CN113653535A - Fire temperature field estimation method for fire-proof plate protection immersed tube tunnel in wall thickness direction - Google Patents
Fire temperature field estimation method for fire-proof plate protection immersed tube tunnel in wall thickness direction Download PDFInfo
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- 229910052918 calcium silicate Inorganic materials 0.000 description 1
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- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 description 1
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- E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
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Abstract
The invention relates to a fire disaster temperature field estimation method in the wall thickness direction of a fire-proof plate protection immersed tube tunnel, and belongs to the field of tunnel engineering. The method comprises the following steps: s1: establishing a fire-proof plate protection sinking pipe tunnel pipe wall temperature field solving model: s2: establishing a temperature distribution function on the boundary of the back fire surface of the fire-proof plate under the action of a fire source function; s3: establishing a cavity heat flow attenuation coefficient expression between the fireproof plate and the pipe wall; s4: establishing a temperature field solving mathematical model of the pipe wall of the immersed tunnel under the combined action of the back fire surface temperature of the fireproof plate and the cavity attenuation; s5: and solving the temperature value of any position at any time in the thickness direction of the pipe wall. The method simplifies the problem of solving the temperature field of the pipe wall of the tunnel with the fireproof plate for protecting the sinking pipe into two one-dimensional transient heat transfer problems. The first problem is solved by fire test data before installation of the fire-proof plate; the second problem is solved by analytical methods. The method enables the solving model to be simpler and the solving result to be more visual.
Description
Technical Field
The invention belongs to the field of tunnel engineering, and relates to a fire disaster temperature field estimation method in the wall thickness direction of a fire-proof plate protection immersed tube tunnel.
Background
The high temperature of the fire can cause the concrete to burst and the mechanical property to deteriorate, and the accurate and rapid measurement and calculation of the temperature field distribution in the thickness direction of the tunnel lining structure after the fire occurs has important significance for the bearing capacity evaluation of the pipe joint structure. At present, three methods related to the distribution and the measurement of the temperature field of the pipe wall of the tunnel with the fireproof plate for protecting the sinking pipe mainly comprise an indoor model test method, a field test method and a numerical simulation method, but the methods have the problems of complex model manufacturing, complex preparation work for embedding a sensor and the like, time consumption, labor consumption and the like, and the measurement results of the methods do not have universality due to the reasons that the actual position of a fire disaster is uncertain, and the fireproof performance of the fireproof plates with different types, sizes and installation modes is different. The fire-proof plate protection immersed tube tunnel fire longitudinal temperature field estimation method is simple in solving process, accurate in measuring and calculating method and universal.
Disclosure of Invention
In view of the above, the present invention provides a method for estimating a fire temperature field in a wall thickness direction of a tunnel with a fire-proof plate protecting a sunken tube. The influence of the fire-proof plate and the cavity between the fire-proof plate and the concrete pipe wall on the pipe wall temperature field is considered, the method is simple in model solving and visual in solving result, the fire test data before the installation of the fire-proof plate is fully utilized, the influence of the height, the shape and the like of the cavity on the pipe wall temperature field is simplified, and the measuring and calculating method is accurate and has universality.
In order to achieve the purpose, the invention provides the following technical scheme:
a fire hazard temperature field estimation method in the wall thickness direction of a fire-proof plate protection immersed tube tunnel comprises the following steps:
s1: establishing a fire-proof plate protection sinking pipe tunnel pipe wall temperature field solving model:
s2: establishing a temperature distribution function on the boundary of the back fire surface of the fire-proof plate under the action of a fire source function;
s3: establishing a cavity heat flow attenuation coefficient expression between the fireproof plate and the pipe wall;
s4: establishing a temperature field solving mathematical model of the pipe wall of the immersed tunnel under the combined action of the back fire surface temperature of the fireproof plate and the cavity attenuation;
s5: and solving the temperature value of any position at any time in the thickness direction of the pipe wall.
