Optical fiber layout, characteristic calculation and compensation method for pipe segment deformation monitoring in rectangular pipe jacking tunnel

Abstract

The present invention discloses a method for laying out optical fibers and calculating and compensating characteristics for deformation monitoring of pipe segments in rectangular jacking tunnels. Firstly, "W"-shaped distributed optical fibers are laid out inside the tunnel. Secondly, deformation characteristics are judged by monitoring the tension and compression states of the optical fibers, including calculation of the accumulated misalignment strain and misalignment amount of the pipe segments and calculation of the torsion characteristics of the pipe segments. Finally, without considering the influence of the optical fiber stretching on the opening strain caused by the vertical misalignment, the vertical misalignment amount is compensated by calculating the tunnel "W" tensile strain error caused by the opening of the pipe segments and the tunnel "W" compression strain error caused by the compression of the pipe segments. In jacking projects with shallow cover, high water pressure, large cross-section, small clear distance, etc., the accumulated misalignment, torsion and opening monitoring of the pipe segments can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of underground space engineering, and more specifically, relates to an optical fiber layout and feature calculation and compensation method for pipe segment deformation monitoring in a rectangular jacking tunnel. Background Art

[0002] With the development of urbanization and the increase of traffic pressure, pipe jacking has been widely used in urban road planning, mostly involving the construction of subways, highway tunnels, public tunnels, culverts and other projects. Based on its construction characteristics, the pipe jacking method has the advantages of high utilization of tunnel section space and high cost performance. It is particularly suitable for the construction of shallow buried tunnel projects that cross existing infrastructure (such as bridges, roads, railways) or underwater.

[0003] During the pipe jacking process, the tunnel is often affected by its rectangular cross-section shape, which often causes complex mechanical and deformation responses. As a flexible joint tunnel, excessive cumulative misalignment, pipe joint twisting, and pipe joint opening will cause tunnel waterproofing failure, resulting in engineering hazards such as water and sand gushing. Therefore, reliable monitoring of pipe jacking operations is of great significance, but it also faces many opportunities and challenges.

[0004] Fiber optic monitoring technology has the advantages of high precision, multi-section monitoring, real-time continuous monitoring, etc. that traditional total station measurement methods do not have. It has been widely used in bridge structure health and safety monitoring, tunnels, slope stability, earth dams, pile foundation construction and other fields. However, there are few monitoring studies on rectangular pipe jacking tunnels. The development of relevant research will help solve the problems of difficult tunnel deformation monitoring, low monitoring accuracy, and insufficient analysis methods under complex working conditions such as high water pressure, large cross-sections, and shallow overburden, and provide an important reference for structural detection of rectangular pipe jacking and other tunnel projects. Summary of the invention

[0005] The present invention is provided to solve the above problems existing in the prior art. Therefore, there is a need for an optical fiber layout and feature calculation and compensation method for rectangular jacking tunnel pipe segment deformation monitoring.

[0006] According to a first aspect of the present invention, there is provided a method for laying optical fibers for monitoring deformation of pipe sections in a rectangular pipe jacking tunnel, the method comprising:

[0007] A mounting plate is fixed on the inner wall of each of the adjacent pipe sections, and W-shaped distributed optical fibers are arranged on the adjacent pipe sections through the mounting plate. When the adjacent pipe sections are misaligned.

[0008] Furthermore, in the vertical direction, the position of the mounting plate is 0.15H away from the center line of the tunnel, so that the vertical projection of the W-type distributed optical fiber is 0.3H, where H is the height of the pipe segment; in the horizontal direction, the mounting plate is located at the center of the tunnel, so that the horizontal projection of the W-type distributed optical fiber is 1T, where T is the thickness of the pipe segment.

[0009] Furthermore, the mounting plate is an acrylic disc, which is glued to the inner wall of the pipe section, and the optical fiber is wound and connected with the acrylic disc to form a W-shaped distributed optical fiber.

