A method for predicting the damage range of a post-fire tunnel lining burst

Abstract

The application discloses a kind of tunnel lining burst damage range prediction methods after fire. Including: tunnel lining smoke temperature distribution test research is carried out, and tunnel lining surface temperature distribution is obtained;Abaqus finite element numerical simulation software is used to establish tunnel lining fire calculation model, obtain the internal temperature field of tunnel lining, calculate the maximum temperature rising rate and temperature difference;Indoor concrete test block high-temperature burst test is carried out and burst standard is formulated;Estimate tunnel lining burst damage range.The application method obtains the tunnel lining surface temperature distribution situation by tunnel lining smoke temperature distribution test, carries out calculation to tunnel lining internal temperature field distribution using finite element calculation simulation software, obtains the concrete burst standard by indoor concrete test block high-temperature burst test, and relies on this standard to predict the burst damage range of tunnel lining, can be more accurate, effectively estimate the burst damage degree of tunnel lining under fire.

Description

Technical Field

[0001] This invention relates to the field of tunnel damage prediction, specifically to a method for predicting the extent of tunnel lining cracking damage after a fire. Background Technology

[0002] Tunnels are widely used in transportation and municipal engineering due to their advantages such as shortening travel distance, improving driving efficiency and safety, protecting the natural environment, saving land resources, and being unaffected by weather conditions. With the rapid advancement of urbanization in my country, the number of traffic tunnels being built is also increasing year by year, and the resulting safety issues are attracting particular attention.

[0003] Fire is the most common and most frequent type of disaster in tunnels, mainly caused by vehicle collisions and fires. When a fire occurs, the tunnel lining surface is exposed to the fire source and smoke. Under high temperature, the concrete on the lining surface will crack, causing the internal steel reinforcement to be directly exposed to the high temperature environment. Affected by the high temperature, the performance of the internal steel reinforcement deteriorates and loses its integrity, resulting in a significant reduction in the load-bearing capacity of the lining structure and seriously affecting the safe use of the tunnel.

[0004] Numerous domestic and international experts and scholars have conducted research on the structural performance of tunnels after a fire, yielding abundant research results. However, many of these studies use standard fire temperature curves, such as IS 834, HC, and RWS, to simulate changes in fire temperature load. However, under actual tunnel fire conditions, due to the presence of smoke layers, the temperature load acting on the lining structure will be lower than the calculated value of the standard fire temperature curve, and its magnitude is related to the distance between the fire source and the lining. Therefore, the results obtained by simulating changes in fire temperature load using standard fire temperature curves do not match the actual results. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention discloses a method for predicting the extent of damage caused by bursting of tunnel lining after a fire. This method can more realistically and accurately predict the extent of internal damage to tunnel lining after a fire.

[0006] This invention is achieved through the following technical solution:

[0007] A method for predicting the extent of damage from bursting of tunnel lining after a fire, characterized by comprising the following steps:

[0008] S1. Conduct experimental research on the temperature distribution of smoke from tunnel lining during a fire to obtain the surface temperature distribution of the tunnel lining. The experimental research on the temperature distribution of smoke from tunnel lining during a fire includes the following steps:

[0009] a1. Select a suitable similar scale to build a tunnel fire test model;

[0010] a2. Set the location and size of the fire source;

[0011] a3. Monitor the stratification and temperature changes of flue gas in the tunnel lining through the monitoring system to clarify the temperature distribution characteristics of the tunnel lining surface.

[0012] S2. A calculation model of tunnel lining fire was established using Abaqus finite element numerical simulation software to obtain the internal temperature field of the tunnel lining and calculate the maximum heating rate and temperature difference at various locations inside the tunnel lining.

[0013] S3. Conduct high-temperature bursting tests on indoor concrete blocks to clarify the high-temperature bursting mechanism of concrete and formulate bursting standards.

[0014] Establishing bursting standards involves the following two steps:

[0015] b1. Plot the temperature-time curves of the concrete specimen at different distances from the fire-exposed surface, and calculate the maximum heating rate and temperature difference at each location.

[0016] b2. Based on the spatiotemporal distribution characteristics of concrete block bursting, compare the maximum heating rate and temperature difference of concrete blocks under the same spatial conditions to determine the standard for concrete block bursting.

[0017] S4. Based on the maximum heating rate and temperature difference at various locations inside the tunnel lining, and using the bursting criteria established in S3, estimate the range of bursting damage to the tunnel lining.

