A high-speed railway tunnel ferri-aluminate concrete lining anti-cracking construction method

Abstract

The application discloses a kind of anti-cracking construction methods for high-speed rail tunnel ferri-aluminate concrete lining, including intermediate cooling circuit and outer cooling circuit, the structure of intermediate cooling circuit and outer cooling circuit is same, all include several cooling pipes that are arranged in parallel and interval, and adjacent cooling pipe is connected by the connecting pipe of U type, two cooling pipes that are located in the left and right sides of tunnel and close to the top surface of side base are respectively provided with water inlet and water outlet, and water inlet and water outlet all exceed the interval to be poured, two cooling pipes that are located in the left and right sides of tunnel and close to the top surface of side base are all left with gap between cooling pipe and side base top surface, further including S1: structure installation;S2: water cooling;S3: stop water.Through intermediate cooling circuit and outer cooling circuit, two water cooling pipes, cooling is carried out to concrete, not only reduce the temperature difference between concrete core and surface layer, but also reduce the temperature difference between concrete surface layer and environment, so that ferri-aluminate concrete solidification process will not crack due to internal and external temperature difference.

Description

Technical Field

[0001] This invention belongs to the field of railway tunnel concrete mixing technology, specifically relating to a crack-resistant construction method for ferroaluminate concrete lining in high-speed railway tunnels. Background Technology

[0002] During the construction of high-speed railway tunnels, various environmental conditions are encountered. In complex geological environments with ultra-high water pressure, ultra-high water inflow, and high sulfate erosion, sulfate erosion can easily lead to the deterioration of the tunnel concrete lining structure, a decrease in load-bearing capacity, and even failure, thus directly threatening the long-term operational safety and durability of the tunnel. Based on the non-corrosive properties of aluminoferrite cement in chemical environments, its use in high-speed railway tunnels is currently being promoted. However, during on-site pouring, it has been found that a large number of irregular circumferential, longitudinal, and diagonal capillary cracks exist in the aluminoferrite concrete after demolding.

[0003] In tunnel construction, common crack control methods include material selection (using raw materials that meet current national and industry standards for cement, fly ash, etc.), mix design optimization, use of temperature-controlled high-efficiency crack-resistant agents, and construction measures (controlling the temperature before placement in the formwork, etc.). Analysis shows that the main factor causing cracks in aluminoferrite concrete linings is the significant temperature difference between the inside and outside.

[0004] Chinese patent CN119686774A discloses a method of pre-embedding cooling pipes in concrete to reduce the temperature inside the concrete during solidification, thereby controlling crack formation. This method is applicable to conventional concrete. However, for aluminoferrite concrete, which solidifies and heats up quickly, unlike ordinary cement, the existing technology is not suitable. Summary of the Invention

[0005] This invention proposes a crack-resistant construction method for ferroaluminate concrete lining in high-speed railway tunnels, which can effectively prevent cracks from appearing in the lining structure during demolding.

[0006] Therefore, the technical solution adopted by the present invention is as follows: a crack-resistant construction method for ferroaluminate concrete lining of high-speed railway tunnels, including an intermediate cooling circuit and an outer cooling circuit. The intermediate cooling circuit is set between the outer and inner steel meshes, and the outer cooling circuit is set on the outer steel mesh. The intermediate and outer cooling circuits have the same structure, each including several cooling pipes arranged side by side at intervals. The arrangement density of the cooling pipes on the outer cooling circuit is greater than that on the intermediate cooling circuit. Adjacent cooling pipes are connected by U-shaped connecting pipes. Two cooling pipes located on the left and right sides of the tunnel and close to the top surface of the foundation are respectively provided with inlets and outlets, and both inlets and outlets extend beyond the area to be poured. The two cooling pipes located on the left and right sides of the tunnel and close to the top surface of the foundation are separated from the top surface of the foundation.