[0010] According to a second aspect of the present invention, a feature calculation method is provided, characterized in that, based on the W-shaped distributed optical fiber arranged by the method as described above, the feature calculation method comprises:

[0011] Determine the triangular relationship after the fiber is stretched:

[0012]

[0013] Among them, △X represents the vertical misalignment (including upward misalignment and downward misalignment), △L s represents the fiber stretching amount, a represents the initial length of the oblique fiber AB, and b represents the length of the initial projection A'B of the oblique fiber AB;

[0014] According to the triangular relationship after the optical fiber is stretched, we can get:

[0015]

[0016] The first microstrain calculation relationship and the second microstrain calculation relationship are introduced as formula (3) and formula (4):

[0017]

[0018] Among them, με a represents the measured value of oblique microstrain for the AC side after deformation (measured value by optical fiber demodulator), με b represents the conversion value of vertical microstrain for the measured value of oblique microstrain, μ represents microstrain;

[0019] Substituting equations (3) and (4) into equation (2), we can obtain the micro-strain calculation results of adjacent pipe segments:

[0020]

[0021] με b Substitute the result into formula (4) to obtain the vertical misalignment;

[0022] The triangular relationship after optical fiber compression is determined as follows:

[0023]

[0024] The second microstrain calculation relationship and the third microstrain calculation relationship are introduced. The third microstrain calculation relationship is as follows:

[0025]

[0026] Substituting equations (4) and (7) into equation (6), we can obtain the vertical misalignment micro-strain transformation result after optical fiber compression:

[0027]

[0028] Furthermore, the method further comprises:

[0029] When the acrylic disc is arranged at the lower part of the side wall, the calculation formula is shown in formula (8):

[0030]

[0031] Among them, με SUMi represents the cumulative misalignment strain value of the i-th pipe section, με bi It represents the relative misalignment between the i-th pipe section and the i-1-th pipe section, i represents the number of pipe sections, and n represents the total number of tunnel pipe sections;

[0032] When the acrylic disc is placed on the upper part of the side wall, the calculation formula is shown in formula (9):

[0033]

[0034] The vertical misalignment of the i-th pipe section ΔX is calculated by the following formula i :

[0035] ΔX i = b·με Si (10)

[0036] Among them, με Si represents the vertical microstrain of the tube section between the i-th section and the i-1-th section.

[0037] Furthermore, the method further comprises:

[0038] When the north-south wall offset ΔX S , ΔX N When there is inconsistency, it is determined that the pipe segment is torsioned, and the torsion form is determined based on the torsion characteristics, wherein the torsion characteristics are the difference in vertical misalignment;

[0039] When the torsion characteristic is ΔX N <0<ΔX S ∩│ΔX N │>│ΔX S │, μγ is calculated by the following formula:

[0040]

[0041] In the formula, μγ represents the micro-angle, and B represents the width of the tunnel outer wall;

[0042] ΔX N and ΔXS Calculated by the following formula

[0043] ΔX N = b·με N (12)

[0044] ΔX S = b·με S (13)

[0045] Substituting equations (12) and (13) into (11), we obtain:

[0046]

[0047] Calculate μs using the following formula:

[0048]

[0049] In the formula, μs represents micro-sedimentation, με N represents the vertical microstrain of the north wall, με S Represents the vertical microstrain of the south wall.

[0050] Further, the torsion form includes four pipe section counterclockwise rotation forms and four pipe section clockwise forms, wherein the four pipe section counterclockwise rotation forms are respectively expressed as Antilockwise (a), Antilockwise (b), Antilockwise (c) and Antilockwise (d), and the four pipe section clockwise forms are respectively expressed as Clockwise (a), Clockwise (b), Clockwise (c) and Clockwise (d). The torsion form is determined based on the torsion characteristics, including:

[0051] When the torsion characteristic is ΔX N <0<ΔX S ∩│ΔX N │>│ΔX S │, the torsion form is determined to be Antilockwise (a);

[0052] When the torsion characteristic is ΔX N <ΔX S <0, the torsion form is determined to be Antilockwise (b);

[0053] When the torsion characteristic is ΔX N <0<ΔX S ∩│ΔX N │<│ΔX S │, the torsion form is determined to be Antilockwise (c);

[0054] When the torsion characteristic is 0<ΔX N <ΔX S , the torsion form is determined to be Antilockwise (d);

[0055] When the torsion characteristic is ΔX S <0<ΔX N ∩│ΔX S │>│ΔX N │, the torsion form is determined as Clockwise (a);

[0056] When the torsion characteristic is ΔX S <ΔX N <0, the torsion form is determined as Clockwise (b);

[0057] When the torsion characteristic is ΔX S <0<ΔX N ∩│ΔX S │<│ΔX N │, the torsion form is determined as Clockwise (c);

[0058] When the torsion characteristic is 0<ΔX S <ΔX N , the torsion form is determined as Clockwise (d).

