Hydraulic dam concrete hydration heat monitoring system and method based on optical fiber temperature technology

Abstract

The application provides a hydraulic dam concrete hydration heat monitoring system and method based on an optical fiber temperature technology.The monitoring system comprises a heating temperature measuring optical fiber, an optical receiver and a control device, the heating temperature measuring optical fiber vertically enters a bottom of a dam concrete structure from a top surface of the dam concrete structure, and is arranged in a meandering shape along a thickness direction of the dam concrete structure from the bottom surface of the dam concrete structure and then is led out from the top surface of the dam concrete structure; the heating temperature measuring optical fiber is arranged side by side by a sensing optical fiber and a waterproof heating wire.The control device continuously and stably supplies power to the heating temperature measuring optical fiber for heating and preheating, in a concrete pouring process, the sensing optical fiber monitors and collects concrete temperature and transmits the concrete temperature to the optical receiver, the optical receiver processes temperature data, and the safety state of the dam concrete structure is judged.The application greatly improves the efficiency of the hydraulic dam concrete hydration heat monitoring and analysis, and has the advantages of full distribution, high precision, short collection time and the like.

Description

Technical Field

[0001] This invention relates to the field of fiber optic temperature monitoring technology, and in particular to a system and method for monitoring the hydration heat of concrete in hydraulic dams based on fiber optic temperature technology. Background Technology

[0002] With the continuous development and utilization of water resources in my country, concrete structures are becoming increasingly widely used in water conservancy and waterway engineering. For concrete dams, internal strain monitoring and crack monitoring are important indicators of dam health. Because temperature changes in the dam concrete have a significant impact on dam deformation, most concrete dams require measures during construction to reduce the temperature difference between the inside and outside of the dam body, prevent temperature cracks, and ensure dam safety.

[0003] Traditional concrete temperature testing typically involves embedding resistance point thermometers, which is cumbersome to install and makes it difficult to establish a continuous temperature field. Using distributed fiber optic temperature sensors to monitor the temperature during the concrete solidification stage of hydraulic dams can timely and accurately reflect the temperature changes throughout the entire pier, and analyze the spatial distribution of temperature and the trend of temperature change over time during the solidification process of large-volume concrete.

[0004] Chinese invention patent application CN112505308B discloses a concrete monitoring system and method based on BOTDA sensing fiber optic technology. The sensing fiber optic unit in this patent is divided into several detection layers, each containing the aforementioned sensing fiber optic cable. The sensing fiber optic cable is arranged in an "S" shape within each detection layer, with adjacent sensing fibers connected. The BOTDA fiber optic demodulator in the prior art uses a layered "S"-shaped fiber optic cable arrangement to collect temperature and stress data to determine the temperature and stress changes in a project. However, when monitoring using the layered "S"-shaped fiber optic cable arrangement in the prior art, the area between two layers of parallel fibers is only monitored by using curved fibers perpendicular to the two fibers at both ends of the parallel fibers. This results in a large area of ​​concrete not being monitored. Therefore, data fitting and state inference of the concrete state in the middle section are performed using data from the parallel and perpendicular fibers. Temperature and stress data in a large area are unknown, and the safety status is often inferred from data monitored by surrounding fibers, resulting in relatively low accuracy. Summary of the Invention

[0005] To address the problems existing in the above-mentioned background technology, this invention proposes a monitoring system and method for the hydration heat of concrete in hydraulic dams based on fiber optic temperature technology. This method can reflect the temperature changes of the entire hydraulic dam in a timely and accurate manner, analyze the spatial distribution law of temperature and the temperature change trend over time during the solidification process of large-volume concrete, and determine whether the concrete construction is in a safe state based on the monitoring results.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a hydraulic dam concrete hydration heat monitoring system based on fiber optic temperature technology, comprising a dam concrete structure, the monitoring system comprising a heating and temperature measuring fiber, a photonic nanometer, and a control device; the dam concrete structure is divided into multiple regions along the horizontal direction, and at least one set of heating and temperature measuring fibers is deployed in each region, each set of heating and temperature measuring fibers vertically entering the bottom of the dam concrete structure from the top surface, and then extending out from the top surface of the dam concrete structure after being laid out in a bent manner along the thickness direction of the dam concrete structure from the bottom surface.

