An optimized design method and system for compartments of immersed tube tunnels based on a sandwich structure

Abstract

The present invention provides an optimized design method and system for compartments of a sandwich-structured immersed tunnel, belonging to the technical field of tunnels. The method includes: collecting and analyzing the detection data of the void defects of the sandwich-structured immersed tunnel; classifying the sandwich-structured immersed tunnel with different compartments according to the collected and analyzed detection data; statistically calculating the void defect probabilities of different compartments according to the classification results; analyzing the void defect rules according to the statistical results to obtain the optimal compartment design strategy. Based on the detection results of the void defects of the sandwich-structured immersed tube by the impact echo method and the neutron method, the present invention comprehensively considers factors such as seasonal temperature, pumping distance, compartment size, placement hole setting, and self-compacting concrete fluidity to analyze the factors affecting the casting quality of the immersed tunnel, and solves the problem that the void defects are prone to occur in the process of precasting and casting of the self-compacting concrete of this immersed tunnel structure through optimizing the compartment design.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunnels, and in particular relates to a compartment optimization design method and system based on a sandwich structure immersed tube tunnel. Background Art

[0002] Immersed tube tunnel structures are widely used in large underwater tunnel construction projects around the world. There are two main structural forms, namely reinforced concrete immersed tube tunnels and combined immersed tube tunnels with thin steel shell as outer lining and embedded reinforced concrete. Both structural forms use reinforced concrete structure as the core component of the immersed tube structure. The prefabrication and pouring process is complicated and has high requirements for the prefabrication site. In the 1990s, in order to solve the limitation that there was no prefabrication site available near the project site, Japan further developed the double-layer steel shell concrete immersed tube structure and proposed to make all steel structures into closed compartments and pour self-compacting concrete during floating. This method is called sandwich structure steel-concrete combined immersed tube. The sandwich structure immersed tube uses steel to wrap concrete, and combines the excellent properties of steel and concrete. It fully utilizes the performance of steel during the construction and operation stages, and has excellent bending, shear and waterproof properties. Concrete, as a ballast, mainly bears pressure and has the advantages of convenient construction and good seismic performance. It can be applied to construction conditions with high water pressure and large spans, and saves costs to a large extent. It is an important development direction for future cross-sea tunnels.

[0003] The sandwich structure immersed tube uses the reserved pouring holes and exhaust holes in the cabin to pour the self-compacting concrete. The pouring process cannot be vibrated. In addition, the complex shear components embedded in the compartment restrict the flow of the self-compacting concrete. The bonding surface between the steel plate and the concrete is very likely to have a cavity defect of loose pouring. Existing experimental studies have found that the existence of cavity defects will reduce the bearing capacity of the immersed tube structure and even cause local buckling of the structure, affecting the overall safety of the structure. In order to improve the pouring quality of the self-compacting concrete of the immersed tube, on the one hand, it is necessary to determine a reasonable concrete mix ratio to improve the fluidity of the self-compacting concrete. On the other hand, it is necessary to formulate a reasonable compartment size, optimize the distribution position and number of pouring holes, exhaust holes and shear stiffening components, and ensure the smooth flow path of the concrete. At present, only two of the immersed tube tunnels that have been completed and operated in the world have fully adopted the sandwich structure method, and both are located in Japan, namely the Naha Tunnel and the Shin-Wakato Tunnel. There is little engineering experience available. Compared with similar projects, the Shenzhen-Zhongshan Tunnel is the world's largest sandwich-structured steel-shell concrete immersed tube tunnel: (1) In terms of tube segment width, the widest tube segment of the Shenzhen-Zhongshan Tunnel is 55.46 m, which is 1.99 times that of the Shin-Wakato Tunnel and 1.5 times that of the Naha Tunnel. (2) In terms of immersed tube tunnel length, the Shenzhen-Zhongshan Tunnel is 5,035 m long, which is 8.9 times that of the Shin-Wakato Tunnel and 5.9 times that of the Naha Tunnel.

[0004] The construction of the Shenzhen-Zhongshan Passage faces multiple engineering challenges, such as complex steel shell structures, intricate configurations, and complicated flow states of self-compacting concrete. Ensuring the high performance and high pouring quality of self-compacting concrete is a technical problem that urgently needs to be solved in the project. Among them, non-destructive testing is an important guarantee for ensuring the high-quality construction and long-term operation safety of steel shell concrete. Through a large number of model test studies, the detection technology for the void defects of steel shell concrete that couples the impact echo method and the neutron method has reached millimeter-level accuracy. Moreover, through on-site blind test verification, the recognition accuracy of the coupled detection method in the void area of defects has reached more than 90%. This method has been well applied in the Shenzhen-Zhongshan Passage project. Currently, the impact echo method has completed the detection of void defects in 6 pipe sections of the Shenzhen-Zhongshan Passage project, including 2 non-standard pipe sections and 4 standard pipe sections. A total of 9,004 compartments have been detected, including 472,438 measuring lines and 14,173,140 measuring points.

