A tunnel structure three-way displacement monitoring device and method

Abstract

The application relates to a tunnel structure three-way displacement monitoring device and method. The device comprises tripods and an optical fiber monitoring instrument. The tripods are multiple in number and are fixedly installed on the inner wall of a tunnel at intervals. Each of the tripods is provided with an anchoring device. Adjacent two tripods are connected by the optical fiber through the anchoring devices. The end of the optical fiber is connected with the optical fiber monitoring instrument. The optical fiber monitoring instrument is an optical fiber strain monitoring device. The strain change amount of the optical fiber arranged in a certain rule is obtained by the monitoring method. The displacement of the tripod through which the optical fiber passes is calculated by using the optical fiber strain change amount. Then, the displacement of the tunnel is obtained. Compared with the prior art, the application has the advantages of simple structure, convenient operation and the like. The three-way displacement of the curved tunnel can be monitored.

Description

Technical Field

[0001] This invention relates to the field of tunnel monitoring technology, and in particular to a device and method for monitoring the three-dimensional displacement of a tunnel structure. Background Technology

[0002] During tunnel construction, the complex relationship between the surrounding rock and the support, as well as geological changes and improper construction, can lead to displacement, deformation, or even instability of the tunnel structure, necessitating displacement monitoring.

[0003] Tunnel structural displacement monitoring is the process of tracking and recording the displacement and deformation of a tunnel structure in real time during construction and operation using specific technologies and equipment. It is crucial for ensuring the safety of tunnel construction and operation. Tunnel structural displacement monitoring can detect structural anomalies in real time and allow for timely intervention, thereby ensuring the safety of construction personnel. Monitoring data can also be used to assess tunnel stability, optimize construction plans, prevent long-term settlement and deformation, and ensure the long-term safe use of the tunnel. Simultaneously, displacement monitoring helps meet relevant regulatory requirements, identifies potential risks early, and improves the efficiency of tunnel maintenance and management.

[0004] Currently, commonly used methods for monitoring tunnel structure displacement include:

[0005] Manual total station monitoring: A series of measuring points are set up in the tunnel, and the coordinates of the measuring points are measured manually using a total station. The displacement is analyzed by comparing the changes in these coordinates. This method is labor-intensive, inefficient, time-consuming, and has limited accuracy.

[0006] Non-contact visual monitoring: Prism targets are embedded in the tunnel, and the displacement changes of the targets are observed using detection instruments such as laser instruments or machine vision instruments. This type of monitoring method requires that the instrument and the target have a line of sight. For tunnels with bends or internal obstructions, multiple observation instruments need to be set up, which increases the workload and cost. The instrument and the target need to be relatively stationary, and its accuracy is easily affected by vibration.

[0007] Patent CN118687516A proposes a planar displacement monitoring system and method for tunnel segments on steep curves. It uses displacement sensors parallel to the tunnel axis to detect the relative posture of each segment ring in the tunnel. However, this method can only obtain a planar view of the position and posture of each tunnel structure and cannot perform detection in three-dimensional space.

[0008] Patent CN118328973A discloses a tunnel segment displacement detection device, mentioning a contact measurement method. This method involves setting multiple coplanar detection points on the arc surface formed by the tunnel segments, and using a translational displacement sensor to detect whether these points are still on the same plane. However, this method can only detect displacement in one dimension of the tunnel and requires translating the displacement sensor within the tunnel, thus placing certain requirements on the tunnel's flatness. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the existing technology that cannot detect the displacement of tunnels in three-dimensional space, and to provide a three-dimensional displacement monitoring device and method for tunnel structures.

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] According to one aspect of the present invention, a three-dimensional displacement monitoring device for a tunnel structure is provided, comprising a tripod and a fiber optic monitoring instrument. The tripods are multiple and fixedly installed at intervals on the inner wall of the tunnel. Each tripod is provided with an anchoring device. An optical fiber is connected between two adjacent tripods through the anchoring device. The end of the optical fiber is connected to the fiber optic monitoring instrument, which is a fiber optic strain monitoring device.

[0012] Furthermore, the tripod is L-shaped, with three anchoring devices on each tripod located at the corner and two ends of the L-shape. Each anchoring device is connected to three anchoring devices on the adjacent tripod by an optical fiber. The optical fiber is straightened between the anchoring devices, and each optical fiber is connected to only one or two of the three anchoring devices between different tripods.

