An automatic monitoring system and method for roadbed settlement based on optical fiber sensing technology

Abstract

The present application relates to the technical field of roadbed monitoring, and particularly relates to a roadbed settlement automatic monitoring system and method based on optical fiber sensing technology, comprising a fiber grating demodulator, a plurality of strain optical cables arranged along the longitudinal direction of the roadbed, and a plurality of transverse deformation correction units, the strain optical cables are arranged between the base bed bottom layer and the base bed surface layer and are connected with the fiber grating demodulator; the plurality of transverse deformation correction units are arranged along the longitudinal direction of the roadbed at intervals, and are used for monitoring the actual deformation amount of each strain optical cable at the cross section. The strain optical cables are arranged along the longitudinal direction of the roadbed, so that long-distance continuous measurement and monitoring can be realized; meanwhile, a plurality of transverse deformation correction units are arranged along the longitudinal direction of the roadbed at intervals, the actual deformation amount of the strain optical cables at a plurality of cross sections is monitored, the deformation amount of the strain optical cables in the whole section is corrected, and the monitoring precision of long-distance continuous monitoring of the optical fiber is improved.

Description

Technical Field

[0001] This invention relates to the field of roadbed monitoring technology, and specifically to an automated roadbed settlement monitoring system and method based on fiber optic sensing technology. Background Technology

[0002] Currently, traditional methods for monitoring railway subgrade settlement deformation mainly employ settlement plates and static leveling. This typically involves setting up monitoring sections at intervals in key locations or sections to monitor subgrade settlement deformation at fixed locations. However, this method has the following drawbacks and limitations: 1. Low monitoring frequency: Traditional monitoring methods rely heavily on manual measurements, resulting in low efficiency due to repeated manual measurements. 2. Damaged components: Harsh environments in soil and rock masses (such as high temperature, low temperature, and high humidity) often cause these monitoring components and probes to rust and corrode, leading to low survival rates and poor durability. 3. Inability to achieve continuous monitoring: The monitoring sections are discontinuous, only providing a point-to-area effect.

[0003] Currently, fiber optic technology has been applied to roadbed settlement monitoring, but the technology is still immature and faces the following problems: 1. Lateral deformation of the fiber optic cable causes axial strain. While the lateral deformation can be calculated by integrating the axial deformation, this method, although highly sensitive, is affected by the integration length. The accuracy of the lateral deformation decreases as the monitoring length increases. How to solve the problem of lateral deformation accuracy of the fiber optic cable? 2. Considering that roadbed engineering is a linear project, it crosses complex terrain, geology, and climate conditions with large temperature deformation ranges. Temperature deformation directly affects the axial strain of the fiber optic cable, thus affecting the monitoring accuracy and causing engineers to misjudge the health status of the roadbed. For example, seasonal temperature changes and local groundwater seepage can cause local temperature effects. How to eliminate the impact of temperature on the accuracy of fiber optic monitoring? 3. How to solve the fiber optic cable deployment and installation process to protect the fiber optic cable from construction damage? 4. How to convert the relative displacement monitored by the fiber optic cable into absolute displacement? Summary of the Invention

[0004] The purpose of this invention is to provide an automated monitoring system and method for roadbed settlement based on fiber optic sensing technology, thereby improving the accuracy of fiber optic monitoring.

[0005] To achieve the above objectives, the technical solution of the present invention is an automated monitoring system for roadbed settlement based on fiber optic sensing technology, comprising a fiber optic demodulator, a strain optical cable arranged longitudinally along the roadbed, and several transverse deformation correction units. The strain optical cable is disposed between the bottom layer and the surface layer of the subgrade and is connected to the fiber optic demodulator. The several transverse deformation correction units are arranged at intervals along the longitudinal direction of the roadbed to monitor the actual deformation at the strain optical cable on their respective cross sections.

[0006] As one implementation method, the lateral deformation correction unit includes a settlement pile, the bottom end of which is located on one side of the strain optical cable, and the top end of which is located above the surface of the subgrade.

[0007] As one implementation method, the strain-coupled optical cable has several strands arranged at intervals.

[0008] As one implementation method, the lateral deformation correction unit further includes several reference plates, several reference point level gauges, and several settlement plates. The settlement plates, reference plates, and reference point level gauges correspond one-to-one with the strain optical cables. The settlement plates are disposed on one side of the corresponding strain optical cables. The settlement plates are connected to the corresponding reference plates. The reference plates are disposed on the foundation surface. The reference point level gauges are disposed on the corresponding reference plates. The settlement piles are disposed on one side of one of the strain optical cables.