[0007] The heating and temperature-measuring optical fiber consists of a sensing optical fiber and a waterproof heating wire arranged side by side. The sensing optical fiber of each group is communicatively connected to a photonic instrument, and the waterproof heating wire of each group is connected to a power control device. The power control device continuously and stably supplies power to multiple groups of heating and temperature-measuring optical fibers. Heating is stopped once the temperature of the heating and temperature-measuring optical fibers reaches a constant level. The sensing optical fiber monitors and collects the concrete temperature at different locations within the dam's concrete structure and transmits this data to the photonic instrument. The photonic instrument processes the temperature data collected by all the heating and temperature-measuring optical fibers to obtain the initial temperature t within the dam's concrete structure. min Maximum temperature t max Maximum temperature difference Δt = t max -t min and cooling rate V t This allows us to determine the safety status of the dam's concrete structure.

[0008] The preferred technical solution of the present invention is as follows: the heating and temperature measuring optical fiber is attached to the longitudinal steel bar of the dam concrete structure, and the sensing optical fiber and waterproof heating wire of each set of heating and temperature measuring optical fibers are tied side by side to the corresponding longitudinal steel bar and are in close contact with each other.

[0009] A preferred technical solution of the present invention: The optical nanometer is a BOTDA fiber optic demodulator. The optical nanometer uses Origin software to plot the temperature data collected by all heating and temperature measuring fibers into distance-temperature curves and time-temperature curves. The initial temperature t inside the dam's concrete structure is determined through these curves. min Maximum temperature t max Maximum temperature difference Δt = t max -t min and cooling rate V t .

[0010] The preferred technical solution of the present invention is as follows: each set of heating and temperature measuring optical fibers is arranged in a Z-shaped or S-shaped bend in the thickness direction of the dam concrete structure. When arranged in a Z-shaped bend, each bend is arc-shaped. Multiple sets of heating and temperature measuring optical fibers in multiple areas are distributed horizontally in parallel or vertically.

[0011] The preferred technical solution of the present invention is as follows: the power control device includes a UPS uninterruptible mobile power supply, a transformer, and a voltage regulator.

[0012] This invention also provides a method for monitoring the heat of hydration of concrete in hydraulic dams based on fiber optic temperature technology. The method uses the aforementioned fiber optic temperature technology-based monitoring system for monitoring the heat of hydration of concrete in hydraulic dams to monitor the concrete pouring process. The specific steps are as follows:

[0013] S1. After the reinforcement cage of the concrete dam is tied and before the concrete is poured, the concrete dam is divided into horizontal sections. At least one set of heating and temperature measuring optical fibers is laid in each section. The heating and temperature measuring optical fibers are attached to the longitudinal surface of the reinforcement and both ends extend from the top surface of the concrete dam. Each set of heating and temperature measuring optical fibers is laid in a bent shape along the height direction of the concrete dam. Multiple sets of heating and temperature measuring optical fibers in multiple sections are distributed horizontally in parallel or vertically. Each set of heating and temperature measuring optical fibers is composed of sensing optical fibers and waterproof heating wires.

[0014] S2. Connect the sensing fibers of multiple sets of heating and temperature measuring optical fibers to the optical nanometer, and connect the waterproof heating wires to the power control device. Before the concrete is poured, adjust the power control device to continuously and stably supply power to the heating and temperature measuring optical fibers and collect temperature data through the sensing fibers. Stop the power control device from heating once the temperature data collected by the sensing fibers is stable, i.e. the temperature of the measuring fiber is constant.

[0015] S3. Start concrete pouring in zones. During the concrete pouring and solidification process in each zone, data is continuously collected through the heating and temperature measuring optical fiber buried in that zone. The monitored data is transmitted to the optical nanometer, which uses Origin software to draw temperature-time curves and temperature-distance curves.

[0016] S4. Obtain the initial temperature t inside the dam concrete in the corresponding region from the curve plotted in step S3. min The highest temperature reached t max Maximum temperature difference Δt = t max -t min and cooling rate V t And assess the dam's safety status in the area during the dam's concrete pouring process:

[0017] If the processed monitoring data simultaneously meet the following three conditions: Δt < 50℃, V t <2.0℃ / d, t max If the temperature is below 75℃, concrete construction is safe.

[0018] If the processed monitoring data cannot simultaneously meet the following three conditions: Δt < 50℃, V t<2.0℃ / d, t max If the temperature is below 75℃, the concrete construction is in an unsafe state.