[0013] Furthermore, the tripod has a T-shaped cross-section, with the horizontal part of the T located outside the right angle of the L-shape. Multiple mounting holes are provided on the outside of the right angle of the L-shape for fixed connection with the inner wall of the tunnel, and the connection method is expansion bolts.

[0014] Furthermore, the anchoring device includes a buckle and a tensioning ring. The buckle is a frustum-shaped cylindrical structure made of high-toughness plastic. The root diameter of the frustum-shaped cylindrical structure is larger than the end diameter, and the end of the frustum-shaped cylindrical structure is provided with a groove. The optical fiber passes through the through hole in the middle of the frustum-shaped cylindrical structure, and the outer surface of the buckle is provided with threads.

[0015] The elastic band is a ring-shaped structure made of rigid material. The inner surface of the ring-shaped structure is threaded, and the thread matches the outer surface of the buckle.

[0016] Furthermore, the fiber optic monitor is a fiber optic strain monitoring device that integrates a fiber optic strain analyzer and a portable computer.

[0017] According to another aspect of the present invention, a monitoring method for a three-dimensional displacement monitoring device for a tunnel structure is provided, characterized by comprising the following steps:

[0018] Tripods were installed at intervals on the inner wall of the tunnel, and a 3D laser scanner was used to scan the tunnel section to determine the initial distance between each anchoring device on each tripod.

[0019] The optical fibers are passed through the tripod from the anchoring position, with three optical fibers passing through each anchoring position, and connected to the three anchoring devices of the adjacent tripod.

[0020] Tensioning the optical fiber to apply a prestress F to it;

[0021] Connect one end of the optical fiber to the optical fiber monitoring instrument to obtain the strain value at each point along the optical fiber.

[0022] The strain values ​​of the optical fibers are processed to calculate the length of the three optical fibers after strain at each anchoring position of each tripod.

[0023] Calculate the coordinate values ​​of each tripod and each anchorage position based on the lengths of the three optical fibers after strain at each anchorage position of each tripod.

[0024] By comparing the coordinate changes of the anchoring position of each tripod over time, the translation and rotation of the tripod's location in space can be obtained, and the three-dimensional displacement of the tunnel structure can be monitored.

[0025] Furthermore, the calculation method for prestress F is as follows:

[0026]

[0027] Where l is the distance between two adjacent tripod anchoring devices, x is the limit value of tunnel structure displacement within this distance, E is the elastic modulus of the optical fiber, and S is the cross-sectional area of ​​the optical fiber.

[0028] Furthermore, the value of l can be 5-15m.

[0029] Furthermore, the length l of the three optical fibers after strain ′ 1, l ′ 2, l ′ 3 are respectively:

[0030] l ′ 1 = l1 + l1·Δσ1

[0031] l ′ 2=l2+l2·Δσ2

[0032] l ′ 3=l3+l3·Δσ3

[0033] Where l1, l2, and l3 are the initial lengths of the three optical fibers, and Δσ1, Δσ2, and Δσ3 are the changes in strain of the three optical fibers.

[0034] Furthermore, the method for calculating the coordinates (x0, y0, z0) of the anchorage location is as follows:

[0035]

[0036] Where (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3) constitute the coordinate values ​​of the three anchoring positions on the tripod preceding the anchoring position to be calculated.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] 1. This invention achieves three-dimensional displacement monitoring of tunnel structure by using a tripod fixed to the inner wall of the tunnel and a fiber optic monitoring instrument. The tripod is equipped with an anchoring device, through which the optical fiber passes and connects to the fiber optic monitoring instrument. The optical fibers are connected in a certain pattern among multiple tripods, which can realize three-dimensional displacement monitoring of tunnel structure. Moreover, the distributed fiber optic sensing technology has the beneficial effects of long monitoring distance and interference resistance. At the same time, the monitoring system has good flexibility and can adapt to the working conditions of curved tunnels.

[0039] 2. The anchoring device of the present invention consists of a buckle and a tension ring. The buckle is a frustum-shaped cylindrical structure of high-toughness plastic with threads engraved on the outer surface and a groove along the axial direction. The tension ring is a rigid ring with internal threads that can be screwed in and out of the buckle. When the optical fiber passes through the buckle, the tension ring is screwed down and tightened, squeezing the buckle inward and thus forming a squeezing force on the optical fiber. The structure is simple and the anchoring effect is good.