[0009] As one implementation method, the spacing between adjacent lateral deformation correction units is 200 to 1000 m.

[0010] As one embodiment, a temperature optical cable is arranged parallel to one side of the strain optical cable, and the temperature optical cable is connected to the fiber optic demodulator.

[0011] As one implementation method, the temperature optical cable and the corresponding strain optical cable are encapsulated in the same package.

[0012] As one embodiment, a fine sand layer is laid below the package body, and a sand layer is laid above the package body.

[0013] The present invention also provides an automated monitoring method for roadbed settlement based on fiber optic sensing technology, using the system described in any of the above embodiments, the method comprising the following steps:

[0014] 1) When the roadbed is filled to the design elevation of the bottom layer of the subgrade, several transverse deformation correction units are arranged at intervals along the longitudinal direction of the roadbed. Settlement piles are fixed near the preset position of one of the strain optical cables, and several settlement plates are fixed near the corresponding preset positions of the strain optical cables. The settlement plates are then connected to the reference plate on one side of the roadbed.

[0015] 2) Lay several strain optical cables along the longitudinal direction of the roadbed and connect the strain optical cables to the fiber optic demodulator;

[0016] 3) Obtain the subgrade settlement along each strain optical cable using a fiber optic demodulator to obtain the strain optical cable monitoring deformation; obtain the relative settlement at each settlement plate location using a level gauge on a reference plate, and obtain the actual deformation at one of the settlement plate locations using a settlement pile, thereby obtaining the actual deformation at each settlement plate location; correct the strain optical cable monitoring deformation at the corresponding cross section using the actual deformation at each cross section, and correct the strain optical cable monitoring deformation for the entire section.

[0017] As one implementation method, in step 2), a temperature optical cable is set parallel to one side of each strain optical cable and connected to a fiber optic grating demodulator; the temperature distribution along each temperature optical cable is obtained through the fiber optic grating demodulator, and the temperature distribution of the corresponding strain optical cable is obtained. Then, the relationship between the strain of the strain optical cable and the temperature change is established through experiments, and the influence of the ambient temperature change on the deformation of the strain optical cable is corrected by temperature correction compensation.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention arranges the strain optical cable along the longitudinal direction of the roadbed, which can continuously and accurately measure the deformation information at any point along the line, and realize long-distance continuous measurement and monitoring of tens of thousands of kilometers; at the same time, several transverse deformation correction units are arranged at intervals along the longitudinal direction of the roadbed, and the actual deformation at the strain optical cable of multiple cross sections is monitored to correct the deformation of the strain optical cable in the entire section, thereby improving the monitoring accuracy of long-distance continuous monitoring of optical fiber.

[0020] (2) The present invention uses distributed optical fiber measurement, which will not miss detection or monitoring. By setting up a lateral deformation correction unit and a temperature optical cable, the influence of lateral deformation on the optical fiber monitoring accuracy and the influence of temperature deformation on the optical fiber monitoring accuracy are respectively corrected, which greatly improves the optical fiber monitoring accuracy.

[0021] (3) Traditional monitoring methods use cross-sectional intervals to arrange monitoring sections. The spacing between sections is small, the workload is large, and the economy is poor. This invention combines the characteristics of optical fiber technology, and only 1-2 monitoring sections are needed for 500-1000m, which greatly saves the equipment and workload of traditional monitoring and has obvious economic benefits.

[0022] (4) The main material of optical fiber is silicon dioxide, which has strong corrosion resistance and good durability.

[0023] (5) The automatic roadbed settlement monitoring system of the present invention is applicable to the roadbed settlement monitoring of linear projects such as railways and highways, especially the deformation monitoring of soft soil station roadbed projects and adjacent operating line roadbeds. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A perspective view of the automated roadbed settlement monitoring system provided in an embodiment of the present invention;

[0026] Figure 2 A partial perspective view of the automated roadbed settlement monitoring system provided in an embodiment of the present invention;

[0027] Figure 3 This is a partial enlarged view of the automated roadbed settlement monitoring system provided in an embodiment of the present invention;

[0028] Figure 4 A partial perspective view of the automated roadbed settlement monitoring system provided in an embodiment of the present invention;

[0029] In the diagram: 1. Strain gauge fiber optic cable; 2. Settlement pile; 3. Temperature fiber optic cable; 4. Protective layer; 5. Encapsulation body; 6. Settlement plate; 7. Reference plate; 8. Reference point level gauge; 9. Fiber optic cable lead-out line; 10. Settlement plate transmission line; 11. Fine sand layer; 12. Sand layer; 13. Solar power supply system; 14. Equipment box. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and for 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, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a number" means at least one.