Optionally, the S1 specifically includes:
simplifying the problem to be researched into two one-dimensional transient heat transfer problems according to the actual fire condition of the immersed tube tunnel;
the first problem is transient heat conduction of the fireproof plate under the action of a fire source;
the second problem is transient heat conduction of the pipe wall of the immersed pipe under the combined action of the back temperature of the fireproof plate and the attenuation of the cavity;
the result of the solution of the first problem is the solution condition of the second problem.
Optionally, the S2 specifically includes:
to address the first problem at S1, a temperature distribution function is established at the boundary of the backfire face of the fire shield by a fire test prior to installation of the fire shield.
Optionally, the S3 specifically includes:
the distance between the fireproof plate and the concrete pipe wall influences the heat transfer mode of the fireproof plate and the concrete pipe wall, the fireproof plate and the concrete pipe wall are usually connected through angle steel and self-tapping screws to ensure that a cavity with a certain height is formed between the fireproof plate and the concrete pipe wall, and the heat transfer mode between the fireproof plate and the concrete pipe wall is thermal radiation and thermal convection at the moment; the cavity is not completely closed, and the side wall is not a complete heat insulator, so that certain convection heat exchange and the like can be generated with the outside, and certain side wall heat flow loss can exist.
Optionally, the S4 specifically includes:
in order to solve the second problem in S1, the boundary condition of the bottom of the tunnel tube wall is given according to the temperature of the back fire surface of the fireproof plate and the cavity attenuation coefficient, the boundary condition of the top of the tunnel tube wall is given according to the underwater earthing, and the initial condition and the one-dimensional transient heat conduction differential equation are combined to solve.
Optionally, the S5 specifically includes:
establishing a fire curve equation according to fire combustion curves of different vehicles in a fire scene, substituting thermal parameters and sizes of a pipe wall and a fire-proof plate and a cavity heat flow attenuation coefficient expression in S3 into a transient temperature field solving model in S4, and solving a temperature value at any position in the pipe wall thickness direction at any time; wherein the more accurate the fire combustion curve and cavity heat flow attenuation coefficient measurements are, the more accurate the temperature estimation in the concrete pipe wall is.
Optionally, in S1, the fire protection plate bottom is subjected to the fire source function Tf(t) the outer wall of the concrete of the tunnel pipe joint is contacted with the underwater earth covering, and the convection heat exchange effect is generated; the temperature of the underwater covering soil is TwThe initial temperature in the concrete wall of the pipe section is T0(y) initial temperature in the fire protection plate is Ta(ii) a A cavity with a certain height is formed between the pipe joint and the fireproof plate, and the heat transfer mode between the fireproof plate and the concrete wall is the comprehensive action of thermal radiation and thermal convection.
Optionally, in S2, the fireproof board has a function T of the fire sourcef(T) Back-fire surface temperature function Tb(t) the flame-retardant board is obtained through a fire-retardant test before installation of the flame-retardant board, and the test is realized through an infrared thermometer or a thermocouple and other temperature measuring elements arranged on the back fire surface of the flame-retardant board; function of fire source Tf(t) the actual conditions of the fire scene are different according to the type of the vehicle; considering that the tunnel space is small, the fire source function is assumed to directly act on the fire-resisting surface of the fire-resisting plate, namely the temperature of the boundary of the fire-resisting surface of the fire-resisting plate is equal to the temperature of the fire source.
Optionally, in the S3, the cavity is attenuatedThe function expression is defined as the heat flow loss q of the cavitycA function of the positive correlation is determined,
η＝qc/qb (1)
cavity heat flow loss qcValue q at the boundary with the back-fire surface of the fire-proof platebMeasured using a heat flow meter, wherein qcTaking the value of the position 5cm outside the center of the side wall of the cavity, or symmetrically taking points around the position 5cm outside the center of the side wall for measurement, and then obtaining the arithmetic mean value; and (3) taking the boundary central value of the back fire surface of the fire-proof plate or symmetrically taking points around the boundary center for measurement, and then obtaining an arithmetic mean value.