[0019] The preferred technical solution of the present invention is as follows: In step S4, when it is determined that the concrete construction is in an unsafe state, it is necessary to stop the work and change the construction plan, construction time, or subsequent construction to lay cooling pipes.

[0020] The preferred technical solution of the present invention is that the preheating monitoring in step S2 and the temperature monitoring during the concrete pouring process in step S3 are both collected once per hour.

[0021] The preferred technical solution of this invention: In step S3, the optical nanometer uses Origin software to plot temperature-time and temperature-distance curves based on the relationship between the Brillouin frequency shift caused by temperature changes in the optical fiber and temperature. The formula for the relationship between the Brillouin frequency shift and temperature is as follows:

[0022]

[0023] In the formula: This refers to the strain of the optical fiber being... The temperature is Brillouin shift at that time; This refers to the strain of the optical fiber being... The temperature is The Brillouin frequency shift is denoted by T0 and T, which represent the initial temperature and the temperature during each measurement period, respectively; ΔT is the temperature change. This is the temperature coefficient.

[0024] The beneficial effects of this invention are:

[0025] (1) The hydraulic dam concrete hydration heat monitoring system of the present invention no longer adopts the traditional method of laying multiple layers of optical fibers at one time, but adopts the method of laying single-layer optical fibers in sections to monitor the entire dam body, thereby increasing the monitoring accuracy and reducing the error caused by instrument defects; each light is vertically laid in the dam body in a similar planar spring shape, further upgrading and optimizing the optical fiber laying method, ensuring that the monitoring range of concrete is increased while maximizing the utilization rate of optical fibers.

[0026] (2) This invention uses data from planar spring-shaped oblique optical fibers to determine the concrete state of the dam body thickness. Compared with the method of layered fiber optic deployment, this increases the monitoring range and accuracy, allowing the concrete state between two parallel optical fibers to be determined without data fitting and state inference, thus eliminating errors caused by human data processing. Since the accuracy of temperature measurement data decreases as the length of the temperature-measuring optical fiber increases, this patent addresses this defect by no longer using the method of multi-layered fiber deployment in the comparative patent. Instead, it uses vertical fiber deployment in sections to monitor the concrete of the entire dam body thickness, further increasing monitoring accuracy and reducing errors caused by instrument defects. Furthermore, this invention further clarifies the method and standard for monitoring the hydration heat of concrete in hydraulic dams using optical fiber temperature technology.

[0027] (3) The hydraulic dam concrete hydration heat monitoring system of the present invention uses a heatable temperature measuring optical fiber. While laying the sensing optical fiber, a waterproof heating wire is laid closely parallel to the sensing optical fiber. The temperature is directly compensated by heating the waterproof heating wire. During data processing, the strain data is effectively corrected by removing the pure temperature strain measured by the compensation optical fiber from the strain monitoring value. The heatable temperature measuring optical fiber of the present invention can be preheated before measurement. After preheating, the hydration heat of the hydraulic dam concrete is monitored. If the temperature is abnormal, there may be unsafe factors at that location. In addition, the electric heating increases the temperature difference effect, which is more conducive to data identification and calculation.

[0028] (4) The hydraulic dam concrete hydration heat monitoring system of the present invention adopts fiber optic temperature technology. By utilizing the fully distributed characteristics of fiber optics, it can effectively avoid the possibility of missed detection in point monitoring. Temperature data can be collected from any part of a fiber optic cable. Compared with the traditional point monitoring method, it has more and more accurate data.

[0029] This invention greatly improves the efficiency of monitoring and analyzing the heat of hydration of concrete in hydraulic dams. It avoids the cumbersome wiring caused by the traditional resistance point thermometer installation, the difficulty in forming a continuous temperature field, and the possibility of missed detection in the monitoring method. Compared with traditional monitoring methods, this technology has the advantages of being fully distributed, highly accurate, and having a short acquisition time. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the hydraulic dam concrete hydration heat monitoring system based on fiber optic temperature technology in this invention.

[0031] Figure 2 This is a schematic diagram of the fiber optic cable layout for each heating and temperature measurement component in this invention.

[0032] Figure 3 This is a flowchart of the method for monitoring the heat of hydration of concrete in hydraulic dams based on fiber optic temperature technology in this invention.

[0033] Figure 4 This is a block diagram illustrating the connection principle between the fiber optic nanometer and the sensing fiber in this invention.