[0059] According to a third aspect of the present invention, there is provided an error compensation method, the error compensation method comprising:

[0060] Without considering the influence of optical fiber stretching on the opening strain caused by vertical misalignment, the vertical misalignment is compensated by calculating the tunnel "W" tensile strain error caused by tube segment opening and the tunnel "W" compressive strain error caused by tube segment compression.

[0061] Furthermore, the steps of compensating the vertical misalignment by calculating the tunnel "W" tensile strain error caused by the pipe segment opening include:

[0062] Compensate for vertical misalignment based on the "W" optical fiber tensile strain caused by the opening of the tube segment;

[0063] The "W" optical fiber tensile strain caused by the tube opening is calculated by the following formula:

[0064]

[0065] After deleting the second-order microstrain, we get:

[0066]

[0067] In formulas (21-(23), c represents the horizontal projection length of the oblique optical fiber when the adjacent tube segments are not opened, μεc represents the optical fiber microstrain monitoring value (here is stretching) caused by the opening or compression of adjacent tube segments, με′ a It represents the oblique micro-strain monitoring value of the optical fiber caused by the opening or compression of the adjacent pipe segments, where

[0068] Furthermore, the steps of compensating the vertical misalignment by calculating the tunnel "W" compression strain error caused by the pipe segment compression include:

[0069] The error amount is calculated by the following formula:

[0070]

[0071] After dividing a on both sides of formula (24), we get:

[0072]

[0073] Where c represents the horizontal projection length of the oblique optical fiber when the adjacent tube segments are not opened, με c It indicates the optical fiber micro-strain monitoring value caused by the opening or compression of adjacent pipe segments (compression in this case).

[0074] The more realistic vertical misalignment can be obtained by subtracting the error from the micro-strain conversion result of the vertical misalignment after the optical fiber is compressed.

[0075] The present invention has at least the following beneficial effects:

[0076] (1) A “W”-shaped optical fiber deployment method is proposed, which can realize the prediction of cumulative misalignment, torsion, and interface opening.

[0077] (2) A cumulative misalignment calculation model is proposed to calculate the cumulative misalignment.

[0078] (3) A torsion calculation model is proposed to calculate the characteristic quantities under different torsion forms.

[0079] (4) An axial optical fiber joint deployment method based on the “W”-shaped optical fiber deployment is proposed, and an axial expansion and compression model is established according to the monitored axial data to compensate for the “W”-shaped monitoring results. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 A schematic diagram of distributed optical fiber deployment according to an embodiment of the present invention is shown.

[0081] Figure 2 A schematic diagram of a distributed optical fiber deployment process according to an embodiment of the present invention is shown.

[0082] Figure 3The figure shows the effect of distributed optical fiber deployment according to an embodiment of the present invention.

[0083] Figure 4 A simplified diagram of a vertical misalignment transformation model for optical fiber stretching according to an embodiment of the present invention is shown.

[0084] Figure 5 A simplified diagram of a vertical misalignment conversion model for optical fiber compression according to an embodiment of the present invention is shown.

[0085] Figure 6 A schematic diagram of a cumulative misalignment calculation model according to an embodiment of the present invention is shown.

[0086] Figure 7 A schematic diagram showing the counterclockwise rotation of the pipe segment according to an embodiment of the present invention is shown.

[0087] Figure 8 A schematic diagram showing a clockwise rotation form of a pipe segment according to an embodiment of the present invention is shown.

[0088] Fig. 9 A simplified diagram of a pipe segment opening detection model according to an embodiment of the present invention is shown.

[0089] Fig.10 A simplified diagram of the tunnel "W" tensile strain error model caused by the pipe segment opening according to an embodiment of the present invention is shown.

[0090] Fig.11 A simplified diagram of a tunnel “W” compression strain error model caused by tube segment compression according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0091] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings and specific embodiments, but are not intended to limit the present invention. For the various steps described herein, if there is no necessity for a causal relationship between each other, the order in which they are described as examples herein should not be regarded as a limitation, and those skilled in the art should know that they can be adjusted in order, as long as the logic between them is not destroyed, resulting in the inability to implement the entire process.