[0007] It also includes the following steps:

[0008] S1: Structural installation, install the middle cooling circuit and the outer cooling circuit, and test whether the two cooling circuits are working properly before pouring;

[0009] S2: Water cooling. After pouring, water cooling begins when the concrete has initially set. During the water cooling process, the difference between the water temperature and the highest temperature of the concrete is controlled to be within 15℃ by adjusting the water flow rate and water temperature. The cooling rate is no more than 2℃ / d and no more than 1℃ / 4h. Throughout the process, the core temperature of the concrete must be kept below 50℃.

[0010] S3: Water shut-off. When the following conditions are met simultaneously: internal temperature drops below 45℃, temperature difference between inner and outer layers is less than 15℃, and temperature difference between core and environment is less than 15℃, water supply is stopped. After water shut-off, cement should be used to seal the two cooling water pipes with grout in a timely manner.

[0011] As a preferred embodiment of the above scheme, in S2, the inlet water temperature needs to be controlled in stages, with the inlet water temperature ranging from 20℃ to 40℃, and the difference between the outlet water temperature and the inlet water temperature being 3℃ to 6℃. The flow rates at the inlet and outlet are between 1.0 and 10.0 m³ / h. 3 / h.

[0012] Further optimization involves steam curing or spraying curing liquid on the concrete lining after water supply is cut off, with the steam temperature between 35℃ and 45℃ and the curing time exceeding 14 days.

[0013] Further preferably, the distance between adjacent cooling pipes in the outer cooling circuit is 30-50cm, the distance between adjacent cooling pipes in the middle cooling circuit is 60-80cm, the distance between the two cooling pipes located on the left and right sides of the tunnel and close to the top surface of the side foundation is 75cm, and the length of the inlet / outlet and the outlet beyond the section to be poured is 50cm.

[0014] Further preferably, the cooling pipe is fixed by multiple hooks, and the distance between adjacent hooks on the same cooling pipe is 60cm.

[0015] Further preferably, both the inlet and outlet are equipped with speed-regulating ball valves to ensure uniform water flow.

[0016] Further preferably, a first temperature sensor for real-time temperature monitoring is provided at both the inlet and outlet, and a second temperature sensor is provided at the outer steel mesh, the inner steel mesh, and the concrete core.

[0017] Further preferably, the inlet and outlet are equipped with pipe covers to prevent debris from entering.

[0018] The beneficial effects of this invention are as follows: By setting an intermediate cooling circuit in the middle of the inner layer of steel reinforcement mesh, the temperature of the middle part of the lining concrete is ensured, reducing the temperature difference between the concrete core and the surface layer, so that the aluminoferrite concrete will not crack due to the temperature difference between the inside and outside during the solidification process; at the same time, an outer cooling circuit is also set, which can cool the surface of the lining concrete, reducing the temperature difference between the concrete surface and the environment, preventing cracking caused by the rapid temperature rise of the concrete surface. The simultaneous cooling inside and outside conforms to the solidification characteristics of aluminoferrite concrete; it reduces the occurrence of cracks, reduces leakage problems caused by concrete cracking that affect the structural service function, and at the same time reduces the transmission of harmful media, protects the steel reinforcement from corrosion, and extends the service life of the structure. Attached Figure Description

[0019] Figure 1 A schematic diagram showing the installation of cooling circuits during the lining of the side walls and vaults.

[0020] Figure 2 This is a schematic diagram of the cooling circuit.

[0021] Figure 3 A schematic diagram showing the installation of a cooling circuit during the lining of the invert arch.

[0022] Figure 4 This is a temperature change curve for aluminoferrite concrete.

