Immersed tube void detection method and repair method

Abstract

The invention relates to the technical field of immersed tube construction, in particular to an immersed tube void detection method and repair method.The detection method comprises the following steps that grids are classified into first-level grids and second-level grids, acoustic wave method detection is carried out on the first-level grids, and neutron method detection is carried out on the second-level grids; when sound wave method detection is carried out on the grid, whether the void exceeds the limit or not is judged according to a sound wave method detection result, if yes, neutron method detection is carried out on the grid, and if not, the grid is recorded to a qualified group; when neutron method detection is carried out on the grid, whether void exceeds the limit or not is judged according to a neutron method detection result, if yes, drilling method detection is carried out on the grid, and if not, the grid is recorded to a qualified group. The invention provides a detection process capable of giving full play to the advantages of a neutron method and an acoustic wave method, and the detection efficiency is greatly improved while the relatively high accuracy is maintained.

Description

Technical Field

[0001] This invention relates to the field of immersed tunnel construction technology, and in particular to a method for detecting and repairing voids in immersed tunnels. Background Technology

[0002] The immersed tunnel method is a common approach to underwater tunnel construction. Its basic unit is the immersed tunnel segment, which can be prefabricated on land and then connected underwater through processes such as floating, sinking, and docking to form a complete tunnel structure. Steel-shell immersed tunnel segments are one type, mainly consisting of a steel shell and concrete. The steel shell encloses several compartments, and concrete is poured inside these compartments. This structure combines the strength of steel with the durability of concrete. After concrete pouring, for safety reasons, it is necessary to inspect the concrete within the compartments for voids to determine if any exceed the limit. Voids within the concrete within the compartments are considered a hidden danger. To minimize damage to the immersed tunnel structure, non-destructive testing (NDT) techniques are prioritized. For large underwater tunnels, the number of standard immersed tunnel sections can reach dozens. Ensuring high testing efficiency is crucial for shortening the construction period. For example, Japan uses the tapping method to confirm the presence of voids. The tapping method involves tapping the surface of the immersed tunnel section, and then the inspectors listen to the sound to identify the voids. The tapping method is closely related to human sensory perception and has the problem of low accuracy. In engineering, the neutron method is also used to detect concrete voids. The neutron method has the characteristics of high detection accuracy but low efficiency. When there are too many immersed tunnel sections, it will slow down the overall construction progress. Summary of the Invention

[0003] The purpose of this invention is to overcome the problem in the prior art that existing detection methods cannot balance efficiency and accuracy when detecting voids in concrete, and to provide a method for detecting and repairing voids in submerged pipes.

[0004] In a first aspect, the present invention provides a method for detecting voids in immersed tunnel sections, comprising immersed tunnel sections divided into several grids, and including the following steps: The grid is classified into primary grid and secondary grid. The primary grid is detected by acoustic wave method, and the secondary grid is detected by neutron method. When performing acoustic wave testing on the grid: determine whether the voiding exceeds the limit based on the acoustic wave testing results. If so, perform neutron wave testing on the grid; otherwise, record the grid in the qualified group. When performing neutron method testing on the grid: determine whether the void exceeds the limit based on the neutron method test results. If so, perform borehole method testing on the grid; otherwise, record the grid in the qualified group. When performing drilling inspection on the grid: find the point corresponding to the maximum void height in the grid, open the first hole at the point, use a depth gauge to insert into the first hole to measure the void height, and determine whether the void exceeds the limit based on the measurement result. If so, record the grid in the exceeding group; otherwise, record the grid in the qualified group.

[0005] Preferably, when classifying the grid: if the grid is at least partially located within the risk area, the grid is classified as a secondary grid; otherwise, it is classified as a primary grid; the risk area includes the hoisting point location area, the mooring post location area, the bracket embedded part location area, the water tank embedded part location area, the thick and thin steel plate splice location area, and the inclined cell location area.

[0006] Preferably, it includes a first pipe section and a second pipe section that are continuously inspected. The first pipe section is an inspected immersed pipe section, and the second pipe section is an uninspected immersed pipe section. The first pipe section and the second pipe section are divided into grids according to the same rules. When classifying the grid of the second pipe section: the grid that is in the same position as the grid of the over-limit group of the first pipe section is classified as a secondary grid; otherwise, it is classified as a primary grid.