[0005] The sandwich-structured immersed tube tunnel combines the advantages of steel structures and concrete structures and is the preferred solution for future high-water-pressure and large-span subsea tunnel projects. During the precast pouring process of self-compacting concrete in this type of immersed tube tunnel, vibration is not possible, and the bonding surface between the steel plate and the concrete is extremely prone to the void defect of incomplete pouring, which reduces the bearing capacity of the immersed tube structure and may even cause local buckling of the structure, affecting the overall safety of the structure. Summary of the Invention

[0006] Aiming at the above deficiencies in the prior art, the present invention provides an optimized design method and system for compartments based on a sandwich-structured immersed tube tunnel, which solves the problem of void defects easily occurring during the precast pouring process of self-compacting concrete in the sandwich-structured immersed tube tunnel.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This solution provides an optimized design method for compartments based on a sandwich-structured immersed tube tunnel, including the following steps:

[0009] S1. Obtain the detection data of the void defects of the sandwich-structured immersed tube tunnel;

[0010] S2. Classify the sandwich-structured immersed tube tunnel using different compartments;

[0011] S3. According to the classification results and the detection data, statistically analyze the probability of void defects in different compartments;

[0012] S4. According to the statistical results, analyze the void defect law and influencing factors of the sandwich-structured immersed tube tunnel to obtain the optimal compartment design strategy and complete the optimized design of the compartments.

[0013] The beneficial effects of the present invention are as follows: By detecting the void defects of the sandwich immersed tube tunnel and classifying the compartments, and through the statistics of the void defect probabilities of different compartments, comprehensively considering the influence of different pouring temperatures caused by seasonal factors on the void defects, the influence of different pumping distances on the void defects, and the influence of the compartment size and the internal structure setting of the compartment on the distribution law of the void defects, analyzing the factors causing different distributions of the void defects inside the compartment, and obtaining the optimal compartment design strategy, the problem that void defects are likely to occur during the precast pouring of self-compacting concrete in the sandwich-structured immersed tube tunnel is solved.

[0014] Further, the step S2 includes the following steps:

[0015] S201. According to the different arrangement intervals of the transverse and longitudinal partitions, the steel shell structure of the sandwich-structured immersed tube tunnel is divided into several compartments with different structural sizes, where the compartments include the bottom plate compartment and the top plate compartment of the sandwich-structured immersed tube tunnel;

[0016] S202. Reserve a pouring hole at the center position or one side of the compartment, arrange several exhaust holes around the compartment, and arrange several T-shaped stiffeners at the top plate position of the compartment to make the internal structure of the compartment different;

[0017] S203. According to the different compartment structural sizes and different internal structures, complete the classification of the compartments of the sandwich-structured immersed tube tunnel.

[0018] The beneficial effects of the above further solution are as follows: By carrying out a detailed and accurate classification of the compartment types used in the sandwich-structured immersed tube tunnel, the classification criteria including the compartment structural size, the internal structure setting of the compartment (including the T-shaped stiffener structure, the position of the pouring hole, and the position of the exhaust hole), and the position of the compartment (the bottom plate compartment and the top plate compartment), it is beneficial to accurately analyze the influence law of factors such as the compartment size and the internal structure setting of the compartment on the occurrence of void defects during the compartment pouring process according to the statistical situation of void defects occurring between different types of compartments.

[0019] Still further, the step S3 includes the following steps:

[0020] S301. According to the classification result, divide the top plate of the compartment into grids, where the horizontal interval of the grids is arranged according to the T-shaped stiffener structure, and the vertical interval of the grids is taken as a fixed value of 1.0 m

[0021] S302. Judge whether there are void defects in the grid. If so, go to step S303; otherwise, repeat step S302;

[0022] S303. Statistically calculate the area of the void defect, and use the area of the void defect as the area prone to void defects;

[0023] S304. According to the area where the void defect is likely to occur, count the total area of the void defects in the grids of each type of compartment.

[0024] S305. Calculate the probability of the void defect occurring in each type of compartment based on the total area of the void defects.

[0025] S306. Statistically analyze the probabilities of the void defects in different compartments according to the probabilities of the void defects occurring in each type of compartment.

[0026] The beneficial effect of the above further solution is: to clarify the distribution law of the void defects, which can provide guidance for the subsequent detection work, can increase the layout density of the detection lines in the areas where defects are likely to occur, and at the same time reduce the layout of the detection lines in the areas where void defects are not likely to occur. By reasonably arranging the layout of the detection lines, the detection efficiency can be improved on the premise of ensuring the detection quality.

[0027] Furthermore, the expression of the probability of the void defect in step S305 is as follows:

[0028]

[0029] Among them, p(j) represents the probability of the void defect occurring in each type of compartment, A i represents the grid area where the void defect occurs, m i represents the number of times the grid has a void, k represents the number of grids on the top plate of this type of compartment, A represents the area of the top plate of this type of compartment, N represents the total number of this type of compartment, and i represents the number of grids on the top plate of this type of compartment.

[0030] Furthermore, step S4 includes the following steps:

[0031] S401. Based on the statistical results, conduct an overall analysis of the occurrence of void defects in different compartments, and obtain the types of compartments where void defects are likely to occur during the pouring process of the sandwich structure immersed tube tunnel by comparing the magnitudes of the probabilities of void defects occurring in different types of compartment structures.

[0032] S402. Analyze the influence of different pouring temperatures caused by seasonal factors on the void defects by analyzing the void defect conditions of the compartments in previous pipe joint pourings.

[0033] S403. Analyze the influence of different pumping distances on the occurrence of void defects during the compartment process by comparing the distribution of void defects when pouring the bottom plate and the top plate of the sandwich structure immersed tube tunnel for the compartment structures with the same structural dimensions.