[0023] Attached reference numerals: 1. Outer steel mesh, 2. Inner steel mesh, 3. Intermediate cooling circuit, a. Cooling pipe, b. Connecting pipe, c. Water inlet, d. Water outlet, 4. Second temperature sensor, 5. Outer cooling circuit. Detailed Implementation

[0024] The present invention will be further described below with reference to the embodiments and accompanying drawings:

[0025] like Figure 1-3As shown, a crack-resistant construction method for ferroaluminate concrete lining in high-speed railway tunnels includes a crack-resistant structure, which mainly consists of an intermediate cooling circuit 3 and an outer cooling circuit 5. The intermediate cooling circuit 3 is located between the outer reinforcing mesh 1 and the inner reinforcing mesh 2, and the outer cooling circuit 5 is located on the outer reinforcing mesh 1. The intermediate cooling circuit lowers the temperature of the concrete core, and the outer cooling circuit further reduces the surface temperature during the solidification of the ferroaluminate concrete. This not only reduces the temperature difference between the core and the surface during concrete solidification, thus reducing the occurrence of cracks, but also, in conjunction with the temperature characteristics of ferroaluminate concrete during solidification, prevents cracking in the tunnel lining when ferroaluminate concrete is used.

[0026] Specifically, the intermediate cooling circuit 3 and the outer cooling circuit 5 have the same structure, both including several cooling pipes a arranged side by side at intervals. The arrangement density of cooling pipes a on the outer cooling circuit 5 is greater than that on the intermediate cooling circuit 3, meaning the arrangement of cooling pipes on the outer cooling circuit is more dense. Adjacent cooling pipes a are connected by a U-shaped connecting pipe b. To facilitate the cooling effect of the cooling circuit, two cooling pipes a located on the left and right sides of the tunnel and close to the top surface of the foundation are respectively equipped with water inlets c and water outlets d, and both water inlets c and water outlets d extend beyond the area to be poured.

[0027] To ensure that the cooling circuit is located inside the concrete, the two cooling pipes a located on the left and right sides of the tunnel and close to the top surface of the side foundation are left with gaps between them and the top surface of the side foundation. Gaps are also left between the front and rear ends of the cooling pipes and the construction joints.

[0028] The cooling pipes and connecting pipes are made of rigid materials, with a diameter of approximately 50mm and a wall thickness of not less than 2mm. The distance between adjacent cooling pipes a in the outer cooling circuit 5 is 30-50cm, and the distance between adjacent cooling pipes a in the middle cooling circuit 3 is 60-80cm. In this embodiment, the length of one construction stage is 6m. Both the cooling pipes and connecting pipes are made of seamless steel pipes with a diameter of 42mm and a wall thickness of 3.5mm. Preferably, the distance between adjacent cooling pipes a in the middle cooling circuit 3 is 75cm, and the distance between adjacent cooling pipes a in the outer cooling circuit 5 is 45cm. The cooling pipes and connecting pipes can be connected by seamless welding or threaded connections. The distance between the lowest cooling pipes on both sides of the tunnel and the top surface of the foundation is 75cm. The inlet / outlet c and outlet d extend 50cm beyond the section to be poured, meaning the distance between the inlet / outlet c and outlet d and the construction joint is 50cm. The gap between the front and rear ends of the cooling pipes and the construction joint is 50cm. Within a single circulating lining, the total length of a single cooling circuit is controlled to be within 200m.

[0029] To ensure the cooling pipes are fixed stably, each cooling pipe is fixed to the inner layer of steel mesh by multiple hooks, and the distance between adjacent hooks on the same cooling pipe is 60cm.

[0030] To ensure uniform cooling, speed regulating ball valves for adjusting flow rate need to be installed at both the inlet and outlet, and flow meters need to be installed at both the inlet and outlet.

[0031] To visually monitor temperature changes, first temperature sensors are installed at both inlet c and outlet d for real-time temperature monitoring. Second temperature sensors 4 are evenly distributed in the outer steel mesh 1, inner steel mesh 2, and concrete core. To ensure comprehensive monitoring, at least four sets are arranged in each cycle of the secondary lining, distributed in the middle of the lining and near the front and rear end caps, with each set containing no fewer than three sensors (one each for the inner steel mesh, the center, and the outer steel mesh). The sensors are located approximately 1.8m from the top surface of the tunnel side foundation, and the temperature sensors at both ends are approximately 0.5m from the end cap of the formwork (or the end of the concrete poured in the previous cycle).