[0092] Embodiment 1:

[0093] The embodiment of the present invention discloses a method for laying out optical fibers for monitoring deformation of pipe sections in a rectangular pipe jacking tunnel. In order to monitor the misalignment, torsion, and joint opening of the pipe jacking tunnel, a "W"-shaped distributed optical fiber is laid inside the tunnel, and the deformation characteristics are determined by monitoring the tension and compression states of the optical fiber.

[0094] Specifically, the specific implementation steps of the optical fiber laying method include: laying "W"-shaped distributed optical fibers in adjacent pipe sections, such as Figure 1 As shown in the figure, when adjacent pipe sections are misaligned, the difference in tension and compression of the optical fiber can be monitored. Before laying the optical fiber, glue the acrylic disc to the inner wall of the pipe section, and then wrap the optical fiber and the acrylic disc around and connect them, as shown in the figure. Figure 2 As shown. The layout position needs to be based on the actual size of the pipe segment. In the vertical direction, the acrylic disc bonding position should be 0.15H away from the center line of the tunnel, that is, the vertical projection of the "W" type optical fiber is 0.3H (H is the height of the pipe segment); in the horizontal direction, the acrylic disc is located in the center of the tunnel, that is, the horizontal projection of the "W" type optical fiber is 1T (T is the thickness of the pipe segment). Before gluing the optical fiber to the acrylic disc, it should be pre-stretched by 2 times the estimated strain. The estimated strain can be referenced by the finite element results to complete the optical fiber compression monitoring. See after the layout is completed Figure 3 .

[0095] Embodiment 2:

[0096] The embodiment of the present invention discloses a characteristic calculation method, which is based on the "W"-shaped distributed optical fiber arranged in Embodiment 1 and specifically includes the following steps:

[0097] Step 1, calculating the cumulative misalignment strain and misalignment amount of the pipe segment, specifically includes the following steps 101 to 103.

[0098] Step 101, calculate the vertical misalignment microstrain transformation after the optical fiber is stretched

[0099] like Figure 4 As shown in the figure, based on the triangular relationship after the optical fiber is stretched, as shown in formula (1):

[0100]

[0101] Among them, △X represents the vertical misalignment (including upward misalignment and downward misalignment), △L s represents the fiber stretching amount, and a represents the initial length of the oblique fiber AB ( Figure 4 , 5, 10, 11 are all applicable), b represents the length of the initial projection A'B of the oblique optical fiber AB ( Figure 4 , 5, 10, and 11 are all applicable).

[0102] It can be concluded that:

[0103]

[0104] Introduce microstrain calculation relationship:

[0105]

[0106] Among them, με arepresents the measured value of oblique microstrain for the AC side after deformation (measured value of optical fiber demodulator), με b It represents the conversion value of vertical microstrain for the measured value of oblique microstrain, and μ represents microstrain.

[0107] Substituting equations (3) and (4) into equation (2), we can obtain the micro-strain calculation results of adjacent pipe segments:

[0108]

[0109] με b Substitute the result into formula (4) to obtain the vertical misalignment.

[0110] Step 102, calculating the vertical misalignment micro-strain transformation after optical fiber compression.

[0111] like Figure 5 As shown in the figure, the triangular relationship after optical fiber compression is as shown in formula (6):

[0112]

[0113] Similarly, the micro-strain calculation formulas (4) and (7) are introduced:

[0114]

[0115] Substituting equations (4) and (7) into (6), we can obtain the vertical misalignment microstrain transformation result after optical fiber compression, which is the same as equation (5):

[0116]

[0117] Step 103, cumulative misalignment calculation.

[0118] like Figure 6 As shown, when the acrylic disc is arranged at the lower part of the side wall, the calculation formula is shown in formula (8)

[0119]

[0120] Among them, με SUMi represents the cumulative misalignment strain value of the i-th pipe section, με bi It represents the relative misalignment between the i-th pipe section and the i-1-th pipe section, i represents the number of pipe sections, and n represents the total number of tunnel pipe sections.