[0007] Preferably, the method includes a first pipe section, a second pipe section, and a third pipe section that are tested sequentially. The first and second pipe sections are tested submerged pipe sections, and the third pipe section is an untested submerged pipe section. The first, second, and third pipe sections are divided into grids according to the same rules. When classifying the grid of the third pipe section: the grid that is in the same position as the grid of the over-limit group of the first or second pipe section is classified as a secondary grid; otherwise, it is classified as a primary grid.

[0008] Preferably, when classifying the grids of the immersed tunnel segment: count the number of times the corresponding position of each grid in the segment to be tested belongs to the out-of-limit group among all the detected immersed tunnel segments, and sort the grids in the segment to be tested in descending order of the number, classify the grids before the first threshold as secondary grids, and classify the grids after the first threshold as primary grids.

[0009] Preferably, the testing equipment is calibrated before testing, including the following steps: A1. Prepare at least three specimens, wherein the void height of at least one specimen is less than a void height threshold, and the void height of at least one specimen is greater than a void height threshold; A2. Use the testing equipment to test all the test pieces. If the test results are all correct, the testing equipment is qualified. Otherwise, calibrate the testing equipment and repeat A2.

[0010] Preferably, the detachment height threshold is any value between 4mm and 5mm.

[0011] Preferably, the neutron method is a slow neutron / thermal neutron detection method.

[0012] Preferably, the acoustic method is an impact echo method or an impact imaging method.

[0013] Preferably, the size of the grid is configured such that both the neutron method detection device and the acoustic method detection device can complete the detection of one grid in a single operation.

[0014] In a second aspect, the present invention provides a method for repairing voids in immersed tunnel sections, which uses the immersed tunnel void detection method described above to detect voids in the tunnel sections and repairs the grid within the excess limit group, including the following steps: The edge of the voided area is determined by tapping, and at least two second openings are made on the edge of the voided area, with the two second openings located on both sides of the first opening; Grouting is injected into the first opening until grout flows out of all the second openings; Seal the first opening and the second opening.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The immersed tube void detection method of this invention classifies the grid and performs acoustic wave detection on the first-level grid with a low probability of void exceeding the limit. Acoustic wave detection is efficient but relatively inaccurate, enabling rapid screening. After acoustic wave detection determines that a grid has exceeded the void limit, neutron wave detection is performed on the same grid to further determine the void status. For the second-level grid with a higher probability of void exceeding the limit and the first-level grid that was determined to have exceeded the void limit by acoustic wave detection, neutron wave detection is performed. Neutron wave detection is less efficient but relatively accurate, enabling a more accurate determination of whether void exceeds the limit. If neutron wave detection determines that void exceeds the limit, drilling detection is finally performed for final confirmation. By using the above method, the advantages of different detection methods can be fully utilized, and the detection efficiency can be significantly improved while maintaining high accuracy. Attached Figure Description

[0016] Figure 1 This is a flowchart of the immersed tube void detection method according to an embodiment of the present invention; Figure 2 This is a top view of the immersed tunnel section described in an embodiment of the present invention; Figure 3 This is a structural schematic diagram of the seam area between thick and thin steel plates as described in an embodiment of the present invention; Figure 4 This is a structural schematic diagram of the inclined storage compartment location area according to an embodiment of the present invention; Figure 5 This is a top view of the vacant area described in an embodiment of the present invention; Figure 6This is a side sectional view of the voided area described in an embodiment of the present invention.

[0017] Marked in the image: 1-Submerged pipe section; 2-First opening; 3-Second opening; 4-Lifting point location area; 5-Mooring post location area; 6-Thick and thin steel plate splice location area; 7-Sloping compartment location area; 71-Weld stud; 8-Void area. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0019] Unless otherwise specified, the use of terms such as "upper," "lower," "left," "right," "center," "inner," and "outer" to indicate orientation or positional relationships in the description of specific embodiments of the present invention is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is typically placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0020] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," and "parallel" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, or parallel, but rather that it can be slightly tilted or have a deviation. For example, "horizontal" merely means that its direction is more horizontal relative to "vertical," not that the structure must be completely horizontal, but that it can be slightly tilted. Alternatively, it can be simplified to mean that the corresponding device / component / element, when set in a "horizontal," "vertical," "suspended," or "parallel" direction, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the present invention.

[0021] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0022] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as 2, 3, 4, 5, 6, 7, 8, or 9, and can even exceed nine.

