Concrete gravity dam horizontal construction joint monitoring device and application

Abstract

The application provides a concrete gravity dam horizontal construction joint monitoring device and application; the device comprises a pre-buried base, a vertical electrode and a strain gauge; the vertical electrode is composed of an upper electrode and a lower electrode which are spliced together; the spliced end of the upper electrode and the lower electrode is a butt joint end, and the other end is a fixed end; the upper electrode and the lower electrode are normally spliced and conductive; the fixed ends of the upper electrode and the lower electrode are respectively inserted and fixed in the vertical insertion slots of the upper base and the lower base; the strain gauge is fixedly attached to the side surface of the vertical electrode; the application has the advantages of simple structure, low cost, far lower operation and maintenance cost than optical fibers, easy popularization, integral pre-buried with dam pouring, no need for punching in the later period, protection of dam structure integrity, and application in long-term safety monitoring of concrete gravity dam horizontal joints, roller compacted concrete dam / arch dam / hydraulic structure horizontal construction joints, reserved expansion joints and structural joints.

Description

Technical Field

[0001] This application relates to the field of safety monitoring technology for water conservancy dams, and in particular to a monitoring device for horizontal construction joints in concrete gravity dams and its application. Background Technology

[0002] Concrete gravity dams, roller-compacted concrete dams, and arch dams all employ a layered casting process, resulting in numerous horizontal construction joints within the dam body and horizontal expansion joints pre-reserved on the surface. These are the weakest and most prone to cracking and leakage interfaces in the dam structure. Under the coupled effects of multiple fields such as water pressure, temperature stress, wet-dry cycles, freeze-thaw cycles, dam settlement, and structural compression, these horizontal joints are highly susceptible to opening and extending inward to form deep, hidden cracks. This leads to dam leakage, excessive deformation, and decreased structural stability, making it one of the main sources of safety risks for reservoir dams.

[0003] Traditional horizontal crack monitoring uses mechanical crack gauges, but these are single-point monitoring methods, only able to monitor deformation at fixed points and unable to cover the entire horizontal crack. This results in a large blind zone, high rates of missed and false detections, and an inability to reflect the true extension shape and depth of the crack. While distributed fiber optic sensing technology can achieve continuous monitoring along the crack, it currently mainly targets vertical cracks or the overall strain field of the dam body. When the crack width exceeds a certain threshold, the fiber optic cable is easily broken. Furthermore, distributed fiber optic cables are expensive, and the deployment, splicing, and debugging processes are complex. Under the high pressure, low temperature, and high humidity conditions of dams, signal loss is significant and signal drift is severe, making it unsuitable for long-term monitoring over decades. Non-destructive testing (NDT) methods have limited detection depth. Ultrasonic testing can only detect shallow cracks within 30cm, but when the crack depth is large or the reinforcement is densely distributed, the ultrasonic wave propagation path becomes complex, the signal attenuation is severe, and the detection error increases significantly. Moreover, it may even fail completely for fully water-saturated cracks. Impact echo testing is only suitable for shallow to medium-depth cracks of 30-150cm and is ineffective for deep horizontal cracks in the dam body. Furthermore, NDT results are greatly affected by aggregate, humidity, and noise, resulting in poor stability. In addition, it can only be performed by manual sampling and cannot continuously monitor crack evolution online. For horizontal cracks deeper than 1.5m, drilling is the only option, which is time-consuming, costly, damages the integrity of the dam body, and is prone to generating secondary microcracks, making routine monitoring impossible.

[0004] In summary, existing technologies cannot achieve long-term, non-destructive, low-cost monitoring of horizontal joints in dams, covering the entire length and depth, all weather conditions. The industry urgently needs intelligent monitoring equipment based on novel principles. Therefore, an improved technical solution is required to address the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this application is to provide a monitoring device and application for horizontal construction joints in concrete gravity dams, so as to solve or alleviate the problems existing in the prior art.

[0006] The core principle of this application is as follows: Insulating pre-embedded bases are pre-embedded in the dam body on both sides of the horizontal joint. Multi-layered paired vertical electrode arrays are arranged in the pre-embedded bases along the depth direction of the horizontal joint, and they are normally connected. When the horizontal joint crack is tensile and cracks open, the upper and lower electrodes separate, and the circuit resistance changes step by step. The depth, position, opening and rate of crack are automatically identified through resistance inspection.