[0032] like Figures 1-3As shown, this embodiment provides an automated monitoring system for roadbed settlement based on fiber optic sensing technology, including a fiber optic demodulator, a strain optical cable 1 arranged longitudinally along the roadbed, and several transverse deformation correction units. The strain optical cable 1 is disposed between the bottom layer and the surface layer of the subgrade and is connected to the fiber optic demodulator. Several transverse deformation correction units are arranged at intervals along the longitudinal direction of the roadbed to monitor the actual deformation at the strain optical cable 1 on the cross section.

[0033] This embodiment uses strain-coated optical cable 1 to monitor settlement deformation along the roadbed. It can measure deformation information at any point along the line, achieving long-distance continuous monitoring. Since the lateral deformation of the optical fiber will cause axial strain, this embodiment arranges several lateral deformation correction units at intervals along the longitudinal direction of the roadbed. By monitoring the actual deformation at multiple cross-sections of strain-coated optical cable 1, the deformation of the strain-coated optical cable monitored in the entire section is corrected, eliminating the influence of lateral deformation of the optical fiber on the monitoring accuracy and improving the monitoring accuracy of long-distance continuous optical fiber monitoring.

[0034] Furthermore, the lateral deformation correction unit includes a settlement pile 2, the bottom end of which is located on one side of the strain optical cable 1, and the top end of which is located above the subgrade surface. Figure 1 As shown, BB' represents the deformation monitored by the strain optical cable 1 at settlement pile 2. This deformation may be amplified or reduced compared to the actual deformation. By using the monitoring results of settlement pile 2 at point B (considered the actual deformation), the overall deformation accuracy of the AC section can be significantly corrected. The spacing between adjacent transverse deformation correction units should be determined based on the actual monitoring accuracy requirements, site conditions, and experiments, generally between 200 and 1000 m. Ensuring 1-2 monitoring sections every 500-1000 m is sufficient, greatly saving on traditional monitoring equipment and workload, resulting in significant economic benefits.

[0035] In this embodiment, there are several strain optical cables 1, which are arranged laterally along the roadbed. Distributed optical fiber measurement is used to ensure that no detection or monitoring is missed. The specific number and location of strain optical cables 1 should be determined according to the actual monitoring accuracy requirements, site conditions and experiments.

[0036] Furthermore, the lateral deformation correction unit also includes several reference plates 7, several reference point level gauges 8, and several settlement plates 6. Each settlement plate 6, reference plate 7, and reference point level gauge 8 corresponds to a strain gauge 1. The settlement plate 6 is positioned on one side of the corresponding strain gauge 1 and connected to the corresponding reference plate 7. The reference plate 7 is positioned on the foundation surface, and the reference point level gauge 8 is positioned on the corresponding reference plate 7. The settlement pile 2 is positioned on one side of one of the strain gauges 1. This embodiment employs a static leveling method. Settlement plates 6 are installed at each strain gauge 1. The relative settlement of each settlement plate 6 can be measured using the level gauges on the corresponding reference plate 7. The actual deformation of each strain gauge 1 can be obtained by measuring the actual deformation using the settlement pile 2 of one strain gauge 1. The monitoring results of the settlement plates 6 and settlement pile 2 can correct the lateral deformation monitoring accuracy of several strain gauges 1.

[0037] Specifically, the settlement plate 6 can be set near the corresponding strain optical cable 1, and each settlement plate 6 is connected to the corresponding reference plate 7 through the settlement plate transmission line 10; the settlement pile 2 can be set near one of the strain optical cables 1; the specific optimal distance between the settlement plate 6 and the settlement pile 2 needs to be determined comprehensively based on the accuracy requirements, indoor tests, site conditions, etc.

[0038] To eliminate the influence of temperature on the accuracy of fiber optic detection, in this embodiment, a temperature optical cable 3 is installed parallel to one side of the strain optical cable 1. The temperature optical cable 3 is connected to the fiber optic demodulator. The temperature optical cable 3 is used to monitor the temperature near the strain optical cable 1 in real time. The relationship between the strain optical cable 1 and temperature changes is established through experiments. Then, the influence of ambient temperature changes on the accuracy of fiber optic monitoring is corrected by temperature correction compensation.

