阅读说明：本技术 一种全隧道安全监测系统及实施方法 (Full-tunnel safety monitoring system and implementation method ) 是由 吕京生 王昌 张发祥 姜劭栋 倪家升 李淑娟 刘小会 于 2018-07-04 设计创作，主要内容包括：本发明涉及一种全隧道安全监测系统,包括分别与数据采集中心电连接的GPS系统、光纤应变监测系统,与光纤应变监测系统电连接且埋设在隧道监控区域下方的应变监测光缆；光纤应变监测系统为光纤分析仪,GPS系统用来实现隧道整体沉降监测；光纤应变监测系统通过连续的光缆实现隧道全方位的应变监测,并提供精确定位,所测形变为相对形变,并可对形变量进行累计。系统监测精度高,能够实现隧道大型事故性形变的前期预警；能够实现隧道形变方向的判断；智能化程度高,对异常情况能够准确定位,并实现多种手段报警；监测寿命长,能够实现隧道全寿命周期内的监测；维护成本低,后期近乎零维护。(The invention relates to a full tunnel safety monitoring system, which comprises a GPS system, an optical fiber strain monitoring system and a strain monitoring optical cable, wherein the GPS system and the optical fiber strain monitoring system are respectively electrically connected with a data acquisition center; the optical fiber strain monitoring system is an optical fiber analyzer, and the GPS system is used for realizing the monitoring of the integral settlement of the tunnel; the optical fiber strain monitoring system realizes the omnibearing strain monitoring of the tunnel through a continuous optical cable, provides accurate positioning, changes the measured deformation into relative deformation and can accumulate the deformation quantity. The system has high monitoring precision and can realize early warning of large-scale accidental deformation of the tunnel; the judgment of the deformation direction of the tunnel can be realized; the intelligent degree is high, the abnormal condition can be accurately positioned, and the alarm by various means is realized; the monitoring service life is long, and monitoring in the whole life cycle of the tunnel can be realized; the maintenance cost is low, and the later period is nearly zero maintenance.)

1. The utility model provides a full tunnel safety monitoring system which characterized in that: the system comprises a GPS system, an optical fiber strain monitoring system and a strain monitoring optical cable, wherein the GPS system and the optical fiber strain monitoring system are respectively electrically connected with a data acquisition center; the optical fiber strain monitoring system is an optical fiber analyzer, and the GPS system is used for realizing the monitoring of the integral settlement of the tunnel; the optical fiber strain monitoring system realizes the omnibearing deformation monitoring of the tunnel through a continuous optical cable.

2. The full tunnel safety monitoring system according to claim 1, wherein: the strain monitoring optical cable adopts an optical fiber strain optical cable; the strain optical cable is a tightly-packed optical cable, and the selected material is a carbon fiber structure or a glass fiber structure; the strain optical cable is high in elasticity and not easy to bend in short distance.

3. The full tunnel safety monitoring system according to claim 2, wherein: the strain monitoring optical cable is bound on a steel bar keel of a tunnel in the tunnel construction process and is cast with steel bars into a whole; the strain monitoring optical cable is in a free state in the binding process, and large bending is avoided.

4. The full tunnel safety monitoring system according to claim 3, wherein: two optical cables are arranged in the concrete at the same position of the tunnel wall of the strain monitoring optical cable, a certain distance is reserved between the two optical cables, and the distance is generally not more than 1 m; the two optical cables are laid completely synchronously, and the trend, the distance and the bending in the concrete are kept consistent; and after the surplus length of the two strain optical cables exceeding 5 meters is reserved at the tail end of the tunnel, the two optical cables are welded to enable the tail ends of the two optical cables to be connected.

5. The full tunnel safety monitoring system according to claim 4, wherein: the optical cable with the extra length at the tail end of the strain monitoring optical cable is placed in an unstressed state in a protection mode; and the two ends of the strain monitoring optical cable at the tunnel opening are connected with the light inlet and the light outlet of the optical fiber analyzer through optical fiber flanges.

6. The full tunnel safety monitoring system according to claim 5, wherein: the method for laying the strain monitoring optical cable is characterized in that the strain monitoring optical cable is laid on two walls of a tunnel, the top of the tunnel and the bottom of the tunnel once.

