A geotechnical body leakage monitoring optical cable, monitoring system and monitoring method

Abstract

The present application relates to geotechnical engineering monitoring technical field, especially point to a kind of geotechnical body leakage monitoring optical cable, monitoring system and monitoring method.The geotechnical body leakage monitoring optical cable includes from inside to outside: optical fiber;Loose cover protection layer, surrounds optical fiber;Heating resistance wire, surrounds loose cover protection layer;Inner layer insulation sheath, surrounds heating resistance wire;Wire, surrounds inner layer insulation sheath;Outer layer insulation sheath, surrounds wire;Percolation sleeve, surrounds outer layer insulation sheath and forms gap between outer layer insulation sheath, percolation sleeve is provided with multiple percolation holes that pass through pipe wall;Wherein, the gap between percolation sleeve and outer layer insulation sheath is provided with multiple water-blocking pads that separate the gap into multiple independent spaces.The present application realizes the integrated design of mechanical protection, accurate heating, insulation isolation and seepage control by composite structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnical engineering monitoring, in particular to a geotechnical body leakage monitoring optical cable based on active heating method, a monitoring system and a monitoring method. BACKGROUND

[0002] The problem of geotechnical body leakage has been a major safety hazard commonly existing in water conservancy projects, underground buildings and karst areas. For example, dam foundation leakage may cause dam landslide or even collapse, soil and water loss in karst areas may cause loss of arable land, and underground engineering leakage may cause waterlogging. Therefore, the identification and early warning of geotechnical body leakage are very important.

[0003] At present, the traditional leakage monitoring technologies mainly include manual visual inspection method, water pressure test method, infrared thermal imaging method, chemical tracer method and osmometer method. These monitoring technologies have problems such as high hysteresis and insufficient spatial resolution, and it is difficult to realize real-time distributed leakage monitoring of geotechnical body.

[0004] Optical fiber monitoring technology has unique advantages such as small size, low cost, high temperature resistance, anti-electromagnetic interference, good durability, distributed and real-time measurement. Combined with the change of temperature field to indirectly reflect the seepage state, it has a wide application prospect. However, the natural temperature field is easily disturbed by seasons, which may cause misjudgment of leakage.

[0005] Therefore, in order to solve the above problems, the Chinese patent application with publication number CN1632496A discloses a dam leakage positioning distributed temperature sensing monitoring device and method. An insulating heating conductor is added to the optical cable structure. The sensing optical cable is heated by the heating device, so that the sensing optical cable and the leakage water reach a certain temperature difference to identify the position of the leakage water. The Chinese patent application with publication number CN105606315A discloses a distributed optical fiber sensing technology scheme and system for monitoring the leakage of a face slab dam. The optical and electrical composite cable is strengthened to greatly strengthen the temperature anomaly signal generated by leakage, thereby ensuring the reliability of leakage diagnosis.

[0006] The above-mentioned prior art is to artificially create a temperature gradient by actively heating the optical fiber to enhance the leakage identification effect. However, since the actively heated optical fiber is directly buried in the geotechnical body, it is affected by the thermal conductivity and water content of the geotechnical body. During the heating process in the saturated geotechnical body, the heat dissipation is relatively large, the temperature rise difference between the optical fiber in the non-seepage area and the leakage area is small, and it is still difficult to effectively identify the low leakage rate in the saturated geotechnical body.

[0007] Therefore, how to provide a geotechnical body leakage monitoring optical cable based on active heating method, effectively reduce the heat dissipation of the directly buried heating optical cable in the saturated geotechnical body, isolate the interference of the water content change of the geotechnical body, and adapt to complex environments such as saturated geotechnical body and low leakage rate is a problem that needs to be solved by those skilled in the art. SUMMARY

[0008] In view of the deficiencies of the prior art, the present application discloses a rock-soil body leakage monitoring optical cable, a monitoring system and a monitoring method.