[0034] S404. By comparing the probabilities of void defects occurring during the pouring process of compartments with the same T-shaped stiffener structure and vent hole settings but different structural dimensions, analyze the influence of different compartment dimensions on the occurrence of void defects inside the compartments, and analyze the design range of the optimal compartment dimensions by comparing the magnitudes of the probabilities of void defects occurring in compartments with different structural dimensions;

[0035] S405. Through statistical analysis of the positions where void defects occur inside the compartments, analyze the influence of the layout of the pouring holes, T-shaped stiffener structure, and vent hole positions inside the compartments on the void defects;

[0036] S406. According to the analysis results of the void laws in steps S401, S402, S403, S404, and S405, comprehensively consider the influence of different pouring temperatures caused by seasonal factors on void defects, the influence of different pumping distances on void defects, and the influence of compartment dimensions and the internal structure settings of the compartments on the distribution law of void defects, analyze the factors causing different distributions of void defects inside the compartments, obtain the optimal compartment design strategy, and complete the optimization design of the compartments.

[0037] The beneficial effects of the above further solution are as follows: clarify the influence of changes in each construction process and construction measures during the pipe joint pouring process on the occurrence of void defects, which can provide guidance for subsequent optimization of the precast pouring process of the immersed tunnel. In the present invention, the temperature influence caused by pouring in different seasons and the influence brought by different pumping distances during the pouring of the bottom slab and top slab of the immersed tunnel are mainly analyzed. The research results show that during construction in low-temperature seasons, the pouring quality of the immersed tunnel is higher and the probability of void defects occurring is lower. While during pouring in high-temperature seasons, the high-temperature exposure of the pump pipes will cause the slump flow of the self-compacting concrete to rapidly decrease, which is an important factor for the decline of the pipe joint pouring quality. Therefore, adjusting the construction technology according to environmental factors in different seasons to ensure the workability of the self-compacting concrete during high-temperature season construction is an important means to improve the precast pouring quality. At the same time, in this application, the influence laws of the compartment structure dimensions and the internal structure design of the compartments (including the setting of pouring holes, the number and setting of vent holes) on the void defects are mainly analyzed, clarify the factors affecting the self-compacting pouring quality of the compartments and the compartments and corresponding positions prone to void defects, thereby providing the layout of the measuring lines for the detection of void defects in the immersed tunnel and providing guidance for optimizing the compartment structure design.

[0038] Based on the above method, the present invention provides a compartment optimization design system for a sandwich-structured immersed tunnel, including:

[0039] A void defect data detection module, used to obtain the detection data of void defects in the sandwich-structured immersed tunnel;

[0040] A compartment classification module, used to classify different compartments of the sandwich-structured immersed tunnel;

[0041] An air void defect probability statistics module, configured to statistically analyze the air void defect probabilities of different compartments according to the classification results and the detection data;

[0042] A compartment optimization module, configured to analyze the air void defect laws and influencing factors of the sandwich structure immersed tunnel according to the statistical results to obtain an optimal compartment design strategy, and complete the optimization design of the compartments.

[0043] The beneficial effects of the present invention are as follows: By detecting the air void defects of the sandwich immersed tunnel and classifying the compartments, and statistically analyzing the air void defect probabilities of different compartments, the present invention comprehensively considers the influence of different pouring temperatures caused by seasonal factors on the air void defects, the influence of different pumping distances on the air void defects, and the influence of the compartment size and the internal structure setting of the compartment on the distribution law of the air void defects, analyzes the factors causing different distributions of the air void defects inside the compartment, and obtains an optimal compartment design strategy, thereby solving the problem that air void defects are likely to occur during the precast pouring of self-compacting concrete in the sandwich structure immersed tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a flowchart of the method of the present invention.

[0045] Figure 2 It is a schematic diagram of the standard compartment structure in this embodiment.

[0046] Figure 3 It is a schematic diagram of the structural layout of the standard pipe section of the immersed tube in this embodiment.

[0047] Figure 4 It is a diagram showing the proportion of air void defects in the bottom plate compartment in this embodiment.

[0048] Figure 5 It is a diagram showing the proportion of air void defects in the top plate compartment in this embodiment.

[0049] Figure 6 It is a schematic diagram showing the influence of the pumping distance on the air void defects in the compartment in this embodiment.

[0050] Figure 7 It is a schematic diagram showing the influence of different compartment sizes on the air void defects in this embodiment.

[0051] Figure 8 It is a schematic diagram of the compartment network division in this embodiment.

[0052] Figure 9 It is a schematic diagram of the air void probability values in different grid areas of the compartment in this embodiment.