[0121] When the acrylic disc is placed on the upper part of the side wall, the calculation formula is shown in formula (9):

[0122]

[0123] The vertical misalignment of the i-th pipe section is:

[0124] ΔX i= b·με Si (10)

[0125] Among them, με Si represents the vertical microstrain of the tube section between the i-th section and the i-1-th section.

[0126] Step 2: Calculation of the torsion characteristics of the pipe segment.

[0127] When the north-south wall offset ΔX S , ΔX N When there is inconsistency, the analysis shows that the pipe segment torsion occurs. Based on the difference in misalignment, there are 8 torsion forms, including four pipe segment counterclockwise rotation forms and four pipe segment clockwise forms. The four pipe segment counterclockwise rotation forms are respectively expressed as Antilockwise (a), Antilockwise (b), Antilockwise (c) and Antilockwise (d), and the four pipe segment clockwise forms are respectively expressed as Clockwise (a), Clockwise (b), Clockwise (c) and Clockwise (d). Figure 7 and Figure 8 As shown, Figure 7 (a)-(b) in the figure correspond to Antilockwise(a), Antilockwise(b), Antilockwise(c) and Antilockwise(d), respectively. Figure 8 (a)-(b) in the figure correspond to Clockwise(a), Clockwise(b), Clockwise(c) and Clockwise(d), respectively.

[0128] by Figure 7 Taking (a) in the figure as an example, when the tube rotates counterclockwise, μγ is negative:

[0129]

[0130] In the formula, μγ represents the micro-angle, B represents the width of the tunnel outer wall, and ΔX N and ΔX S Take

[0131] ΔX N = b·με N (12)

[0132] ΔX S = b·με S (13)

[0133] Substituting equations (12) and (13) into (11), we can obtain

[0134]

[0135] The microstrain can be calculated as:

[0136]

[0137] In the formula, μs represents micro-sedimentation, με N represents the vertical microstrain of the north wall, με S Represents the vertical microstrain of the south wall.

[0138] Similarly, different micro-rotation angles and micro-settlement under 8 torsion forms can be obtained, as shown in Table 1.

[0139] Table 1. Calculation results of μγ and μs under different torsion characteristics

[0140]

[0141] Embodiment 3:

[0142] The embodiment of the present invention discloses an error compensation method for performing error compensation on the features calculated in embodiment 2. Specifically, the joint opening monitoring is achieved by laying optical fibers along the axial direction of the tunnel, such as Fig. 9 As shown in the figure, the optical fiber is also wound on the acrylic disc of the "W" optical fiber. The optical fiber microstrain reading is directly multiplied by the optical fiber length between the two discs to obtain the opening amount ΔC. However, during the calculation process, the following error compensation needs to be paid attention to.

[0143] 1) Effect of fiber stretching caused by vertical misalignment on opening strain

[0144] Fig. 9 In the V is the vertical misalignment value, ΔL S is the axial fiber stretch caused by misalignment, according to the geometric relationship

[0145]

[0146] Where με AOF The strain monitored for the axial optical fiber.

[0147] Solve (17) by common denominator and let με AOF 2 is 0, we can get

[0148] ΔC=c·με AOF (18)

[0149] Because ΔX V There is a relationship between ΔC

[0150]

[0151] ΔX V =ΔX=μεb When b, the relationship is as follows

[0152]

[0153] Therefore, let με AOF 2 is 0, we get

[0154] ΔC≈0

[0155] That is, the influence of vertical misalignment on the opening of the pipe joint can be ignored.

[0156] 2) Tunnel "W" tensile strain error caused by pipe segment opening

[0157] The schematic diagram of the tunnel "W" tensile strain error model caused by the opening of the pipe segment is as follows: Fig.10 As shown, the calculation process is as follows:

[0158]

[0159] After deleting the second-order microstrain

[0160]

[0161] In formulas (21-(23), c represents the horizontal projection length of the oblique optical fiber when the adjacent tube segments are not opened, με c represents the optical fiber microstrain monitoring value (here is stretching) caused by the opening or compression of adjacent tube segments, με′ a It represents the oblique micro-strain monitoring value of the optical fiber caused by the opening or compression of the adjacent pipe segments, where

[0162] Therefore, the tensile strain of the "W" optical fiber caused by the opening of the pipe joint is obtained. The actual monitored "W" type optical fiber result should be minus this part of the error to get a more realistic vertical misalignment.