[0009] The technical solutions adopted by the present application are as follows:

[0010] In a first aspect, a rock-soil body leakage monitoring optical cable is provided, which comprises, from inside to outside:

[0011] an optical fiber;

[0012] a loose tube protection layer surrounding the optical fiber;

[0013] a heating resistance wire surrounding the loose tube protection layer

[0014] an inner layer insulation sheath surrounding the heating resistance wire;

[0015] a wire surrounding the inner layer insulation sheath;

[0016] an outer layer insulation sheath surrounding the wire;

[0017] a percolation sleeve surrounding the outer layer insulation sheath and forming a gap between the outer layer insulation sheath, the percolation sleeve being provided with a plurality of percolation holes penetrating the wall thereof;

[0018] wherein the gap between the percolation sleeve and the outer layer insulation sheath is provided with a plurality of water-blocking pads separating the gap into a plurality of independent spaces.

[0019] In an embodiment of the present application, the diameter of the percolation hole is 1.5mm-3mm.

[0020] In an embodiment of the present application, the water-blocking pad is made of fluororubber material and is radially used to block the diffusion of leakage water in the gap along the axial direction of the rock-soil body leakage monitoring optical cable.

[0021] In an embodiment of the present application, a plurality of the water-blocking pads are uniformly arranged along the axial direction of the rock-soil body leakage monitoring optical cable.

[0022] In an embodiment of the present application, the heating resistance wire is woven into a net to wrap the loose tube protection layer.

[0023] In an embodiment of the present application, the wire is woven into a net to wrap the inner layer insulation sheath.

[0024] In an embodiment of the present application, the inner layer insulation sheath and / or the outer layer insulation sheath is made of polyethylene material.

[0025] In an embodiment of the present application, the radial thickness of the gap is 10mm-15mm.

[0026] In a second aspect, a geotechnical body leakage monitoring system is provided, comprising:

[0027] The geotechnical body leakage monitoring optical cable described above is used to be buried in a geotechnical body to be monitored.

[0028] A thermal pulse generator is connected to one end of the geotechnical body leakage monitoring optical cable, and is configured to inject a periodic pulse signal to the heating resistance wire of the geotechnical body leakage monitoring optical cable to heat the optical fiber of the geotechnical body leakage monitoring optical cable.

[0029] A distributed optical fiber temperature demodulator is connected to the optical fiber of the geotechnical body leakage monitoring optical cable, and is configured to demodulate and collect temperature data of each section of the optical fiber.

[0030] In a third aspect, a geotechnical body leakage monitoring method is provided, which utilizes the geotechnical body leakage monitoring system described above and comprises the following steps:

[0031] S1. The geotechnical body leakage monitoring optical cable described above is buried in a geotechnical body to be monitored.

[0032] S2. The heating resistance wire of the optical cable is powered to heat the optical fiber of the optical cable.

[0033] S3. Temperature values of each section of the optical fiber are collected, and the temperature values of each section of the optical fiber are compared. If the temperature value of a section or some sections is lower than that of other sections and the difference is greater than a preset value, it is determined that leakage exists in the section or the sections.

[0034] The above technical solutions of the present application have the following advantages compared with the prior art:

[0035] The geotechnical body leakage monitoring optical cable described in the present application realizes the integrated design of mechanical protection, precise heating, insulation isolation and seepage control through the composite structure of "optical fiber-mild protective layer-heating resistance wire-double-layer insulation sheath-micro-porous filtration sleeve".

[0036] The gap formed between the micro-porous filtration sleeve and the outer insulation sheath allows heat to accumulate, significantly reducing heat conduction loss to the geotechnical body, significantly increasing the background temperature rise to 10℃, while the leakage temperature rise is only 3℃, forming a temperature difference threshold of 7℃, greatly enhancing the signal-to-noise ratio, allowing the identification of small leaks, amplifying the temperature difference signal in the seepage area, and improving the temperature response sensitivity. The micro-porous structure of the micro-porous filtration sleeve and the design of the water-blocking pad allow only seepage water to enter, effectively avoiding the interference of static water to reduce the background temperature rise due to changes in the water content of the geotechnical body, while blocking the lateral diffusion of seepage water in the cavity, avoiding distortion of the background temperature rise, reducing the misjudgment rate, and being suitable for saturated geotechnical bodies and low leakage rate environments. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to make the content of the present application more easily understood, the present application is further described in detail below according to specific embodiments of the present application and in conjunction with the accompanying drawings.