7. The full tunnel safety monitoring system according to claim 6, wherein: the optical fiber analyzer can simultaneously monitor the stress-strain data of 4 optical cables; the optical fiber analyzer can describe strain information of each point along the optical fiber distance; the optical fiber analyzer realizes position correspondence of two optical cables at the same position of the tunnel on software in a field calibration mode through the software.

8. The full tunnel safety monitoring system according to claim 7, wherein: the optical fiber analyzer selects the strain on the inner (or outer) optical cable from the strain of the optical cable at the same position as a basis through software, subtracts the strain on the outer (or inner) optical cable, correspondingly displays a difference value and a geographical position in an interface, judges whether the tunnel is inwards concave or outwards convex according to the positive and negative values of the difference value, and further judges the deformation direction of the tunnel.

9. An implementation method of a full-tunnel safety monitoring system is characterized by comprising the following steps: the method comprises the following steps:

the embedded optical cable is implemented as follows:

1) determining an optical cable laying path, and preparing a related optical cable;

2) after the steel bar keel is laid, optical cables are laid before cement paste is poured, the optical cables are bound with the steel bar keel in parallel, the radian of the optical cables with the radius of more than 20cm is ensured when the optical cables meet corners, and all the optical cables are in a stretched straight state except the corners; (ii) a

3) Extra length control is well done in the laying process, particularly relating to a gap changing position, and an optical cable tensioner is added;

4) pouring concrete to completely and tightly fix the optical cable and the tunnel wall;

5) calibrating the installation optical cable by using an optical fiber distributed monitor, and determining the corresponding relation between the position of the optical cable and the tunnel coordinate;

6) joint butt joint processing is well carried out;

7) carrying out jumper wire and optical cable terminal box installation splicing protection work;

8) and connecting the monitoring equipment to operate.

Technical Field

The invention belongs to the technical field of tunnel safety, and particularly relates to a full tunnel safety monitoring system and an implementation method.

Background

Disclosure of Invention

In order to solve the technical problem, the invention provides a full tunnel safety monitoring system and an implementation method.

The invention is realized by the following technical scheme, and on one hand, the invention provides a full tunnel safety monitoring system which comprises a GPS system, an optical fiber strain monitoring system and a strain monitoring optical cable, wherein the GPS system and the optical fiber strain monitoring system are respectively electrically connected with a data acquisition center; the optical fiber strain monitoring system is an optical fiber analyzer, and the GPS system is used for realizing the monitoring of the integral settlement of the tunnel; the optical fiber strain monitoring system realizes the omnibearing strain monitoring of the tunnel through a continuous optical cable.

Preferably, the strain monitoring optical cable is an optical fiber strain optical cable; the strain optical cable is a tightly-packed optical cable, and the selected material is a carbon fiber structure or a glass fiber structure; the strain optical cable is high in elasticity and not easy to bend in short distance.

Preferably, the strain monitoring optical cable is bound on a steel bar keel of the tunnel in the tunnel construction process and is cast with steel bars into a whole; the strain monitoring optical cable is in a free state in the binding process, and large bending is avoided.

Preferably, two optical cables are arranged in the concrete at the same position of the tunnel wall of the strain monitoring optical cable, and the two optical cables have a certain distance which is generally not more than 1 m; the two optical cables are laid completely synchronously, and the trend, the distance and the bending in the concrete are kept consistent; and after the surplus length of the two strain optical cables exceeds 5 meters is reserved at the tail end of the tunnel, the two optical cables are welded to enable the tail ends of the two optical cables to be connected.

Preferably, the excess length optical cable at the tail end of the strain monitoring optical cable is placed in an unstressed state in a protection manner; and the two ends of the strain monitoring optical cable at the tunnel opening are connected with the light inlet and the light outlet of the optical fiber analyzer through optical fiber flanges.

Preferably, the method for laying the strain monitoring optical cable lays the strain monitoring optical cable once on two walls of the tunnel, the top of the tunnel and the bottom of the tunnel.

Preferably, the optical fiber analyzer can simultaneously monitor the stress strain data of the 4 optical cables; the optical fiber analyzer can describe strain information of each point along the optical fiber distance; the optical fiber analyzer realizes position correspondence of two optical cables at the same position of the tunnel on software in a field calibration mode through the software.