[0007] To achieve the above objectives, this application provides the following technical solution: This application provides a monitoring device for horizontal construction joints of concrete gravity dams, including a pre-embedded base, vertical electrodes, and strain gauges; The embedded base includes an upper base and a lower base, which are assembled into a single unit. Each of the upper and lower bases has a vertical slot and a wiring channel communicating with the vertical slot. The vertical electrode consists of an upper electrode and a lower electrode joined together. The joined ends of the upper and lower electrodes are mating ends, and the other end is a fixed end. The upper and lower electrodes are normally joined and conductive. The fixed ends of the upper and lower electrodes are respectively inserted and fixed into the vertical slots of the upper and lower bases and connected to shielded cable leads. The shielded cable leads are led out of the embedded base through the wiring channel. The strain gauge is attached and fixed to the side of the vertical electrode for collecting the opening and closing displacement of the upper and lower electrodes. When the horizontal joint is not cracked, all layer electrode circuits remain in a low-resistance conductive state; when the horizontal joint is stretched and extends into the depth of the dam body, the electrodes of the corresponding layer at the crack location separate with the deformation of the joint body, the circuit resistance increases or the circuit is broken, and the system determines the crack development depth layer by layer from shallow to deep, realizing full-length, full-depth, blind-spot-free online monitoring of the horizontal reserved joints and horizontal construction joints of the concrete dam.

[0008] Furthermore, the upper electrode and the lower electrode are fitted with the vertical slot with a clearance, and at least one of the upper electrode and the lower electrode can slide relative to the vertical slot after being subjected to vertical force, so as to avoid damage to the upper electrode and the lower electrode.

[0009] Furthermore, the upper and lower electrodes are made of corrosion-resistant stainless steel and are covered with waterproof and insulating sleeves, with only the mating ends exposed for electrical conduction; the embedded base is made of high-strength insulating epoxy fiberglass reinforced plastic.

[0010] Furthermore, the mating surfaces of the upper and lower bases are non-planar and have a mating structure that restricts the upper and lower bases to only move relative to each other in the vertical direction.

[0011] Furthermore, the interlocking structure is one or more of the following: concave-convex key, V-shaped key, trapezoidal key, U-shaped key, or corrugated key.

[0012] Furthermore, the monitoring device for horizontal construction joints of concrete gravity dams also includes a thermal sensor, which is pre-installed inside the embedded base.

[0013] Furthermore, one or more vertical electrodes are installed in a pre-embedded base; when there are multiple vertical electrodes, the spacing between the vertical electrodes is 10cm to 20cm and the spacing is equal.

[0014] The aforementioned monitoring device for horizontal construction joints in concrete gravity dams involves pre-embedding and fixing the upper and lower bases within the concrete pouring layers on both sides of the horizontal joint during the pouring of the concrete dam body. Vertical electrodes are arranged in a linear array within the pre-embedded bases, which are arranged along the entire length of the horizontal joint to cover the required monitoring range. This allows the single-layer electrode array to form a continuous monitoring array covering the required monitoring range of the horizontal joint. The shielded cable leads of each layer are electrically connected to a multi-channel inspection module, and the on / off status of each vertical electrode in each layer is polled layer by layer to monitor the crack depth of the horizontal joint. The strain gauges of each layer are electrically connected to a strain sensing module to collect data on the opening and closing width of the horizontal joint, thereby monitoring the crack width of the horizontal joint.

[0015] Furthermore, one to two sets of spare vertical electrodes are added to key monitoring layers with a depth greater than 1m. When the main electrode fails, the multi-channel inspection module automatically switches to the spare circuit.

[0016] The technical solution of this application has the following beneficial effects: This application features a simple structure, low cost, and maintenance costs far lower than optical fiber, making it easy to popularize. It is pre-embedded along with the dam pouring, eliminating the need for subsequent drilling and protecting the structural integrity of the dam. When pre-embedded in the horizontal joints of the concrete dam, the monitoring depth can reach over 3m, exceeding the 1.5m depth limit for non-destructive monitoring, and enabling 24-hour continuous monitoring. It can capture micro-deformation, micro-cracking, and long-term creep propagation processes. It can segment and locate specific crack sections and sense crack width through strain gauges, achieving dual-parameter monitoring of crack width and depth, and fully restoring the three-dimensional development morphology of horizontal cracks.