[0040] 3. The monitoring method proposed in this invention obtains the strain change of optical fibers connected and arranged in a certain pattern through an optical fiber monitoring instrument. The displacement of the tripod through which the optical fiber passes is calculated using the strain change of the optical fiber, and then the displacement of the tunnel is obtained. All data processing algorithms are integrated into the optical fiber monitoring instrument, which converts the strain information of the optical fiber into the coordinate information of the tripod. It can realize the three-dimensional displacement monitoring of the tunnel structure, and the data acquisition is convenient. After installation, the optical fiber monitoring instrument continuously and automatically collects data, which can realize continuous monitoring around the clock, saving time and effort. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the overall invention;

[0042] Figure 2 This is a schematic diagram of the tripod structure;

[0043] Figure 3 This is a schematic diagram of the anchoring device structure;

[0044] Figure 4 This is a schematic diagram of the geometric model of the present invention;

[0045] In the diagram, 1 is the tripod, 2 is the fiber optic monitor, 11 is the mounting hole, 12 is the anchoring device, 121 is the buckle, and 122 is the elastic ring. Detailed Implementation

[0046] 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, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0047] This invention relates to a three-dimensional displacement monitoring device for tunnel structures, comprising a series of tripods 1 and a fiber optic monitoring instrument 2, such as... Figure 1 As shown. The main body of the tripod 1 is a T-shaped steel beam bent at a right angle in an L-shape. The horizontal part of the T-shape is located outside the right angle of the L-shape. Multiple mounting holes 11, preferably four, are pre-drilled on the flange of the vertical side of the tripod 1, i.e., the horizontal part of the T-shape, to facilitate fixing the tripod 1 to the tunnel wall using expansion bolts. The web of the tripod 1 has multiple anchoring devices 12, preferably three. When the three anchoring devices 12 are connected in pairs, they form a right-angled triangle, as shown. Figure 2 As shown. The anchoring device 12 consists of a buckle 121 and a tensioning ring 122. The buckle 121 is made of a high-toughness plastic that is prone to elastic deformation. It has a frustum-shaped cylindrical structure with a through hole in the middle, and the outer surface is engraved with threads. There are three grooves along the axial direction that divide the upper part of the buckle 121. The tensioning ring 122 is a relatively rigid ring with internal threads, which can be screwed in and out of the buckle. Figure 3 As shown, when the optical fiber passes through the through hole of the buckle 121, the tightening ring 122 tightens downwards, squeezing the buckle 121 inwards to form a compressive force to achieve the anchoring effect of the optical fiber.

[0048] The fiber optic monitoring instrument 2 integrates a fiber optic strain analyzer and a portable computer. By connecting one end of the fiber optic cable to the instrument, it can monitor the strain of the fiber optic cable and calculate the displacement changes of each tripod, thereby reflecting the three-dimensional displacement of the tunnel structure.

[0049] This invention also relates to a method for monitoring the three-dimensional displacement of a tunnel structure. The steps include: installing tripods 1 at intervals on the inner wall of the tunnel; scanning the tunnel section using a three-dimensional laser scanner to determine the initial distance between each anchoring device 12 on each tripod 1; passing optical fibers through the tripods 1 from the anchoring positions 12, wherein each anchoring position 12 passes through three optical fibers; using a tensioning jack to tension the optical fibers and apply a prestress F to the optical fibers; connecting one end of the optical fiber to an optical fiber monitoring instrument 2 to obtain the strain value at each point along the optical fiber; processing the strain value of the optical fiber to calculate the length of the three optical fibers after strain at each anchoring position 12 of each tripod 1; calculating the coordinate value of each anchoring position 12 of each tripod 1 based on the length of the three optical fibers after strain at each anchoring position 12 of each tripod 1; comparing the changes in the coordinate values ​​of each anchoring position 12 of each tripod 1 over time to obtain the translation and rotation of the tripod position in space, and monitoring the three-dimensional displacement of the tunnel structure.

[0050] In engineering applications, the tripod 1 is first fixed inside the tunnel using the mounting holes 11, in a location that facilitates installation without affecting other works. One tripod is installed every 5-10 meters. After installation, a 3D laser scanner is used to scan the tunnel section to determine the initial distance between the anchoring devices 12 on each tripod 1.