[0032] To prevent debris from entering during pouring, pipe covers are installed at the inlet c and outlet d.

[0033] The crack resistance method is as follows:

[0034] Step 1: Structural Installation. Two cooling circuits are installed between the inner layer of steel reinforcement mesh using hooks. Before pouring, it is necessary to test whether the two cooling circuits can flow water normally. The specific operation is as follows: a low-flow-rate water leakage test is conducted. During the test, it is also necessary to observe whether each cooling circuit is deformed to prevent deformation and instability of each cooling circuit and intrusion into the protective layer. If a leak is found, it is recorded and sealed after the water is drained. If the deformation of the cooling circuit exceeds the limit, the water flow test should be stopped immediately and reinforcement treatment should be carried out.

[0035] Step 2: Water cooling. After pouring, water cooling begins when the concrete has initially set. During the water cooling process, the difference between the water temperature and the highest temperature of the concrete is controlled to be within 15℃ by adjusting the water flow rate and water temperature. The cooling rate is no more than 2℃ / d and no more than 1℃ / 4h.

[0036] The temperature change curve of the aluminoferrite concrete obtained from the experiment is shown in Figure 4. It exhibits a trend of rapid increase in the early stage followed by a slow decrease. Therefore, it is necessary to control the inlet water temperature in stages, with the inlet water temperature ranging from 20℃ to 40℃, and the difference between the outlet water temperature and the inlet water temperature ranging from 3℃ to 6℃. Simultaneously, the flow rate at the inlet and outlet should be controlled to ensure that the flow rate is between 1.0 and 10.0 m³ / h. 3 / h, and the maximum temperature at the center of the concrete should not exceed 50℃ throughout the entire water flow process.

[0037] The specific control method is as follows: steadily increase the water injection volume of the outer cooling circuit until it reaches 10.0m. 3 The water flow rate is maintained at 10.0 m / h, while the temperature difference between the cooling water and the concrete surface in the outer cooling circuit is controlled within 25°C. During the later stages of solidification, as the concrete surface temperature stabilizes, the water flow rate is gradually reduced until it is stopped. For the intermediate cooling circuit, a flow rate of 10.0 m / h is maintained for the first 12 hours. 3 The water injection rate is set at / h, while the temperature difference between the cooling water and the concrete surface in the intermediate cooling circuit is controlled within 25℃. When the intermediate concrete reaches its peak value, the water injection rate is reduced.

[0038] Step 3: Stop the water supply. Water supply should be stopped when all of the following conditions are met simultaneously: internal temperature drops below 45℃, temperature difference between the inner and outer layers is less than 15℃, and temperature difference between the core and the environment is less than 15℃. If only one or two conditions are met, reduce the water supply appropriately until all conditions are met before stopping the water supply. After stopping the water supply, the cooling water pipes need to be sealed with cement using grouting. After stopping the water supply, to prevent sudden cooling of the aluminate concrete lining, the concrete lining needs to be steam-cured or sprayed with curing liquid. The steam temperature should be between 35℃ and 45℃, and the curing time should exceed 14 days.

[0039] To further prevent cracking, the weight ratio of each component in the secondary lining concrete is as follows: cement: fly ash: manufactured sand: gravel: medium aggregate: large aggregate: water: water-reducing agent: retarder: air-entraining agent: fiber = 323:107:823:193:581:193:160:1.55%:1.7%:0.5%:1. The fiber used is POM, with a length of 36mm. Further prevention of cracking is achieved by adding polyoxymethylene (POM), where the gravel is 5-10mm in diameter, the medium aggregate is 10-16mm in diameter, and the large aggregate is 16-31.5mm in diameter.