[0053] Figure 10 It is a schematic diagram of the system structure of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] The specific embodiments of the present invention will be described below to facilitate those skilled in the art of the present technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0055] Embodiment 1

[0056] The immersed tube tunnel with a sandwich structure combines the advantages of steel structures and concrete structures and is the preferred solution for future high-water-pressure and large-span undersea tunnel projects. During the process of precast pouring of self-compacting concrete for this structure of immersed tube tunnel, vibration cannot be carried out, and the bonding surface between the steel plate and the concrete is extremely prone to the defect of non-compact casting holes, reducing the bearing capacity of the immersed tube structure and even causing local buckling of the structure, affecting the overall safety of the structure. Based on the detection results of the void defects of 5 immersed tube tunnels with a sandwich structure by the impact echo method and the neutron method, this invention comprehensively considers factors such as seasonal temperature, pumping distance, compartment size, pouring hole setting, and the fluidity of self-compacting concrete to analyze the factors affecting the pouring quality of the immersed tube tunnel, such as Figure 1 As shown, this invention provides an optimized design method for the compartments of an immersed tube tunnel with a sandwich structure, and its implementation method is as follows:

[0057] S1. Obtain the detection data of the void defects of the immersed tube tunnel with a sandwich structure;

[0058] S2. Classify the immersed tube tunnel with a sandwich structure using different compartments, and its implementation method is as follows:

[0059] S201. According to the different arrangement intervals of the transverse and longitudinal partitions, divide the steel shell structure of the immersed tube tunnel with a sandwich structure into several compartments with different structural sizes. Among them, the compartments include the bottom plate compartment and the top plate compartment of the immersed tube tunnel with a sandwich structure;

[0060] S202. Reserve a pouring hole at the center position or one side of the compartment, arrange several exhaust holes around the compartment, and arrange several T-shaped stiffeners at the top plate position of the compartment to make the internal structure of the compartment different;

[0061] S203. Complete the classification of the compartments of the immersed tube tunnel with a sandwich structure according to the different compartment structural sizes and different internal structures.

[0062] In this embodiment, within the compartment structure, the internal structure of the compartment also varies. This includes leaving a casting hole at the central position or offset to one side of the compartment, and the number of exhaust holes arranged around the compartment and the number of T-shaped stiffeners arranged at the position of the compartment roof are not the same in different design schemes. According to the different sizes of the compartments and the different settings of the internal structure of the compartments, the sandwich-structured immersed tunnel can be classified.

[0063] In this embodiment, the external steel shell structure of the sandwich-structured immersed tunnel consists of inner and outer panels, transverse and longitudinal diaphragms, transverse and longitudinal stiffeners, and stud nails. The transverse and longitudinal diaphragms serve as shear-resistant members to connect the inner and outer panels. At the same time, under the division of the transverse and longitudinal diaphragms, the entire steel shell structure is divided into several airtight compartments of different sizes, as shown in Figure 2 (a). The longitudinal spacing of the transverse diaphragms generally takes 3.0 m, while the transverse spacing of the longitudinal diaphragms is set according to the shear-bearing capacity requirements at different positions of the structure. On the bottom plate of the immersed tunnel, the transverse spacing of the longitudinal diaphragms generally takes 1.8 m, 3.5 m, 2.5 m, 2.4 m; while on the roof, the transverse spacing of the transverse and longitudinal diaphragms generally takes 2.5 m, 2.8 m, 3.5 m, 1.4 m, 4.5 m, 2.4 m. Since the longitudinal diaphragms adopt different spacing widths at different structural positions, the sizes of the compartments of the steel shell concrete immersed tunnel show various types. Among them, on the bottom plate structure, there are 4 types of compartments, namely 1.8 m×3.0 m×1.5 m, …, 2.4 m×3.0 m×1.5 m; while in the roof compartments, there are 6 types of compartments, namely 1.4 m×3.0 m×1.5 m, …, 4.5 m×3.0 m×1.5 m, 2.4 m×3.0 m×1.5 m.

[0064] In this embodiment, within the immersed tube segment, the position of the casting hole reserved in the compartment and the number and distribution of the exhaust holes also have different layout schemes in compartments of different sizes. Taking the compartment with a size of 3.5 m×3.0 m×1.5 m as an example, as shown in Figure 2 (b), a casting hole is reserved at the central position of the compartment, and a total of 10 large exhaust holes with a diameter of 90 mm are arranged around the compartment, and 4 small exhaust holes with a diameter of 50 mm are arranged near the outer T-shaped stiffeners. According to the different sizes of the compartment structure and the arrangement of components, a total of 9 types of compartments are statistically analyzed for the void defect situation in this time. The detailed parameters of different compartments are shown in Table 1, and the distribution is as shown in Figure 3 shown.

[0065] Table 1

[0066]

[0067] S3. According to the classification results and the detection data, the void defect probabilities of different compartments are statistically analyzed, and the implementation method is as follows:

[0068] S301. According to the classification result and the detection data, perform grid division on the top plate compartment. Among them, the horizontal interval of the grid is arranged according to the structure of the T-shaped stiffener, and the longitudinal interval of the grid is taken as a fixed value of 1.0 m;

[0069] S302. Determine whether there is a void defect in the grid. If so, go to step S303; otherwise, repeat step S302;

[0070] S303. Statistically calculate the area of the void defect, and use the area of the void defect as the area where void defects are likely to occur;

[0071] S304. According to the area where void defects are likely to occur, statistically calculate the total area of the grids with void defects in each type of compartment;

[0072] S305. According to the total area of the void defects, calculate the probability of void defects occurring in each type of compartment:

[0073]

[0074] Among them, p(j) represents the probability of void defects occurring in each type of compartment, A i represents the area of the grid with void defects, m i represents the number of times the grid has voids, k represents the number of grids on the top plate of this type of compartment, A represents the area of the top plate of this type of compartment, N represents the total number of this type of compartment, and i represents the number of grids on the top plate of this type of compartment;

[0075] S306. According to the probability of void defects occurring in each type of compartment, statistically calculate the void defect probabilities of different compartments.

