A tunnel settlement convergence monitoring system and monitoring method based on fiber grating sensor

Abstract

The present invention discloses a tunnel settlement convergence monitoring system and a monitoring method based on a fiber grating sensor. A plurality of tunnel designated positions on an arched tunnel section are used to fix a plurality of fiber grating displacement monitoring devices, a plurality of fiber grating inclination monitoring devices and a plurality of monitoring anchor points. All the fiber grating displacement monitoring devices and all the fiber grating inclination monitoring devices are connected to a fiber grating demodulator through an optical cable. The fiber grating demodulator transmits the collected data to a monitoring platform outside the tunnel through a wireless relay station. The monitoring platform derives and calculates the data after processing, and then obtains the tunnel convergence and settlement conditions. The deformation conditions of the arched tunnel section are displayed in real time through three-dimensional modeling. The data are monitored according to preset data quality standards and rules. Once the data is found to be abnormal or exceeds a preset range, an alarm is immediately issued.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber grating sensors, and in particular relates to a tunnel settlement convergence monitoring system and a monitoring method based on fiber grating sensors. Background Art

[0002] During the tunnel construction process, the initial support is an important part of the composite village masonry. The initial support must not only deform together with the surrounding rock, but also have sufficient strength and rigidity to control the deformation of the surrounding rock. The composition of the initial support should be determined according to the engineering geology and hydrogeology, tunnel clearance and covering thickness and other factors. The main support forms are: shotcrete support, shotcrete mesh support steel frame shotcrete support, etc. Different from the intuitive observation of the deformation of the masonry surface, the initial support deformation is more dangerous to the construction, mainly manifested in the arch sinking and convergence deformation around the tunnel after tunnel excavation. The initial support is squeezed by the surrounding rock and becomes unstable, which may even lead to collapse accidents. Safety monitoring of the deformation of the initial support is one of the important means to prevent safety hazards in tunnels. At present, the total station is mainly used to intermittently monitor the fixed anchor points of each cycle, but this monitoring method has problems such as high cost, complex operation, poor real-time performance, and poor durability. The real-time online monitoring of tunnels is to timely discover the deformation of tunnel structures during construction, evaluate their safety status, and prevent potential safety hazards. Through real-time online monitoring of tunnel structure deformation, a scientific basis can be provided for the design, construction, and maintenance of tunnels, thereby improving the construction quality of tunnels. Therefore, the present invention proposes a tunnel settlement convergence monitoring system and monitoring method based on fiber grating sensors to meet the needs of real-time, online, efficient, and high-precision monitoring of initial tunnel support. At the same time, the monitoring device can be repeatedly used in a back-and-forth cycle, which is economical and easy to operate.

[0003] Fiber Bragg grating sensor is a wavelength modulated fiber optic sensor. The basic working principle is that light enters the grating area through the optical fiber, and through the change of external quantity, it causes multiple parameters of light in the grating area to change, such as wavelength, intensity, amplitude, frequency, etc., so as to measure the external quantity and realize data transmission. Fiber Bragg grating sensor has the characteristics of strong anti-interference ability, no electromagnetic interference, high measurement accuracy, easy distributed networking, good environmental adaptability, etc. Fiber Bragg grating sensor is a safety product, widely used in remote, online, real-time, intelligent monitoring of mines, bridges, tunnels, deep foundation pits, high slopes, prefabricated buildings, etc.

[0004] At present, domestic and foreign manufacturers engaged in fiber grating sensing technology generally use epoxy resin, fiber grating and sensor matrix to encapsulate the substrate. The epoxy resin glue is only combined with the sensor matrix through physical bonding. The bonding method is not strong and the epoxy resin glue is easily damaged and falls off in high temperature, high humidity, strong ultraviolet rays and corrosive environments, which needs further improvement. Summary of the invention

[0005] The present invention provides a tunnel settlement convergence monitoring system and monitoring method based on fiber grating sensors, which can solve the problems of high cost, complex installation and operation, poor real-time performance and poor durability of traditional monitoring methods.

