A temperature sensitive distributed optical cable and method for monitoring leakage in a tunnel

Abstract

The application discloses a temperature-sensitive distributed optical cable and method for monitoring tunnel leakage. The optical cable comprises a multi-mode optical fiber layer and a yarn cover layer, and the multi-mode optical fiber layer is located in the yarn cover layer. The multi-mode optical fiber layer comprises an encapsulation sheath, a first optical fiber and a second optical fiber, the first optical fiber and the second optical fiber are located in the encapsulation sheath, the core diameter to outer diameter ratio of the first optical fiber is different from that of the second optical fiber, and the yarn cover layer is made of a wet ball gauze. The monitoring method mainly comprises calculating the temperature difference between a monitoring point and an adjacent monitoring point, and when the temperature of the monitoring point and the adjacent monitoring point reaches a set threshold value, it is judged that there is a leakage point near the monitoring point. The distributed optical cable and the monitoring method realize distributed measurement of the tunnel leakage, improve the success rate and accuracy of the leakage monitoring, and effectively improve the missed detection problem existing in the FBG quasi-distributed measurement.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of distributed optical fiber sensing, and specifically relates to a temperature-sensitive distributed optical cable and method for monitoring tunnel leakage. BACKGROUND

[0002] Water seepage is the most common disease in the process of tunnel operation, and there is a saying in the tunnel industry that "nine out of ten tunnels are leaking". The harm of water seepage to tunnel operation mainly manifests in the following aspects: first, tunnel driving safety, long-term water seepage causes ground water, which deteriorates the driving environment and makes the vehicle prone to skidding; second, it affects the service life of the facilities in the tunnel, the tunnel is generally equipped with lighting, ventilation, monitoring and other mechanical and electrical systems, which are prone to rust in a humid environment, affecting the service life and posing the risk of electric leakage and short circuit; third, it affects the safety of tunnel lining, long-term water leakage can cause the lining structure to peel off and weather, reducing the reliability of the tunnel operation, and the strength and stability of the tunnel surrounding rock will decrease under long-term erosion. Therefore, the monitoring of water seepage during the operation of the tunnel is of great significance to the health of the tunnel structure.

[0003] The traditional tunnel monitoring method based on point type and electric measurement sensing principle has low reliability, poor durability, easy to miss detection and other problems, and the monitoring range is relatively limited, making it difficult to fully grasp the safety status of the tunnel. The distributed optical fiber sensing technology, which has developed rapidly in recent years, can well make up for the above shortcomings.

[0004] Distributed optical fiber sensing technology can measure the continuous distribution information of the measured physical quantity at any position along the sensing optical cable, with a maximum measurement length of tens to hundreds of kilometers, which is suitable for long-term real-time monitoring of various infrastructure, and can realize distributed monitoring of multiple parameters and multiple targets such as structure stress, strain, displacement, humidity and seepage.

[0005] There are many studies on monitoring strain using distributed optical cables, and various types of sensing optical cables have been developed according to engineering requirements, but there are few sensing optical cables specifically applied to tunnel water damage monitoring. Chinese patent application 201711009400.9 discloses a device and method for quasi-distributed real-time monitoring of pipeline leakage, which monitors pipeline leakage based on fiber Bragg grating (FBG) quasi-distributed optical fiber monitoring technology, and uses optical fiber sensing technology to solve the problem that small leakage cannot be retained, resulting in small temperature changes near the optical fiber that are difficult to detect. However, this method is quasi-distributed monitoring, and the monitoring range is limited, which may miss some information. In addition, this method needs to set up a fiber Bragg grating thermometer as a control group to judge the temperature difference caused by leakage, and when the leakage range is large, the thermometer may fail.

[0006] In summary, how to overcome the shortcomings of existing tunnel leakage monitoring technology is still an urgent task to be solved in the field. SUMMARY

[0007] The present application provides a temperature-sensitive distributed optical cable and method for monitoring tunnel leakage, which has the advantages of distributed measurement, easy installation, high sensitivity, strong reliability, anti-electromagnetic interference, good safety, etc.