[0023] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to common connection methods in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0024] Example The immersed tunnel method is a common method for underwater tunnel construction. Its basic unit is the immersed tunnel section 1, which can be prefabricated on land and then connected underwater through processes such as floating, sinking, and docking to form a complete tunnel structure. A steel-shell immersed tunnel section 1 is one type, mainly consisting of a steel shell and concrete. The steel shell encloses several compartments, and concrete is poured inside these compartments. This structure combines the strength of steel with the durability of concrete. After the concrete pouring is completed, for safety reasons, it is necessary to inspect the concrete within the compartments for voids to determine if any voids exceed the limit. Voids within the concrete within the compartments are considered... To minimize damage to the immersed tunnel structure, non-destructive testing (NDT) techniques are prioritized for concealed damage. For large underwater tunnels, the number of standard immersed tunnel sections can reach dozens. Ensuring high testing efficiency is crucial for shortening the construction period. For example, Japan uses the tapping method to confirm the presence of voids. The tapping method involves tapping the surface of the immersed tunnel section 1, and then the inspectors listen to the sound to identify the voids. The tapping method is closely related to human sensory perception and has the problem of low accuracy. In engineering, the neutron method is also used to detect concrete voids. The neutron method has the characteristics of high detection accuracy but low efficiency. When there are too many immersed tunnel sections 1, it will slow down the overall construction progress.

[0025] To balance the efficiency and accuracy of concrete void detection for the immersed tunnel section 1, such as Figure 1 As shown, in a first aspect, embodiments of this application provide a method for detecting voids in immersed tunnel sections, including an immersed tunnel section 1, wherein the immersed tunnel section 1 is divided into several grids, and includes the following steps: The grid is classified into primary grid and secondary grid. The primary grid is detected by acoustic wave method, and the secondary grid is detected by neutron method. When performing acoustic wave testing on the grid: determine whether the voiding exceeds the limit based on the acoustic wave testing results. If so, perform neutron wave testing on the grid; otherwise, record the grid in the qualified group. When performing neutron method testing on the grid: determine whether the void exceeds the limit based on the neutron method test results. If so, perform borehole method testing on the grid; otherwise, record the grid in the qualified group. When performing drilling inspection on the grid: find the point corresponding to the maximum void height in the grid, open the first hole 2 at the point, use a depth gauge to extend into the first hole 2 to measure the void height, and determine whether the void exceeds the limit based on the measurement result. If it does, record the grid in the exceeding group; otherwise, record the grid in the qualified group.

[0026] In this embodiment, the immersed tunnel section 1 is a steel shell immersed tunnel section 1. The grid can be divided on the top plate, bottom plate, and side plate of the immersed tunnel section 1. Since both the acoustic wave method and the neutron method have a certain detection depth, the same vertical position of the top plate or bottom plate can be divided into the same grid. During the inspection, the detection can be carried out from the top surface of the top plate or bottom plate. The same horizontal position of the side plate can be divided into the same grid. During the inspection, the detection can be carried out from one side of the side plate. Of course, if the thickness of the top plate, bottom plate, or side plate is too large, the grid can also be divided on both sides for inspection.

[0027] Classifying the grid refers to dividing it into primary grids or secondary grids. Each grid is assigned to only one category. Primary grids are those with a low probability of void leakage exceeding the limit, while secondary grids are those with a high probability. For primary grids with a low probability of void leakage exceeding the limit, acoustic detection can be performed directly to quickly determine the void leakage situation. For secondary grids with a high probability of void leakage exceeding the limit, neutron detection can be performed directly to more accurately determine the void leakage situation. Acoustic detection has the characteristics of high detection efficiency but low accuracy, while neutron detection has the characteristics of high detection accuracy but low efficiency.

[0028] Whether the void exceeds the limit refers to whether the void exceeds the requirements of the relevant specifications or structural safety, mainly referring to whether it exceeds the requirement of void height. For the convenience of describing this solution, this embodiment uses a void height threshold to represent the maximum allowable void height, which refers to the gap between the concrete surface and the steel plate. In some embodiments, the void height threshold is any value between 4mm and 5mm; taking a void height threshold of 5mm as an example, if the acoustic wave method or neutron method determines that the void height in the grid is ≥5mm, the inspector can proceed to the next inspection step for a more accurate judgment; if the acoustic wave method or neutron method determines that the void height in the grid is <5mm, the inspector can record the grid in the qualified group.