[0017] This application, in addition to its application to horizontal joints in concrete gravity dams, can also be used for long-term safety monitoring of horizontal construction joints, reserved expansion joints, and structural joints in roller-compacted concrete dams / arch dams / hydraulic structures. The monitoring device described in this application is easy to construct, requires no subsequent structural disturbance, has high monitoring accuracy, strong environmental adaptability, and a lifespan that matches the dam's service life, making it highly valuable for engineering implementation and industrialization. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation thereof. Wherein: Figure 1 This is a schematic diagram illustrating the application of the monitoring device for horizontal construction joints in concrete gravity dams according to this application. Figure 1 .

[0019] Figure 2 This is a schematic diagram illustrating the application of the monitoring device for horizontal construction joints in concrete gravity dams according to this application. Figure 2 .

[0020] Figure 3 This is a schematic diagram of the structure of the monitoring device for horizontal construction joints of a concrete gravity dam according to an embodiment of this application.

[0021] Figure 4 This is a schematic diagram of the structure of the vertical electrode in an embodiment of this application.

[0022] Explanation of reference numerals in the attached figures: 1-Dam surface, 2-Upper dam body, 3-Lower dam body, 4-Horizontal joint, 5-Upper base, 6-Lower base, 7-Vertical electrode array, 71-Upper electrode, 72-Lower electrode, 8-Shielded cable lead, 9-Acquisition host, 10-Middle joint of dam surface base, 11-Upper joint of dam surface base, 12-Lower joint of dam surface base, 13-Vertical electrode mating surface, 14-Wire routing channel, 15-Intermediate cavity, 16-Strain gauge. Detailed Implementation

[0023] The present application will now be described in detail with reference to the accompanying drawings and embodiments. Various examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present application without departing from the scope or spirit thereof. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present application encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0024] In the following description, the terms "first / second / third" are used merely to distinguish similar objects and do not represent a specific order of objects. It is understood that "first / second / third" may be interchanged in a specific order or sequence where permitted, so that the embodiments of this application described herein can be implemented in an order other than that illustrated or described herein.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing embodiments of this disclosure only and is not intended to limit this disclosure.

[0026] In the description of this application, the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and do not require this application to be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0027] like Figures 1 to 4 As shown, a monitoring device for horizontal construction joints of a concrete gravity dam includes an embedded base, a vertical electrode, and a strain gauge 16. The pre-embedded base includes an upper base 5 and a lower base 6, which are assembled into a single unit. The upper base 5 and lower base 6 each have several vertical slots and wiring channels 14 communicating with these slots. The vertical electrode consists of an upper electrode 71 and a lower electrode 72, which are joined together vertically. The joined ends of the upper electrode 71 and lower electrode 72 are mating ends, while the other end is a fixed end. The upper electrode 71 and lower electrode 72 are normally joined and conductive. The fixed ends of the upper electrode 71 and lower electrode 72 are respectively inserted and fixed into the vertical slots of the upper base 5 and lower base 6 and connected to shielded cable leads 8. The shielded cable leads 8 are led out of the pre-embedded base through the wiring channels 14. The strain gauge 16 is attached and fixed to the side of the vertical electrode for collecting the opening and closing displacement of the upper electrode 71 and lower electrode 72. When horizontal joint 4 is not cracked, all layer electrode circuits remain in a low-resistance conductive state. When horizontal joint 4 is stretched and extends deeper into the dam body, the electrodes of the corresponding layer at the crack location separate with the deformation of the joint, the circuit resistance increases or the circuit is broken. The system determines the crack development depth layer by layer from shallow to deep, realizing full-length, full-depth, blind-spot-free online monitoring of horizontal reserved joints and horizontal construction joints in concrete dams. Horizontal joint 4 includes both horizontal reserved joints and horizontal construction joints; for example... Figure 1 , 2 As shown, horizontal joint 4 is the joint surface between the upper dam body 2 and the lower dam body 3.