[0018] The beneficial effects of this invention are as follows: This invention proposes a method for predicting the extent of tunnel lining cracking damage after a fire. This method obtains the surface temperature distribution of the tunnel lining through a tunnel fire smoke temperature distribution test, then uses finite element simulation software to calculate the internal temperature field distribution of the tunnel lining, and finally uses an indoor high-temperature cracking test of concrete test blocks to obtain the concrete cracking standard. Based on this standard, the extent of tunnel lining cracking damage can be predicted, which can accurately and effectively estimate the degree of tunnel lining cracking damage under fire. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for predicting the damage range of tunnel lining bursting after a fire, according to the present invention.

[0020] Figure 2 This is a front view of the tunnel fire test model of the present invention;

[0021] Figure 3 This is a schematic diagram of the monitoring system of the present invention. Figure 1 ;

[0022] Figure 4 This is a schematic diagram of the basic system of the present invention. Figure 2 ;

[0023] Figure 5 This is a temperature distribution curve of the tunnel lining surface in Embodiment C1 of the present invention;

[0024] Figure 6 This is a diagram showing the internal temperature field distribution characteristics of the concrete specimen in Embodiment C1 of the present invention.

[0025] Figure 7 This is a diagram showing the distribution characteristics of bursting in the concrete test block of Embodiment C1 of the present invention;

[0026] Figure 8 This is a temperature distribution characteristic diagram of the tunnel lining roof in Embodiment C1 of the present invention;

[0027] Figure 9 This is a temperature distribution characteristic diagram at a depth of 1.8m below the tunnel lining roof in Embodiment C1 of the present invention;

[0028] Figure 10 This is a temperature distribution characteristic diagram at a depth of 2.10m below the tunnel lining roof in Embodiment C1 of the present invention;

[0029] Figure 11 This is a temperature distribution characteristic diagram at a depth of 2.8m below the tunnel lining roof in Embodiment C1 of the present invention;

[0030] Figure 12 This is a temperature distribution characteristic diagram at a depth of 3.60m below the tunnel lining roof in Embodiment C1 of the present invention;

[0031] Figure 13 This is a temperature distribution characteristic diagram at a depth of 5.10m below the tunnel lining roof in Embodiment C1 of the present invention;

[0032] Figure 14 This is a temperature distribution characteristic diagram at a depth of 6.10m below the tunnel lining roof in Embodiment C1 of the present invention;

[0033] Figure 15 This is a temperature distribution characteristic diagram at a depth of 7.10m below the tunnel lining roof in Embodiment C1 of the present invention;

[0034] Figure 16 This is a diagram showing the distribution characteristics of tunnel lining burst damage in Embodiment C1 of the present invention.

[0035] In the diagram, 1 is the fire test model, 2 is the fireproof glass, 3 is the fire source, 4 is the base, 5 is the digital camera, 6 is the K-type thermocouple, and 7 is the TST static (temperature) strain gauge. Detailed Implementation

[0036] The present invention will be further described below with reference to specific embodiments. These specific embodiments are further explanations of the principles of the present invention and are not intended to limit the present invention in any way. Any technology that is the same as or similar to the present invention does not exceed the scope of protection of the present invention.

[0037] This invention provides a method for predicting the extent of damage caused by bursting of tunnel lining after a fire. The method includes the following steps:

[0038] S1. Conduct experimental research on the temperature distribution of smoke from tunnel lining during a fire to obtain the surface temperature distribution of the tunnel lining. The tunnel lining smoke temperature distribution test includes the following three steps:

[0039] a1. Select a suitable similar scale to build a tunnel fire test model 1;

[0040] a2. Set the location and size of fire source 3;

[0041] a3. Monitor the stratification and temperature changes of flue gas in the tunnel lining through the monitoring system to clarify the temperature distribution characteristics of the tunnel lining surface.

[0042] In step S1, a2, the location of the ignition source 3 is determined based on the actual situation, that is, according to the test requirements for different fire locations. The ignition source 3 is an oil pool fire; similarly, the size of the ignition source 3 is determined based on the test results of the actual fire size.