[0076] In this embodiment, in order to accurately statistically calculate the probability of void defects occurring in compartments of different structural types, obtain the types of compartments where void defects are likely to occur, and analyze the factors affecting the void distribution, the present invention proposes a defect statistical method based on area ratio. First, perform grid division on the top plate of the compartment. Experimental research finds that void defects are likely to occur on both sides of the T-shaped stiffener structure. Therefore, the horizontal interval of the grid is arranged according to the T-shaped stiffener structure. According to the different sizes of the compartment structure, the T-rib spacing is generally 0.5 - 0.7 m; the longitudinal interval of the grid is taken as a fixed value of 1.0 m. Taking a standard compartment of 3.5 m × 3.0 m × 1.5 m as an example, as Figure 2 (b) shows, the compartment is divided into 15 grids of 0.7 m × 1.0 m. If there is a void defect in the grid, statistically calculate its area as the area where void defects are likely to occur, statistically calculate the total area of the grids with void defects in each type of compartment, and introduce the following formula to calculate the probability of void defects occurring in each type of compartment:

[0077]

[0078] Meanwhile, to accurately count and describe the distribution law of void defects in the compartments, statistical analysis is carried out on the positions where void defects are likely to occur inside each type of compartment. According to the different distances from the grid to the casting holes, the grids are divided into 5 categories, corresponding to the numbers 1#, 2#, 3#, 4#, and 5# respectively, as shown in Figure 4 , considering the symmetry of the structure, those with the same structure are regarded as one category.

[0079] S4. According to the above statistical results, analyze the void defect law and influencing factors of the sandwich-structured immersed tunnel to obtain the optimal compartment design strategy and complete the optimization design of the compartment. The implementation method is as follows:

[0080] S401. According to the above statistical results, conduct an overall analysis of the occurrence of void defects in different compartments. By comparing the probabilities of void defects occurring in different types of compartment structures, obtain the types of compartments in which void defects are likely to occur during the casting process of the sandwich-structured immersed tunnel;

[0081] S402. By analyzing the void defect conditions of the compartments in previous pipe joint castings, analyze the influence of different casting temperatures caused by seasonal factors on void defects;

[0082] S403. By comparing the distribution of void defects that occur during the bottom plate casting and top plate casting of the sandwich-structured immersed tunnel for compartments with the same structural dimensions, analyze the influence of different pumping distances on the occurrence of void defects during the compartment process;

[0083] S404. By comparing the probabilities of void defects occurring during the casting process for compartments with different structural dimensions but the same T-shaped stiffening rib structure and exhaust hole settings, analyze the influence of different compartment sizes on the occurrence of void defects inside the compartments, and by comparing the magnitudes of the probabilities of void defects occurring in compartments with different structural dimensions, analyze the design range of the optimal compartment size;

[0084] S405. Through statistical analysis of the positions where void defects occur inside the compartments, analyze the influence of the layout of the casting holes, T-shaped stiffening rib structure, and exhaust hole positions inside the compartments on void defects, provide a reference for optimizing the internal structure layout, and at the same time serve for subsequent inspection work. The positions where void defects are likely to occur in different compartments are the key inspection parts in subsequent inspection work;

[0085] S406. Based on the analysis results of the degassing rules of step S401, step S402, step S403, step S404 and step S405, comprehensively consider the influence of different pouring temperatures on degassing defects caused by seasonal factors, the influence of different pumping distances on degassing defects, and the influence of compartment size and compartment internal structure settings on the distribution law of degassing defects, analyze the factors that cause different distributions of degassing defects inside the compartments, obtain the optimal compartment design strategy, and complete the optimization design of the compartments.

[0086] In this embodiment, according to the statistical method described above, the test results of 5 pipe sections are statistically analyzed, among which only the data of the top plate compartments are counted for the E1 pipe section. Since the casting production methods of the sandwich structure immersed tube tunnel on the bottom plate structure and the top plate structure are slightly different, the bottom plate compartments and the top plate compartments are counted separately. The statistical results of the emptying of the 4 types of compartments in the bottom plate structure of the immersed tube and the 6 types of compartments in the top plate structure are as follows: Figure 4 and Figure 5 shown.

[0087] In this embodiment, Figure 4 It can be seen that among the E2-E5 pipe segment bottom plate compartments, the 1.8m×3.0m×1.5m compartments (hereinafter referred to as 1.8m compartments) have the largest proportion of hollow defects, which are 1.62%, 1.21%, 1.62%, and 2.12% respectively, and the average proportion in the four pipe segments is 1.64%. The proportion of hollow defects in the 2.4m compartments and 3.5m compartments is relatively small, and the average proportion in the four pipe segments is 0.76% and 0.745% respectively. Among them, the 1.8m compartment is located at the side wall, and the top surface of the compartment is a slope structure, which makes it difficult to fill and compact the self-compacting concrete, so it is most prone to hollow defects. From the overall situation of the casting of the previous pipe segments, the proportion of hollow defects gradually increased from the E3 pipe segment to the E5 pipe segment, indicating that the overall quality of the compartment casting reached a good level in the E3 pipe segment, but the overall casting quality declined in the E4 and E5 pipe segments.