[0034] Figure 5 This is a top view of multiple sets of heating and temperature measuring optical fibers being deployed inside the dam gate abutment in an embodiment of the present invention.

[0035] Figure 6 This is a schematic diagram of the fiber optic cable layout for the first loop in an embodiment of the present invention;

[0036] Figure 7 This is a concrete temperature-distance curve of the first loop monitored by optical fiber in an embodiment of the present invention;

[0037] Figure 8 This is a concrete temperature-time curve of the first loop heating process monitored by optical fiber in an embodiment of the present invention.

[0038] Figure 9 This is a concrete temperature-time curve of the first loop cooling process monitored by optical fiber in an embodiment of the present invention.

[0039] Figure 10 This is a concrete temperature-time curve of the first loop heating process monitored by a point thermometer in an embodiment of the present invention.

[0040] Figure 11 This is a concrete temperature-time curve of the first loop cooling process monitored by a point thermometer in an embodiment of the present invention.

[0041] In the diagram: 1—dam concrete structure; 2—heating and temperature measurement fiber optic cable; 3—optical nanometer; 4—electrical control device; 5—longitudinal reinforcement. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments. The technical solutions presented in the embodiments are specific solutions of the embodiments of the present invention and are not intended to limit the scope of the claimed invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0043] An embodiment provides a monitoring system for the hydration heat of concrete in hydraulic dams based on fiber optic temperature technology, such as... Figure 1 , Figure 2 and Figure 4As shown, the system includes a dam concrete structure 1. The monitoring system includes a heating and temperature-measuring optical fiber 2, a photonic nanometer 3, and a control device 4. The dam concrete structure 1 is divided into multiple areas along the horizontal direction. At least one set of heating and temperature-measuring optical fibers 2 is deployed in each area. Each set of heating and temperature-measuring optical fibers 2 enters vertically from the top surface of the dam concrete structure 1 to the bottom surface of the dam concrete structure 1, and is then bent along the thickness direction of the dam concrete structure 1 from the bottom surface before exiting from the top surface of the dam concrete structure 1. Multiple sets of heating and temperature-measuring optical fibers 2 are distributed horizontally in parallel or vertically within the multiple areas. The heating and temperature-measuring optical fibers 2 are attached to the longitudinal reinforcing bars 5 of the dam concrete structure 1. The sensing optical fiber and waterproof heating wire of each set of heating and temperature-measuring optical fibers 2 are tied side by side to the corresponding longitudinal reinforcing bars 5 and are in close contact with each other. Each set of heating and temperature-measuring optical fibers 2 is bent in a Z-shape or S-shape along the thickness direction of the dam concrete structure 1. In the attached figure of the embodiment, the heating and temperature-measuring optical fiber 2 is bent in a Z-shape, and each bend is arc-shaped.

[0044] In this embodiment, the heating and temperature measuring optical fiber 2 consists of a sensing optical fiber and a waterproof heating wire arranged side by side. The sensing optical fiber of each group of heating and temperature measuring optical fibers 2 is communicatively connected to the photonics instrument 3, and the waterproof heating wire of each group of heating and temperature measuring optical fibers 2 is connected to the power control device 4. The power control device 4 includes a UPS uninterruptible power supply, a transformer, and a voltage regulator. The power control device 4 provides continuous and stable power to multiple groups of heating and temperature measuring optical fibers 2. After the temperature of the heating and temperature measuring optical fiber 2 reaches a constant value, heating is stopped. The sensing optical fiber monitors and collects the concrete temperature at different locations within the dam concrete structure 1 and transmits it to the photonics instrument 3. The photonics instrument 3 processes the temperature data collected by all the heating and temperature measuring optical fibers 2 to obtain the initial temperature t inside the dam concrete structure. min Maximum temperature t max Maximum temperature difference Δt = t max -t min and cooling rate V t This allows for the determination of the safety status of the dam's concrete structure 1. The optical nanometer 3 is a BOTDA fiber optic demodulator. The optical nanometer 3 uses Origin software to plot the temperature data collected by all heating and temperature-measuring optical fibers 2 into distance-temperature and time-temperature curves. These curves are then used to determine the initial temperature t within the dam's concrete structure. min Maximum temperature t max Maximum temperature difference Δt = t max -t min and cooling rate V t .