[0051] After positioning and anchoring device 12, the optical fibers are tensioned between the tripods 1. For the entire monitoring system, the three anchoring devices of tripod 1 are denoted as A, B, and C. The paths of the nine optical fibers through a series of tripods are: AAA-…, BBB-…, CCC-…, ABA-…, BAB-…, ACA-…, CAC-…, BCB-…, CBC-…. After the optical fibers have traversed the path, tensioning jacks are used to tension them, providing a certain prestress F to ensure that the optical fibers always have a certain initial strain before the tunnel segment experiences its ultimate displacement. The value of the prestress can be preliminarily estimated based on the distance l between two adjacent tripod anchoring devices, the design limit value x of the tunnel structure displacement within that distance, the elastic modulus E of the optical fiber used, and the cross-sectional area S. The simplified calculation formula is as follows:

[0052]

[0053] After the fiber optic cable is tensioned, one end of the fiber optic cable is connected to the fiber optic monitoring instrument 2 to obtain the strain values ​​at various points along the fiber optic cable and perform data processing.

[0054] The data processing procedure is explained using two adjacent tripods as an example:

[0055] like Figure 4As shown, points a1, a2, and a3 are three anchor points on a known tripod (denoted as #1), with known coordinates, denoted as (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3); ​​b1 is the anchor point to be measured on another tripod (denoted as #2), with coordinates denoted as (x0, y0, z0); the initial lengths of the three optical fibers between the anchor points are l1, l2, and l3, respectively.

[0056] After the tripod #2 is displaced, the strain of the three optical fibers changes accordingly. Let the changes in strain be Δσ1, Δσ2, and Δσ3, respectively, and their values ​​can be obtained by monitoring the optical fiber monitor 2.

[0057] Therefore, after the #2 tripod shifted, the lengths of the three optical fibers l can be determined. ′ 1, l ′ 2, l ′ 3 are respectively:

[0058] l ′ 1 = l1 + l1·Δσ1

[0059] l ′ 2=l2+l2·Δσ2

[0060] l ′ 3=l3+l3·Δσ3

[0061] According to the known l 1 1, l ′ 2, l ′ 3. There are:

[0062]

[0063] By solving the system of equations, the coordinates (x0, y0, z0) of the anchor point b_1 can be obtained.

[0064] Similarly, the coordinates of anchor points b2 and b3 can be obtained, and then the position of tripod #2 after displacement can be determined.

[0065] Similarly, based on the known coordinates of the three anchor points of tripod #2 and the strain change of the optical fiber, the coordinates of the three anchor points of tripod #3 can be obtained, and so on, to obtain the coordinates of the three anchor points of all tripods.

[0066] The data processing algorithm is integrated into the fiber optic monitor 2, which monitors the strain of the fiber optic cable in real time and simultaneously converts the strain data into coordinate data of the three anchor points of the tripod.

[0067] By comparing the changes in the anchor point coordinates of the same tripod over time, we can know the translation and rotation of the tripod's location in space, thus enabling the monitoring of the three-dimensional displacement of the tunnel structure. If combined with 3D modeling software, a 3D displacement model of the tunnel structure can be intuitively constructed.

[0068] The specific implementation of the present invention will be described below through an example.

[0069] This invention proposes a three-dimensional displacement monitoring device and method for tunnel structures, which can detect the displacement of tunnel structures in three-dimensional space.

[0070] Distributed fiber optic sensing technology is a sensing technology that uses optical fiber as the sensing element and the signal transmission medium. This technology can accurately measure the strain at any point along the fiber from one end. It has advantages such as long distance, high durability, anti-interference, and good flexibility, and is very suitable for tunnel monitoring.

[0071] This embodiment is implemented through a certain method, using nine optical fibers to form a three-dimensional network, and converting the strain measured by the optical fibers into displacement changes at the measuring points, thereby realizing the monitoring of the three-dimensional displacement of the tunnel structure.

[0072] In this embodiment, displacement monitoring is performed on a pipe jacking tunnel.

[0073] During equipment installation, a tripod 1 is installed on the side of the tunnel segment every 10m. After installation, the initial distance between each tripod 1 is measured and recorded using a 3D laser scanner as the primary method and traditional tape measure as a secondary method.

[0074] The optical fiber is then tensioned between the anchoring devices 12. Referring to the aforementioned formula, for an elastic modulus of 70 GPa and a cross-sectional area of ​​1.5 mm²... 2 For the optical fiber, the acceptable segment displacement in the tunnel is 50mm, requiring a tension force of approximately 525N. Tension jacks are used to tension all optical fibers to the set value.

[0075] After tensioning is completed, the optical fiber is connected to the optical fiber testing instrument 2. The optical fiber testing instrument 2 continuously collects the optical fiber strain and calculates the coordinate data of the tripod anchor points. The coordinate changes of the tripod anchor points can intuitively reflect the displacement changes of the tunnel segments, such as translation and rotation. Staff can collect monitoring data on-site from the optical fiber testing instrument. If combined with wireless transmission technologies such as 4G / 5G, monitoring data can be obtained remotely.