Optionally, in S4, the transient heat conduction of the immersed tube wall under the combined action of the fire-back surface temperature of the fire-proof plate and the cavity attenuation is solved by the following mathematical model:
the differential equation is as follows:
boundary conditions:
initial conditions:
Ti(y,0)＝T0(y) 0≤y≤d1 (4)
wherein, T1(y, T) is the transient temperature at the y position in the concrete pipe wall at the time T after the fire occurs, T1(0, T) is the temperature of the concrete outer wall of the pipe section at time T, T1(d1And t) is the temperature of the inner wall of the pipe joint concrete at the moment t; eta is a cavity heat flow attenuation function after the fire disaster occurs; d1The total thickness of the concrete layer on the wall of the tunnel pipe is the total thickness of the concrete layer; neglecting the height of the cavity and the thickness of the fireproof plate;
temperature value T of any position at any time in the pipe wall thickness direction of immersed tube tunnel in S51(y, t) is solved by:
in the formula:
The invention has the beneficial effects that:
(1) the problem of solving the temperature field of the tube wall of the tunnel with the fireproof plate for protecting the sinking tube is simplified into two one-dimensional transient heat transfer problems. The first problem is solved by fire test data before installation of the fire-proof plate; the second problem is solved by analytical methods. The method enables the solving model to be simpler and the solving result to be more visual.
(1) The method considers the influence of the fire-proof plate and the cavity between the fire-proof plate and the concrete pipe wall on the pipe wall temperature field, so that the solving result is more in line with the field reality.
(2) The cavity heat flow attenuation coefficient is introduced to quantify the influence of the cavity on the tube wall temperature field, the influence of the height, the shape and the like of the cavity on the tube wall temperature field is simplified, and the measuring and calculating method is accurate and universal.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
Drawings
For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a schematic diagram of a solution model.
Reference numerals: 1-covering soil at the bottom of water; 2-concrete pipe wall; 3-a cavity; 4-fire-proof plate; 5-fire source.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.
Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not an indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes, and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific situations.
The invention provides a fire temperature field estimation method in the wall thickness direction of a fire-proof plate protection immersed tube tunnel, aiming at the problems that the existing measurement and calculation method has complex model manufacturing, complicated preparation work for embedding a sensor and the like, time consumption and labor consumption and the like, and the measurement and calculation method has no universality and the like.
Referring to fig. 1, the method includes the following steps:
(1) establishing a fire-proof plate protection sinking pipe tunnel pipe wall temperature field solving model: the problem to be researched can be simplified into two one-dimensional transient heat transfer problems according to the actual fire condition of the immersed tube tunnel. The first problem is transient heat conduction of the fireproof plate under the action of a fire source; the second problem is transient heat conduction of the pipe wall of the immersed pipe under the combined action of the temperature of the back surface of the fireproof plate and the attenuation of the cavity, and the solving result of the first problem is the solving condition of the second problem.
(2) And establishing a temperature distribution function on the boundary of the back fire surface of the fire-proof plate under the action of the fire source function. This step is to solve the first problem in step (1), and the temperature distribution function on the boundary of the backfire face of the fire retardant panel may be established by a fire test before installation of the fire retardant panel.
(3) Establishing an expression of cavity heat flow attenuation coefficient between the fireproof plate and the pipe wall: the distance between the fireproof plate and the concrete pipe wall influences the heat transfer mode of the fireproof plate and the concrete pipe wall, the fireproof plate and the concrete pipe wall are usually connected through angle steel and self-tapping screws to ensure that a cavity with a certain height is formed between the fireproof plate and the concrete pipe wall, and the heat transfer mode between the fireproof plate and the concrete pipe wall is thermal radiation and thermal convection at the moment; the cavity is not completely closed, and the side wall is not a complete heat insulator, so that certain convection heat exchange and the like can be generated with the outside, and certain side wall heat flow loss can exist.
(4) Establishing a temperature field solving mathematical model of the pipe wall of the immersed tunnel under the combined action of the back fire surface temperature of the fireproof plate and the cavity attenuation: the step (1) is to solve the second problem, the boundary condition of the bottom of the tunnel tube wall is given according to the temperature of the back fire surface of the fireproof plate and the cavity attenuation coefficient, the boundary condition of the top of the tunnel tube wall is given according to the bottom earthing, and the solution can be carried out by combining the initial condition and the one-dimensional transient heat conduction differential equation.