[0006] To solve the above problems, the technical solution provided by the present invention is as follows:

[0007] The embodiment of the present invention provides a tunnel settlement convergence monitoring system based on a fiber Bragg grating sensor, which includes a plurality of fiber Bragg grating displacement monitoring devices 1, a plurality of fiber Bragg grating inclination monitoring devices 2, a plurality of monitoring anchor points 3, a fiber Bragg grating demodulator 4, an optical cable 5, a wireless relay station 6, a monitoring platform 7 and a mobile terminal 8;

[0008] A plurality of tunnel designated positions are arranged on the cross section of the arched tunnel, and the plurality of tunnel designated positions are used to fix a plurality of fiber grating displacement monitoring devices 1, a plurality of fiber grating inclination monitoring devices 2 and a plurality of monitoring anchor points 3; all the fiber grating displacement monitoring devices 1 and all the fiber grating inclination monitoring devices 2 are connected to the fiber grating demodulator 4 through the optical cable 5, and the fiber grating demodulator 4 transmits the collected data to the monitoring platform 7 outside the tunnel through the wireless relay station 6, and the monitoring platform 7 derives and calculates the data after processing, and then obtains the convergence and settlement of the tunnel, and displays the deformation of the cross section of the arched tunnel in real time through three-dimensional modeling, and monitors the data according to the preset data quality standards and rules, and immediately issues an alarm once the data is found to be abnormal or exceeds the preset range; the monitoring platform 7 can also send the data to the mobile terminal 8, and the mobile terminal 8 is used to timely issue accident warnings to complete the monitoring of an arched tunnel cross section.

[0009] According to an optional embodiment of the present invention, the fiber Bragg grating displacement monitoring device 1 includes a plurality of fiber Bragg grating displacement sensors 101, a rotating bracket 102, a bearing 103, a displacement sensor support seat 104 and a displacement sensor mounting plate 105; wherein the fiber Bragg grating displacement sensor 101 includes a displacement sensor body 101-1, a displacement sensor pull rod 101-2 and a displacement sensor pull ring 101-3; the displacement sensor body 101-1 is embedded and fixed on the rotating bracket 102, the rotating bracket 102 is penetrated by the bearing 103, the bearing 103 is mounted on the displacement sensor support seat 104, and the displacement sensor support seat 104 is fixed on the displacement sensor mounting plate 105; the displacement sensor mounting plate 105 is fixed to a predetermined position of the tunnel by a plurality of the first bolt groups 106, and the mounting angle of the displacement sensor mounting plate 105 can be adjusted by the plurality of first bolt groups 106; the other end of the displacement sensor pull ring 101-3 is fixed in the first through hole 302 opened at the monitoring anchor point 3.

[0010] According to an optional embodiment of the present invention, one end of the rotating bracket 102 is two L-shaped plates 102-1, the two L-shaped plates 102-1 are embedded in the displacement sensor body 101-1, and a cylinder 102-2 is opened in the center of the side of the L-shaped plate 102-1, and the cylinder 102-2 is embedded in the bearing 103; the displacement sensor support seat 104 is a concave structure, and the bearing positions 104-1 opened on its two ears are used to install the bearing 103.

[0011] According to an optional embodiment of the present invention, the fiber grating inclination monitoring device 2 includes a fiber grating inclination sensor 201, an inclination sensor angle adjustment device 202 and an inclination sensor mounting plate 203; the inclination sensor mounting plate 203 is fixed to a designated position in the tunnel by a second bolt group 204, and the mounting angle of the inclination sensor mounting plate 203 can be adjusted by the second bolt group 204; the one-axis fixing plate 202-1 of the inclination sensor angle adjustment device 202 is installed on the inclination sensor mounting plate 203, and the angle relative to its plane can be adjusted on the inclination sensor mounting plate 203; the two-axis fixing plate 202-2 of the inclination sensor angle adjustment device 202 is connected to the fiber grating inclination sensor 201, and the angle of the two-axis fixing plate 202-2 can be adjusted by a spring 202-3.

[0012] According to an optional embodiment of the present invention, one end of the monitoring anchor point 3 is a cross-cylindrical shape, and its vertical cylindrical end 301 is a pointed cone. A plurality of first through holes 302 are provided on its horizontal cylindrical end. The horizontal cylindrical end is connected to a square plate 303, and a surveying target 304 is provided on the square plate 303. The target 304 surface is perpendicular to the tunnel advancement direction.