[0045] The fiber optic temperature technology-based hydration heat monitoring system for hydraulic dam concrete in this invention can monitor the temperature during concrete pouring. This is because the relationship between the Brillouin frequency shift of the optical fiber due to temperature changes and temperature can be expressed by the following formula ①:

[0046] ①

[0047] In the formula: This refers to the strain of the optical fiber being... The temperature is Brillouin shift at that time; This refers to the strain of the optical fiber being... The temperature is The Brillouin frequency shift is denoted by T0 and T, which represent the initial temperature and the temperature during each measurement period, respectively; ΔT is the temperature change. This is the temperature coefficient.

[0048] Therefore, in monitoring the temperature during the solidification stage of concrete in hydraulic dams, the internal temperature and strain of the concrete will inject signals into the optical fiber tied to the reinforcing steel. The linear relationship between the Brillouin frequency shift of the optical fiber and the internal temperature of the concrete conforms to the above equation ①, thus enabling distributed monitoring of the internal temperature of the concrete.

[0049] To facilitate understanding of the advantages of fiber optic monitoring and the content of this invention, the method of this invention will be further explained below with reference to specific embodiments. The embodiments monitor the concrete temperature during the setting period of the concrete poured for the gate head pier. Continuous temperature measurement data are obtained during the concrete pouring and curing stages after pouring through heated temperature-measuring fiber optic cables and point thermometers. The process of concrete temperature change over time during the setting period, the temperature distribution pattern at different depths, and the rate of temperature change are analyzed. The heat release effect of concrete is evaluated by combining the temperature monitoring results of fiber optic cables and point thermometers, and the advantages and disadvantages of the two monitoring methods are compared.

[0050] The embodiment uses the right-side pier of the upper gate of the Hushanzui section, a key large-volume concrete structure of the Xinjiang Bazizui Hydropower Project, as the test object to monitor the temperature change during the hydration heat generated during the pouring of this pier. The gate pier includes a hollow structure and a gate chamber structure, while the other parts are reinforced concrete pouring sections. This project adopted a hydraulic dam concrete hydration heat monitoring system and method based on fiber optic temperature technology of the present invention to monitor the hydration heat generated during the pouring of the right-side pier of the upper gate of the Hushanzui section, thereby determining the dam's safety status. The specific monitoring process of the embodiment is as follows: Figure 3 As shown, the specific process is as follows:

[0051] S1. After the reinforcement cage of the concrete dam is tied and before the concrete is poured, the concrete dam is divided into horizontal sections, and a set of heating and temperature-measuring optical fibers 2 are installed in each section, as follows: Figure 2The heating and temperature-sensing optical fiber 2 is attached to the longitudinal surface of the reinforcing steel, with both ends extending from the top surface of the concrete dam. Each set of heating and temperature-sensing optical fibers is arranged in a bent shape along the height of the concrete dam, similar to a planar spring. Multiple sets of heating and temperature-sensing optical fibers are distributed horizontally or vertically in multiple areas. Each set of heating and temperature-sensing optical fibers consists of a sensing optical fiber and a waterproof heating wire. The specific arrangement of the temperature-sensing optical fibers in this embodiment is as follows: Figure 4 As shown in the diagram, the white area represents the hollow structure of the side pier and the gate chamber; this part has no fiber optic cable installation. The remaining part is the reinforced concrete section, where the fiber optic cable is installed. Based on the gate head pouring sequence, the fiber optic cable installation is divided into six areas, with one set of heating and temperature-sensing fiber optic cable 2 installed in each area, forming six independent loops. See [reference needed]. Figure 4 The thickened lines represent heating and temperature-sensing fiber optic cables 2, with loops 1-6 from right to left. Loops 1, 3, 4, and 6 are parallel to the dam body, extending in a planar spring shape into the dam body as a single layer of temperature-sensing fiber optic cable. Loops 2 and 5 are perpendicular to the dam body, extending in a planar spring shape into the dam body as a single layer of temperature-sensing fiber optic cable. The monitoring loops in this case are loops 1, 2, 4, and 5. The fiber optic cable layout in each loop module is generally consistent; regardless of whether the six modules are parallel or perpendicular, each group of heating and temperature-sensing fiber optic cables follows the same pattern. Figure 2 As shown, the light is incident perpendicularly to the dam body. The monitoring data of the heating and temperature measuring fiber 2 in loop 1 of the embodiment are described in detail. The fiber optic cable of loop 1 extends into the dam body to the other edge of the dam body, and then extends parallel to the dam body to the right edge of loop 1.