[0008] The present application discloses a temperature-sensitive distributed optical cable and method for monitoring tunnel leakage, which monitors the temperature difference caused by water evaporation through distributed optical fiber temperature sensing technology (DTS). The technology is only sensitive to temperature and is not affected by other physical quantities, avoiding interference factors in the temperature measurement process and achieving high accuracy.

[0009] To achieve the above-mentioned application purposes, the present application adopts the following technical solutions:

[0010] A temperature-sensitive distributed optical cable for monitoring tunnel leakage, comprising a multi-mode optical fiber layer and a yarn sleeve layer, the multi-mode optical fiber layer being located in the yarn sleeve layer; the multi-mode optical fiber layer comprises an encapsulation sheath, a first optical fiber and a second optical fiber, the first optical fiber and the second optical fiber being located in the encapsulation sheath, the core diameter to outer diameter ratio of the first optical fiber being different from that of the second optical fiber; the yarn sleeve layer is made of wet ball gauze. The wet ball gauze has good water absorption and can effectively collect leakage water even in the case of small leakage. When the leakage stops, the wet ball gauze can be dried and the leakage monitoring can still be carried out, which has good repeatability.

[0011] Further, the core diameter to outer diameter ratio of the first optical fiber is 50 / 125 μm, and the core diameter to outer diameter ratio of the second optical fiber is 62.5 / 125 μm.

[0012] Further, a metal armored pipe is arranged between the multi-mode optical fiber layer and the yarn sleeve layer, and the metal armored pipe is sleeved on the multi-mode optical fiber layer.

[0013] Further, a Kevlar fiber mesh is arranged between the metal armored pipe and the yarn sleeve layer, and the Kevlar fiber mesh is fixed to the surface of the metal armored pipe by a wire mesh. The multi-mode optical fiber layer is placed in the armored pipe, which is wrapped with a wire mesh and a Kevlar fiber mesh, which improves the protection of the optical fiber and facilitates heat transfer.

[0014] Further, the weaving method of the yarn sleeve layer is one of tight wrapping and winding, the tight wrapping weaving method is to tightly wrap the wet ball gauze into a shaped sheath on the outermost layer of the temperature-sensitive distributed optical cable for monitoring tunnel leakage, and the winding weaving method is to tightly wind the strip-shaped wet ball gauze on the outermost layer of the temperature-sensitive distributed optical cable for monitoring tunnel leakage.

[0015] A method for monitoring tunnel leakage using the temperature-sensitive distributed optical cable for monitoring tunnel leakage described above, comprising the following steps:

[0016] 1) installing the temperature-sensitive distributed optical cable for monitoring tunnel leakage along the length direction of the tunnel on the inner surface of the tunnel;

[0017] 2) determining a plurality of monitoring points on the temperature-sensitive distributed optical cable for monitoring tunnel leakage using a distributed optical fiber temperature measurement system (DTS), and collecting and calculating the temperature at the monitoring points in real time;

[0018] 3) calculating the temperature difference between a monitoring point and an adjacent monitoring point, and when the temperature difference between a monitoring point and an adjacent monitoring point reaches a set threshold value, it is determined that there is leakage near the monitoring point.

[0019] Further, the process of collecting and calculating the temperature at the monitoring points is to obtain the temperature by analyzing the light intensity of the monitoring point cable, and the calculation formula is:

[0020]

[0021] where R(T) is a function of the temperature at the collection point, I F is the anti-Stokes light intensity, I S is the Stokes light intensity, v F is the Stokes light center frequency, c is the speed of light in vacuum, v is the Raman frequency shift, h is the Planck constant, K is the Boltzmann constant, and T is the absolute temperature.