Claims

1. A crack-resistant construction method for ferroaluminate concrete lining in high-speed railway tunnels, characterized in that: It includes an intermediate cooling circuit (3) and an outer cooling circuit (5). The intermediate cooling circuit (3) is located between the outer steel mesh (1) and the inner steel mesh (2), and the outer cooling circuit (5) is located on the outer steel mesh (1). The intermediate cooling circuit (3) and the outer cooling circuit (5) have the same structure, both including several cooling pipes (a) arranged side by side at intervals. The arrangement density of the cooling pipes (a) on the outer cooling circuit (5) is greater than that on the intermediate cooling circuit (3). Adjacent cooling pipes (a) are connected by a U-shaped connecting pipe (b). The two cooling pipes (a) located on the left and right sides of the tunnel and close to the top surface of the foundation are respectively provided with water inlet (c) and water outlet (d). The water inlet (c) and water outlet (d) both extend beyond the area to be poured. The two cooling pipes (a) located on the left and right sides of the tunnel and close to the top surface of the foundation are separated from the top surface of the foundation. It also includes the following steps: S1: Structural installation, install the middle cooling circuit (3) and the outer cooling circuit (5), and before pouring, it is necessary to test whether the two cooling circuits are in normal water flow; S2: Water cooling. After pouring, water cooling begins when the concrete has initially set. During the water cooling process, the difference between the water temperature and the highest temperature of the concrete is controlled to be within 15℃ by adjusting the water flow rate and water temperature. The cooling rate is no more than 2℃ / d and no more than 1℃ / 4h. Throughout the process, the core temperature of the concrete must be kept below 50℃. S3: Water shut-off. When the following conditions are met simultaneously: internal temperature drops below 45℃, temperature difference between inner and outer layers is less than 15℃, and temperature difference between core and environment is less than 15℃, water supply is stopped. After water shut-off, cement should be used to seal the two cooling water pipes with grout in a timely manner.

2. The crack-resistant construction method for ferroaluminate concrete lining of high-speed railway tunnels according to claim 1, characterized in that: In S2, the inlet water temperature needs to be controlled in stages, with the inlet water temperature ranging from 20℃ to 40℃, and the difference between the outlet water temperature and the inlet water temperature being 3℃ to 6℃. The flow rates at the inlet and outlet are 1.0-10.0 m³ / h. 3 / h.

3. The crack-resistant construction method for ferroaluminate concrete lining of high-speed railway tunnels according to claim 1, characterized in that: After the water supply is shut off, the concrete lining needs to be steam cured or sprayed with curing liquid, and the steam temperature should be between 35℃ and 45℃, with a curing time of more than 14 days.

4. The crack-resistant construction method for ferroaluminate concrete lining of high-speed railway tunnels according to claim 1, characterized in that: The distance between adjacent cooling pipes (a) in the outer cooling circuit (5) is 30-50cm, the distance between adjacent cooling pipes (a) in the middle cooling circuit (3) is 60-80cm, the distance between the two cooling pipes (a) located on the left and right sides of the tunnel and close to the top surface of the side foundation is 75cm, and the length of the inlet / outlet (3c) and the outlet (3d) extending beyond the section to be poured is 50cm.

5. The crack-resistant construction method for ferroaluminate concrete lining of high-speed railway tunnels according to claim 1, characterized in that: The cooling pipe (3a) is fixed by multiple hooks, and the distance between adjacent hooks on the same cooling pipe (3a) is 60cm.

6. The crack-resistant construction method for ferroaluminate concrete lining of high-speed railway tunnels according to claim 1, characterized in that: Both the inlet (3c) and outlet (3d) are equipped with speed regulating ball valves to ensure uniform water flow.

7. The crack-resistant construction method for ferroaluminate concrete lining of high-speed railway tunnels according to claim 1, characterized in that: The inlet (3c) and outlet (3d) are each equipped with a first temperature sensor for real-time temperature monitoring, and the outer steel mesh (1), inner steel mesh (2) and concrete core are each equipped with a second temperature sensor (4).

8. The crack-resistant construction method for ferroaluminate concrete lining of high-speed railway tunnels according to claim 1, characterized in that: The inlet (3c) and outlet (3d) are equipped with pipe covers to prevent debris from entering.

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