[0013] The present invention also provides a tunnel settlement convergence monitoring method based on a fiber grating sensor, which is implemented by a tunnel settlement convergence monitoring system based on a fiber grating sensor as in the above embodiment, wherein the tunnel settlement convergence monitoring method comprises the following steps:

[0014] Step S1, setting a designated position ABCDEFGHI on the cross section of the arched tunnel, the designated position ABCDEFG is simplified to the point ABCDEFGHI, and installing a monitoring anchor point 3 for monitoring of a fiber Bragg grating displacement monitoring device 1 at the five points ACDEG, and installing a fiber Bragg grating inclination monitoring device 2 at the points A and G, respectively, for measuring the inclination change of the walls on both sides of the tunnel; all sensors are connected to a fiber Bragg grating demodulator 4 through an optical cable 5, wherein the fiber Bragg grating displacement sensor 101 is connected to the monitoring anchor point 3 between the points AB, BC, BD, DF, EF, and FG by a rigid cable, and the length of the connection line can be directly measured, the arch of the arched tunnel is by default a section of an arc of a perfect circle, the point O is the center of the arc, and the height from the vertex D of the two sides to the bottom is set to h0;

[0015] Step S2: When the arched tunnel is affected by external stress, it will sink inwards. The walls on both sides and the tunnel arch will have different degrees of deformation and settlement. According to the data measured at points ABCDEFGHI on the cross section of the arched tunnel, three existing problems will be derived and calculated: 1. The settlement of the walls on both sides and the corresponding convergence changes of points BF and AG, 2. The settlement change of point D on the arch part, 3. The convergence change of the arc on the arch part;

[0016] Step S3, the wall changes on both sides of the arch tunnel: Point A and point G to the bottom have no change by default due to the large structural strength. AB , the inclination angle θ1 and the trigonometric formula are combined to calculate the vertical settlement of the wall:

[0017] L BH0 -(L AB +L AH )×cosθ1;

[0018] The convergence values ​​of point A and point B in the horizontal direction are:

[0019] L AH ×sinθ1;

[0020] (L AB +L AH )×sinθ1;

[0021] Similarly, the settlement and convergence values ​​in the vertical direction on the other side and in the horizontal direction at points F and G are:

[0022] L FI0 -(L FG +L GI )×cosθ2;

[0023] (L FG +L GI )×sinθ2;

[0024] Therefore, the distance L between BF and AG after the convergence change under the influence of external force can be obtained. BF , L AG for:

[0025] L BF =L BF0 -(L AB +L AH )×sinθ1-(L FG +L GI )×sinθ2;

[0026] L AG =L AG0 -L AH×sinθ1-L GI ×sinθ2;

[0027] Step S4, the settlement change of the dome part D point; the distance L between BF after convergence is known BF According to the Pythagorean theorem, the distance between D and BD can be calculated. The height h from point D to the bottom after being affected by external force is the height from D to BF plus the height from BF to the bottom, that is:

[0028]

[0029] Therefore, the settlement convergence value of point D is:

[0030]

[0031] Step S5, the arc of the dome part converges and changes. The intersection point of BF and DO in the dome part is set to N, and BF⊥DO. Therefore, the length of DN can be calculated according to the Pythagorean theorem as:

[0032]

[0033] θ3 can be calculated:

[0034]

[0035] Since C is the midpoint of BD, the radius r can be calculated as:

[0036]

[0037] At the same time, θ4 is calculated as:

[0038] θ4=π-2θ3; According to the central angle formula, the arc length of BD can be calculated as:

[0039]

[0040] Since the points of BCDEF are evenly distributed on the arc of the vault, the convergence rate of the upper vault can be obtained by the same logic as for the other arcs:

[0041]

[0042] Compared with the prior art, the embodiment of the present invention provides a tunnel settlement convergence monitoring system and monitoring method based on fiber grating sensors, which has the following beneficial effects:

[0043] (1) The initial support monitoring of tunnels is currently mainly carried out by using a total station to intermittently monitor the fixed anchor points of each cycle, but this monitoring method has the problems of high cost, complex operation, poor real-time performance, and poor durability. The monitoring method of the present invention realizes real-time online monitoring of tunnels, can timely detect the deformation of tunnel structures during construction, evaluate their safety status, and prevent potential safety hazards. Through real-time online monitoring of tunnel structure deformation, it can provide a scientific basis for the design, construction, and maintenance of tunnels, and improve the construction quality of tunnels.

[0044] (2) The tunnel settlement convergence monitoring system of the present invention is simple and efficient to deploy, and is suitable for the initial support monitoring of tunnel construction using the drilling and blasting method, and is not affected by construction. It uses optical fiber Bragg grating sensors for monitoring, and has low energy consumption. Compared with traditional measurement methods, the system of the present invention has a simple structure, low cost, and is reusable and easy to promote and apply.