[0022] Further, the calculation method of the temperature difference between a monitoring point and an adjacent monitoring point is:

[0023] 31) calculating the mass of water evaporation at a monitoring point, and the calculation formula is as follows:

[0024]

[0025] where M is the mass of water evaporation, E is the saturated water vapor pressure (hPa) corresponding to the temperature when the optical cable is wet, e is the actual water vapor pressure in the air (hPa), c is the water exchange coefficient between air and wet ball yarn, s is the evaporation area (cm 2 ), and p is the atmospheric pressure (hPa).

[0026] The heat consumed in this evaporation process is:

[0027]

[0028] where Q1 is the heat consumed in evaporation, and L is the latent heat of evaporation.

[0029] If the certain monitoring point is wetted, heat is transferred from the air to the wetted optical cable, and the transferred heat is expressed as:

[0030] Q2 = hs (T - T w ) (4)

[0031] In the formula, Q2 is the heat transferred from the air to the wetted optical cable, h is the heat exchange coefficient, T is the air temperature (i.e. the temperature of the adjacent non-wetted monitoring point), and T w is the temperature of the certain wetted monitoring point.

[0032] When the temperature of the wetted optical cable is stable, Q1 and Q2 are in equilibrium, and Q1 = Q2. By combining formula (3) and (4), we obtain:

[0033]

[0034] According to the principle of measuring air humidity by using a dry and wet bulb, a dry and wet bulb coefficient A is introduced (5) is simplified as:

[0035] e = E - Ap (T - T w ) (6)

[0036] The air humidity U is expressed as:

[0037]

[0038] In the formula, e w is the saturated water vapor pressure of the air (hPa).

[0039] The temperature difference Δt between the adjacent non-wetted monitoring point and the certain wetted monitoring point is obtained from formula (7):

[0040]

[0041] The dry and wet bulb coefficient A is calculated by using the fitting formula (9):

[0042]

[0043] Therefore, the temperature difference Δt is obtained:

[0044]

[0045] Further, the temperature-sensitive distributed optical cable for monitoring tunnel leakage is connected with a distributed optical fiber temperature measurement system (DTS), the real-time acquisition and calculation of the temperature at the monitoring point and the calculation of the temperature difference between a certain monitoring point and an adjacent monitoring point are completed by the distributed optical fiber temperature measurement system, and the results are displayed by the distributed optical fiber temperature measurement system.

[0046] Further, the temperature-sensitive distributed optical cable for monitoring tunnel leakage is arranged horizontally along the length direction of the tunnel and closely adheres to the inner wall of the tunnel.

[0047] The application discloses a temperature-sensitive distributed optical cable and method for monitoring tunnel leakage, realizes distributed measurement, effectively improves the easy-to-miss problem of FBG quasi-distributed measurement, and obtains data with better continuity in space. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 is a structure schematic diagram of a temperature-sensitive distributed optical cable for monitoring tunnel leakage provided by the application (with a tight wrapping yarn layer);

[0049] Figure 2 is a structure schematic diagram of a temperature-sensitive distributed optical cable for monitoring tunnel leakage provided by the application (with a winding yarn layer);

[0050] Figure 3 is a schematic diagram of cable laying in a tunnel in the monitoring method provided by the application;

[0051] Figure 4 is a schematic diagram of cable fixed-point laying in the monitoring method provided by the application;

[0052] Figure 5 is a schematic diagram of monitoring results in the embodiment of the application;

[0053] Figure 6 is a schematic diagram of a permeation area in the embodiment of the application. DETAILED DESCRIPTION

[0054] The temperature-sensitive distributed optical cable and method for monitoring tunnel leakage are described in detail below with reference to the drawings. In the description of the present application, it should be understood that the terms "left side", "right side", "upper part", "lower part", "bottom", and the like indicate the orientation or positional relationship shown in the drawings, and are only used for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and "A", "B", "C", and the like do not represent the importance of the parts, and therefore cannot be understood as limiting the present application; the specific dimensions used in the present embodiment are only used to illustrate the technical solutions and do not limit the protection scope of the present application.