[0088] In this embodiment, Figure 5 As shown in the figure, among the compartments of the top plate structure, the E3 pipe segment has the best overall casting quality of the top plate structure, and the probability of hollowing defects in the six types of compartments is less than 0.8%, which is consistent with the statistical result that the E3 pipe segment has good quality in the bottom plate compartments of the immersed tube. The 4.5m compartment and the 2.4m compartment showed good quality performance in the casting of the top plate structure. The average proportion of hollowing defects in the 4.5m compartment among the five pipe segments was only 0.32%. It reserved two casting holes and had 24 exhaust holes, which may be an important reason for ensuring good casting quality.

[0089] In this embodiment, from the overall pouring condition of the pipe segments, it can be seen that the 1.8m compartments and 2.5m compartments are located near the side walls, and the pouring quality is poor, indicating that the pouring near the bottom slab and side walls is a weak link in the construction quality. The construction organization process near the bottom slab and side walls should be improved. At the same time, the inclined design of the compartment top slab should be improved, which is not conducive to the exclusion of gas during pouring. In addition, from the pouring data, it can be seen that the E2 and E3 pipe segments were constructed in seasons with relatively low temperatures, while the E4 and E5 pipe segments were constructed in the hot summer, and the daily average temperature can reach above 30°C. The self-compacting concrete is significantly more sensitive to environmental temperature than ordinary concrete. The high-temperature exposure of the pump pipes will cause the slump flow of the self-compacting concrete to rapidly decrease, which may be an important factor leading to the decline in the pouring quality of the E4 and E5 pipe segments. Adjusting the construction technology in different seasons, doing a good job in heat preservation during the process of concrete raw materials and pouring and transportation, ensuring the workability of the self-compacting concrete during construction in high-temperature seasons, and at the same time reducing the concrete pouring temperature to avoid excessive hydration heat rise of the concrete during construction in high-temperature seasons are important means to improve the precast pouring quality.

[0090] In this embodiment, the layout of the (3.5m×3.0m×1.5m) compartment structure used in the immersed tube top slab structure and the bottom slab structure is exactly the same. However, when pouring the top slab and bottom slab of the pipe segment, there is a difference in the pumping distance of the self-compacting concrete. The pouring of the top slab of the pipe segment requires vertical pumping for about 14 meters, which increases the pump loss of the self-compacting concrete. The present invention analyzes the influence of the pumping distance on the pouring quality of the immersed tube by comparing the occurrence of void defects in the 3.5m compartment during the pouring of the top slab and the bottom slab. As Figure 6 shown, in the E2-E4 pipe segments, the proportion of void defects in the top slab compartments is basically about 1.0%, while in the bottom slab compartments, the proportion of void defects is basically stable at about 0.8%. Compared with the top slab, the pouring quality of the 3.5m compartment in the bottom slab is better, indicating that factors such as the increase in the pumping distance have a certain impact on the pouring quality of the pipe segment, but the difference between the top slab and the bottom slab is not significant, indicating that as long as a reasonable concrete mix ratio is ensured and the pouring time and construction process are strictly controlled, the pouring quality can also be better guaranteed.

[0091] In this embodiment, due to the different transverse dimensions of the compartments, the farthest distance that the self-compacting concrete needs to fill is different. Existing experimental studies have found that the farther away from the pouring hole, the worse the fluidity of the self-compacting concrete, which has a greater impact on the pouring quality. The present invention studies the influence of the compartment size on the pouring quality of the self-compacting concrete by comparing the probability of void defects occurring in different-sized compartments with the same T-shaped stiffening rib structure and vent hole settings during the pouring process. Figure 8 (a) shows the void defect conditions of the 3.5m and 2.5m compartments in the immersed tube top slab structure. It can be seen from the figure that the ratio of void defects occurring in the 2.5m compartment during each pipe segment pouring process is smaller, indicating that when the longitudinal dimension of the compartment is fixed at 3m, appropriately reducing the transverse dimension of the compartment can improve the pouring quality of the compartment. HoweverFigure 8 (b) shows the opposite pattern. The 1.4 m compartments of the immersed tube top slab and the 2.4 m compartments of the bottom slab have the same T-shaped stiffener structure layout and exhaust hole settings, and their transverse dimensions are also smaller than those of the 2.4 m compartments. The self-compacting concrete needs to fill a shorter distance transversely in the compartments, but it is more likely to have void defects. The average reduction coefficient of 0.8 is used to reduce the disadvantages caused by the long-distance pumping of the concrete in the top slab compartments. The proportion of void defects is still worse than that of the 2.4 m compartments. Therefore, the present invention proposes the aspect ratio (B / L) parameter of the compartments to evaluate the influence of the compartment size. The aspect ratios of the 3.5 m compartments, 2.5 m compartments, 2.4 m compartments, and 1.4 m compartments are 1.17, 0.83, 0.8, and 0.46 respectively. The statistical results show that when the aspect ratio is about 0.8, the casting quality of the compartments is the best. The casting holes of the compartments are generally set in the center of the compartments. During the casting process, the self-compacting concrete flows from the center to the surroundings. If the transverse and longitudinal dimensions of the compartments differ greatly within the fillable range, it will lead to a large liquid level difference between the transverse end and the longitudinal end of the self-compacting concrete, which is not conducive to the discharge of gas. At the same time, considering the obstruction of the T-shaped rib plate to the transverse concrete, the flow performance of the concrete in the transverse direction of the compartments is reduced. Therefore, when designing the compartment size, according to the arrangement of the T-shaped ribs, the transverse dimension of the structure is shortened, so that the aspect ratio of the compartments between 0.8 and 0.85 can achieve better casting quality results.