[0045] (3) Chinese patent CN112230327A discloses "an all-glass packaging device and packaging method for fiber grating". The present invention is based on the patent technology to innovatively develop a new fiber grating sensor substrate. On the basis of the fiber grating sensor's strong anti-interference ability, no electromagnetic interference, high measurement accuracy, easy distributed networking, good environmental adaptability and other characteristics, it solves the current fiber grating sensor's poor durability and stability problems.

[0046] (4) Based on a novel fiber grating sensor substrate, the present invention has developed a novel fiber grating sensor that uses the fiber grating sensing principle to achieve high-precision measurement of tunnel settlement and convergence. The monitoring system can monitor displacement, tilt, temperature and other parameters separately, and the monitoring data are independently monitored without interfering with each other. A dynamic model can be established with the initial surveying and mapping data to display its changes in real time. Setting alarm thresholds can achieve segmented early warning, and monitoring data can be wirelessly transmitted in real time to achieve remote and local synchronous early warning, which can effectively avoid accidents. Centralized management and analysis of data can be achieved through a remote monitoring platform, reducing the complexity and errors of manual operations.

[0047] (5) The sensors in the monitoring system are modularly installed, which is convenient and efficient to install, meets the needs of on-site engineering construction, and is easy to repair and replace. They can be reused, and the optical fiber layout of the monitoring device is scientific and reasonable, which can effectively reduce losses;

[0048] Therefore, the present invention proposes a tunnel settlement convergence monitoring system and monitoring method based on fiber grating sensors to meet the needs of real-time, online, efficient and high-precision monitoring of initial tunnel support. At the same time, the monitoring device can be used repeatedly in a forward and backward cycle, which is economical and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0050] Figure 1 A schematic diagram of a tunnel settlement convergence monitoring system based on a fiber grating sensor provided in an embodiment of the present application.

[0051] Figure 2 A schematic structural diagram of a fiber Bragg grating displacement monitoring device in a tunnel settlement convergence monitoring system based on a fiber Bragg grating sensor provided in an embodiment of the present application.

[0052] Figure 3 A schematic structural diagram of a fiber Bragg grating inclination monitoring device in a tunnel settlement convergence monitoring system based on a fiber Bragg grating sensor provided in an embodiment of the present application.

[0053] Figure 4 A front view of a monitoring anchor point in a tunnel settlement convergence monitoring system based on a fiber grating sensor provided in an embodiment of the present application.

[0054] Figure 5 A right view of a monitoring anchor point in a tunnel settlement convergence monitoring system based on a fiber grating sensor provided in an embodiment of the present application.

[0055] Figure 6 A schematic diagram of tunnel designated positions ABCDEFGHI set on an arched tunnel section provided in an embodiment of the present application.

[0056] Figure 7 This is a schematic diagram of installing a fiber Bragg grating displacement monitoring device, a fiber Bragg grating inclination monitoring device and a monitoring anchor point on an arched tunnel section provided in an embodiment of the present application.

[0057] Figure 8 This is an overall cross-sectional view of the arched tunnel provided in an embodiment of the present application.

[0058] Fig. 9 A simplified point-and-line diagram of the tunnel location ABCDEFGHI provided in an embodiment of the present application.

[0059] Fig.10 This is a diagram showing changes in the lower half of the tunnel provided in an embodiment of the present application.

[0060] Fig.11 A schematic diagram of a tunnel vault portion provided in an embodiment of the present application. DETAILED DESCRIPTION

[0061] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0062] like Figure 1 As shown, an embodiment of the present invention provides a tunnel settlement convergence monitoring system based on fiber grating sensors, including multiple fiber grating displacement monitoring devices 1, multiple fiber grating inclination monitoring devices 2, multiple monitoring anchor points 3, fiber grating demodulators 4, optical cables 5, wireless relay stations 6, monitoring platforms 7 and mobile terminals 8.

