δl of the optical fiber, and the strain reduction coefficient α = 0.9 - 1.0; and / or, the coefficient of variation β = 0.2 to 1.0; and / or, the coefficient of variation β is obtained by calculation according to formula (3): and / or, based on the sum of the relative settlement distance and the absolute settlement distance, the overall settlement distance of the airport roadbed is obtained, and the absolute settlement distance is measured by an overall settlement measuring instrument (23) and a single-point settlement measuring instrument (24).

7. A computer-readable storage medium, on which a computer program is stored, it is characterized in that when the program is executed by a processor, the steps of the method for monitoring the settlement of airport roadbed based on distributed optical fiber embedding according to any one of claims 1 to 6 are implemented.

8. A device for processing the method for monitoring the settlement of airport roadbed based on distributed optical fiber embedding, including: a processor and a memory, the memory is used for storing a computer program, and the processor is used for executing the computer program stored in the memory so that the device executes the steps of the method for monitoring the settlement of airport roadbed based on distributed optical fiber embedding according to any one of claims 1 to 6.

9. A device for processing the method for monitoring the settlement of airport roadbed based on distributed optical fiber embedding, the device including: Estimated actual strain A calculation module, configured to calculate and obtain the estimated actual strain according to Equation (1) Among them, is the average strain; ε(x) is the difference between the strain of the metal-based cable optical cable (22) and the strain of the temperature compensation optical cable (21), x ∈ [0, l]; α is the strain reduction coefficient, which characterizes the degree of fiber relaxation; β is the coefficient of variation, which characterizes the internal strain redistribution of the optical fiber; The maximum settlement position calculation module is used to determine the maximum settlement position according to Equation (2). The zero point x = x of the function Y(x) 0 is the maximum settlement position: Among them, Estimated displacement A calculation module that calculates the estimated displacement according to Equation (5) it further includes an overall settlement distance calculation module, which is used for obtaining the overall settlement distance of the airport roadbed based on the sum of the relative settlement distance and the absolute settlement distance.

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