[0029] Acoustic wave testing is a method of determining the internal quality of concrete by analyzing the propagation characteristics of sound waves in the concrete (wave velocity, attenuation, frequency, etc.). Examples include ultrasonic pulse testing, impact echo testing, and acoustic emission testing. To ensure greater accuracy and objectivity, acoustic wave testing uses appropriate testing equipment, such as the CTS-9006 ultrasonic flaw detector. Acoustic wave testing equipment can be purchased or customized; this embodiment does not impose excessive restrictions on the model, as long as it meets the testing requirements. Neutron wave testing is a non-destructive testing technique that utilizes the principle of neutron-matter interaction to detect the internal structure or defects of materials. Examples include thermal neutron imaging and neutron backscattering. Neutron wave testing uses appropriate testing equipment, such as a neutron void detector. Preferably, the acoustic wave method is the impact echo method or impact imaging method; the neutron method is the slow neutron / thermal neutron detection method. The slow neutron / thermal neutron detection method is based on the interaction between neutrons and hydrogen atoms, identifying void regions by measuring changes in thermal neutron flux or secondary gamma rays.

[0030] To help better understand this application, let's take a certain level of grid as an example: First, perform acoustic wave detection on the first level of grid. If the acoustic wave detection determines that the voids are within the limit, record the first level of grid in the qualified group. If the acoustic wave detection determines that the voids are within the limit, perform neutron wave detection on the first level of grid for a more accurate determination. If the neutron wave detection determines that the voids are within the limit, record the first level of grid in the qualified group. If the neutron wave detection determines that the voids are within the limit, perform borehole drilling detection on the first level of grid for a final determination.

[0031] Taking a certain secondary grid as an example: if the neutron method is used to detect the secondary grid, and the neutron method determines that the voiding is within the limit, the primary grid is recorded in the qualified group. If the neutron method determines that the voiding exceeds the limit, the drilling method is used to detect the primary grid for final determination. Of course, the acoustic method can also be used to make a comprehensive judgment before or after the neutron method is used to detect the secondary grid.

[0032] For immersed tunnel segment 1, acoustic wave detection and neutron wave detection can be performed simultaneously. Acoustic wave detection can be performed on all first-level grids while neutron wave detection is performed on second-level grids. After neutron wave detection has been performed on all second-level grids, neutron wave detection is performed on the first-level grids that were determined by acoustic wave detection to have exceeded the void limit. Alternatively, acoustic wave detection can be performed on all grids while neutron wave detection is performed on second-level grids. After neutron wave detection has been performed on all second-level grids, neutron wave detection is performed on the first-level grids that were determined by acoustic wave detection to have exceeded the void limit. In other words, either acoustic wave detection can be used to detect all first-level grids or acoustic wave detection can be used to detect all grids.

[0033] Drilling inspection refers to connecting the voided area 8 to the outside world by drilling a hole, and then using tools such as a depth gauge to measure the voided height by inserting them into the voided area 8 through the hole. Drilling inspection will cause some damage to the immersed tube section 1, so it is used as the final inspection and judgment method. Generally, drilling inspection is only used when other methods have been used and the suspicion of exceeding the void limit still cannot be eliminated. Multiple previous inspections and judgments are used to reduce the occurrence of misjudgments and avoid drilling the steel shell compartments for verification due to misjudgments, which would artificially affect the durability of the steel shell. When using the drilling method for inspection: First, determine the point corresponding to the maximum void height. This step can be determined by acoustic wave detection equipment, neutron detection equipment, or tapping. It is preferable to use a combination of methods. Acoustic wave detection equipment and neutron detection equipment can usually provide a rough value of the void height, and tapping can also roughly determine the location corresponding to the maximum void height. After finding the point corresponding to the maximum void height, open the first hole 2 at that point. Measure the void height by inserting a depth gauge vertically. If the depth gauge shows that the void is still beyond the limit, record the grid in the "exceeding limit" group. If the depth gauge shows that the void is not beyond the limit, record the grid in the "acceptable" group.