[0063] A plurality of tunnel designated positions are arranged on the cross section of the arched tunnel, and the plurality of tunnel designated positions are used to fix a plurality of fiber grating displacement monitoring devices 1, a plurality of fiber grating inclination monitoring devices 2 and a plurality of monitoring anchor points 3; all the fiber grating displacement monitoring devices 1 and all the fiber grating inclination monitoring devices 2 are connected to the fiber grating demodulator 4 through the optical cable 5, and the fiber grating demodulator 4 transmits the collected data to the monitoring platform 7 outside the tunnel through the wireless relay station 6, and the monitoring platform 7 derives and calculates the data after processing, and then obtains the convergence and settlement of the tunnel, and displays the deformation of the cross section of the arched tunnel in real time through three-dimensional modeling, and monitors the data according to the preset data quality standards and rules, and immediately issues an alarm once the data is found to be abnormal or exceeds the preset range; the monitoring platform 7 can also send the data to the mobile terminal 8, and the mobile terminal 8 is used to timely issue accident warnings to complete the monitoring of an arched tunnel cross section.

[0064] like Figure 2 As shown, the fiber Bragg grating displacement monitoring device 1 includes a plurality of fiber Bragg grating displacement sensors 101, a rotating bracket 102, a bearing 103, a displacement sensor support seat 104 and a displacement sensor mounting plate 105; wherein, the fiber Bragg grating displacement sensor 101 includes a displacement sensor body 101-1, a displacement sensor pull rod 101-2 and a displacement sensor pull ring 101-3; the displacement sensor body 101-1 is embedded and fixed on the rotating bracket 102, the rotating bracket 102 is provided with a bearing 103, the bearing 103 is mounted on the displacement sensor support seat 104, and the displacement sensor support seat 104 is fixed on the displacement sensor mounting plate 105; the displacement sensor mounting plate 105 is fixed to a predetermined position of the tunnel by a plurality of first bolt groups 106, and the mounting angle of the displacement sensor mounting plate 105 can be adjusted by the plurality of first bolt groups 106; the other end of the displacement sensor pull ring 101-3 is fixed in the first through hole 302 opened at the monitoring anchor point 3.

[0065] One end of the rotating bracket 102 is two L-shaped plates 102-1, and the two L-shaped plates 102-1 are embedded in the displacement sensor body 101-1. A cylinder 102-2 is opened in the center of the side of the L-shaped plate 102-1, and the cylinder 102-2 is embedded in the bearing 103; the displacement sensor support seat 104 is a concave structure, and the bearing positions 104-1 opened on its two ears are used to install the bearing 103.

[0066] like Figure 3 As shown, the fiber grating inclination monitoring device 2 includes a fiber grating inclination sensor 201, an inclination sensor angle adjustment device 202 and an inclination sensor mounting plate 203; the inclination sensor mounting plate 203 is fixed to a designated position in the tunnel by a second bolt group 204, and the mounting angle of the inclination sensor mounting plate 203 can be adjusted by the second bolt group 204; the one-axis fixing plate 202-1 of the inclination sensor angle adjustment device 202 is installed on the inclination sensor mounting plate 203, and the angle relative to its plane can be adjusted on the inclination sensor mounting plate 203; the two-axis fixing plate 202-2 of the inclination sensor angle adjustment device 202 is connected to the fiber grating inclination sensor 201, and the angle of the two-axis fixing plate 202-2 can be adjusted by a spring 202-3.

[0067] like Figure 4 and Figure 5 As shown, one end of the monitoring anchor point 3 is a cross-cylindrical shape, and its vertical cylindrical end 301 is a pointed cone. A plurality of first through holes 302 are provided on its horizontal cylindrical end. The horizontal cylindrical end is connected to a square plate 303, and a surveying target 304 is provided on the square plate 303. The target 304 surface is perpendicular to the tunnel advancement direction.

[0068] like Figure 6 As shown, designated positions ABCDEFGHI are set on the cross section of the arched tunnel, and a monitoring anchor point 3 is installed at designated position A, and a fiber Bragg grating inclination monitoring device 2 is installed at monitoring anchor point 3. A fiber Bragg grating displacement monitoring device 1 is installed at designated position B, a monitoring anchor point 3 is installed at designated position C, a monitoring anchor point 3 is installed at designated position D, a monitoring anchor point 3 is installed at designated position E, a monitoring anchor point 3 is installed at designated position F, a monitoring anchor point 3 is installed at designated position G, a fiber Bragg grating inclination monitoring device 2 is installed at monitoring anchor point 3, and a monitoring anchor point 3 is installed at designated position I.

[0069] like Figure 7 As shown, three monitoring anchor points 3, one fiber Bragg grating displacement monitoring device 1 and one fiber Bragg grating inclination monitoring device 2 are installed on the tunnel section.