[0043] In step S1a3, the monitoring system consists of K-type thermocouples 6, a TST static temperature strain gauge 7, and a digital camera 5. In this example, there are 13 K-type thermocouples 6, arranged on the tunnel sidewalls and the tunnel arch. On the tunnel sidewalls, four K-type thermocouples 6 are symmetrically distributed along the tunnel centerline, with coordinates (distance from the tunnel sidewall, distance from the tunnel bottom) of (20mm, 54mm), (20mm, 114mm), (20mm, 174mm), and (20mm, 234mm), respectively. On the tunnel arch, five K-type thermocouples 6 are symmetrically distributed along the tunnel centerline, with coordinates (distance from the tunnel sidewall, distance from the tunnel top) of (20mm, 20mm), (150mm, 20mm), (300mm, 20mm), (450mm, 20mm), and (580mm, 20mm), respectively.

[0044] S2. A fire simulation model of the tunnel lining is established using Abaqus finite element method software to obtain the internal temperature field of the tunnel lining and calculate the maximum heating rate and temperature difference at various locations inside the tunnel lining. The specific steps are as follows:

[0045] (1) Establish horseshoe-shaped structural components: the horseshoe-shaped structure is a solid unit;

[0046] (2) Define the material properties of the horseshoe structure: Create a cross section through the Abaqus material properties settings panel to assign thermal conductivity, specific heat capacity and density parameters to the horseshoe structure;

[0047] (3) Assembly: Assemble the horseshoe-shaped structural components and the defined material properties to obtain the tunnel lining structure;

[0048] (4) Set up the analysis step: Create a heating time analysis step using transient heat transfer analysis;

[0049] (5) Establish interaction: The interaction of the tunnel lining fire-exposed surface is established using the interaction module in Abaqus;

[0050] (6) Set up a predefined field: Use the predefined field module in Abaqus to establish the initial temperature field of the tunnel lining;

[0051] (7) Mesh generation: The tunnel lining calculation mesh was created using the mesh generation module in Abaqus. The mesh control attribute was hexahedral structured mesh, and the element type was heat transfer element.

[0052] (8) Submit the established model to the Abaqus job module for calculation to obtain the internal temperature field of the tunnel lining. Based on the spatiotemporal distribution characteristics of the temperature field, calculate the maximum heating rate and temperature difference at each location inside the tunnel lining.

[0053] In step S2(5) above, the fire-exposed surface of the tunnel lining is divided into multiple regions along the height direction. The height value of each region of the fire-exposed surface of the tunnel lining is set as small as possible to ensure accuracy. The interaction between the fire-exposed surfaces of each region of the tunnel lining is set as surface heat exchange conditions and surface heat radiation.

[0054] The surface heat exchange conditions and surface heat radiation amplitude of each area of ​​the tunnel lining exposed to fire are set according to the temperature distribution obtained in step S1a3.

[0055] Except for the fire-exposed surface in step S2 (5), the other unmentioned surfaces are adiabatic surfaces, with absolute zero taken as -273.15℃ and the Stefan Boltzmann constant as 3.402 × 10⁻⁶. -6 .

[0056] S3. Conduct high-temperature bursting tests on indoor concrete specimens to clarify the high-temperature bursting mechanism of concrete and establish bursting standards. Establishing bursting standards includes the following two steps:

[0057] b1. Plot the temperature-time curves of the concrete specimen at different distances from the fire-exposed surface, and calculate the maximum heating rate and temperature difference at each location.

[0058] b2. Based on the spatiotemporal distribution characteristics of concrete block bursting, compare the maximum heating rate and temperature difference of concrete blocks under the same spatial conditions to determine the standard for concrete block bursting.

[0059] S4. Based on the maximum heating rate and temperature difference at various locations inside the tunnel lining, and using the bursting criteria established in S3, estimate the range of bursting damage to the tunnel lining.

[0060] Example C1

[0061] The method of the present invention will be described below with reference to specific experimental setups, the data obtained, and the processing thereof.

[0062] S1. Conduct experimental research on the temperature distribution of smoke from tunnel lining during fires to obtain the surface temperature distribution of tunnel lining.

[0063] In this embodiment, the tunnel fire test model has a similarity ratio of 1:16, a length of 8.5m, a width of 0.6m, and a height of 0.44m. The fire source is a gasoline pool fire, located in the middle of the cross-section of the test model, 20mm away from the bottom of the model. The parameters of the gasoline pool fire are shown in Table 1.