[0038] Figure 1 is a schematic diagram of the geotechnical body leakage monitoring optical cable in the present application.

[0039] Figure 2 is Figure 1 a sectional view at A-A in the present application.

[0040] Figure 3 is Figure 1 a sectional view at B-B in the present application.

[0041] Figure 4 is a schematic diagram of the geotechnical body leakage monitoring system in the present application.

[0042] Figure 5 is a temperature curve of the soil body leakage measured by the leakage monitoring system in the present application.

[0043] Figure 6 is a temperature curve of the soil body leakage measured by the leakage monitoring system in the comparative example.

[0044] Explanation of the reference signs in the drawings:

[0045] 1. Geotechnical body leakage monitoring optical cable; 11. Optical fiber; 12. Protective layer; 13. Heating resistance wire; 14. Inner layer insulation sheath; 15. Lead wire; 16. Outer layer insulation sheath; 17. Microporous percolation sleeve; 18. Water-blocking pad;

[0046] 2. Distributed optical fiber temperature demodulator;

[0047] 3. Thermal pulse generator;

[0048] 4. Soil body model; 41. Soil body leakage area; 42. Soil body non-leakage area;

[0049] 5. Peristaltic pump; 51. Connection pipe. DETAILED DESCRIPTION

[0050] The present application is further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it.

[0051] EMBODIMENT

[0052] In the prior art, the geotechnical body leakage monitoring technology has long been faced with the problem of serious heat dissipation in the saturated geotechnical body. The traditional active heating optical fiber is directly buried in the geotechnical body. Due to the influence of the thermal conductivity and water content of the geotechnical body, the heat quickly spreads during the heating process, resulting in weak temperature rise difference between the non-leakage area and the leakage area, and it is difficult to effectively identify the leakage position, especially under the condition of low leakage rate. For example, in the dam foundation leakage or underground building water seepage scenarios in water conservancy engineering, the prior art cannot accurately capture the small seepage signal, causing monitoring lag or misjudgment.

[0053] In order to solve the above problems, it is necessary to design a structure that can gather heat and accelerate heat dissipation in the leakage area. By analyzing the heat transfer path, if a controllable seepage channel is formed outside the optical cable, the heat can be quickly taken away by the leakage water, which can enhance the temperature difference signal. Further considering the interference of the water content change of the geotechnical body on the temperature field, an isolation layer needs to be arranged in the optical cable structure to stabilize the thermal environment. Based on this, a sleeve structure with a percolation function is constructed outside the optical cable, and a gap is formed inside to accommodate the leakage water, while the water flow is limited from spreading laterally through a water-blocking structure, thereby forming a significant temperature difference in the leakage area.

[0054] Therefore, in combination Figures 1 to 3 The present embodiment proposes a geotechnical body leakage monitoring optical cable 1 comprising, from the inside out, an optical fiber 11, a loose sleeve protective layer 12, a heating resistance wire 13, an inner layer insulation sheath 14, a lead wire 15, an outer layer insulation sheath 16, and a microporous percolation sleeve 17. A gap is formed between the microporous percolation sleeve 17 and the outer layer insulation sheath 16. The percolation sleeve 17 is provided with a plurality of percolation holes penetrating the wall. A plurality of water-blocking pads 18 are arranged in the gap between the percolation sleeve 17 and the outer layer insulation sheath 16 to divide the gap into a plurality of independent spaces.

[0055] The optical fiber 11 adopts a distributed optical fiber temperature sensing technology based on Raman scattering effect, which is used to collect temperature data and transmit data to a distributed optical fiber temperature demodulator 2.

[0056] The loose sleeve protective layer 12 refers to a buffer structure wrapping the optical fiber 11, which can be implemented by a spiral-wound loose sleeve, and is used to protect the optical fiber 11 from mechanical stress.