[0034] During the testing process, the status of each completed grid can be recorded. Specifically, this includes the grid number and whether the void exceeds the limit. Other information, such as the void height measured by acoustic wave testing, neutron testing, and borehole testing, can also be recorded. Based on the final judgment of whether the grid exceeds the void limit, the grid is divided into an over-limit group and a qualified group. Grids in the over-limit group need to be grouted for repair. Grids in the qualified group do not need additional treatment if they have not undergone borehole testing. If they have undergone borehole testing, they can be grouted for repair, or they can be directly sealed to restore the original state without grooving repair.

[0035] The immersed tube void detection method of this invention first classifies the grid. For the first-level grid with a low probability of void exceeding the limit, acoustic wave detection is performed. Acoustic wave detection is efficient but relatively inaccurate, enabling rapid screening. After acoustic wave detection determines that a grid has exceeded the void limit, neutron wave detection is performed on that grid to further determine the void status. For the second-level grid with a higher probability of void exceeding the limit and the first-level grid determined by acoustic wave detection to have exceeded the void limit, neutron wave detection is performed. Neutron wave detection is less efficient but relatively more accurate, enabling a more precise determination of whether void exceeds the limit. If neutron wave detection determines that void exceeds the limit, drilling detection is finally performed for final confirmation. By using the above method, the advantages of different detection methods can be fully utilized, significantly improving detection efficiency while maintaining high accuracy.

[0036] The immersed tube void detection method of the present invention adopts a combination of acoustic wave method and neutron method. Compared with the scheme of using neutron method to detect all grids, it omits a large number of first-level grids with low void exceedance probability and can significantly shorten the detection time. Compared with the scheme of using acoustic wave method or knocking method to detect all grids, it can significantly improve the detection accuracy and reduce the probability of false judgment.

[0037] This embodiment provides a first grid classification method. When classifying grids: if a grid is at least partially located within a risk area, it is classified as a secondary grid; otherwise, it is classified as a primary grid. A risk area refers to an area with a high risk of venting. The corresponding silos in this area usually have complex structures, such as a large number of embedded parts, which are assessed as potentially having a significant impact on silo ventilation, thereby causing venting to exceed limits. Risk areas include lifting point location area 4, mooring post location area 5, bracket embedded part location area, water tank embedded part location area, thick and thin steel plate splice location area 6, and inclined silo location area 7, etc.

[0038] like Figure 2 As shown, lifting point location area 4 refers to the location on the top surface of the immersed tunnel section 1 where there are zipper lifting points. Each immersed tunnel section 1 may have 6-8 zipper lifting points. During the installation of the immersed tunnel section 1, the zipper lifting points are used for floating and installation of the section. It is equivalent to all the force being concentrated in this area. Therefore, the structure has a large area, the embedded parts are deep and large in size, some steel plates are thickened, and there is a compartment that is blocked by 3 embedded parts. At the same time, the areas blocked by the 3 embedded parts include the middle position, the lower left corner and the lower right corner, which affect the air exhaust of the compartment to varying degrees, thus affecting the compaction.

[0039] like Figure 2 As shown, area 5, where the mooring post is located, refers to the location on the top surface of the immersed tunnel section 1 where the mooring post is located. The mooring post is usually located at the four corners of the top plate of the immersed tunnel section 1 and is mainly used for the hoisting and installation of the immersed tunnel section 1. The structure needs to be equipped with cable piles on the outside. Therefore, in addition to the pre-embedded steel plate anchor bars, it is also necessary to pre-embed larger bolts and screws to facilitate the subsequent installation of mooring posts. Therefore, the compartment at this location has anchor bars + pre-embedded nuts and screws, which makes the structure more complex and affects the filling.

[0040] The area where the corbel embedded parts are located refers to the location on the immersed tube section 1 where the corbel embedded parts are installed. The corbel embedded parts are mainly used to support the end seal of the immersed tube. Since the end seal needs to withstand the water pressure of tens of meters underwater, the corbel embedded parts need to have sufficient force to support the end seal. The corbels are arranged densely and the anchor bars are large in size. Some parts need to be combined with bolts and anchor bars. Because of the complexity of the structure, it will affect the arrangement of the vent holes of the compartment. The vent holes cannot be arranged in the conventional way, which will affect the venting and cause the compartment to become detached.

[0041] The water tank embedded part location area refers to the location on the immersed tube section 1 where the water tank embedded part is located. The water tank embedded part is mainly used to support the water pressure inside the water tank in the tube section later. The water pressure is usually within 5.5m. It usually involves anchor bars and bolts, but the size and quantity are small, and the impact on the inside of the compartment is slightly lower. Other embedded parts and embedded structures besides the water tank location will be smaller.