(5) And solving the temperature value of any position at any moment in the thickness direction of the pipe wall: establishing a fire curve equation according to fire combustion curves of different vehicles in a fire scene, substituting thermal parameters, sizes and the like of the pipe wall and the fireproof plate and the cavity heat flow attenuation coefficient expression in the step (3) into the transient temperature field solving model in the step (4), and solving the temperature value of any position in the pipe wall thickness direction at any time; wherein the more accurate the fire combustion curve and cavity heat flow attenuation coefficient measurements are, the more accurate the temperature estimation in the concrete pipe wall is.
The schematic diagram of the solved model in the step (1) is shown in a figure 2, and comprises underwater soil covering 1, a concrete pipe wall 2, a cavity 3, a fireproof plate 4 and a fire source 5.
In the model, the fire source function T is received at the bottom of the fire-proof plate 4f(t) the outer wall of the concrete of the tunnel pipe joint is contacted with the underwater earth covering, and the convection heat exchange effect is generated; the temperature of the underwater covering soil is TwThe initial temperature in the concrete wall of the pipe section is T0(y) initial temperature in the fire protection plate is Ta. A cavity with a certain height is formed between the pipe joint and the fireproof plate, and the heat transfer mode between the fireproof plate and the concrete wall is the comprehensive action of heat radiation and heat convection;
in the step (2), the fire-proof plate has a fire source function Tf(t) EffectTemperature function T of lower back fire surfacebAnd (t) can be obtained through a fire test before the installation of the fire-proof plate, and can be realized through an infrared thermometer or by installing temperature measuring elements such as a thermocouple and the like on the back fire surface of the fire-proof plate in the test. Where the function of the source of fire Tf(t) the actual conditions of the fire scene are different according to the type of the vehicle; and considering that the tunnel space is small, the fire source function is assumed to directly act on the fire-resisting surface of the fire-resisting plate, namely the temperature of the boundary of the fire-resisting surface of the fire-resisting plate is equal to the temperature of the fire source.
In step (3), the cavity damping function expression can be defined as the cavity heat flow loss qcA function of the positive correlation is determined,
η＝qc/qb (1)
cavity heat flow loss qcValue q at the boundary with the back-fire surface of the fire-proof platebAll can be measured by a heat flow meter, wherein qcTaking the value of 5cm outside the center of the side wall of the cavity, or symmetrically taking point measurement around 5cm outside the center of the side wall, and then obtaining the arithmetic mean value; the central value of the boundary of the back fire surface of the fire-proof plate can be taken, and points can be symmetrically taken around the center of the boundary for measurement, and then the arithmetic mean value is obtained.
In the step (4), the transient heat conduction of the pipe wall of the immersed pipe under the combined action of the back fire surface temperature of the fireproof plate and the cavity attenuation can be solved through the following mathematical model:
the differential equation is as follows:
boundary conditions:
initial conditions:
Ti(y,0)＝T0(y) 0≤y≤d1 (4)
wherein, T1(y, t) is the moment at the y position in the concrete pipe wall at the time t after the fire occursTemperature of state, further T1(0, T) is the temperature of the concrete outer wall of the pipe section at time T, T1(d1And t) is the temperature of the concrete inner wall of the pipe section at the moment t. Eta is the cavity heat flow attenuation function after the fire occurs. d1The total thickness of the concrete layer on the wall of the tunnel pipe is the total thickness of the concrete layer; neglecting the height of the cavity and the thickness of the fire plate.
And (5) measuring the temperature T of any position at any time in the thickness direction of the immersed tunnel wall1(y, t) can be solved by:
in the formula:
Example 1
(1) C50 concrete is adopted for a pipe joint structure of a certain immersed tube tunnelThe thickness of the tube wall is 1500 mm. The fireproof calcium silicate board with the thickness of 35mm is adopted, the fireproof board and the concrete pipe wall can be connected through angle steel and self-tapping screws, so that a cavity with a certain height is formed between the fireproof board and the concrete pipe wall, and the heat conductivity coefficient lambda of the concrete is ensuredc1W/(m.K), specific heat capacity Cc1000J/(kg. DEG C.), the tunnel outside is cooled at normal temperature (T)w20 deg.C seawater and backfill soil body, and the initial temperature field in the pipe joint and the fireproof plate is also normal temperature Ta＝20℃。
(2) When a fire disaster occurs on the spot, the determined fire source function is approximate to a RABT curve:
t-time, min, duration of fire 2 hours.