[0055] As shown in Figure 1 , a temperature-sensitive distributed optical cable for monitoring tunnel leakage includes a multi-mode optical fiber layer and a yarn cover layer 1, and the multi-mode optical fiber layer is located in the yarn cover layer 1. The multi-mode optical fiber layer includes a packaging sheath 5, a first optical fiber 6 and a second optical fiber 7, and the first optical fiber 6 and the second optical fiber 7 are located in the packaging sheath 5. The core diameter to outer diameter ratio of the first optical fiber 6 is 50 / 125 μm, and the core diameter to outer diameter ratio of the second optical fiber 7 is 62.5 / 125 μm, so as to meet the requirements of different types of DTS demodulation equipment. The yarn cover layer 1 is made of wet ball gauze.

[0056] The weaving method of the yarn cover layer 1 is one of tight wrapping type or winding type. As shown in Figure 1 , the tight wrapping type weaving method is to tightly wrap the wet ball gauze into a shaped sheath on the outermost layer of the temperature-sensitive distributed optical cable for monitoring tunnel leakage. As shown in Figure 2 , the winding type weaving method is to tightly wind the strip-shaped wet ball gauze on the outermost layer of the temperature-sensitive distributed optical cable for monitoring tunnel leakage. Through experimental measurement, the two weaving methods have no obvious effect on the test effect of the present application.

[0057] Preferably, a metal armor pipe 4 is arranged between the multi-mode optical fiber layer and the yarn cover layer 1, and the metal armor pipe 4 is sleeved on the multi-mode optical fiber layer. A Kevlar fiber net 3 is arranged between the metal armor pipe 4 and the yarn cover layer 1, and the Kevlar fiber net 3 is double-helically wound by a metal wire winding net 2 and fixed to the surface of the metal armor pipe 4.

[0058] A method for monitoring tunnel leakage using the above-mentioned temperature-sensitive distributed optical cable for monitoring tunnel leakage includes the following steps:

[0059] 1) as shown in Figure 3 and 4As shown, the temperature-sensitive distributed optical cable for monitoring tunnel leakage is installed along the length direction of the tunnel on the inner surface of the tunnel; considering the movement track of the tunnel leakage water, the temperature-sensitive distributed optical cable for monitoring tunnel leakage is arranged along the horizontal direction and closely adheres to the inner wall of the tunnel. The distributed optical cable is arranged along the length direction of the tunnel at the tunnel arch foot or side wall, which can monitor the whole tunnel or can be arranged along the joint at the tunnel segment joint to monitor the leakage of the key part of the tunnel. When installed, the yarn cover layer made of wet ball gauze is in a dry state.

[0060] 2) Select several monitoring points on the temperature-sensitive distributed optical cable for monitoring tunnel leakage, and collect and calculate the temperature at the monitoring points in real time.

[0061] 3) Calculate the temperature difference between a monitoring point and an adjacent monitoring point, and when the temperature of a monitoring point and an adjacent monitoring point reaches a set threshold, it is judged that there is a leakage point near the monitoring point.

[0062] 4) Connect the temperature-sensitive distributed optical cable for monitoring tunnel leakage with the distributed optical fiber temperature measurement system (DTS), collect and calculate the temperature at the monitoring points in real time, and calculate the temperature difference between a monitoring point and an adjacent monitoring point by the distributed optical fiber temperature measurement system, and the result is displayed by the distributed optical fiber temperature measurement system. The distributed optical cable is not bent, the optical path is unobstructed, the connection with the distributed optical fiber temperature measurement system (DTS) is reliable, and the test signal has good signal-to-noise ratio.