[0163] 3) Tunnel "W" compression strain error caused by pipe segment compression

[0164] The simplified diagram of the tunnel "W" compression strain error model caused by pipe segment compression is as follows: Fig.11 As shown, the calculation process is as follows:

[0165]

[0166] After dividing a by the two equations, we get:

[0167]

[0168] The same as formula (23), c represents the horizontal projection length of the oblique optical fiber when the adjacent tube segments are not opened, με cIt indicates the optical fiber micro-strain monitoring value caused by the opening or compression of adjacent pipe segments (compression in this case).

[0169] Therefore, when the axial compression of the pipe segment is monitored, the “W” type optical fiber result should be minus this part of the error to obtain a more realistic vertical misalignment.

[0170] The above description is intended to be illustrative rather than restrictive. For example, the above examples (or one or more of them) can be used in combination with each other. For example, those of ordinary skill in the art can use other embodiments when reading the above description. In addition, in the above-mentioned specific embodiments, various features can be grouped together to simplify the present invention. This should not be interpreted as a feature of an invention that is not claimed for protection being necessary for any claim. On the contrary, the subject matter of the present invention may be less than all the features of the embodiments of a specific invention. Thus, the following claims are incorporated into the specific embodiments as examples or embodiments, wherein each claim is independently used as a separate embodiment, and it is considered that these embodiments can be combined with each other in various combinations or arrangements. The scope of the present invention should be determined with reference to the full scope of the equivalent forms of the attached claims and these claims.

Claims

1. A feature calculation method, characterized in that: The W-shaped distributed optical fiber is laid out by the following method: a mounting plate is fixed on the inner wall of each of the adjacent multiple pipe sections, the W-shaped distributed optical fiber is laid out on the adjacent multiple pipe sections through the mounting plate, and when the adjacent pipe sections are misaligned, the difference in tension and compression state of the optical fiber is monitored; Based on the laid W-shaped distributed optical fiber, the characteristic calculation method includes: Determine the triangular relationship after the fiber is stretched: Among them, △X represents the vertical misalignment, △L s represents the fiber stretching amount, a represents the initial length of the oblique fiber AB, and b represents the length of the initial projection A'B of the oblique fiber AB; According to the triangular relationship after the optical fiber is stretched, we can get: The first microstrain calculation relationship and the second microstrain calculation relationship are introduced as formula (3) and formula (4): Among them, με a represents the measured value of oblique microstrain for the deformed AC side, με b It represents the conversion value of vertical microstrain for the measured value of oblique microstrain, μ represents microstrain; Substituting equations (3) and (4) into equation (2), we can obtain the micro-strain calculation results of adjacent pipe segments: με b Substitute the result into formula (4) to obtain the vertical misalignment; The triangular relationship after optical fiber compression is determined as follows: The second microstrain calculation relationship and the third microstrain calculation relationship are introduced. The third microstrain calculation relationship is as follows: Substituting equations (4) and (7) into equation (6), we can obtain the vertical misalignment micro-strain transformation result after optical fiber compression: 。 2. The feature calculation method according to claim 1, characterized in that: The method further comprises: When the acrylic disc is arranged at the lower part of the side wall, the calculation formula is shown in formula (8): Among them, με SUMi represents the cumulative misalignment strain value of the i-th pipe section, με bi It represents the relative misalignment between the i-th pipe section and the i-1-th pipe section, i represents the number of pipe sections, and n represents the total number of tunnel pipe sections; When the acrylic disc is placed on the upper part of the side wall, the calculation formula is shown in formula (9): The vertical misalignment of the i-th pipe section ΔX is calculated by the following formula i : ΔX i =b·with Si (10) Among them, με Si represents the vertical microstrain of the tube section between the i-th section and the i-1-th section.

3. The feature calculation method according to claim 2, characterized in that: The method further comprises: When the north-south wall offset ΔX S , ΔX N When there is inconsistency, it is determined that the pipe segment is torsioned, and the torsion form is determined based on the torsion characteristics, wherein the torsion characteristics are the difference in vertical misalignment; When the torsion characteristic is ΔX N <0<ΔX S ∩│ΔX N │>│ΔX S │, μγ is calculated by the following formula: In the formula, μγ represents the micro-angle, and B represents the width of the tunnel outer wall; ΔX N and ΔX S Calculated by the following formula ΔX N =b·with N (12) ΔX S =b·with S (13) Substituting equations (12) and (13) into (11), we obtain: Calculate μs using the following formula: In the formula, μs represents micro-sedimentation, με N represents the vertical microstrain of the north wall, με S Represents the vertical microstrain of the south wall.