[0028] Furthermore, such as Figure 3 As shown, to facilitate the installation of shielded cable leads 8 and electrodes during dam construction, the upper base 5 is composed of a first base and a second base joined together, and the lower base 6 is composed of a third base and a fourth base joined together. The joint between the first base and the second base is the upper joint 11 of the dam surface base, the joint between the second base and the third base is the middle joint 10 of the dam surface base (i.e., the joint between the upper base 5 and the lower base 6), and the joint between the third base and the fourth base is the lower joint 12 of the dam surface base. The positions of the upper joint 11 and the lower joint 12 of the dam surface base correspond to the cable routing channel 14. The middle joint 10 of the dam surface base corresponds to the horizontal joint 4 / construction joint of the dam body.

[0029] Furthermore, such as Figure 3As shown, the mating surfaces of the upper base 5 and the lower base 6 are non-planar and have a mating structure that restricts the upper base 5 and the lower base 6 to opening and closing only vertically; the mating structure is one or more of the following: an array of concave and convex points, concave and convex keys, V-shaped keys, trapezoidal keys, U-shaped keys, or corrugated keys; preferably, the mating surfaces of the upper base 5 and the lower base 6 are concave and convex keys. Specifically, the lower surface of the upper base 5 has a rectangular groove, and the upper surface of the lower base 6 has a rectangular protrusion that matches the rectangular groove.

[0030] Furthermore, such as Figures 1-3 As shown, an intermediate cavity 15 is provided at the joint of the upper base 5 and the lower base 6, and the joint end of the vertical electrode is located within the intermediate cavity 15. During use, it is not required that the joint end of the vertical electrode be strictly collinear with the horizontal seam 4; as long as the joint end of the vertical electrode is within the intermediate cavity 15, it will not affect the jointing and disjointing of the upper electrode 71 and the lower electrode 72. The strain gauge 16 is also located within the intermediate cavity 15. For the installation of the strain gauge 16 and the cable lead-out, a through hole is provided between the intermediate cavity 15 and the wiring channel 14.

[0031] Furthermore, the upper electrode 71 and lower electrode 72 are made of corrosion-resistant stainless steel and are covered with a waterproof insulating sleeve, with only the mating ends exposed for electrical conduction; one or more vertical electrodes are set in a pre-embedded base; when there are multiple vertical electrodes, the spacing between them is 10cm to 20cm and the spacing is equal, where 20cm is the standard spacing, and the spacing is increased to 10cm in the high-precision monitoring area; preferably, such as Figure 1 As shown, multiple vertical electrodes are set in a pre-embedded base to form a vertical electrode array 7. In use, one or more monitoring devices for the horizontal construction joints of concrete gravity dams are pre-embedded in each layer of horizontal joint 4, and the lateral spacing between two adjacent pre-embedded bases is determined by different engineering requirements.

[0032] Furthermore, the upper electrode 71 and the lower electrode 72 are fitted with the vertical slot with a clearance; under a certain external pressure, the upper electrode 71 and the lower electrode 72 can be displaced in the vertical slot to avoid deforming or even breaking the electrodes; at the same time, when the upper base 5 and the lower base 6 move away from each other, they can drive the upper electrode 71 and the lower electrode 72 to separate, forming an open circuit.

[0033] Furthermore, such as Figure 4 As shown, the mating ends of the upper electrode 71 and the lower electrode 72 are respectively processed into convex-concave arc-shaped electrode structures. The mating end of the upper electrode 71 has a downward-facing convex surface, and the mating end of the lower electrode 72 has a concave surface that matches the convex surface. The convex-concave arc-shaped electrode structure facilitates the alignment of the upper electrode 71 and the lower electrode 72. The cross-sectional area of ​​the mating ends of the upper electrode 71 and the lower electrode 72 is not less than 25 mm². 2 ; Figure 4 The vertical electrode mating surface 13 is schematically drawn in the figure.

[0034] Furthermore, the pre-embedded base is made of high-strength insulating epoxy fiberglass reinforced plastic (FRP), and its size is adapted to the conventional horizontal joint 4 of the dam. Its insulation level meets the requirements of the high-pressure and humid environment of hydraulic engineering. When pre-embedded, it is firmly bonded to the dam concrete without slippage or gaps.

[0035] Furthermore, the aforementioned monitoring device for horizontal construction joints of concrete gravity dams also includes a thermal sensor, which is pre-installed inside a pre-embedded base for real-time acquisition of the internal temperature of the dam body; the thermal sensor is a PT100 platinum resistance thermometer. An NTC thermistor is also provided for acquiring ambient temperature. During use, a temperature compensation module is included, which adaptively corrects vertical electrode temperature drift based on the thermal sensor and the NTC thermistor.