[0063] The distributed optical fiber temperature sensing technology (DTS) is an optical fiber monitoring technology based on the principle of Raman scattering, which realizes continuous measurement of the temperature of any point along the optical fiber by combining optical time domain reflection technology (OTDR), and realizes distributed temperature measurement by detecting Raman scattered light in the optical fiber. When a pulse of a certain energy of pump light is injected into the optical fiber, photons collide with optical fiber molecules to produce sound waves, and inelastic collision between photons and phonons occurs Raman scattering, producing two components of different wavelengths, namely Stokes light and anti-Stokes light, the wavelength of the former is greater than that of the incident light, and the wavelength of the latter is less than that of the incident light. The DTS demodulator obtains the temperature information of the measurement point by analyzing the light intensity.

[0064] Specifically, the process of collecting and calculating the temperature at the monitoring point is to obtain the temperature by analyzing the light intensity of the monitoring point optical cable, and the calculation formula is:

[0065]

[0066] In the formula, R(T) is a function of the temperature of the collection point, I F is the anti-Stokes light intensity, I S is the Stokes light intensity, v Fwhere f0is the center frequency of the Stokes light, c is the speed of light in vacuum, v is the Raman shift, h is the Planck constant, K is the Boltzmann constant, and T is the absolute temperature.

[0067] The calculation process of the temperature difference between a monitoring point and an adjacent monitoring point is as follows:

[0068] 31) When the leaking water contacts the sensing optical cable, water evaporation occurs on the surface of the wetted wet bulb gauze, heat is taken away, a temperature difference is formed, and the evaporation mass of a monitoring point can be expressed by the Dalton law as follows:

[0069]

[0070] In the formula, M is the evaporation mass, E is the saturated water vapor pressure (hPa) corresponding to the temperature of the wetted optical cable, e is the actual water vapor pressure (hPa) in the air, c is the water exchange coefficient of the air and the wet bulb gauze, s is the evaporation area (cm 2 ), and p is the atmospheric pressure (hPa).

[0071] The heat consumed in the evaporation process is as follows:

[0072]

[0073] In the formula, Q1 is the heat consumed in the evaporation, and L is the latent heat of evaporation.

[0074] If the monitoring point is wetted, heat is transferred from the air to the wetted optical cable, and the transferred heat is expressed as follows:

[0075] Q2 = hs (T - T w ) (4)

[0076] In the formula, Q2 is the heat transferred from the air to the wetted optical cable, h is the heat exchange coefficient, T is the air temperature (i.e., the temperature of an adjacent non-wetted monitoring point), and T w is the temperature of the wetted monitoring point.

[0077] When the temperature of the wetted optical cable is stable, Q1 and Q2 are in equilibrium, and Q1 = Q2, and formula (3) and (4) are combined to obtain:

[0078]

[0079] According to the principle of measuring air humidity by using a dry and wet bulb, a dry and wet bulb coefficient (5) is simplified as:

[0080] e = E - Ap (T - T w ) (6)

[0081] The air humidity U is expressed as:

[0082]

[0083] In the formula, e w Saturation vapor pressure of air (hPa).

[0084] The temperature difference Δt between the adjacent non-wetted monitoring point and the certain wetted monitoring point is obtained from formula (7) :

[0085]

[0086] The dry-wet ball coefficient A is calculated by using the fitting formula (9) :

[0087]

[0088] Therefore, the temperature difference Δt is obtained:

[0089]

[0090] Formula (9) only considers the air flow rate flowing through the surface of the wetted part, i.e. the surface of the wet ball gauze, and does not consider the influence of the ambient temperature (the temperature T of the non-wetted optical cable), so there is a certain error. Under the conditions of the comprehensive ambient temperature and the air flow rate, part of the measured results of the dry-wet ball coefficient A are shown in Table 1:

[0091] Table 1 Relationship between wind speed, temperature and dry-wet ball coefficient

[0092]

[0093]

[0094] The effect of the temperature-sensitive distributed optical cable and method for monitoring tunnel leakage disclosed in the present application is tested through experiments, and the specific process is as follows:

[0095] The performance of the distributed optical cable of the present application in different leakage speeds and reusability is tested respectively.