[0064] Table 1 Gasoline Pool Ignition Parameters

[0065]

[0066] The actual temperature rise curve is the HC curve:

[0067] ΔT H,max =20+1080(1-0.325e) -0.167t -0.675e -2.5t (Equation 1)

[0068] In the formula, T is the temperature, °C; t is the time, min;

[0069] The surface temperature distribution curve of the tunnel lining is obtained, such as Figure 5 As shown, fitting the curve yields the following formula for calculating the surface temperature distribution of the tunnel lining:

[0070]

[0071] In the formula, △T H,max Excess temperature of the ceiling, °C; △T h,max The excess temperature at vertical height h is expressed in °C; h / H is the ratio of vertical height to tunnel height (in place of radial position).

[0072] S2. A calculation model for tunnel lining fire was established using Abaqus finite element numerical simulation software to obtain the internal temperature field of the tunnel lining and calculate the maximum heating rate and temperature difference at various locations inside the tunnel lining; specifically:

[0073] (1) The tunnel lining is made of ordinary concrete with a strength grade of C30. The longitudinal length is 2000mm. The tunnel cross section is horseshoe-shaped with a cross section size of 14100mm×8700mm. The surface of the tunnel lining is the heat-receiving surface, the road surface at the bottom of the tunnel is the heat-dissipating surface, and the rest are the heat-insulating surfaces.

[0074] (2) Define the material properties of the tunnel lining structure. The selection of concrete thermal conductivity and specific heat capacity are shown in Tables 2 and 3, respectively. The density is taken as 2300 kg / m³. 3 ;

[0075] Table 2 Comparison of the relationship between the thermal conductivity coefficient of concrete and temperature

[0076]

[0077] Table 3. Comparison of the specific heat capacity of concrete with temperature.

[0078]

[0079] (3) Assembly to obtain the tunnel lining structure;

[0080] (4) Set the analysis step, and set the analysis step time step to 3600s;

[0081] (5) Establish interaction: The fire-exposed surface of the tunnel lining is divided into 87 regions along the height direction. The height value of each region is set to 100 mm. The interaction of all regions is set as surface heat exchange conditions and surface heat radiation. The amplitude is calculated by Equation 1 and Equation 2, see Table 4.

[0082] Table 4. Amplitude of interaction conditions in different areas of the tunnel's fire-exposed surface.

[0083]

[0084]

[0085] (6) Set a predefined field, with the initial temperature field set to 20℃;

[0086] (7) Mesh generation: The mesh size of the tunnel lining is 5mm, and the total number of meshes is 11068. The entire tunnel lining structure adopts a hexahedral structured mesh and an eight-node linear heat transfer hexahedral unit.

[0087] (8) Submit the established model to the Abaqus job module for calculation to obtain the internal temperature field of the tunnel lining. Based on the spatiotemporal distribution characteristics of the temperature field, calculate the maximum heating rate and temperature difference at each location inside the tunnel lining, as shown in Table 5.

[0088] Table 5. Maximum heating rate and temperature difference at various locations inside the tunnel lining.

[0089]

[0090]

[0091] Table 5 shows that during the initial heating phase of the tunnel lining top, at 0 cm from the fire-exposed surface, the maximum heating rate was 472℃ / min, with a maximum temperature difference of 606℃ 1 cm from the inner layer; at 0.5 cm from the fire-exposed surface, the maximum heating rate was 233℃ / min, with a maximum temperature difference of 307℃ 1 cm from the inner layer; at 1 cm from the fire-exposed surface, the maximum heating rate was 111℃ / min, with a maximum temperature difference of 151℃ 1 cm from the inner layer; and at 1.5 cm from the fire-exposed surface... The maximum heating rate is 58.1℃ / min, and the maximum temperature difference with the inner layer is 114℃. At 2cm from the fire-exposed surface, the maximum heating rate is 31.1℃ / min, and the maximum temperature difference with the inner layer is 63℃. At 2.5cm from the fire-exposed surface, the maximum heating rate is 22.1℃ / min, and the maximum temperature difference with the inner layer is 62.6℃. When the distance from the fire-exposed surface exceeds 3cm, the maximum heating rate is less than 21.8℃ / min.