4. The feature calculation method according to claim 3, characterized in that: The torsion forms include four pipe section counterclockwise rotation forms and four pipe section clockwise forms, wherein the four pipe section counterclockwise rotation forms are respectively expressed as Antilockwise (a), Antilockwise (b), Antilockwise (c) and Antilockwise (d), and the four pipe section clockwise forms are respectively expressed as Clockwise (a), Clockwise (b), Clockwise (c) and Clockwise (d). The torsion form is determined based on the torsion characteristics, including: When the torsion characteristic is ΔX N <0<ΔX S ∩│ΔX N │>│ΔX S │, the torsion form is determined to be Antilockwise (a); When the torsion characteristic is ΔX N <ΔX S <0, the torsion form is determined to be Antilockwise (b); When the torsion characteristic is ΔX N <0<ΔX S ∩│ΔX N │<│ΔX S │, the torsion form is determined to be Antilockwise (c); When the torsion characteristic is 0<ΔX N <ΔX S , the torsion form is determined to be Antilockwise (d); When the torsion characteristic is ΔX S <0<ΔX N ∩│ΔX S │>│ΔX N │, the torsion form is determined as Clockwise (a); When the torsion characteristic is ΔX S <ΔX N <0, the torsion form is determined as Clockwise (b); When the torsion characteristic is ΔX S <0<ΔX N ∩│ΔX S │<│ΔX N │, the torsion form is determined as Clockwise (c); When the torsion characteristic is 0<ΔX S <ΔX N , the torsion form is determined as Clockwise (d).

5. The feature calculation method according to claim 1, characterized in that: In the vertical direction, the installation disk is located at a distance of 0.15H from the center line of the tunnel, so that the vertical projection of the W-type distributed optical fiber is 0.3H, where H is the height of the pipe segment; in the horizontal direction, the installation disk is located at the center of the tunnel, so that the horizontal projection of the W-type distributed optical fiber is 1T, where T is the thickness of the pipe segment.

6. The feature calculation method according to claim 1, characterized in that: The installation disk is an acrylic disk, which is glued to the inner wall of the pipe section. The optical fiber is wound and connected with the acrylic disk to form a W-shaped distributed optical fiber.

7. A method for compensating errors of features calculated by the method according to any one of claims 1 to 6, characterized in that: The error compensation method comprises: Without considering the effect of fiber stretching on the opening strain caused by vertical misalignment, the vertical misalignment is compensated by calculating the tunnel W tensile strain error caused by tube segment opening and the tunnel W compressive strain error caused by tube segment compression.

8. The error compensation method according to claim 7, characterized in that: The steps of compensating the vertical misalignment by calculating the tunnel W tensile strain error caused by the pipe segment opening include: The vertical misalignment is compensated according to the W optical fiber tensile strain caused by the opening of the tube segment; The tensile strain of the W optical fiber caused by the opening of the tube segment is calculated by the following formula: After deleting the second-order microstrain, we get: In formulas (21-(23), △X represents the tension or compression of the adjacent pipe segments, c represents the horizontal projection length of the oblique optical fiber when the adjacent pipe segments are not opened, and με c Indicates the optical fiber micro-strain monitoring value caused by the opening or compression of adjacent pipe segments, με' a It represents the oblique micro-strain monitoring value of the optical fiber caused by the opening or compression of the adjacent pipe segments, where 9. The error compensation method according to claim 7, characterized in that: The steps of compensating the vertical misalignment by calculating the tunnel "W" compression strain error caused by the pipe segment compression include: The error amount is calculated by the following formula: After dividing a on both sides of formula (24), we get: Where c represents the horizontal projection length of the oblique optical fiber when the adjacent tube segments are not opened, με c Indicates the optical fiber micro-strain monitoring value caused by the opening or compression of adjacent pipe sections. The more realistic vertical misalignment can be obtained by subtracting the error from the micro-strain conversion result of the vertical misalignment after the optical fiber is compressed.

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