[0096] Two working conditions of fast and slow leakage are set in the leakage speed, and the test process is defined: the flow rate is 90-100 ml / min when the fast leakage is performed, and the flow rate is 5-20 ml / min when the slow leakage is performed. The maximum temperature difference and the temperature drop rate under the two working conditions are shown in Table 2:

[0097] Table 2 Maximum temperature difference and temperature drop rate of the temperature-sensitive distributed optical cable for monitoring tunnel leakage under different leakage speeds

[0098]

[0099] For the distributed optical cable of the application, the leakage rate has little effect on its monitoring performance. In the same test, fast leakage and slow leakage have no obvious effect on the maximum temperature difference and cooling rate, proving the accuracy of the optical cable in monitoring small leakage.

[0100] The distributed optical cable of the application still shows good monitoring performance after five wet-dry cycles. The temperature difference at the leakage point is obvious, as shown in Table 3, and the maximum temperature difference and cooling rate monitored by the optical cable are obvious, proving that the new sensing optical cable has good reusability.

[0101] Table 3 Maximum temperature difference and cooling rate of temperature-sensitive distributed optical cable for monitoring tunnel leakage under reuse

[0102]

[0103] When a leakage event occurs, the temperature of the part of the optical cable that is wetted due to leakage is relatively low compared to the part that is not wetted. The temperature distribution at each point on the optical cable is shown in Figure 5 According to the temperature difference calculation formula (8), the temperature difference of any monitoring point of the sensing optical cable at a certain sampling time is calculated according to formula (11):

[0104]

[0105] In the formula, i is the number of monitoring points; t is the sampling time; is the average value of the temperature change in the range of 5 times the DTS spatial resolution length before and after the monitoring point i.

[0106] The distribution of temperature differences of typical adjacent monitoring points is shown in Figure 6 When the temperature difference reaches a certain threshold and above, for this embodiment, the temperature difference threshold is -0.5℃, it can be judged that the monitoring point is the most or the leakage area.

[0107] Extract the time series of the temperature of each sampling point in the most or the leakage area, and calculate the cooling rate. When the cooling rate reaches a certain threshold, for this embodiment, the cooling rate threshold is -0.4℃ / h, it is considered that the tunnel has leakage. The test data is shown in Tables 2 and 3.

[0108] Through repeated test verification, the distributed optical fiber and monitoring method of the application have achieved good monitoring effect.

[0109] The test of this embodiment was carried out under the condition that the environmental humidity was 90% and the indoor temperature was about 21℃. The saturated vapor pressure at the corresponding temperature was brought into formula (8), and the actual dry-wet bulb coefficient A in Table 1 was combined for calculation, and the results are shown in Table 4:

[0110] Table 4 Comparison of theoretical calculation value and actual value

[0111]

[0112] The actual temperature difference in the experiment is 1 DEG C, the corresponding theoretical calculation value and the actual temperature difference have higher fitting degrees under the conditions of cases 4, 5 and 6 close to the experimental temperature, and it is proved that the distributed optical fiber and the monitoring method have good practicability.

[0113] Based on the description of the preferred embodiments of the present application, it should be clear that the present application defined by the appended claims is not restricted to the specific details described herein, but embraces any and all modifications within the scope of the present application.