[0039] like Figure 4 As shown, in this embodiment, the surfaces of the strain optical cable 1 and the temperature optical cable 3 are respectively provided with protective layers 4 for protecting the optical fibers. Optimally, the temperature optical cable 3 and the corresponding strain optical cable 1 are encapsulated in the same encapsulation body 5, ensuring that the strain optical cable 1 and the temperature optical cable 3 are laid synchronously and parallel, facilitating installation.

[0040] As one implementation method, such as Figure 2 As shown, a total of 3 optical cables are laid on the calibration cross section. Each optical cable includes a strain optical cable 1 and a temperature optical cable 3. Three settlement plates 6 are arranged at the three optical cables to provide a reference displacement for observation. A settlement pile 2 is arranged around one of the optical cables.

[0041] In an optimized embodiment, a fine sand layer 11 is laid below the encapsulation body 5, and a sand layer 12 is laid above the encapsulation body 5. For example... Figure 3As shown, in order to protect the optical fiber from damage during construction, in this embodiment, when the base is filled to the surface of the base bed, a fine sand layer 11 of a certain thickness is first laid along the position where the optical fiber is to be laid, and then the strain optical cable 1 and the temperature optical cable 3 are laid along the fine sand layer 11. After that, a sand layer 12 of a certain thickness is laid on the strain optical cable 1 and the temperature optical cable 3. As one embodiment, the thickness of the fine sand layer 11 is 2 cm, and the thickness of the sand layer 12 is 2 cm.

[0042] In this embodiment, the fiber Bragg grating demodulator and wireless transmission equipment are all housed in the equipment box 14. The equipment box 14 is connected to the solar power supply system 13, which powers the fiber Bragg grating demodulator and other equipment. The fiber Bragg grating demodulator is connected to the processor of the monitoring center via the wireless transmission equipment.

[0043] This embodiment also provides an automated monitoring method for roadbed settlement based on fiber optic sensing technology, using any of the systems described above, and the method includes the following steps:

[0044] 1) Embankment construction: According to the requirements for roadbed construction, the roadbed shall be filled in layers to the design elevation of the bottom layer of the subgrade;

[0045] 2) Install settlement plates 6 and settlement piles 2: Install several settlement plates 6 and settlement piles 2 at important cross-sectional positions along the longitudinal direction of the roadbed. Fix the settlement piles 2 near the preset position of one of the strain optical cables 1. Fix several settlement plates 6 near the preset positions of the corresponding strain optical cables 1. Lead the transmission line of the settlement plate 6 to the reference plate 7. The reference plate 7 is required to be stable in long-term deformation. Protect the settlement plate transmission line 10.

[0046] 3) Install optical cable: Lay a 2cm thick layer of fine sand 11 longitudinally at the pre-installation position of the optical cable, then lay strain optical cable 1 along the line, and then lay a 2cm thick layer of sand 12 to protect the optical fiber from being damaged during construction. The strain optical cable 1 is connected to the fiber optic grating demodulator through the optical cable lead-out line 9, and the optical cable lead-out line 9 is protected.

[0047] 4) Complete the roadbed filling: Complete the surface filling of the subgrade;

[0048] 5) Installation of power supply, equipment box 14, wireless transmission and other systems: The power supply system uses solar power; equipment box 14 is mainly used to protect the fiber optic demodulator, wireless transmission equipment, etc.; the wireless transmission system uses 4G or 5G network.

[0049] 6) Automated Real-Time Monitoring: The roadbed settlement along each strain optical cable 1 is acquired using a fiber optic demodulator to obtain the deformation of the strain optical cable 1. The relative settlement at each settlement plate 6 is obtained using a reference point level gauge 8 on the reference plate 7. The actual deformation at one of the settlement plates 6 is obtained using a settlement pile 2. The actual deformation at each settlement plate 6 is obtained by adding the difference between the actual deformation at the settlement pile 2 and the relative deformation to the relative settlement of the other settlement plates 6. The actual deformation at each cross-section of the strain optical cable 1 is used to correct the deformation of the strain optical cable at the corresponding cross-section. The deformation of the strain optical cable in the entire section is also corrected based on the difference between the actual deformation at both ends of the section and the deformation of the strain optical cable, combined with the deformation curve of the strain optical cable in the entire section. This is carried out automatically for a long period of time during railway operation.