[0052] S2. This invention employs a direct compensation method. While laying the optical fiber, waterproof heating wires and sensing optical fibers are laid closely parallel to each other, achieving direct compensation by heating the waterproof heating wires. After the heating and temperature-measuring optical fibers are laid out, the sensing optical fibers of multiple sets of heating and temperature-measuring optical fibers are connected to the optical nanometer 3, and the waterproof heating wires are all connected to the power control device 4. Before concrete pouring, the power control device 4 is adjusted to continuously and stably supply power to the heating and temperature-measuring optical fibers for heating, and temperature is collected through the sensing optical fibers. Once the temperature data collected by the sensing optical fibers stabilizes, i.e., the temperature of the measuring optical fiber is constant, the heating of the power control device is stopped. Before monitoring begins, the optical fibers are heated to ambient temperature to reduce errors. This invention employs a direct compensation method, and during data processing, the pure temperature strain measured by the compensation optical fibers is removed from the strain monitoring values, thereby achieving effective correction of the strain data.

[0053] S3. Begin concrete pouring in designated zones. During the concrete pouring and setting process in each zone, data is continuously collected via the embedded heating and temperature-measuring optical fibers. The collected data is then transmitted to a photonics instrument, which uses Origin software to generate temperature-time and temperature-distance curves. In this embodiment, concrete is first poured in the zone containing loop 1, and data is continuously collected during the pouring process via the embedded heating and temperature-measuring optical fibers of loop 1. The fiber optic cables in loop 1 are arranged as follows: Figure 5 As shown, to demonstrate the accuracy of fiber optic temperature measurement in this invention, multiple point-type thermometers are simultaneously deployed for monitoring during fiber optic cable installation, such as... Figure 5 As shown, six temperature measuring points (a, b, c, d, e, and f) are arranged in the optical fiber of loop 1 to provide a comparison with the fiber optic temperature measurement. Three temperature measuring points are randomly selected on the optical fiber as comparison one, comparison two, and comparison three. Monitoring is carried out synchronously from the start of pouring. Due to the low air temperature (local air temperature is approximately 3°C to 10°C), and considering that the gate head pier is not a solid concrete pour, but includes some hollow layer structures and machine room gate chambers, the heat of hydration of the concrete is expected to dissipate relatively quickly. To accurately find the temperature peak, the monitoring frequency is once per hour.

[0054] S4. After step S3 is completed, temperature data is extracted, and all the obtained heating temperature measurement fiber optic data are plotted using Origin software. In this embodiment, representative monitoring data is selected for display. Figure 7 , Figure 8 , Figure 9 The figures show the concrete temperature-distance curve for fiber optic monitoring loop 1 and the concrete temperature-time rise and fall curves for fiber optic monitoring loop 1. Figure 10 and Figure 11 This is a graph showing the temperature rise and fall of concrete over time in loop 1 of the point-type thermometer monitoring system; through... Figure 8 , Figure 9 It can be seen that the temperature-time curves of the three selected points in the optical fiber, compared with those of the six point thermometers (a, b, c, d, e, f), show a consistent trend. The data from this monitoring of the optical fiber loops show a consistent trend, indicating that all samples survived. Figures 8 to 11It can be seen that the fiber optic monitoring curve of loop 1 is largely consistent with the trend of the point monitoring curve, leading to roughly the same conclusion: the hydration heat temperature of concrete undergoes a process of continuous rapid rise, followed by a slow rise, and then plateauing. The period of fastest rise in loop 1 is two hours after pouring. However, fiber optic monitoring provides full-line temperature monitoring with a wide coverage area, avoiding misjudgments due to missed measurements. The instrument resolution reaches 5 cm, and the sampling interval is 10 cm, while point thermometers can only be used for point monitoring. Furthermore, the highest accuracy of fiber optic temperature monitoring is 0.35℃, higher than the 0.5℃ accuracy of thermometers. During the monitoring process, some point thermometers were damaged, resulting in the loss of some temperature data, while the entire fiber optic loop survived, and there were no missing segments in the temperature data for each period. Therefore, it can be seen that the fiber optic monitoring in this application is more accurate. Figure 8 , Figure 9 The initial temperature t inside the concrete hydraulic dam can be obtained from the data monitored by loop 1. min =22℃, the highest temperature t reached max =49℃, maximum temperature difference Δt1=t max -t min =27℃; by Figure 9 It can be known that the overall cooling rate V over 20 hours t1 =0.9℃ / d.