[0036] An application of a monitoring device for horizontal construction joints in a concrete gravity dam involves pre-embedding and fixing upper base 5 and lower base 6 within the concrete layers on both sides of the horizontal joint 4 during the pouring of the concrete dam body. Vertical electrodes are arranged in a linear array within the pre-embedded bases, which are arranged along the entire length of the horizontal joint 4, forming a continuous monitoring array 7 covering the required monitoring range of the horizontal joint 4. During dam pouring, several monitoring devices are installed in each layer of horizontal joints. After dam pouring is completed, the shielded cable leads 8 of each layer of monitoring devices are electrically connected to a multi-channel inspection module. The on / off status of each vertical electrode in each layer is polled layer by layer to monitor the crack depth of the horizontal joint 4. Strain gauges 16 in each layer are electrically connected to a strain sensing module to collect data on the opening and closing width of the horizontal joint 4, thus monitoring the crack width of the horizontal joint 4. This application, by arranging vertical electrodes along the entire length of the horizontal joint 4 and distributing them in multiple layers, completely solves the problem of blind spots in traditional single-point monitoring. The multi-channel inspection module used in this application is a multi-channel resistance inspection circuit module, including resistance signal conditioning and amplification filtering circuits, which is a mature existing technology. For horizontal joints 4 / construction joints with a length exceeding 10m, the monitoring device for horizontal construction joints of concrete gravity dams is segmented and networked, with each segment independently coded and inspected, in order to accurately output structured data of segmentation, layering, depth, and opening.

[0037] Preferably, after the pre-embedded base is embedded in the concrete dam, the end face of the pre-embedded base is flush with or nearly flush with the dam surface 1, so as to facilitate the cable leads of the shielded cable lead 8, the thermal sensor, and the strain gauge 16 to be led out of the pre-embedded base and electrically connected to the corresponding multi-channel inspection module, temperature compensation module, and strain sensing module; Figure 1 In this paper, the multi-channel inspection module, temperature compensation module, and strain sensing module are all represented by the data acquisition host 9.

[0038] The multi-channel inspection module, temperature compensation module, and strain sensing module are connected to the main control processing unit, which has functions such as data processing, algorithm correction, and data transmission.

[0039] Furthermore, one to two sets of spare vertical electrodes (backup electrodes) are added to key monitoring layers with a depth greater than 1m. When the main electrode fails, the multi-channel inspection module automatically switches to the backup circuit. This application ensures long-term service without failure through backup electrodes, extending the overall service life of the monitoring device. The principle for determining the crack depth and width of construction joints is as follows: By pre-embedding bases and installing vertical electrodes during the pouring of the concrete gravity dam, a multi-layered monitoring device is ultimately formed within the dam. Each layer comprises several monitoring devices arranged linearly to cover the horizontal cracks within the required monitoring range. After a horizontal crack opens, the upper and lower bases separate, causing the upper and lower electrodes to separate as well. The vertical electrodes change from a normally conducting state to an open state, resulting in infinite resistance and a sudden change in current. Each vertical electrode has a unique number, corresponding one-to-one with its location. The multi-channel resistance monitoring circuit polls the resistance status of each electrode circuit layer by layer and outputs resistance data with coded identifiers. This data is processed by the main control unit to determine the location of the cracked vertical electrode. The opening width of the horizontal crack is accurately measured by strain gauges under tensile strain.

[0040] The main control processing unit (MCU) incorporates temperature compensation and temperature drift correction algorithms. It dynamically compensates for the temperature coefficient of resistance using a built-in fitting algorithm, eliminating resistance drift errors caused by thermal expansion and contraction. The algorithm correction circuit logic is as follows: the MCU synchronously reads the original resistance value of the electrode circuit, the real-time substrate temperature, and the ambient temperature, and calls the built-in temperature-resistance fitting correction model R. 真实 =R 实测 -K·ΔT; where K is the electrode temperature resistivity; ΔT is the difference between the current temperature and the calibration reference temperature; this temperature compensation automatically offsets the resistance drift caused by the thermal expansion and contraction of the stainless steel electrode, avoiding misjudgment of crack opening at low / high temperatures.