[0042] like Figure 3 As shown, area 6, the seam between the thick and thin steel plates, refers to the junction of the thick and thin steel plates inside the storage compartment. There is a slope here, and gas may accumulate at this slope, causing cavitation.

[0043] like Figure 4 As shown, the inclined cell location area 7 refers to the intersection of the side plate and the bottom plate. To reduce stress concentration, an inclined surface is usually provided at this location for transition connection. Inside the cell, gas accumulation is likely to occur at the root of the weld stud 71 connected to the inclined surface, leading to cavitation.

[0044] This embodiment provides a second grid classification method: including a first and a second pipe section to be continuously inspected. The first pipe section is the inspected immersed pipe section 1, and the second pipe section is the uninspected immersed pipe section 1. Both the first and second pipe sections are standard immersed pipe sections with similar shapes and structures, allowing them to be divided into grids according to the same rules. The first pipe section is inspected according to the above-mentioned void detection method. When classifying the grid of the second pipe section: the grids that are in the same position as the grids of the first pipe section in the over-limit group are classified as secondary grids; otherwise, they are classified as primary grids. That is, for a certain grid of the second pipe section, if the grids in the first pipe section that are in the same position as that grid belong to the over-limit group, then that grid of the second pipe section is classified as a secondary grid. In other words, the grid classification of the subsequently inspected pipe section is determined based on the void over-limit distribution obtained from the first inspected pipe section. Since the shapes and structures of the first and second pipe sections are similar, the distribution of the void areas 8 should also be roughly the same. The former has greater reference significance for the latter. The above-mentioned grid classification method can make the grid classification of the second pipe section more scientific and reasonable.

[0045] This embodiment provides a third grid classification method: including sequentially inspecting a first, second, and third pipe section. The first and second pipe sections are inspected immersed pipe sections 1, and the third pipe section is an uninspected immersed pipe section 1. The first, second, and third pipe sections are all standard immersed pipe sections, with similar shapes and structures, and can be divided into grids according to the same rules. The first and second pipe sections are inspected according to the above-mentioned void detection method. When classifying the grid of the third pipe section: the grid that is in the same position as the grid of the first or second pipe section in the over-limit group is classified as a secondary grid; otherwise, it is classified as a primary grid. That is, for a certain grid of the third pipe section, if the grid in the first or second pipe section that is in the same position as that grid belongs to the over-limit group, then that grid of the third pipe section is classified as a secondary grid. This makes the grid classification more rigorous and minimizes random errors.

[0046] Taking a specific project as an example: This project requires the fabrication of dozens of standard immersed tunnel sections. The steel shell construction, concrete pouring, and void detection of the same immersed tunnel section 1 are sequential. Different immersed tunnel sections 1 are constructed in sequence, thus ensuring that void detection of each immersed tunnel section 1 is conducted sequentially. When conducting void detection on the first immersed tunnel section 1, since there are no other reference materials, the risk areas can be identified through the structural characteristics of the immersed tunnel section 1. Based on these risk areas, a grid classification method can be used, as described in the first grid classification method above. When conducting void detection on the second immersed tunnel section 1... During void detection, the mesh of the second immersed tunnel section 1 can be classified by referring to the void detection results of the first immersed tunnel section 1. Specifically, refer to the second mesh classification method mentioned above. When detecting voids in the third immersed tunnel section 1, the mesh of the third immersed tunnel section 1 can be classified by referring to the void detection results of the first two immersed tunnel sections 1. Specifically, refer to the third mesh classification method mentioned above. By summarizing the void patterns of the previously detected immersed tunnel sections 1, the accuracy can be continuously improved and the time to find the void exceeding the limit can be shortened.

[0047] The first, second, or third grid classification method can be used for the immersed tunnel segment 1. Starting from the fourth immersed tunnel segment 1, subsequent immersed tunnel segments 1 can refer to the voiding status of all previous immersed tunnel segments 1, or they can refer only to the one, two, or three immersed tunnel segments 1 in front of them, depending on the specific needs.