[0070] In another embodiment, the displacement sensor pull ring 101 - 3 can be replaced by a bolt locking structure.

[0071] In another embodiment, the tip end of the monitoring anchor point 3 is a cross-cylindrical shape, and the pointed cone 301 at the end of the vertical cylinder can be replaced by an expansion screw or a bolt to engage with the embedded threaded hole of the initial support.

[0072] In another embodiment, all sensors can be connected in series to the fiber Bragg grating demodulator 4 , or can be connected to the fiber Bragg grating demodulator 4 individually through optical cables 5 .

[0073] The present invention also provides a tunnel settlement convergence monitoring method based on a fiber grating sensor, which is implemented by a tunnel settlement convergence monitoring system based on a fiber grating sensor as in the above embodiment, and is characterized in that the tunnel settlement convergence monitoring method comprises the following steps:

[0074] Step S1, such as Figure 8 and Fig. 9 As shown, a designated position ABCDEFGHI is set on the cross section of the arched tunnel, and the designated position ABCDEFG is simplified to the point ABCDEFGHI. A fiber Bragg displacement monitoring device 1 and a monitoring anchor point 3 are installed at the five points ACDEG respectively, and a fiber Bragg inclination monitoring device 2 is installed at the points A and G respectively, so as to measure the inclination change of the walls on both sides of the tunnel; all sensors are connected to the fiber Bragg demodulator 4 through an optical cable 5, wherein the fiber Bragg displacement sensor 101 and the monitoring anchor point 3 are connected between the points AB, BC, BD, DF, EF, and FG by a rigid cable, and the length of the connection line can be directly measured. The arch of the arched tunnel is assumed to be a section of an arc of a perfect circle, and the point O is the center of the arc, and the height from the vertex D of the two sides to the bottom is set to be h0.

[0075] The fiber Bragg grating demodulator 4 in this embodiment transmits the collected data to the monitoring platform 7 outside the tunnel through the wireless relay station 6. The monitoring platform 7 derives and calculates the data after processing, and then obtains the tunnel convergence and settlement conditions, and displays the deformation conditions in real time through three-dimensional modeling. According to the preset data quality standards and rules, the data is monitored. Once the data is found to be abnormal or exceeds the preset range, an alarm will be issued immediately; the monitoring platform 7 can also send the data to the mobile terminal 8 for timely accident warning; after the monitoring of a section is completed, it can be dismantled and installed in the new initial support section of excavation, so as to realize the reuse of a tunnel settlement convergence monitoring system based on fiber Bragg grating sensors.

[0076] Step S2, such as Fig. 9 As shown in the figure, when the arched tunnel is affected by external stress, it will sink inward, and the walls on both sides and the tunnel arch will have different degrees of deformation and settlement. According to the measured data of points ABCDEFGHI on the section of the arched tunnel, three existing problems will be deduced and calculated: 1. The settlement of the walls on both sides and the corresponding convergence changes of points BF and AG, 2. The settlement change of point D on the arch part, and 3. The convergence change of the arc on the arch part.

[0077] Step S3, such as Fig.10 As shown in the figure, the wall changes on both sides of the arch tunnel: Point A and point G to the bottom have no change by default due to the strong structural strength. AB , the inclination angle θ1 and the trigonometric formula are combined to calculate the vertical settlement of the wall:

[0078] L BH0 -(L AB +L AH )×cosθ1;

[0079] The convergence values ​​of point A and point B in the horizontal direction are:

[0080] L AH ×sinθ1;

[0081] (L AB +L AH )×sinθ1;

[0082] Similarly, the settlement and convergence values ​​in the vertical direction on the other side and in the horizontal direction at points F and G are:

[0083] L FI0 -(L FG +L GI )×cosθ2;

[0084] (L FG +L GI )×sinθ2;

[0085] Therefore, the distance L between BF and AG after the convergence change under the influence of external force can be obtained. BF , L AG for:

[0086] L BF =L BF0 -(L AB +L AH )×sinθ1-(L FG +L GI )×sinθ2;

[0087] L AG =L AG0 -L AH ×sinθ1-L GI ×sinθ2;

[0088] Step S4, the settlement change of the dome part D point; the distance L between BF after convergence is known BF According to the Pythagorean theorem, the distance between D and BD can be calculated. The height from D to the bottom after being affected by external force is the height from D to BF plus the height from BF to the bottom, that is:

[0089]

[0090] Therefore, the settlement convergence value of point D is:

[0091]

[0092] Step S5, such as Fig.11 As shown, the arc of the dome part converges and changes. The intersection of BF and DO in the dome part is set to N, and BF⊥DO. Therefore, the length of DN can be calculated according to the Pythagorean theorem:

[0093]

[0094] θ3 can be calculated:

[0095]

[0096] Since C is the midpoint of BD, the radius r can be calculated as:

[0097]

[0098] At the same time, θ4 is calculated as:

[0099] θ4=π-2θ3;

[0100] According to the central angle formula, the arc length of BD can be calculated as:

[0101]

[0102] Since the points of BCDEF are evenly distributed on the arc of the vault, the convergence rate of the upper vault can be obtained by the same logic as for the other arcs:

[0103]

[0104] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited to them. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered within the protection scope of the present invention. Ordinary technicians in this field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be based on the scope defined by the claims.

Claims

1. A tunnel settlement convergence monitoring system based on fiber grating sensors, characterized in that: It comprises a plurality of fiber Bragg grating displacement monitoring devices (1), a plurality of fiber Bragg grating inclination monitoring devices (2), a plurality of monitoring anchor points (3), a fiber Bragg grating demodulator (4), an optical cable (5), a wireless relay station (6), a monitoring platform (7) and a mobile terminal (8); A plurality of tunnel designated positions are arranged on the cross section of the arched tunnel, and the plurality of tunnel designated positions are used to fix a plurality of fiber grating displacement monitoring devices (1), a plurality of fiber grating inclination monitoring devices (2) and a plurality of monitoring anchor points (3); all the fiber grating displacement monitoring devices (1) and all the fiber grating inclination monitoring devices (2) are connected to the fiber grating demodulator (4) through an optical cable (5); the fiber grating demodulator (4) transmits the collected data to a monitoring platform (7) outside the tunnel through the wireless relay station (6); the monitoring platform (7) processes the data and performs deduction and calculation, thereby obtaining the convergence and settlement of the tunnel, and displays the deformation of the cross section of the arched tunnel in real time through three-dimensional modeling; the data is monitored according to preset data quality standards and rules, and an alarm is immediately issued once the data is found to be abnormal or exceeds a preset range; the monitoring platform (7) can also send the data to the mobile terminal (8); the mobile terminal (8) is used to timely issue accident warnings, and complete the monitoring of a cross section of the arched tunnel.

2. A tunnel settlement convergence monitoring system based on fiber grating sensors according to claim 1, characterized in that: The fiber grating displacement monitoring device (1) comprises a plurality of fiber grating displacement sensors (101), a rotating bracket (102), a bearing (103), a displacement sensor support seat (104) and a displacement sensor mounting plate (105); wherein the fiber grating displacement sensor (101) comprises a displacement sensor body (101-1), a displacement sensor pull rod (101-2) and a displacement sensor pull ring (101-3); the displacement sensor body (101-1) is embedded and fixed on the rotating bracket (102), and the bearing is passed through the rotating bracket (102). (103), the bearing (103) is mounted on the displacement sensor support seat (104), and the displacement sensor support seat (104) is fixed on the displacement sensor mounting plate (105); the displacement sensor mounting plate (105) is fixed at a predetermined position in the tunnel by a plurality of first bolt groups (106), and the mounting angle of the displacement sensor mounting plate (105) can be adjusted by the plurality of first bolt groups (106); the other end of the displacement sensor pull ring (101-3) is fixed in a first through hole (302) opened at the monitoring anchor point (3).

3. A tunnel settlement convergence monitoring system based on fiber grating sensors according to claim 2, characterized in that: One end of the rotating bracket (102) is provided with two L-shaped plates (102-1), the two L-shaped plates (102-1) are embedded in the displacement sensor body (101-1), a cylinder (102-2) is provided at the center of the side surface of the L-shaped plate (102-1), and the cylinder (102-2) is embedded in the bearing (103); the displacement sensor support seat (104) is a concave structure, and the bearing positions (104-1) provided at its two ears are used to install the bearing (103).