[0092] At the initial stage of heating 1.8m below the top of the tunnel lining, at 0cm from the fire-exposed surface, the maximum heating rate is 370℃ / min, with a maximum temperature difference of 470℃ 1cm from the inner layer. At 0.5cm from the fire-exposed surface, the maximum heating rate is 189℃ / min, with a maximum temperature difference of 248℃ 1cm from the inner layer. At 1cm from the fire-exposed surface, the maximum heating rate is 91℃ / min, with a maximum temperature difference of 124℃ 1cm from the inner layer. At 1.5cm from the fire-exposed surface, the maximum heating rate is 48℃ / min, with a maximum temperature difference of 95℃ 1cm from the inner layer. At 2cm from the fire-exposed surface, the maximum heating rate is 25.7℃ / min, with a maximum temperature difference of 52.2℃ 1cm from the inner layer. After the distance from the fire-exposed surface exceeds 2cm, the maximum heating rate is less than 21.8℃ / min.

[0093] At the initial stage of heating 2.1m below the top of the tunnel lining, at 0cm from the fire-exposed surface, the maximum heating rate is 339℃ / min, with a maximum temperature difference of 427℃ 1cm from the inner layer. At 0.5cm from the fire-exposed surface, the maximum heating rate is 175℃ / min, with a maximum temperature difference of 230℃ 1cm from the inner layer. At 1cm from the fire-exposed surface, the maximum heating rate is 85℃ / min, with a maximum temperature difference of 116℃ 1cm from the inner layer. At 1.5cm from the fire-exposed surface, the maximum heating rate is 45.4℃ / min, with a maximum temperature difference of 89℃ 1cm from the inner layer. At 2cm from the fire-exposed surface, the maximum heating rate is 24.4℃ / min, with a maximum temperature difference of 49.4℃ 1cm from the inner layer. After the distance from the fire-exposed surface exceeds 2cm, the maximum heating rate is less than 21.8℃ / min.

[0094] At the initial stage of heating 2.8m below the top of the tunnel lining, at 0cm from the fire-exposed surface, the maximum heating rate is 290℃ / min, and the maximum temperature difference with the inner layer (1cm) is 364℃. At 0.5cm from the fire-exposed surface, the maximum heating rate is 151℃ / min, and the maximum temperature difference with the inner layer (1cm) is 199℃. At 1cm from the fire-exposed surface, the maximum heating rate is 73℃ / min, and the maximum temperature difference with the inner layer (1cm) is 100℃. At 1.5cm from the fire-exposed surface, the maximum heating rate is 39.2℃ / min, and the maximum temperature difference with the inner layer (1cm) is 77℃. After the distance from the fire-exposed surface exceeds 1.5cm, the maximum heating rate is less than 21.8℃ / min.

[0095] At the initial stage of heating 3.6m below the top of the tunnel lining, at 0cm from the fire-exposed surface, the maximum heating rate is 225℃ / min, and the maximum temperature difference with the inner layer (1cm) is 278℃. At 0.5cm from the fire-exposed surface, the maximum heating rate is 121℃ / min, and the maximum temperature difference with the inner layer (1cm) is 158℃. At 1cm from the fire-exposed surface, the maximum heating rate is 59.2℃ / min, and the maximum temperature difference with the inner layer (1cm) is 81℃. At 1.5cm from the fire-exposed surface, the maximum heating rate is 32.4℃ / min, and the maximum temperature difference with the inner layer (1cm) is 64℃. After the distance from the fire-exposed surface exceeds 1.5cm, the maximum heating rate is less than 21.8℃ / min.

[0096] At the initial stage of heating 5.1m below the top of the tunnel lining, at 0cm from the fire-exposed surface, the maximum heating rate is 154℃ / min, and the maximum temperature difference with the inner layer (1cm) is 191℃. At 0.5cm from the fire-exposed surface, the maximum heating rate is 83.7℃ / min, and the maximum temperature difference with the inner layer (1cm) is 110℃. At 1cm from the fire-exposed surface, the maximum heating rate is 41℃ / min, and the maximum temperature difference with the inner layer (1cm) is 86℃. At 1.5cm from the fire-exposed surface, the maximum heating rate is 23.1℃ / min, and the maximum temperature difference with the inner layer (1cm) is 46℃. After the distance from the fire-exposed surface exceeds 1.5cm, the maximum heating rate is less than 21.8℃ / min.

[0097] At the initial stage of heating 6.1m below the top of the tunnel lining, at 0cm from the fire-exposed surface, the maximum heating rate is 130℃ / min, and the maximum temperature difference with the inner layer is 144℃ (1cm). At 0.5cm from the fire-exposed surface, the maximum heating rate is 64℃ / min, and the maximum temperature difference with the inner layer is 84℃ (1cm). At 1cm from the fire-exposed surface, the maximum heating rate is 31.3℃ / min, and the maximum temperature difference with the inner layer is 43℃ ​​(1cm). After the distance from the fire-exposed surface exceeds 1cm, the maximum heating rate is less than 21.8℃ / min.