[0048] In some embodiments, when classifying the grids of the immersed tunnel segment 1: the number of grids corresponding to each grid in all the detected immersed tunnel segments that belong to the out-of-limit group is counted; that is, the number of grids corresponding to each position in the segment to be tested that belong to the out-of-limit group in all the detected immersed tunnel segments is counted, and the grids are sorted in descending order of the number. Grids sorted before a first threshold are classified as secondary grids, and grids sorted after the first threshold are classified as primary grids. The first threshold can be any value between 30% and 50% of the total number of grids. For example, if the first threshold is 40% of the total number of grids, then the first 40% of the grids are classified as secondary grids, and the last 60% of the grids are classified as primary grids.

[0049] In some embodiments, calibrating the testing equipment before testing includes the following steps: A1. Prepare at least three specimens, with at least one specimen having a void height less than the void height threshold and at least one specimen having a void height greater than the void height threshold. A2. Use the testing equipment to test all specimens. If the test results are all correct, the testing equipment is qualified. Otherwise, calibrate the testing equipment and repeat A2.

[0050] In some embodiments, the vacancy height of at least one specimen is equal to a vacancy height threshold, and calibration can be guided by repeatedly testing the specimen when calibrating the testing equipment.

[0051] In some embodiments, the acoustic detection equipment is calibrated so that when it detects specimens with a void height equal to or slightly less than the void height threshold, it can make a judgment that the void height exceeds the limit, prompting the tester to further judge using the neutron method, thereby reducing the probability of incorrect judgment. "Slightly less than the void height threshold" can be 0 to 1 mm smaller than the void height threshold. For example, if the void height threshold is 5 mm, the acoustic detection equipment can be calibrated so that it can basically detect specimens with a void height greater than 4 mm.

[0052] For example, the void height within the specimen can be a gradient set artificially: 0mm, 1mm, 2mm, 3mm, 4mm, 5mm, and 6mm. During verification, if both the acoustic wave testing equipment and the neutron wave testing equipment can accurately judge the specimen, the equipment is considered qualified. The acoustic wave method can basically judge the range of 0mm, 1mm to 4mm, and greater than 4mm. If the test result shows the first two ranges, the void requirement is met. If it shows the last range, there may be a void exceeding the limit, and the neutron wave method needs to be used for further judgment. The neutron wave method can detect with an accuracy of 0.1mm. However, because the neutron wave method is affected by environmental interference and measures only a grid range, it cannot be 100% accurate as the true void situation. Therefore, the drilling method is ultimately needed to verify the true situation and provide a basis for the grid classification of the subsequent immersed tube section 1.

[0053] In some embodiments, the grid size is configured such that both the neutron method detection device and the acoustic method detection device can complete the detection of one grid at a time. That is, the grid size is determined based on the detection range that the detection device can detect in a single operation. This reduces the number of measurements required by the inspector, thereby improving detection efficiency. Preferably, the grid size is slightly smaller than the detection range that the detection device can detect in a single operation, achieving edge coverage and avoiding inaccurate detection results at boundary locations. In an example, the grid size can be 10cm × 10cm.

[0054] In some embodiments, the method further includes the following steps: repairing the voids in the mesh within the over-limit group, and re-inspecting after the void repair is completed. The inspection method may be the acoustic method, neutron method, or other methods mentioned above. Passing the re-inspection is considered as passing the inspection.

[0055] In some embodiments, after the void detection is completed: all grids are inspected for voids and corrosion. If there are no problems with the void and corrosion detection, the inspection work is completed.

[0056] like Figure 5 and Figure 6 As shown, in a second aspect, embodiments of this application provide a method for repairing voids in immersed tunnel sections. This method uses the aforementioned method for detecting voids in immersed tunnel sections to inspect the tunnel segments and repairs the grid within the excess limit group. The method includes the following steps: The edge of the voided area 8 is determined by tapping, and at least two second openings 3 are made on the edge of the voided area 8, with the two second openings 3 located on both sides of the first opening 2. Grout is injected into the first opening 2 until grout flows out of all the second openings 3; The first opening 2 and the second opening 3 can be sealed by re-welding steel plates.

[0057] As shown in the figure, the two second openings 3 are located on opposite sides of the first opening 2. The two second openings 3 can reduce the occurrence of air closure and improve the repair quality. Preferably, the first opening 2 is located on the line connecting the two second openings 3.