Preferably, the optical fiber analyzer selects the strain on the inner (or outer) optical cable from the optical cable strain at the same position as a basis through software, subtracts the strain on the outer (or inner) optical cable, displays the difference value and the geographical position in an interface correspondingly, judges whether the tunnel is inwards concave or outwards convex according to the positive and negative values of the difference value, and further judges the deformation direction of the tunnel.

An implementation method of a full-tunnel safety monitoring system comprises the following steps:

A. the externally laid optical cable is implemented as follows:

1) surveying the tunnel field environment, and determining an installation path;

2) cleaning, dedusting and descaling the installation path;

3) installing an optical cable, laying the thin and tight strain optical cable along a path, fixing the optical cable every 0.5m or 1m, wherein the fixing mode can be a mortise and cone mode or a drawing pin mode, so as to ensure firmness, and applying certain stress to the optical cable before fixing to enable the optical cable to be in a stretched state;

4) in order to ensure the coverage rate of system monitoring, a dense laying mode is mainly used as much as possible, the distance is controlled within 1 meter, and site and tunnel design, equipment management and construction unit investigation are determined;

5) spraying structural colloid along the fixed optical cable to completely fix the optical cable and the tunnel wall;

6) calibrating the installation optical cable by using the optical fiber distributed vibration monitor, and determining the corresponding relation between the position of the optical cable and the tunnel coordinate;

7) joint butt joint processing is well carried out, and all optical cable continuous joints are placed at the bottom of the tunnel;

8) the installation and splicing work of the jumper and the optical cable terminal box is done;

9) connecting monitoring equipment, and starting a system to operate;

B. the embedded optical cable is implemented as follows:

1) determining an optical cable laying path, and preparing a related optical cable;

2) after the steel bar keel is laid, optical cables are laid before cement paste is poured, the optical cables are bound with the steel bar keel in parallel, the radian of the optical cables with the radius of more than 20cm is ensured when the optical cables meet corners, and all the optical cables are in a stretched straight state except the corners; (ii) a

3) Extra length control is well done in the laying process, particularly relating to a gap changing position, and an optical cable tensioner is added;

4) pouring concrete to completely and tightly fix the optical cable and the tunnel wall;

5) calibrating the installation optical cable by using an optical fiber distributed monitor, and determining the corresponding relation between the position of the optical cable and the tunnel coordinate;

6) joint butt joint processing is well carried out;

7) carrying out jumper wire and optical cable terminal box installation splicing protection work;

8) and connecting the monitoring equipment, and starting the system to operate.

The judgment mechanism of the inward recess and the outward protrusion of the tunnel is that deformation quantities of two optical cables at different positions are different due to different bending radiuses at the same position, when the optical cables are inwardly recessed, the deformation quantity of the optical cables inside is large, and when the optical cables are outwardly protruded, the deformation quantity of the optical cables outside is large. The distributed strain monitoring optical cable adopts an optical cable fixed in a direction parallel to the tunnel, and is bound or poured on the top end and two walls of the tunnel to monitor the tunnel cracks, bulges and relative deformation settlement in the tunnel; the optical cable for monitoring vibration in the tunnel is laid at the bottom of the tunnel, so that invasion of foreign matters in the tunnel can be monitored and positioned in real time, particularly, the foreign matters fall off from the top end of the tunnel, and the optical fiber distributed vibration monitoring system can monitor and find the time of the falling foreign matters and accurately position the falling foreign matters.

1) A GPS system is arranged in the tunnel monitoring system; the GPS system is used for realizing the overall settlement monitoring of the tunnel, two monitoring base stations are respectively arranged at two ends of a tunnel opening, and a GPS settlement observation point is arranged every 200-500 meters in a tunnel section;

2) a distributed optical fiber monitoring system is arranged in the tunnel; the distributed optical fiber monitoring system is divided into a distributed strain monitoring system and a distributed vibration monitoring system, wherein the distributed strain monitoring system adopts an optical cable fixed in a direction parallel to the tunnel, and the optical cable is bound or poured on the top end and two wings of the tunnel to monitor the tunnel cracks, bulges and relative deformation settlement in the tunnel; the optical cable for monitoring vibration in the tunnel is laid at the bottom of the tunnel, so that invasion of tunnel foreign matters can be monitored and positioned in real time, particularly, foreign matters fall off from the top end of the tunnel, and the optical fiber distributed vibration monitoring system can monitor time for finding the fallen foreign matters and accurately position the fallen foreign matters.