[0041] The method for converting the real-time joint width of construction joints is as follows: (1) Definition of basic calibration parameters; The necessary parameters for calibrating the monitoring device for horizontal construction joints of concrete gravity dams include the strain gauge sensitivity coefficient. Initial reference resistance of strain gauge Effective baseline measurement length of strain gauge Temperature strain coefficient of stainless steel electrodes Critical threshold for cracking of construction joints .

[0042] (2) Strain gauge gap width calculation; The device collects real-time resistance changes of strain gauges, and combines this with temperature compensation to eliminate temperature-induced strain, thus obtaining the true mechanical strain of the structure. The calculation formula is as follows: = ; In the formula: To represent the actual micro-strain of the strain gauge structure; This represents the change in resistance of the strain gauge; T represents the real-time temperature difference change.

[0043] The real-time seam width at the measuring point is calculated based on the effective baseline length: = B; In the formula: Real-time seam width at the measuring point; 0 indicates that the gap is open. 0 indicates that the gap is compressed and closed.

[0044] (3) Calculation method for cracking depth of horizontal joints / construction joints; This device deploys multiple rows of sensing points in layers along the thickness direction of the upstream and downstream of the dam body at the construction joint. By varying the joint width data at multiple sensing points, it achieves precise calculation of the penetration depth inside the joint.

[0045] Firstly, the critical threshold for cracking is used. As a benchmark for crack determination (generally 0.02 mm), all layered measuring points along the depth direction are traversed to determine the cracking state of each layer. For the critical transition region where adjacent layered measuring points exhibit both open and closed cracking, a linear interpolation algorithm is used to calculate the precise critical cracking depth. The calculation formula is as follows: ; In the formula: d is the effective penetration depth of the construction joint; , Pre-embed the depth of adjacent upper and lower measuring points; , The measured joint width is the corresponding layer measurement point.

[0046] By using global layered traversal interpolation, the crack depth of construction joints can be accurately identified.

[0047] (4) Timing calculation method for gap propagation rate; Set the collection times for the two sets of data as follows: , Time interval The opening and closing expansion rate of the gap width for: ; Rate of depth extension of the crack along the thickness direction of the dam body for: ; Based on this, the crack area change can be calculated by integrating the crack width at all measuring points, which can further solve the crack surface expansion rate and achieve a comprehensive quantitative evaluation of the overall deterioration rate of the construction joint.

[0048] The present application will be further described in detail below with reference to specific embodiments.

[0049] A concrete gravity dam in a frigid region has a horizontal pre-reserved joint on the upstream dam face, with a depth of 1.6m. Starting from the upstream dam face and moving downstream, a horizontal construction joint monitoring device for the concrete gravity dam is pre-embedded at the horizontal pre-reserved joint to monitor the changes in the pre-reserved joint as it is opened and closed, and its expansion into the dam.

[0050] The embedded base in this embodiment includes an upper base and a lower base. The upper base is composed of a first base and a second base joined together, and the lower base is composed of a third base and a fourth base joined together. After assembly, the intermediate cavity contains upper and lower electrodes and strain gauges, and cables are laid in the upper and lower wiring channels. Vertical slots are respectively opened on the second base and the third base. The fixed ends of the upper and lower electrodes are respectively inserted and fixed in the vertical slots of the second base and the third base, and the strain gauges are pasted and fixed to the sides of the vertical electrodes. The grooves forming the wiring channels are in the first base and the second base. The embedded base is made of high-strength insulating epoxy fiberglass reinforced plastic. The embedded base is 3m long, 15cm wide in cross section, and 20cm high. A total of 14 pairs of vertical electrodes are set in the base, with a spacing of 20cm. The vertical electrodes are cylindrical stainless steel with a diameter of 6mm, and the height of the upper and lower electrodes is 5cm.

[0051] As the concrete dam body is poured, the upper and lower bases are pre-embedded and fixed inside the concrete pouring layers on both sides of the horizontal joint of the concrete dam. The joints in the bases correspond to the reserved horizontal joints / construction joints of the dam body.