4. A tunnel settlement convergence monitoring system based on fiber grating sensors according to claim 3, characterized in that: The fiber Bragg grating inclination monitoring device (2) comprises a fiber Bragg grating inclination sensor (201), an inclination sensor angle adjustment device (202) and an inclination sensor mounting plate (203); the inclination sensor mounting plate (203) is fixed at a predetermined position in a tunnel by a second bolt group (204), and the mounting angle of the inclination sensor mounting plate (203) can be adjusted by the second bolt group (204); a single-axis fixing plate (202-1) of the inclination sensor angle adjustment device (202) is installed on the inclination sensor mounting plate (203), and the angle relative to the plane thereof can be adjusted on the inclination sensor mounting plate (203); a double-axis fixing plate (202-2) of the inclination sensor angle adjustment device (202) is connected to the fiber Bragg grating inclination sensor (201), and the angle of the double-axis fixing plate (202-2) can be adjusted by a spring (202-3).

5. A tunnel settlement convergence monitoring system based on fiber grating sensors according to claim 4, characterized in that: One end of the monitoring anchor point (3) is in the shape of a cross cylinder, the vertical cylindrical end (301) thereof is a pointed cone, a plurality of first through holes (302) are provided on the horizontal cylindrical end, the horizontal cylindrical end is connected to a square plate (303), a surveying target (304) is provided on the square plate (303), and the target (304) is perpendicular to the tunnel advancement direction.

6. A tunnel settlement convergence monitoring method based on fiber Bragg grating sensors, implemented by a tunnel settlement convergence monitoring system based on fiber Bragg grating sensors as claimed in claim 5, characterized in that: The tunnel settlement convergence monitoring method comprises the following steps: Step S1, setting a designated position ABCDEFGHI on the cross section of the arched tunnel, the designated position ABCDEFG is simplified to the point ABCDEFGHI, installing a fiber Bragg grating displacement monitoring device (1) and a monitoring anchor point (3) at the five points ACDEG, and installing a fiber Bragg grating inclination monitoring device (2) at the points A and G, respectively, for measuring the inclination change of the walls on both sides of the tunnel; all sensors are connected to a fiber Bragg grating demodulator (4) through an optical cable (5), wherein the fiber Bragg grating displacement sensor (101) and the monitoring anchor point (3) are connected between the points AB, BC, BD, DF, EF, and FG by a rigid cable, and the length of the connection line can be directly measured, the arch of the arched tunnel is assumed to be a section of an arc of a perfect circle, the point O is the center of the arc, and the height from the arch vertex point D on both sides to the bottom is set to h0; Step S2: When the arched tunnel is affected by external stress, it will sink inwards. The walls on both sides and the tunnel arch will have different degrees of deformation and settlement. According to the data measured at points ABCDEFGHI on the cross section of the arched tunnel, three existing problems will be derived and calculated:

1. The settlement of the walls on both sides and the corresponding convergence changes of points BF and AG, 2. The settlement change of point D on the arch part, 3. The convergence change of the arc on the arch part; Step S3, the wall changes on both sides of the arch tunnel: Point A and point G to the bottom have no change by default due to the large structural strength. AB , the inclination angle θ1 and the trigonometric formula are combined to calculate the vertical settlement of the wall: L BH0 -(L AB +L AH )×cosθ1; The convergence values ​​of point A and point B in the horizontal direction are: L AH ×sinθ1; (L AB +L AH )×sinθ1; Similarly, the settlement and convergence values ​​in the vertical direction on the other side and in the horizontal direction at points F and G are: L FI0 -(L FG +L GI )×cosθ2; (L FG +L GI )×sinθ2; Therefore, the distance L between BF and AG after the convergence change under the influence of external force can be obtained. BF , L AG for: L BF =L BF0 -(L AB +L AH )×sinθ1-(L FG +L GI )×sinθ2; L AG =L AG0 -L AH ×sinθ1-L GI ×sinθ2; Step S4, the settlement change of the dome part D point; the distance L between BF after convergence is known BF According to the Pythagorean theorem, the distance between D and BD can be calculated. The height h from point D to the bottom after being affected by external force is the height from D to BF plus the height from BF to the bottom, that is: Therefore, the settlement convergence value of point D is: Step S5, the arc of the dome part converges and changes. The intersection point of BF and DO in the dome part is set to N, and BF⊥DO. Therefore, the length of DN can be calculated according to the Pythagorean theorem as: θ3 can be calculated: Since C is the midpoint of BD, the radius r can be calculated as: At the same time, θ4 is calculated as: θ4=π-2θ3; According to the central angle formula, the arc length of BD can be calculated as: Since the points of BCDEF are evenly distributed on the arc of the vault, the convergence rate of the upper vault can be obtained by the same logic as for the other arcs:

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