[0092] In this embodiment, the present invention conducts a statistical analysis on the positions where void defects occur inside the compartments, analyzes the influence of the layout of the casting holes, T-shaped stiffener structure, and exhaust hole positions inside the compartments on the void defects, provides a reference for optimizing the internal structure layout, and serves for subsequent inspection work. The positions where void defects are likely to occur in various compartments are the key inspection parts in subsequent inspection work. According to the numbers of the compartment divisions, the number of times void defects occur in different division areas of the compartments is counted, and the proportion in the total number of such divisions is calculated to characterize the degree to which such divisions are likely to have void defects.

[0093] In this embodiment, as Figure 9As shown in the figure, the compartments with the same casting holes and T-shaped stiffeners have similar distribution laws of void defects. When the casting holes are arranged at the center of the compartment, the 2#, 3#, and 4# grids near the casting holes are most likely to have void defects. The 1# grid is the area with relatively good casting quality. However, when the casting holes are arranged on the right side, the 2# grid becomes the area with good quality, and the risk of void defects in the 1# grid area increases significantly. This shows that the position of the casting holes is an important factor affecting the distribution of void defects inside the compartment. By comparing the defect distribution of the four types of compartments, it can be seen that the area near the casting holes is the most likely to have void defects, and the grids located in the long side direction are more likely to have void defects. For example, for the 3.5m compartment with B / L>1, the 2# grid is the most likely to have void defects, while for the 2.8m, 2.5m, and 2.4m compartments with B / L<1, the 3# grid is the most likely to have void defects. The 5# grid is the area with relatively optimal casting quality, and the probability of having void defects is only 0.45% at the minimum. It is calculated that in the 3.5m, 2.8m, 2.5m, and 2.4m compartments, the distances from the centroid of the 5# grid to the centroid of the casting hole are 1.4m, 1.4m, 1.2m, and 0.95m respectively. In the 2.4m compartment, the 1# grid is the area with the best casting quality, and the distance from its centroid to the centroid of the casting hole is 1.379m. It is speculated that the probability of having void defects is greater in the areas where the distance from the casting hole is too close or too far. When the diameter of the casting hole is 330mm, the longitudinal length of the compartment is 3m, and the height is 1.5m, the area at a distance of 1.2 - 1.4m from the casting hole is the range where the self-compacting concrete has a better flow state.

[0094] Based on the detection results of the void defects in 6995 compartments of 5 sandwich-structured steel shell concrete immersed tubes in the Shenzhen-Zhongshan Link project, this invention analyzes the laws of void defects occurring in the self-compacting concrete during the casting of compartments. By comparing the void conditions of different types of compartments and analyzing the factors affecting the casting quality of compartments, the main conclusions are as follows:

[0095] (1) From the overall casting situation of the pipe section, the casting quality in the low-temperature season is better than that in the high-temperature season, and the working performance of the self-compacting concrete is significantly affected by high temperature; due to the increase in the pumping distance, the probability of having void defects in the casting of the top plate of compartments with the same size and structural settings is about 0.2% higher than that in the casting of the bottom plate.

[0096] (2) The 1.8-compartment of the immersed tube bottom plate is the compartment type with the worst casting quality. The inclined design of the compartment top plate should be improved, as it is not conducive to the exclusion of gas during the casting process. The statistical results show that whether the transverse size of the compartment is too large or too small, it will lead to an increase in the probability of having void defects. It is speculated that due to the blocking effect of the longitudinal T-shaped stiffener structure, the transverse size of the compartment should be slightly smaller than the longitudinal size. When the transverse-longitudinal ratio of the compartment is 0.8 - 0.85, the casting quality is the best.

[0097] (3) The position of the casting hole and the layout of the T-shaped stiffener structure affect the distribution of the internal void defects in the compartment. At the same time, there is no exhaust hole near the casting hole, which is prone to void defects. Moreover, the most severe voids occur on both sides of the casting hole in the long side direction of the compartment, which is the key part for detecting void defects in the immersed tunnel. On the premise of ensuring the structural force safety, reducing the T-shaped stiffener structure in the compartment and adding exhaust holes near the casting hole are beneficial to reducing the probability of void defects in the compartment.

[0098] (4) If it is too close to the casting hole, the gas incorporated due to the casting agitation is not easily discharged. If it is too far, the fluidity of the self-compacting concrete decreases. The compartments with the best casting quality inside the compartment all appear in the area 1.2 - 1.4 m away from the casting hole. From this, it is inferred that this range is the area with the best filling performance.

[0099] Example 2

[0100] As Figure 10 shown, the present invention provides a compartment optimization design system for an immersed tunnel based on a sandwich structure, including:

[0101] A void defect data detection module for obtaining the detection data of the void defects in the immersed tunnel with a sandwich structure;

[0102] A compartment classification module for classifying different compartments of the immersed tunnel with a sandwich structure;

[0103] A void defect probability statistics module for statistically analyzing the void defect probabilities of different compartments according to the classification results and the detection data;

[0104] A compartment optimization module for analyzing the void defect law and influencing factors of the immersed tunnel with a sandwich structure according to the statistical results to obtain the optimal compartment design strategy and complete the optimization design of the compartment.