[0057] The heating resistance wire 13 refers to a conductive material, such as nickel-chromium alloy wire, woven into a mesh structure around the loose-tube protective layer 12. This mesh structure converts electrical energy into heat energy and evenly transfers it to the optical fiber 11. Specifically, the surface of the loose-tube protective layer 12 is completely covered by the mesh heating resistance wire layer 13. When energized, the heating resistance wire 13 forms evenly distributed heating points through the mesh nodes, and the heat is conducted along the surface of the loose-tube protective layer 12 to the optical fiber 11. Because the heating resistance wire 13 wraps the loose-tube protective layer 12 in a mesh structure, heat can be evenly diffused during heating, preventing localized overheating that could damage the optical fiber 11, while also improving heating efficiency. For example, the mesh density of the heating resistance wire 13 can be adjusted according to actual needs, such as using a weaving density of 5 to 10 cross nodes per square centimeter to make the heat distribution more uniform.

[0058] The inner insulating sheath 14 and the outer insulating sheath 16 refer to the insulating layers that respectively cover the heating resistance wire 13 and the conductor 15. For example, they are made of extruded polyethylene material and are used to prevent current leakage and maintain a stable thermal field. Specifically, after the inner insulating sheath 14 wraps the heating resistance wire 13, the low thermal conductivity of its polyethylene material slows down the diffusion of heat towards the conductor 15, concentrating heat around the optical fiber 11 to form a stable temperature field. When the outer insulating sheath 16 wraps the conductor 15, the water resistance of polyethylene prevents external leakage water from penetrating to the surface of the conductor 15, avoiding resistance changes caused by conductor moisture. When the two sheaths work together, the mechanical strength of the polyethylene can withstand the extrusion deformation of the soil and rock, maintaining the stability of the gap structure, thereby ensuring the directional flow of leakage water within the gap between the microporous filter sleeve 17 and the outer insulating sheath 16.

[0059] The conductor 15 is wrapped with a copper wire mesh to form an inner insulating sheath 14. The copper wire mesh refers to a mesh structure formed by multiple copper wires using a braiding process, specifically cross-weaving or spiral winding. This structure increases the conductor's surface area and mechanical strength. Wrapping the inner insulating sheath 14 involves tightly adhering the braided copper wire mesh to the outer surface of the inner insulating sheath 14. This arrangement ensures uniform current distribution and enhances structural stability. Specifically, the copper wire mesh increases the conductor's surface area, reducing resistance and allowing the Joule heat generated during current transmission to diffuse more evenly to the inner insulating sheath 14. After the inner insulating sheath 14 is wrapped with the copper wire mesh, a continuous conductive layer is formed on its outer surface, facilitating lateral heat conduction. When a thermal pulse signal is applied to the conductor 15, the mesh structure of the copper wire mesh prevents localized overheating and accelerates heat transfer to the optical fiber region by increasing the contact area.

[0060] Microporous permeation sleeve 17 refers to a tubular structure with through holes on its surface, such as one prepared by laser drilling, used to allow seepage water to enter the gaps while filtering soil and rock particles.

[0061] The water-blocking pad 18 refers to a sealing material attached to the surface of the micro-porous percolation sleeve 17, such as a fluororubber strip, which is implemented through annular wrapping or segmented fitting, to block the lateral flow of seepage water along the gap. The fluororubber material refers to a synthetic rubber formed by copolymerization of vinylidene fluoride, hexafluoropropylene, or tetrafluoroethylene monomers, which can be implemented using a vulcanization molding process, and has high temperature resistance, chemical corrosion resistance, and low compression permanent deformation characteristics. Specifically, when seepage water enters the gap through the micro-porous percolation sleeve 17, the water-blocking pad 18 forms a physical barrier through its hydrophobic properties and elastic deformation capability, forcing the seepage water to only accumulate in the local area between adjacent two water-blocking pads 18. This segmented barrier design prevents seepage water from freely diffusing along the axial direction of the optical cable, thereby forming independent and clearly bounded temperature response intervals between the seepage area and the adjacent non-seepage area. For example, during the heat pulse heating process, the seepage area has a reduced temperature rise due to the heat carried away by the water flow, while the non-seepage area maintains a normal temperature rise, and the water-blocking pad 18 differentiates the contrast of the temperature signal by limiting the heat transfer path.