[0098] At the initial stage of heating 7.1m below the top of the tunnel lining, at a distance of 0cm from the fire-exposed surface, the maximum heating rate is 90℃ / min, and the maximum temperature difference with the inner layer is 118℃ (1cm). At a distance of 0.5cm from the fire-exposed surface, the maximum heating rate is 43.9℃ / min, and the maximum temperature difference with the inner layer is 60℃ (1cm). After the distance from the fire-exposed surface exceeds 0.5cm, the maximum heating rate is less than 21.8℃ / min.

[0099] S3. Conduct high-temperature bursting tests on indoor concrete blocks to clarify the high-temperature bursting mechanism of concrete and formulate bursting standards, specifically as follows:

[0100] (1) Plot the temperature-time curves of the concrete specimen at different distances from the exposed surface, such as... Figure 6 As shown.

[0101] (2) Calculate the maximum heating rate and temperature difference at various points inside the concrete. Figure 6 A and B represent the inflection points of the temperature rise curves at distances of 1 cm and 2 cm from the surface exposed to the fire, respectively. The inflection points occur because the concrete at these locations has already cracked. Generally, inflection points appear in the early stages of heating (heating time less than 10 min). Calculations show that the maximum heating rate before inflection point A is 63.2℃ / min, the maximum heating rate before inflection point B is 54.3℃ / min, the maximum heating rate at 3 cm from the surface exposed to the fire is 41.6℃ / min, and the maximum heating rate at 4 cm from the surface exposed to the fire is 21.8℃ / min. In addition to the heating rate, excessive temperature differences between the inside and outside of the concrete at the same time can also lead to concrete cracking. Calculations show that at the same time, the maximum temperature differences between the surface of the fire exposed to the surface and 1 cm, as well as between 1 cm and 2 cm, are all above 100℃, while the maximum temperature differences between 2 cm and 3 cm, as well as between 3 cm and 4 cm, are all less than 70℃.

[0102] (3) Combining the characteristics of concrete specimen burst distribution, such as Figure 7 As shown, the burst depth is approximately 2.5 cm. Therefore, the thermal stress-induced burst standard can be obtained as follows:

[0103] 1) Concrete will not burst when the maximum heating rate in the initial stage is below 21.8℃ / min, or when the maximum heating rate in the initial stage is between 21.8 and 46.1℃ / min and the temperature difference between the concrete and the inner layer at 1cm is below 70℃.

[0104] 2) Concrete may burst if the maximum heating rate is between 21.8 and 46.1℃ / min and the temperature difference between the concrete and the inner layer (1cm) is greater than 70℃ during the initial heating phase, or if the maximum heating rate is between 46.1 and 54.3℃ / min and the temperature difference between the concrete and the inner layer (1cm) is less than 70℃ during the initial heating phase.

[0105] 3) When the maximum heating rate in the initial stage of heating is 46.1 to 54.3℃ / min and the temperature difference with the inner layer 1cm is more than 70℃, or when the maximum heating rate in the initial stage of heating is higher than 54.3℃ / min and the temperature difference with the inner layer 1cm is less than 100℃, the concrete will experience incomplete bursting.

[0106] 4) When the maximum heating rate exceeds 54.3℃ / min in the initial stage of heating and the temperature difference with the inner layer 1cm is more than 100℃, the concrete will completely burst.

[0107] S4. Based on the maximum heating rate and temperature difference at various locations inside the tunnel lining, and using the thermal stress-induced bursting standards 1), 2), 3), and 4) established in S3, the predicted range of tunnel lining bursting damage is shown in Table 5. Figure 16 The specific judgment process is as follows:

[0108] Complete blasting occurred at the following locations: 0cm-1.5cm from the top of the tunnel lining to the fire-exposed surface; 0cm-1cm from the top of the tunnel lining to the fire-exposed surface at 1.8m below the top of the tunnel lining, with a possible blast at 1.5cm; 0cm-1cm from the top of the tunnel lining to the fire-exposed surface at 2.1m below the top of the tunnel lining, with a possible blast at 1.5cm; 0cm-1cm from the top of the tunnel lining to the fire-exposed surface at 2.8m below the top of the tunnel lining, with a possible blast at 1.5cm; 0cm-0.5cm from the top of the tunnel lining to the fire-exposed surface at 3.6m below the top of the tunnel lining, with an incomplete blast at 1cm; 0cm-0.5cm from the top of the tunnel lining to the fire-exposed surface at 5.1m below the top of the tunnel lining, with a possible blast at 1cm; 0cm from the top of the tunnel lining to the fire-exposed surface at 6.1m below the top of the tunnel lining, with an incomplete blast at 0.5cm; and 0cm from the top of the tunnel lining to the fire-exposed surface at 7.1m below the top of the tunnel lining.