[0058] In some embodiments, both the first opening 2 and the second opening 3 are provided with grouting heads. The grouting head can be understood as a closed component. The grouting head allows gas to pass through under a certain pressure. Once the grout flows out of the grouting head, it means that the gas has been discharged and the grouting has reached the compaction stage.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for detecting voids in immersed tubes, characterized in that, The process includes immersed tunnel sections (1), which are divided into several grids, and includes the following steps: The grid is classified into primary grid and secondary grid. The primary grid is detected by acoustic wave method, and the secondary grid is detected by neutron method. When performing acoustic wave testing on the grid: determine whether the voiding exceeds the limit based on the acoustic wave testing results. If so, perform neutron wave testing on the grid; otherwise, record the grid in the qualified group. When performing neutron method testing on the grid: determine whether the void exceeds the limit based on the neutron method test results. If so, perform borehole method testing on the grid; otherwise, record the grid in the qualified group. When performing drilling inspection on the grid: find the point corresponding to the maximum void height in the grid, open the first hole (2) at the point, use a depth gauge to insert into the first hole (2) to measure the void height, and judge whether the void exceeds the limit based on the measurement result. If so, record the grid to the exceeding group; otherwise, record the grid to the qualified group.

2. The method for detecting voids in immersed tubes according to claim 1, characterized in that, When classifying the grid: if the grid is at least partially located within the risk area, the grid is classified as a secondary grid; otherwise, it is classified as a primary grid. The risk area includes the hoisting point location area (4), the mooring post location area (5), the bracket embedded part location area, the water tank embedded part location area, the thick and thin steel plate splice location area (6), and the inclined cell location area (7).

3. The method for detecting voids in immersed tubes according to claim 1, characterized in that, It includes a first pipe section and a second pipe section that are continuously inspected. The first pipe section is the inspected immersed pipe section (1), and the second pipe section is the uninspected immersed pipe section (1). The first pipe section and the second pipe section are divided into grids according to the same rules. When classifying the mesh of the second pipe section: meshes that are in the same position as the meshes of the over-limit group of the first pipe section are classified as secondary meshes; otherwise, they are classified as primary meshes.

4. The method for detecting voids in immersed tubes according to claim 1, characterized in that, The first, second and third pipe sections are tested sequentially. The first and second pipe sections are the tested immersed pipe sections (1), and the third pipe section is the untested immersed pipe section (1). The first, second and third pipe sections are divided into grids according to the same rules. When classifying the mesh of the third pipe section: meshes that are in the same position as the meshes of the over-limit group of the first or second pipe section are classified as secondary meshes; otherwise, they are classified as primary meshes.

5. The method for detecting voids in immersed tubes according to claim 1, characterized in that, When classifying the grid of the immersed tunnel segment (1): count the number of times the corresponding position of each grid in the segment to be tested belongs to the over-limit group in all the detected immersed tunnel segments, and sort the grids in the segment to be tested in descending order of the number. Classify the grids sorted before the first threshold as secondary grids and classify the grids sorted after the first threshold as primary grids.

6. The method for detecting voids in immersed tubes according to claim 1, characterized in that, The testing equipment must be calibrated before testing, including the following steps: A1. Prepare at least three specimens, wherein the void height of at least one specimen is less than a void height threshold, and the void height of at least one specimen is greater than a void height threshold; A2. Use the testing equipment to test all the test pieces. If the test results are all correct, the testing equipment is qualified. Otherwise, calibrate the testing equipment and repeat A2.

7. The method for detecting voids in immersed tubes according to claim 6, characterized in that, The threshold for the detachment height is any value between 4mm and 5mm.

8. The method for detecting voids in immersed tubes according to any one of claims 1-7, characterized in that, The neutron method is a slow neutron / thermal neutron detection method; the acoustic method is an impact echo method or an impact imaging method.

9. The method for detecting voids in immersed tubes according to any one of claims 1-7, characterized in that, The size of the grid is configured such that both the neutron method detection device and the acoustic method detection device can complete the detection of one grid in a single operation.

10. A method for repairing voids in submerged tunnel sections, characterized in that, The immersed tunnel section is inspected using the immersed tunnel void detection method as described in any one of claims 1-9, and the grid within the excess group is repaired, including the following steps: The edge of the voided area (8) is determined by tapping, and at least two second openings (3) are made on the edge of the voided area (8), with the two second openings (3) located on both sides of the first opening (2); Grout is injected into the first opening (2) until grout flows out of all the second openings (3); Seal the first opening (2) and the second opening (3).

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