[0076] Preferably, the tripod 1 does not necessarily need to be installed alone, but can also be integrated with other tunnel facilities such as cable brackets, thereby further simplifying the installation steps and saving tunnel space.

[0077] Preferably, the fiber tension stress calculation method described in this paper is only a simplified method, and it can also be determined by empirical formulas or other methods in engineering applications.

[0078] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A three-dimensional displacement monitoring device for a tunnel structure, characterized in that, Includes tripods (1) and fiber optic monitoring instruments (2). There are multiple tripods (1) and they are fixedly installed at intervals on the inner wall of the tunnel. Each tripod (1) is equipped with an anchoring device (12). An optical fiber is connected between two adjacent tripods (1) through the anchoring device (12). The end of the optical fiber is connected to the fiber optic monitoring instrument (2). The fiber optic monitoring instrument (2) is a fiber optic strain monitoring device. The tripod (1) is L-shaped, and each tripod (1) has three anchoring devices (12) located at the corners and two ends of the L-shape. Each anchoring device (12) is connected to the three anchoring devices (12) on the adjacent tripod (1) by an optical fiber, which is straightened between the anchoring devices (12). The tripod (1) has a T-shaped cross section, with the horizontal part of the T-shape located outside the right angle of the L-shape. The right angle of the L-shape is provided with multiple mounting holes (11) for fixed connection with the inner wall of the tunnel, and the connection method is expansion bolts. The anchoring device (12) includes a buckle (121) and a tension ring (122). The buckle (121) is a frustum-shaped cylindrical structure made of high-toughness plastic. The root diameter of the frustum-shaped cylindrical structure is larger than the end diameter, and the end of the frustum-shaped cylindrical structure is provided with a groove. The optical fiber passes through the through hole in the middle of the frustum-shaped cylindrical structure. The outer surface of the buckle (121) is provided with threads. The elastic ring (122) is a ring-shaped structure made of rigid material. The inner surface of the ring-shaped structure is provided with threads, which cooperate with the outer surface of the buckle (121).

2. The tunnel structure three-dimensional displacement monitoring device according to claim 1, characterized in that, The fiber optic monitoring instrument (2) is a fiber optic strain monitoring device that integrates a fiber optic strain analyzer and a portable computer.

3. A monitoring method for a three-dimensional displacement monitoring device for a tunnel structure according to any one of claims 1-2, characterized in that, Includes the following steps: Tripods (1) are installed at intervals on the inner wall of the tunnel. A three-dimensional laser scanner is used to scan the tunnel section to determine the initial distance between each anchoring device (12) on each tripod (1). The optical fiber is passed through the tripod (1) from the anchor position (12), where three optical fibers pass through each anchor position (12) and the three anchoring devices (12) of the adjacent tripod (1) are connected. Tensioning the optical fiber to apply a prestress F to it; Connect one end of the optical fiber to the optical fiber monitoring instrument (2) to obtain the strain value at each point along the optical fiber; The strain value of the optical fiber is processed, and the length of the three optical fibers after strain is calculated at each anchoring position (12) of each tripod (1). Based on the length of the three optical fibers after strain at each anchoring position (12) of each tripod (1), calculate the coordinate value of each anchoring position (12) of each tripod (1); By comparing the coordinate changes of the anchoring position (12) of each tripod (1) over time, the translation and rotation of the tripod position in space are obtained, and the three-dimensional displacement of the tunnel structure is monitored.

4. The monitoring method according to claim 3, characterized in that, The calculation method for the prestress F is as follows: Where l is the distance between two adjacent tripod anchoring devices, x is the limit value of tunnel structure displacement within this distance, E is the elastic modulus of the optical fiber, and S is the cross-sectional area of ​​the optical fiber.

5. The monitoring method according to claim 4, characterized in that, The value of l is 5-15m.

6. The monitoring method according to claim 3, characterized in that, The lengths of the three optical fibers after strain , , They are respectively: in, , , These are the initial lengths of the three optical fibers. , , These represent the changes in strain of the three optical fibers.

7. The monitoring method according to claim 3, characterized in that, The method for calculating the coordinates (x0, y0, z0) of the anchorage position (12) is as follows: Among them, (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3) respectively constitute the coordinate values ​​of the three anchoring positions (12) on the tripod (1) preceding the anchoring position (12) to be calculated.

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