[0062] The present embodiment further proposes that the diameter of the percolation hole is between 1.5 mm and 3 mm. The percolation hole refers to a through-hole that penetrates the wall of the micro-porous percolation sleeve 17, which can be implemented using a laser drilling or mechanical punching process, and the hole diameter range is designed to allow seepage water to flow into the gap but block sand particles from entering.

[0063] The diameter range of the percolation hole refers to the size of the hole being controlled within a specific interval, for example, it can be between 1.5 mm and 3 mm, which can be achieved by adjusting the processing parameters. This range ensures effective percolation of seepage water while avoiding sand blockage due to excessively large hole diameter or excessively high seepage resistance due to excessively small hole diameter.

[0064] Specifically, the micro-porous percolation sleeve 17 is provided with multiple percolation holes, allowing seepage water in the soil to enter the gap between the micro-porous percolation sleeve 17 and the outer insulating sheath 16 through the holes. The diameter range of the percolation hole is optimized to allow water to flow into the gap at a controllable rate and effectively filter sand particles to prevent the gap from being blocked. When seepage water enters the gap, it exchanges heat with the heat generated by the heating resistance wire 13, causing a significant difference in temperature between the seepage area and the non-seepage area. By controlling the hole diameter range, the sensitivity of the leakage detection and the anti-blocking performance can be balanced to ensure stable collection of the leakage signal.

[0065] The present embodiment further proposes that multiple water-blocking pads 18 are uniformly arranged along the axial direction of the rock-soil leakage monitoring optical cable. Uniform arrangement refers to the water-blocking pads 18 being distributed at fixed intervals on the surface of the micro-porous percolation sleeve 17, which can be implemented using equidistant segmentation, for example, one water-blocking pad 18 is set every certain distance, thereby dividing the rock-soil leakage monitoring optical cable 1 into multiple independent monitoring units, each unit only reflects the leakage status of the corresponding area.

[0066] This embodiment further proposes that a gap of 10mm-15mm be formed between the microporous permeation sleeve 17 and the outer insulating sheath 16.

[0067] The gap refers to the annular space reserved between the microporous permeation sleeve 17 and the outer insulating sheath 16. This space can be adjusted by changing the difference between the inner diameter of the microporous permeation sleeve 17 and the outer diameter of the outer insulating sheath 16. This gap is designed to accommodate the inflow of leaking water while preventing excessive heat loss due to an excessively large space. The gap size is limited to 10mm-15mm. This size range balances the inflow rate of leaking water with the heat retention requirements. If the gap is too small, it may hinder the entry of leaking water; if the gap is too large, heat will be rapidly lost through air convection.

[0068] Specifically, the gap between the microporous permeation sleeve 17 and the outer insulating sheath 16 is designed as a channel for the accumulation of leaking water. When leaking water enters the gap through the permeation holes of the microporous permeation sleeve 17, the size of the gap ensures that the leaking water accumulates within a limited space, while simultaneously limiting heat convection loss caused by airflow within the gap. During active heating, the leaking water within the gap interacts with the heat generated by the heating resistance wire 13, resulting in a significantly lower temperature rise in the leaking area compared to the non-leaking area due to the thermal conductivity of the water. The size of the gap is optimized to allow a sufficient amount of leaking water to flow in and form a temperature difference signal, while avoiding excessive heat loss due to an excessively large gap, which would weaken the temperature difference contrast.