Claims

1. A method for monitoring tunnel leakage by using a temperature-sensitive distributed optical cable for monitoring tunnel leakage, comprising the following steps: 1) installing the temperature-sensitive distributed optical cable for monitoring tunnel leakage on the inner surface of the tunnel along the length direction of the tunnel; 2) collecting and calculating the temperature at the monitoring points in real time by selecting a plurality of monitoring points on the temperature-sensitive distributed optical cable for monitoring tunnel leakage; 3) calculating the temperature difference between a certain monitoring point and an adjacent monitoring point, and determining that there is leakage near the monitoring point when the temperature difference between the certain monitoring point and the adjacent monitoring point reaches a set threshold value; The process of collecting and calculating the temperature at the monitoring points is to obtain the temperature by analyzing the light intensity of the optical cable at the monitoring points, and the calculation formula is: where R(T) is a function of the temperature of the collection point, I F is the anti-Stokes intensity, I S is the Stokes intensity, v F is the Stokes central frequency, c is the speed of light in vacuum, v is the Raman shift, h is the Planck constant, K is the Boltzmann constant, and T is the absolute temperature; The process of calculating the temperature difference between a certain monitoring point and an adjacent monitoring point is: 31) calculating the mass of water evaporation at a certain monitoring point, and the calculation formula is as follows: Wherein, M is the mass of water evaporation, E is the saturated water vapor pressure corresponding to the temperature when the optical cable is wet, e is the actual water vapor pressure in the air, c is the water exchange coefficient of the air and the wet ball gauze, s is the evaporation area, and p is the atmospheric pressure; The heat consumed in the evaporation process is: Wherein, Q1 is the heat consumed in the evaporation, and L is the latent heat of evaporation; If the certain monitoring point is wet, the heat is transferred from the air to the wet optical cable, and the transferred heat is represented as: Q2 = hs(T-T W ) (4) where Q2 is the heat transferred from the air to the wetted optical cable, h is the heat exchange coefficient, T is the air temperature, i.e. the temperature of the adjacent non-wetted monitoring point; T w is the temperature of the certain wetted monitoring point. When the temperature of the wet optical cable stabilizes, Q1 and Q2 are in equilibrium, and Q1=Q2, and the formulas (3) and (4) are combined to obtain: According to the principle of measuring air humidity by dry and wet bulb, the dry and wet bulb coefficient is introduced (5) is abbreviated as: e = E - Ap(T - T w ) (6) The air humidity U is represented as: wherein e w the saturated water vapor pressure for air; The temperature difference Δt between the adjacent non-wet monitoring point and the certain wet monitoring point is obtained from formula (7): The dry and wet ball coefficient A is calculated by using the fitting formula (9): Therefore, the temperature difference Δt is obtained: The temperature-sensitive distributed optical cable for monitoring tunnel leakage comprises a multi-mode optical fiber layer and a gauze layer, the multi-mode optical fiber layer is located in the gauze layer; the multi-mode optical fiber layer comprises a packaging sheath, a first optical fiber and a second optical fiber, the first optical fiber and the second optical fiber are located in the packaging sheath, the core diameter to outer diameter ratio of the first optical fiber is different from that of the second optical fiber; the gauze layer is made of wet ball gauze; The core diameter to outer diameter ratio of the first optical fiber is 50 / 125 μm, and the core diameter to outer diameter ratio of the second optical fiber is 62.5 / 125 μm; A metal armored pipe is arranged between the multi-mode optical fiber layer and the gauze layer, and the metal armored pipe is sleeved on the multi-mode optical fiber layer; A Kevlar fiber net is arranged between the metal armored pipe and the gauze layer, and the Kevlar fiber net is fixed on the surface of the metal armored pipe by a metal wire winding net; The weaving method of the gauze layer is one of a tight package type and a winding type, the tight package type weaving method is to tightly package the wet ball gauze into a shaped sheath on the outermost layer of the temperature-sensitive distributed optical cable for monitoring tunnel leakage, and the winding type weaving method is to tightly wind the strip-shaped wet ball gauze on the outermost layer of the temperature-sensitive distributed optical cable for monitoring tunnel leakage.

2. The monitoring method according to claim 1, characterized in that, The temperature-sensitive distributed optical cable for monitoring tunnel leakage is connected with a distributed optical fiber temperature measurement system, and the distributed optical fiber temperature measurement system is used to collect and calculate the temperature at the monitoring point and the temperature difference between the monitoring point and the adjacent monitoring point in real time, and the result is displayed by the distributed optical fiber temperature measurement system.

3. The monitoring method of claim 1, wherein, The temperature-sensitive distributed optical cable for monitoring tunnel leakage is arranged horizontally along the length direction of the tunnel and closely adheres to the inner wall of the tunnel.

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