[0052] The above embodiments are designed for the most common situation where the dam face experiences the greatest tensile stress, the crack opening is at its maximum, the horizontal crack gradually decreases inward, and the overall crack is wedge-shaped or conical. When facing the condition that there are defects or stress concentration areas inside the dam, or the coupling effect of multiple factors, resulting in the horizontal crack shape being small on the outside and large on the inside, large in the middle and small at both ends, or irregularly distributed, multiple pre-embedded bases are embedded longitudinally at a horizontal crack, and 2 to 10 vertical electrodes are inserted in each pre-embedded base. Thus, when a crack occurs at a certain point in the horizontal crack, only the upper and lower bases at the corresponding position are affected, causing the vertical electrodes to separate and the strain gauges to be stretched, thereby knowing the location, direction, opening, and crack rate of the horizontal crack.

[0053] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A monitoring device for horizontal construction joints of a concrete gravity dam, characterized in that, Includes embedded base, vertical electrode and strain gauge (16); The pre-embedded base includes an upper base (5) and a lower base (6), which are assembled vertically. The upper base (5) and the lower base (6) are respectively provided with vertical slots and wiring channels (14) connected to the vertical slots. The vertical electrode is composed of an upper electrode (71) and a lower electrode (72) that are assembled vertically. The assembly ends of the upper electrode (71) and the lower electrode (72) are docking ends, and the other end is a fixed end. The upper electrode (71) and the lower electrode (72) are normally connected when assembled. The fixed ends of the upper electrode (71) and the lower electrode (72) are respectively inserted and fixed in the vertical slots of the upper base (5) and the lower base (6) and connected with shielded cable leads (8). The shielded cable leads (8) are led out of the pre-embedded base through the wiring channel (14). The strain gauge (16) is pasted and fixed on the side of the vertical electrode for collecting the opening and closing displacement of the upper electrode (71) and the lower electrode (72).

2. The monitoring device for horizontal construction joints of concrete gravity dams according to claim 1, characterized in that: The upper electrode (71) and lower electrode (72) are fitted with the vertical slot with a clearance.

3. The monitoring device for horizontal construction joints of concrete gravity dams according to claim 1, characterized in that: The upper electrode (71) and lower electrode (72) are made of corrosion-resistant stainless steel and are covered with waterproof insulating sleeves, with only the docking ends exposed for electrical conduction; the pre-embedded base is made of high-strength insulating epoxy fiberglass reinforced plastic.

4. The monitoring device for horizontal construction joints of concrete gravity dams according to claim 1, characterized in that: The mating surfaces of the upper base (5) and the lower base (6) are non-planar and have a mating structure that restricts the upper base (5) and the lower base (6) to only move relative to each other in the vertical direction.

5. The monitoring device for horizontal construction joints of concrete gravity dams according to claim 4, characterized in that: The interlocking structure is one or more of the following: concave-convex key, V-shaped key, trapezoidal key, U-shaped key, or corrugated key.

6. The monitoring device for horizontal construction joints of concrete gravity dams according to claim 1, characterized in that: It also includes a thermal sensor, which is pre-installed inside a pre-embedded base.

7. The monitoring device for horizontal construction joints of concrete gravity dams according to claim 1, characterized in that: One or more vertical electrodes are installed in a pre-embedded base; when there are multiple vertical electrodes, the spacing between the vertical electrodes is 10cm to 20cm and the spacing is equal.

8. The application of a monitoring device for horizontal construction joints of concrete gravity dams as described in any one of claims 1 to 7, characterized in that: As the concrete dam body is poured, the upper base (5) and lower base (6) are pre-embedded and fixed inside the concrete pouring layer on both sides of the horizontal joint (4) of the concrete dam. The vertical electrodes are arranged in a linear array in the pre-embedded base. The pre-embedded base is arranged along the entire length of the horizontal joint (4) to cover the required monitoring range of the horizontal joint (4), so that the single-layer electrode array forms a continuous monitoring array covering the required monitoring range of the horizontal joint (4). The shielded cable lead (8) of each layer is electrically connected to the multi-channel inspection module, and the on / off status of each vertical electrode in each layer is polled layer by layer to realize the cracking depth monitoring of the horizontal joint (4). The strain gauge (16) of each layer is electrically connected to the strain sensing module to collect the opening and closing width data of the horizontal joint (4) to realize the crack width monitoring of the horizontal joint (4).

9. The application of the monitoring device for horizontal construction joints of concrete gravity dams according to claim 8, characterized in that: One to two sets of spare vertical electrodes are added to key monitoring layers with a depth greater than 1m. When the main electrode fails, the multi-channel inspection module automatically switches to the spare circuit.

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