[0069] like Figure 4 As shown, this embodiment also provides a soil and rock leakage monitoring system, including a soil model 4, a soil and rock leakage monitoring optical cable 1, a peristaltic pump 5, a thermal pulse generator 3, and a distributed fiber optic temperature demodulator 2. The soil and rock leakage monitoring optical cable 1 is buried within the soil model 4 along its length, and the soil model 4 is filled with sand. The peristaltic pump 5 is connected to the soil model 4 via a connecting pipe 51, used to simulate seepage water flow into the soil model 4, forming a soil leakage zone 41 and a soil non-leakage zone 42. The thermal pulse generator 3 is connected to one end of the soil and rock leakage monitoring optical cable 1, used to inject periodic pulse signals into the heating resistance wire 13 of the soil and rock leakage monitoring optical cable 1, actively heating the optical fiber 11. The distributed fiber optic temperature demodulator 2 is connected to the optical fiber of the soil and rock leakage monitoring optical cable 1, used to demodulate and collect temperature data from each section of the data optical fiber 11.

[0070] Among them, soil model 4 refers to the experimental device used to simulate the actual seepage environment of soil and rock. Specifically, it can be realized by using a transparent plexiglass box or tank, which is filled with sand to simulate real geological conditions.

[0071] The peristaltic pump 5 refers to a device for controlling the input of water flow, which can be implemented by a micro pump with adjustable flow rate, and injects water flow into the soil model 4 through the connecting pipe 51 to simulate the seepage process.

[0072] The thermal pulse generator 3 refers to a device that periodically outputs electrical signals, which can be implemented by a pulse width modulation circuit, and generates thermal pulses by applying current to the heating resistance wire 13 to cause changes in the temperature field of the optical fiber 11.

[0073] The distributed optical fiber temperature demodulator 2 locates and analyzes the low-frequency Stokes light and high-frequency anti-Stokes light. The intensity ratio of the two can realize temperature field analysis, and the analysis formula is: ; in the formula, is a function of the temperature to be measured; is the anti-Stokes light intensity, is the anti-Stokes light frequency; is the Stokes light intensity, is the Stokes light frequency; c is the speed of light; V is the Raman shift amount; h is the Planck constant; K is the Boltzmann constant; T is the absolute temperature. The distributed optical fiber temperature demodulator 2 transmits temperature data in real time to the monitoring system through Ethernet or 4 / 5G signals, and establishes a temperature field space-time distribution model along the rock-soil seepage monitoring optical cable 1.

[0074] Specifically, after the rock-soil seepage monitoring optical cable 1 is buried in the soil model 4, the sand filling makes the rock-soil seepage monitoring optical cable 1 in close contact with the surrounding medium. The peristaltic pump 5 injects water flow into the soil model 4 through the connecting pipe 51 to simulate the seepage process, so that the soil model 4 is divided into a soil seepage area 41 and a soil non-seepage area 42. The thermal pulse generator 3 periodically drives the heating resistance wire 13 to generate heat, and the temperature field of the optical fiber 11 forms a temperature rise background under the action of conduction and convection. When the seepage water enters the gap through the micro-porous filtration sleeve 17, the heat is quickly dissipated, resulting in a significant lower temperature rise of the optical fiber 11 in the soil seepage area 41 than in the soil non-seepage area 42. The distributed optical fiber temperature demodulator 2 identifies the area with a temperature rise lower than the set threshold by analyzing the temperature difference, thereby locating the seepage position.

[0075] In some specific embodiments, the size of the soil model 4 can be adjusted according to experimental requirements, for example, a box structure with a length of 2 meters, a width of 0.5 meters, and a height of 1 meter can be used. The sand filling density can be controlled by layer-by-layer compaction, for example, each layer has a thickness of 10 centimeters and a compaction degree of more than 90%. The flow rate of the peristaltic pump 5 can be set to 10 to 100 milliliters per minute to simulate different seepage rates. The pulse period of the thermal pulse generator 3 can be set to 15 to 20 minutes, and the current intensity can be adjusted to 0.1 to 15 amperes. The sampling interval of the distributed optical fiber temperature demodulator 2 can be configured to 0.4 to 1 meter, and the temperature resolution can reach 0.1 degrees Celsius.