[0050] In the above embodiment, in step 3), an encapsulation body 5 containing strain optical cable 1 and temperature optical cable 3 is laid along the line, and the temperature optical cable 3 is connected to the fiber optic grating demodulator; in step 6), the temperature distribution along the line of each temperature optical cable 3 is obtained through the fiber optic grating demodulator, and the temperature distribution of the corresponding strain optical cable 1 is obtained. Then, the relationship between the strain of the strain optical cable and the temperature change is established through experiments, and the influence of the ambient temperature change on the deformation of the strain optical cable is corrected by temperature correction compensation.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An automated monitoring system for roadbed settlement based on fiber optic sensing technology, characterized in that: The system includes a fiber Bragg grating demodulator, strain gauge optical cables arranged longitudinally along the roadbed, and several transverse deformation correction units. The strain gauge optical cables are positioned between the bottom and surface layers of the subgrade and connected to the fiber Bragg grating demodulator. The transverse deformation correction units are spaced apart longitudinally along the roadbed to monitor the actual deformation at the strain gauge optical cable on their respective cross-sections. Each transverse deformation correction unit includes a settlement pile, with its bottom end located on one side of the strain gauge optical cable and its top end above the subgrade surface. The transverse deformation correction unit also includes several reference plates, several reference point level gauges, and several settlement plates. Each settlement plate, reference plate, and reference point level gauge corresponds one-to-one with a strain gauge optical cable. The settlement plate is positioned on one side of the corresponding strain gauge optical cable and connected to the corresponding reference plate. The reference plate is positioned on the foundation surface, the reference point level gauge is positioned on the corresponding reference plate, and the settlement pile is positioned on one side of one of the strain gauge optical cables.

2. The automated roadbed settlement monitoring system based on fiber optic sensing technology as described in claim 1, characterized in that: The strain gauge optical cable consists of several strands arranged at intervals.

3. The automated roadbed settlement monitoring system based on fiber optic sensing technology as described in claim 1, characterized in that: The spacing between adjacent lateral deformation correction units is 200~1000m.

4. The automated monitoring system for roadbed settlement based on fiber optic sensing technology as described in claim 1, characterized in that: A temperature optical cable is arranged parallel to one side of the strain optical cable, and the temperature optical cable is connected to the fiber optic demodulator.

5. The automated roadbed settlement monitoring system based on fiber optic sensing technology as described in claim 4, characterized in that: The temperature optical cable and the corresponding strain optical cable are encapsulated in the same package.

6. The automated roadbed settlement monitoring system based on fiber optic sensing technology as described in claim 5, characterized in that: A layer of fine sand is laid at the bottom of the package, and a layer of sand is laid at the top of the package.

7. An automated monitoring method for roadbed settlement based on fiber optic sensing technology, characterized in that, The method using the system according to any one of claims 1-6 comprises the following steps: 1) When the roadbed is filled to the design elevation of the bottom layer of the subgrade, several transverse deformation correction units are arranged at intervals along the longitudinal direction of the roadbed. Settlement piles are fixed near the preset position of one of the strain optical cables, and several settlement plates are fixed near the corresponding preset positions of the strain optical cables. The settlement plates are then connected to the reference plate on one side of the roadbed. 2) Lay several strain optical cables along the longitudinal direction of the roadbed and connect the strain optical cables to the fiber optic demodulator; 3) Obtain the subgrade settlement along each strained optical cable using a fiber optic grating demodulator to obtain the strained optical cable monitoring deformation. The relative settlement at each settlement plate location is obtained by level gauges on the reference plate, and the actual deformation at one of the settlement plate locations is obtained by settlement piles, thus obtaining the actual deformation at each settlement plate location; the actual deformation at the strain optical cable on each cross section is used to correct the strain optical cable monitoring deformation at the corresponding cross section, and the strain optical cable monitoring deformation of the entire interval is also corrected.

8. The automated monitoring method for roadbed settlement based on fiber optic sensing technology as described in claim 7, characterized in that: In step 2), a temperature optical cable is set up in parallel on one side of each strain optical cable and connected to a fiber Bragg grating demodulator. The temperature distribution along each temperature optical cable is obtained through the fiber Bragg grating demodulator, and the temperature distribution of the corresponding strain optical cable is obtained. Then, the relationship between the strain of the strain optical cable and the temperature change is established through experiments, and the influence of the ambient temperature change on the deformation of the strain optical cable is corrected by temperature correction compensation.

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