[0055] S5. The temperature data from the heating and temperature measurement fiber optic cables of the remaining monitoring loops are processed using the same steps as in S3 and S4 to obtain the initial temperature t inside the concrete hydraulic dam. min =15℃, the highest temperature t reached max =50℃, maximum temperature difference Δt=t max -t min =35℃, and cooling rate V t =1.3℃ / d;

[0056] S6. Further, according to GB 50496-2018 Standard for Construction of Mass Concrete, JTG / T 3650-2020 Technical Specification for Construction of Highway Bridges and Culverts, and JTS / T 2021-2022 Technical Specification for Temperature Crack Control of Mass Concrete in Waterway Engineering, it can be concluded that:

[0057] (1) The maximum temperature rise of the concrete casting should not exceed 50℃ (based on the temperature at which it is poured into the mold).

[0058] (2) The concrete cooling rate shall not exceed 2.0℃ / d;

[0059] (3) The maximum internal temperature of large-volume concrete should not exceed 75℃;

[0060] The safety status of the dam in this area during the dam concrete pouring process should be assessed based on the following conditions:

[0061] If the processed monitoring data simultaneously meet the following three conditions: Δt < 50℃, V t <2.0℃ / d, t max If the temperature is below 75℃, concrete construction is safe.

[0062] If the processed monitoring data cannot simultaneously meet the following three conditions: Δt < 50℃, V t <2.0℃ / d, t max If the temperature is below 75℃, the concrete construction is in an unsafe state.

[0063] Based on step S5, the initial temperature t can be determined. min =15℃, the highest temperature t reached max =50℃, maximum temperature difference Δt=t max -t min =35℃, and cooling rate V t =1.3℃ / d, therefore Δt < 50℃, V t <2.0℃ / d, t max The temperature is below 75℃, which indicates that the right-side pier of the gate head in the Hushanzui section is in a safe condition during the concrete pouring process.

[0064] The above description is merely one embodiment of the present invention, and while it is detailed and specific, it should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A monitoring system for the heat of hydration of concrete in a hydraulic dam based on fiber optic temperature technology, comprising a dam concrete structure (1), characterized in that: The monitoring system includes a heating and temperature measuring fiber (2), a light nanometer (3), and a power control device (4); the dam concrete structure (1) is divided into multiple areas along the horizontal direction, and at least one set of heating and temperature measuring fibers (2) is laid in each area. Each set of heating and temperature measuring fibers (2) enters the bottom of the dam concrete structure (1) vertically from the top surface of the dam concrete structure (1), and is laid out in a bent shape along the thickness direction of the dam concrete structure (1) from the bottom surface of the dam concrete structure (1) and then leads out from the top surface of the dam concrete structure (1). Each set of heating and temperature measuring fibers (2) is bent in a Z-shape in the thickness direction of the dam concrete structure (1), and each bend is arc-shaped. Multiple sets of heating and temperature measuring fibers (2) in multiple areas are distributed horizontally in parallel or vertically. The heating and temperature measuring fiber (2) consists of a sensing fiber and a waterproof heating wire arranged side by side. The sensing fiber of each group of heating and temperature measuring fibers (2) is connected to the photonics instrument (3), and the waterproof heating wire of each group of heating and temperature measuring fibers (2) is connected to the power control device (4). The power control device (4) provides continuous and stable power to multiple groups of heating and temperature measuring fibers (2). After the temperature of the heating and temperature measuring fiber (2) becomes constant, heating is stopped. The temperature of the concrete at different locations in the dam concrete structure (1) is monitored and collected by the sensing fiber and transmitted to the photonics instrument (3). The photonics instrument (3) processes the temperature data collected by all heating and temperature measuring fibers (2) to obtain the initial temperature t inside the dam concrete structure. min Maximum temperature t max Maximum temperature difference Δt = t max -t min and cooling rate V t Thus, the safety status of the dam's concrete structure (1) can be determined.

2. The fiber optic temperature technology-based concrete hydration heat monitoring system for hydraulic dams according to claim 1, characterized in that: The heating and temperature measuring optical fiber (2) is attached to the longitudinal steel bar (5) of the dam concrete structure (1). The sensing optical fiber and waterproof heating wire of each set of heating and temperature measuring optical fiber (2) are tied side by side to the corresponding longitudinal steel bar (5) and are in close contact with each other.