[0076] The working principle of the embodiment is as follows:

[0077] S1, the geotechnical body leakage monitoring optical cable 1 is buried in the soil body model 4, and the sand is filled; the optical fiber 11 of the geotechnical body leakage monitoring optical cable 1 is connected to the distributed optical fiber temperature demodulator 2; the heating resistance wire 13 of the geotechnical body leakage monitoring optical cable 1 is connected to the thermal pulse generator 3;

[0078] S2, the peristaltic pump 5 simulates the leakage water flow into the soil body model 4, forming the soil body leakage area 41 and the soil body non-leakage area 42; the periodic pulse signal is injected to the heating resistance wire 13 through the thermal pulse generator 3, and the optical fiber 11 is actively heated; the temperature field in the vicinity of the optical fiber is generated by the conduction and convection, and the background temperature rise is formed; the leakage water flows into the gap through the microporous filtration sleeve 17, and the heat accumulated in the gap is rapidly dissipated, so that the temperature rise value of the geotechnical body leakage monitoring optical cable 1 in the soil body leakage area 41 is significantly reduced, and a significant temperature difference is formed between the geotechnical body leakage monitoring optical cable 1 in the soil body non-leakage area 42;

[0079] S3, the leakage identification preset value which has a significant difference with the background temperature rise is set, if the temperature value of a certain or some sections is lower than that of other sections and the difference is greater than the preset value, it is judged that there is leakage in the section or the sections, then the leakage signal is determined, so that the leakage signal is identified from the background temperature rise to determine the position and range of the leakage.

[0080] It should be noted that, since the geotechnical body leakage monitoring optical cable 1 provided by the embodiment adopts the microporous filtration sleeve 17, there is a gap in the geotechnical body leakage monitoring optical cable 1, and the heat generated by the heating of the geotechnical body leakage monitoring optical cable 1 is accumulated in the gap, greatly reducing the heat conduction loss of the geotechnical body leakage monitoring optical cable 1 to the geotechnical body, as shown in Figure 5 , the background temperature rise is significantly improved, up to 10℃. When the leakage occurs, the leakage water flows through the optical cable, and the temperature field of the soil body leakage area 41 produces abnormal temperature rise due to the convection, that is, the leakage signal, which is usually less than 3℃, and has a significant difference with the background temperature rise value of 10℃. The monitoring system sets the leakage identification threshold value to 3℃, and when the temperature rise value is less than 3℃, it is determined that the leakage signal is determined, so that the leakage signal is identified from the background temperature rise to determine the position and range of the leakage.

[0081] Compared with the prior art, the existing active heating optical fiber method directly buries the optical cable into the rock-soil body, and the heat is easily dissipated quickly by the saturated rock-soil body, resulting in a weak temperature difference between the leakage area and the non-leakage area. The present application uses the microporous infiltration sleeve 17 and the gap structure to make the leakage water flow into the gap and directly contact with the rock-soil body leakage monitoring optical cable 1, accelerate heat dissipation, and significantly increase the temperature difference signal. In addition, the water-blocking pad 18 can block the lateral diffusion of leakage water, avoid temperature field interference, and further improve the spatial resolution of leakage identification.

[0082] Comparative example

[0083] The basic difference between the example and the comparative example is that the rock-soil body leakage monitoring optical cable 1 without the microporous infiltration sleeve 17 structure in the example is used for leakage simulation test, and the soil body model 4, the distributed optical fiber temperature demodulator 2, the heat pulse generator 3, the simulated leakage water flow mode and the leakage identification threshold remain unchanged. The peristaltic pump 5 is used to simulate the leakage water flow, which flows into the soil body model 4 through the connecting pipe 51 to form the soil body leakage area 41 and the soil body non-leakage area 42, and the heat pulse generator 3 injects a periodic pulse signal into the heating resistance wire 13 of the rock-soil body leakage monitoring optical cable 1 to actively heat the optical fiber 11.

[0084] As shown in Figure 6 , the background temperature rise value measured by the rock-soil body leakage monitoring system is 3-5℃, and the leakage temperature rise value is 1-3℃.