Claims

1. A method for predicting the extent of damage caused by bursting of tunnel lining after a fire, characterized in that... Includes the following steps: S1. Conduct experimental research on the temperature distribution of smoke from tunnel lining during fires to obtain the surface temperature distribution of tunnel lining. S2. A calculation model for tunnel lining fire was established using Abaqus finite element numerical simulation software to obtain the internal temperature field of the tunnel lining and calculate the maximum heating rate and temperature difference at various locations inside the tunnel lining; including: (1) establishing arch structure components: the arch structure is a solid element; (2) defining the material properties of the arch structure: the cross section was created through the Abaqus material property setting panel to assign thermal conductivity, specific heat capacity and density parameters to the arch structure; (3) assembly: the arch structure components and the defined material properties were assembled to obtain the tunnel lining structure; (4) setting the analysis step: the heating time analysis step was created using transient heat transfer analysis; 5) Establish interaction: Use the interaction module in Abaqus to establish the interaction of the fire-exposed surface of the tunnel lining; (6) Set predefined field: Use the predefined field module in Abaqus to establish the initial temperature field of the tunnel lining; (7) Mesh generation: Use the mesh generation module in Abaqus to establish the computational mesh of the tunnel lining. The mesh control attribute is hexahedral structured mesh, and the element type is heat transfer element; (8) Submit the established model to the work module in Abaqus to obtain the internal temperature field of the tunnel lining. According to the spatiotemporal distribution characteristics of the temperature field, calculate the maximum heating rate and temperature difference at each location inside the tunnel lining. S3. Conduct indoor high-temperature bursting tests on concrete test blocks to clarify the high-temperature bursting mechanism of concrete and formulate bursting standards; including: b1. Plotting temperature-time change curves of concrete test blocks at different distances from the fire-exposed surface, and calculating the maximum heating rate and temperature difference at each location; b2. Combining the spatiotemporal distribution characteristics of concrete test block bursting, comparing the maximum heating rate and temperature difference of concrete test blocks under the same spatial conditions, and determining the standards for concrete test blocks that do not burst, may burst, completely burst, and incompletely burst. S4. Based on the maximum heating rate and temperature difference at various locations inside the tunnel lining, and according to the standards established in S3 for no bursting, possible bursting, complete bursting, and incomplete bursting, estimate the range of bursting damage to the tunnel lining.

2. The method for predicting the extent of tunnel lining bursting damage after a fire, as described in claim 1, is characterized in that: Step S1 includes: a1. Selecting a suitable similar scale to build a tunnel fire test model; a2. Setting the location and size of the fire source; a3. Monitoring the stratification and temperature changes of the tunnel lining smoke through a monitoring system to clarify the temperature distribution characteristics of the tunnel lining surface.

3. The method for predicting the extent of tunnel lining bursting damage after a fire, as described in claim 2, is characterized in that: In step a2, the location of the fire source is determined according to the actual fire location. The fire source is an oil pool fire, and the size of the fire source is determined according to the actual fire situation.

4. The method for predicting the extent of tunnel lining bursting damage after a fire, as described in claim 2, is characterized in that: In step a3, the monitoring system consists of a K-type thermocouple, a TST static temperature strain gauge, and a digital camera.

5. The method for predicting the extent of tunnel lining bursting damage after a fire, as described in claim 1, is characterized in that: In step (5), the fire-exposed surface of the tunnel lining is divided into multiple regions along the height direction, and the interaction between each region is set as surface heat exchange conditions and surface heat radiation; except for the fire-exposed surface in step (5) in S2, the rest are insulated surfaces.

6. The method for predicting the extent of tunnel lining bursting damage after a fire, as described in claim 5, is characterized in that: The surface heat exchange conditions and surface heat radiation amplitude of the fire-exposed surfaces in each area of ​​the tunnel lining are obtained through step S1.

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