The optical fiber distributed sensing technology has the characteristics of long distance, high precision, durability, real-time property, low cost and the like, is arranged in a tunnel lining structure to monitor the health condition of a tunnel in a long-term and real-time manner, is combined with a GPS system, can realize the monitoring of the tunnel from settling to local settlement and deformation, can be automatically carried out, cannot cause interference to traffic, and can enable tunnel workers to master the health condition of the tunnel at any time through real-time output data information. The arrangement of the optical fiber monitoring network needs to comprehensively consider the surrounding rock grade, the surrounding rock stress level, the economical efficiency and the like of the tunnel. The optical fiber sensors arranged along the cross section of the tunnel are required to determine the arranged circumferential distance according to the grade of the surrounding rocks, namely the circumferential distance of the sensors is required to be correspondingly reduced along with the increase of the grade of the surrounding rocks of the tunnel, and the sensors are arranged near the tunnel portal in an appropriately encrypted manner.

The optical fiber distributed railway tunnel lining structure monitoring system can quickly monitor the strain information of the tunnel settlement structure in real time, realize scientific, comprehensive, accurate and real-time monitoring of the tunnel lining structure, improve the safety of the tunnel lining structure and has important significance for guaranteeing the safety of railway transportation.

The technical principle is as follows:

1) optical fiber strain monitoring technical principle: when a laser beam is injected into the Optical fiber, various scattering effects occur, and such scattering effects are related to the strain, temperature and the like of the Optical fiber, wherein the translation amount of the center Frequency of Brillouin scattering light is linearly related to the strain amount of the Optical fiber, and distributed measurement of the strain of each point in the Optical fiber is realized by utilizing a Time domain or Frequency domain technology, which is called Brillouin Optical Time/Frequency domain reflection technology.

The Brillouin scattering is affected by strain and temperature at the same time, when the temperature along the optical fiber changes or axial strain exists, the frequency of the back Brillouin scattering light in the optical fiber shifts, and the shift amount of the frequency and the strain and the temperature of the optical fiber have a good linear relation, so that the distribution information of the temperature and the strain along the optical fiber can be obtained by measuring the frequency shift amount (vB) of the back natural Brillouin scattering light in the optical fiber. The strain measurement principle of BOTDR is shown in fig. 1-3.

As described above, to obtain the strain distribution along the optical fiber, the BOTDR needs to obtain the brillouin scattering spectrum along the optical fiber, that is, to obtain the vb distribution along the optical fiber. The measurement principle of the BOTDR is very similar to the OTDR (Optical Time-domain reflectometer) technology, pulsed light is incident from one end of an Optical fiber at a certain frequency, the incident pulsed light interacts with an acoustic phonon in the Optical fiber to generate brillouin scattering, the back brillouin scattering light returns to the incident end of the pulsed light along an Optical fiber primary path, enters a light receiving part and a signal processing unit of the BOTDR, and power distribution of brillouin back scattering light along the Optical fiber can be obtained through a series of complex signal processing. The distance Z from the position where scattering occurs to the incident end of the pulsed light, i.e., to the BOTDR, can be calculated by equation (1). Then, the frequency of the incident light is changed at certain intervals according to the method, and the spectral diagram of the brillouin scattered light of each sampling point on the optical fiber can be obtained through repeated measurement, as shown in fig. 2, the brillouin back scattering spectrum is in a lorentzian shape theoretically, and the frequency corresponding to the peak power of the brillouin back scattering spectrum is brillouin frequency shift vbs.

（1）

Wherein c is the speed of light in vacuum;

n is the refractive index of the optical fiber;

t is the time interval between the emitted pulsed light and the received scattered light.

The brillouin frequency shift and the optical fiber strain are in a linear relation, the slope of the linear relation depends on the wavelength of the probe light and the type of the adopted optical fiber, and calibration needs to be carried out before the test, namely VB (0) and C values in an equation (2) need to be determined. As shown in fig. 4.