[0105] As Figure 10 shown, the compartment optimization design system for an immersed tunnel based on a sandwich structure provided by the embodiment can execute the technical solutions shown in the above method embodiments, and its implementation principle and beneficial effects are similar, which will not be elaborated here.

Claims

1. An optimized design method for compartments of a sandwich - structured immersed tunnel, characterized in that, it includes the following steps: S1. Obtain the detection data of the void defects of the sandwich - structured immersed tunnel; S2. Classify the sandwich - structured immersed tunnel with different compartments; S3. According to the classification results and the detection data, statistically analyze the probability of void defects in different compartments; S4. According to the statistical results, analyze the laws and influencing factors of the void defects of the sandwich - structured immersed tunnel to obtain the optimal compartment design strategy, and complete the optimized design of the compartments. Specifically: S401. According to the statistical results, conduct an overall analysis of the occurrence of void defects in different compartments. By comparing the probabilities of void defects in different types of compartment structures, obtain the types of compartments prone to void defects during the casting process of the sandwich - structured immersed tunnel; S402. By analyzing the void defect conditions of the compartments in each pipe - joint casting, analyze the influence of different casting temperatures caused by seasonal factors on the void defects; S403. By comparing the distribution of void defects when casting the bottom plate and the top plate of the sandwich - structured immersed tunnel for compartment structures with the same structural dimensions, analyze the influence of different pumping distances on the occurrence of void defects during the compartment process; S404. By comparing the probabilities of void defects in compartments with different structural dimensions but the same T - shaped stiffening rib structure and exhaust hole settings during the casting process, analyze the influence of different compartment sizes on the occurrence of void defects inside the compartments, and by comparing the magnitudes of the probabilities of void defects in different - sized compartments, analyze the design range of the optimal compartment size; S405. By statistically analyzing the positions where void defects occur inside the compartments, analyze the influence of the arrangement of casting holes, T - shaped stiffening rib structures, and exhaust hole positions inside the compartments on the void defects; S406. According to the analysis results of the void laws in steps S401, S402, S403, S404, and S405, comprehensively consider the influence of different casting temperatures caused by seasonal factors on the void defects, the influence of different pumping distances on the void defects, and the influence of compartment sizes and internal structure settings on the distribution law of void defects, analyze the factors causing different distributions of void defects inside the compartments, obtain the optimal compartment design strategy, and complete the optimized design of the compartments.

2. The optimized design method for compartments of a sandwich - structured immersed tunnel according to claim 1, characterized in that, the step S2 includes the following steps: S201. According to the different arrangement intervals of the transverse and longitudinal partitions, divide the steel shell structure of the sandwich - structured immersed tunnel into several compartments with different structural dimensions. Among them, the compartments include the bottom - plate compartments and the top - plate compartments of the sandwich - structured immersed tunnel; S202. Reserve casting holes at the center position or one side of the compartment, arrange several exhaust holes around the compartment, and arrange several T - shaped stiffening ribs at the top - plate position of the compartment to make the internal structure of the compartment different; S203. According to the different structural dimensions and internal structures of the compartments, complete the classification of the compartments of the sandwich - structured immersed tunnel.

3. The optimization design method for compartments of a sandwich - structured immersed tunnel according to claim 2, characterized in that, the step S3 includes the following steps: S301. According to the classification result and the detection data, perform grid division on the top - plate compartments. Among them, the lateral interval of the grid is arranged according to the structure of the T - shaped stiffening rib, and the longitudinal interval of the grid is taken as a fixed value of 1.0 m; S302. Judge whether there is a void defect in the grid. If so, go to step S303; otherwise, repeat step S302; S303. Statistically calculate the area of the void defect, and take the area of the void defect as the area where void defects are likely to occur; S304. According to the area where void defects are likely to occur, statistically calculate the total area of the grids with void defects in each type of compartment; S305. According to the total area of the void defects, calculate the probability of void defects occurring in each type of compartment; S306. According to the probability of void defects occurring in each type of compartment, statistically calculate the probability of void defects in different compartments.

4. The optimization design method for compartments of a sandwich - structured immersed tunnel according to claim 3, characterized in that, the probability expression of the void defect in step S305 is as follows: Among them, represents the probability of the occurrence of void defects in each type of compartment, represents the grid area where void defects occur, represents the number of times voids occur in the grid, represents the number of grids on the top plate of this type of compartment, represents the top plate area of this type of compartment, represents the total number of this type of compartment, represents the number of grids on the top plate of this type of compartment.

5. An optimization design system for compartments of a sandwich - structured immersed tunnel for implementing the optimization design method for compartments of a sandwich - structured immersed tunnel according to any one of claims 1 - 4, characterized in that, it includes: A void defect data detection module, used to obtain the detection data of the void defects of the sandwich - structured immersed tunnel; A compartment classification module, used to classify different compartments of the sandwich - structured immersed tunnel; A void defect probability statistics module, used to statistically calculate the probability of void defects in different compartments according to the classification result and the detection data; A compartment optimization module, used to analyze the void defect law and influencing factors of the sandwich - structured immersed tunnel according to the statistical result to obtain the optimal compartment design strategy, and complete the optimization design of the compartments.

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