3. A monitoring system for the heat of hydration of concrete in hydraulic dams based on fiber optic temperature technology, as described in claim 1 or 2, characterized in that: The optical nanometer (3) is a BOTDA fiber demodulator. The optical nanometer (3) uses Origin software to plot the temperature data collected by all the heating and temperature measuring fibers (2) into distance-temperature curves and time-temperature curves. The initial temperature t inside the dam concrete structure is determined by the curves. min Maximum temperature t max Maximum temperature difference Δt = t max -t min and cooling rate V t .

4. A monitoring system for the heat of hydration of concrete in hydraulic dams based on fiber optic temperature technology, as described in claim 1 or 2, characterized in that: The power control device (4) includes a UPS uninterruptible mobile power supply, a transformer, and a voltage regulator.

5. A method for monitoring the heat of hydration of concrete in hydraulic dams based on fiber optic temperature technology, characterized in that, The specific steps of using the fiber optic temperature technology-based concrete hydration heat monitoring system for hydraulic dams, as described in any one of claims 1 to 4, to monitor the concrete pouring process of dams are as follows: S1. After the reinforcement cage of the concrete dam is tied and before the concrete is poured, the concrete dam is divided into horizontal sections. At least one set of heating and temperature measuring optical fibers is laid in each section. The heating and temperature measuring optical fibers are attached to the longitudinal surface of the reinforcement and both ends extend from the top surface of the concrete dam. Each set of heating and temperature measuring optical fibers is laid in a bent shape along the height direction of the concrete dam. Multiple sets of heating and temperature measuring optical fibers in multiple sections are distributed horizontally in parallel or vertically. Each set of heating and temperature measuring optical fibers is composed of sensing optical fibers and waterproof heating wires. S2. Connect the sensing fibers of multiple sets of heating and temperature measuring optical fibers to the optical nanometer, and connect the waterproof heating wires to the power control device. Before the concrete is poured, adjust the power control device to continuously and stably supply power to the heating and temperature measuring optical fibers and collect temperature data through the sensing fibers. Stop the power control device from heating once the temperature data collected by the sensing fibers is stable, i.e. the temperature of the measuring fiber is constant. S3. Start concrete pouring in zones. During the concrete pouring and solidification process in each zone, data is continuously collected through the heating and temperature measuring optical fiber buried in that zone. The monitored data is transmitted to the optical nanometer, which uses Origin software to draw temperature-time curves and temperature-distance curves. S4. Obtain the initial temperature t inside the dam concrete in the corresponding region from the curve plotted in step S3. min The highest temperature reached t max Maximum temperature difference Δt = t max -t min and cooling rate V t And assess the dam's safety status in the area during the dam's concrete pouring process: If the processed monitoring data simultaneously meet the following three conditions: Δt < 50℃, V t <2.0℃ / d, t max If the temperature is below 75℃, concrete construction is safe. If the processed monitoring data cannot simultaneously meet the following three conditions: Δt < 50℃, V t <2.0℃ / d, t max If the temperature is below 75℃, the concrete construction is in an unsafe state.

6. The method for monitoring the heat of hydration of concrete in hydraulic dams based on fiber optic temperature technology according to claim 5, characterized in that: In step S4, if it is determined that the concrete construction is in an unsafe state, work must be stopped to change the construction plan, construction time, or subsequent construction to install cooling pipes.

7. The method for monitoring the heat of hydration of concrete in hydraulic dams based on fiber optic temperature technology according to claim 5, characterized in that: The preheating monitoring in step S2 and the temperature monitoring during the concrete pouring process in step S3 are both collected once per hour.

8. The method for monitoring the heat of hydration of concrete in hydraulic dams based on fiber optic temperature technology according to claim 5, characterized in that: In step S3, the optical nanometer uses Origin software to plot temperature-time and temperature-distance curves. This is based on the relationship between the Brillouin frequency shift caused by temperature changes in the optical fiber and temperature. The formula for the relationship between the Brillouin frequency shift and temperature is as follows: In the formula: This refers to the strain of the optical fiber being... The temperature is Brillouin shift at that time; This refers to the strain of the optical fiber being... The temperature is The Brillouin frequency shift is denoted by T0 and T, which represent the initial temperature and the temperature during each measurement period, respectively; ΔT is the temperature change. This is the temperature coefficient.

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