The strain amount and brillouin frequency shift of the optical fiber can be expressed by the following formula:

wherein v is_B(epsilon) is the amount of drift in brillouin frequency when strain is applied;

v_B(0) is the amount of drift of the brillouin frequency when strain is 0;

is a scaling factor of about 493MHz (/% strain);

is the amount of strain in the fiber.

The BOTDR technology adopted by the distributed optical fiber test can realize strain demodulation of the sensing optical cable. And the strain data is analyzed and processed to realize the extraction, analysis, judgment and early warning of displacement information such as bulges, cracks and the like in the tunnel.

2) Optical fiber vibration monitoring technical principle

When light is transmitted in the optical cable, rayleigh scattered light is continuously transmitted backward due to the interaction between photons and fiber core lattices, as shown in fig. 5-6. When external vibration occurs, the fiber core in the optical cable is deformed, so that the length and the refractive index of the fiber core are changed, the phase of the back Rayleigh scattering light is changed, and the signal light carrying external vibration information is reflected back to a system host, is processed by an optical system, converts weak phase change into light intensity change, and enters a computer for data analysis after photoelectric conversion and signal processing. And the system judges the vibration event near the optical fiber cable according to the analysis result and positions the vibration event, and the positioning precision reaches the meter level. As shown in fig. 5-6.

Utilize brillouin scattering that light transmission arouses in the optic fibre, through monitoring brillouin scattered light and then confirm the change of stress strain in the optic fibre, because monitoring optical cable and tunnel wall rigid connection, when the train passes through the tunnel, can bring certain vibration and air current influence for the tunnel, because rigid connection, so the air current influence can be got rid of, the vibration is used in whole monitoring optical cable, influence to whole monitoring through background system filtering vibration interference source, strain monitoring belongs to static absolute monitoring, it is insensitive to the developments, the interference that vibration interference source arouses to the monitoring effect can be neglected, ensure the accuracy of monitoring data.

The adopted pure optical fiber monitoring system does not set any electrical element on the sensing site, and can ensure that the optical fiber equipment on the spot is not interfered by high-voltage electromagnetism of a contact net.

The distributed optical fiber sensing technology monitoring scheme has the following advantages: real-time on-line testing: carrying out continuous all-weather real-time online monitoring for 24 hours and 365 days; safe and reliable: the sensing site, optical sensing and optical transmission, the quality is safe; the environmental adaptation is strong: the data is not electrified and is not interfered by electromagnetism, and the data fidelity is good; distributed testing: monitoring along the optical cable, wherein the position of the optical cable has no blind area and no dead angle; the testing distance is far: the single device can realize the monitoring of dozens of kilometers, and meet the monitoring requirements of large projects; the measurement accuracy is high, and the location is accurate: the distance of tens of kilometers can be positioned to the meter; the false alarm rate and the missing report rate are low: professional alarm software has a mode recognition function, so that the false alarm rate and the missing alarm rate are greatly reduced; the maintenance cost is low: long service life of optical cable, no damage by external force

The invention has the beneficial effects that:

1. real-time online deformation monitoring of the whole length of the tunnel is realized;

2. the monitoring precision is high, and early warning of large-scale accidental deformation of the tunnel can be realized;

3. the judgment of the deformation direction of the tunnel can be realized;

4. the intelligent degree is high, the abnormal condition can be accurately positioned, and the alarm by various means is realized;

5. intrusion monitoring in the tunnel is realized, and early warning and positioning can be carried out on the foreign matter falling track in real time;

6. the monitoring service life is long, and monitoring in the whole life cycle of the tunnel can be realized;

7. the maintenance cost is low, and the later period is nearly zero maintenance.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIGS. 1-3 are schematic diagrams of strain measurements for fiber optic distributed strain systems;

FIG. 4 is a linear relationship of Brillouin frequency shift and strain;

FIG. 5 illustrates the Rayleigh scattering principle of an optical fiber;

FIG. 6 is a schematic diagram of distributed optical fiber vibration monitoring;

FIG. 7 is a schematic view of an overall monitoring implementation;

FIG. 8 is a schematic diagram of distributed optical fiber strain monitoring;

FIG. 9 is a cable treatment at the varied gap;

fig. 10 is a diagram of an embodiment of an externally-laid fiber optic cable.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The application of the principles of the present invention will be further described with reference to the accompanying drawings and specific embodiments.