[0085] From the above, the difference between the background temperature rise value and the leakage temperature rise value in the comparative example is small or none. If the background temperature rise value and the leakage temperature rise value are close, the temperature gradient is not obvious, which will affect the accuracy of the positioning algorithm, reduce the positioning accuracy of the leakage point, and cannot accurately point out the specific leakage position, which is very unfavorable for timely repair measures. In addition, the difference between the background temperature rise value and the leakage temperature rise value is small, which will reduce the signal-to-noise ratio of the monitoring data, reduce the stability and reliability of the data, cause frequent false alarms or no alarms in the actual operation of the monitoring system, reduce the credibility and practical value of the monitoring system, and make it difficult for the detection personnel to make correct decisions based on the monitoring results.

[0086] Obviously, the above examples are only examples for clear illustration, and are not limited to the embodiments. For ordinary skilled persons in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A geotechnical seepage monitoring optical cable characterized by, From inside to outside, it comprises: an optical fiber (11); a loose protective layer (12) surrounding the optical fiber (11); a heating resistance wire (13) surrounding the loose protective layer (12); an inner layer insulation sheath (14) surrounding the heating resistance wire (13); a wire (15) surrounding the inner layer insulation sheath (14); an outer layer insulation sheath (16) surrounding the wire (15); a percolation sleeve (17) surrounding the outer layer insulation sheath (16) and forming a gap between the outer layer insulation sheath (16) and the percolation sleeve (17), the percolation sleeve (17) is provided with a plurality of percolation holes penetrating the wall; wherein the gap between the percolation sleeve (17) and the outer layer insulation sheath (16) is provided with a plurality of water-blocking pads (18) for separating the gap into a plurality of independent spaces.

2. The geotechnical leakage monitoring optical cable of claim 1, wherein, The diameter of the percolation hole is 1.5mm-3mm.

3. The geotechnical leakage monitoring optical cable of claim 1, wherein, The water-blocking pad (18) is made of fluororubber material and is radially used to block the diffusion of seepage water in the gap along the axial direction of the rock-soil seepage monitoring optical cable.

4. The geotechnical leakage monitoring optical cable of claim 1, wherein, A plurality of water-blocking pads (18) are uniformly arranged along the axial direction of the rock-soil seepage monitoring optical cable.

5. The geotechnical leakage monitoring optical cable of claim 1, wherein, The heating resistance wire (13) is woven into a net to wrap the loose protective layer (12).

6. The geotechnical leakage monitoring optical cable of claim 1, wherein, The wire (15) is made of copper wire and is woven into a net to wrap the inner layer insulation sheath (14).

7. The geotechnical leakage monitoring optical cable of claim 1, wherein, The inner layer insulation sheath (14) and / or the outer layer insulation sheath (16) is made of polyethylene material.

8. The geotechnical leakage monitoring optical cable of claim 1, wherein, The radial thickness of the gap is 10mm-15mm.

9. A geotechnical mass leakage monitoring system, comprising: It comprises: the rock-soil seepage monitoring optical cable (1) according to any one of claims 1-8, which is used for being buried in the rock-soil to be monitored; a heat pulse generator (3) connected with one end of the rock-soil seepage monitoring optical cable (1); the heat pulse generator (3) is configured to inject a periodic pulse signal to the heating resistance wire (13) of the rock-soil seepage monitoring optical cable (1) to heat the optical fiber (11) of the rock-soil seepage monitoring optical cable (1); a distributed optical fiber temperature demodulator (2) connected with the optical fiber (11) of the rock-soil seepage monitoring optical cable (1); the distributed optical fiber temperature demodulator (2) is configured to demodulate and collect the temperature data of each section of the optical fiber (11).

10. A method of monitoring the leakage of a geotechnical mass, characterized in that, The rock-soil seepage monitoring system according to claim 9 comprises the following steps: S1, burying the rock-soil seepage monitoring optical cable (1) according to any one of claims 1-8 in the rock-soil to be monitored; S2, energizing the heating resistance wire (13) of the optical cable (1) to heat the optical fiber (11) of the optical cable (1); S3, collecting the temperature values of each section of the optical fiber (11) and comparing the temperature values of each section of the optical fiber (11), if the temperature value of a section or some sections is lower than that of other sections and the difference is greater than a preset value, it is determined that there is seepage in the section or the sections.

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