Tf(t) -maximum temperature in the tunnel at time t, C.
The depth of the wall thickness direction of the concrete pipe affected by the fire after the fire occurs and the maximum temperature suffered by the fire need to be measured and calculated.
(3) Establishing a solving model through step 1, and measuring a fire source function T of the fire-proof plate according to step 2f(T) back fire surface temperature scatter values under the action of matlab piecewise fitting to function Tb(t)：
t-time in min, fire lasted 2 hours.
The maximum temperature in the tunnel at time T-T is given in degrees C.
(4) After the step (3), the cavity attenuation coefficient is measured at a position 5cm away from the center of the cavity side wall under the condition of no wind in the early fire test, and is approximately equal to 0.2.
(2) And (4) substituting the correlation value into the step (5) based on the mathematical model in the step (4) to obtain the maximum temperature of the concrete pipe wall in the fire occurrence process of 297.47 ℃, wherein the maximum temperature occurs at the innermost position of the pipe wall in the 102 th minute. During a fire, the temperature rise in the depth of 20cm in the thickness direction of the tube wall is not more than 1 ℃, and the temperature rise in the depth range of 15cm in the thickness direction of the tube wall is not more than 10 ℃.
Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.
Claims (10)
1. A fire hazard temperature field estimation method in the wall thickness direction of a fire-proof plate protection immersed tube tunnel is characterized by comprising the following steps: the method comprises the following steps:
s1: establishing a fire-proof plate protection sinking pipe tunnel pipe wall temperature field solving model:
s2: establishing a temperature distribution function on the boundary of the back fire surface of the fire-proof plate under the action of a fire source function;
s3: establishing a cavity heat flow attenuation coefficient expression between the fireproof plate and the pipe wall;
s4: establishing a temperature field solving mathematical model of the pipe wall of the immersed tunnel under the combined action of the back fire surface temperature of the fireproof plate and the cavity attenuation;
s5: and solving the temperature value of any position at any time in the thickness direction of the pipe wall.
2. The fire disaster temperature field estimation method in the wall thickness direction of the fire-proof plate protection immersed tube tunnel according to claim 1, characterized in that: the S1 specifically includes:
simplifying the problem to be researched into two one-dimensional transient heat transfer problems according to the actual fire condition of the immersed tube tunnel;
the first problem is transient heat conduction of the fireproof plate under the action of a fire source;
the second problem is transient heat conduction of the pipe wall of the immersed pipe under the combined action of the back temperature of the fireproof plate and the attenuation of the cavity;
the result of the solution of the first problem is the solution condition of the second problem.
3. The fire disaster temperature field estimation method in the wall thickness direction of the fire-proof plate protection immersed tube tunnel according to claim 2, characterized in that: the S2 specifically includes:
to address the first problem at S1, a temperature distribution function is established at the boundary of the backfire face of the fire shield by a fire test prior to installation of the fire shield.
4. The fire disaster temperature field estimation method in the wall thickness direction of the fire-proof plate protection immersed tube tunnel according to claim 3, characterized in that: the S3 specifically includes:
the distance between the fireproof plate and the concrete pipe wall influences the heat transfer mode of the fireproof plate and the concrete pipe wall, the fireproof plate and the concrete pipe wall are usually connected through angle steel and self-tapping screws to ensure that a cavity with a certain height is formed between the fireproof plate and the concrete pipe wall, and the heat transfer mode between the fireproof plate and the concrete pipe wall is thermal radiation and thermal convection at the moment; the cavity is not completely closed, and the side wall is not a complete heat insulator, so that certain convection heat exchange and the like can be generated with the outside, and certain side wall heat flow loss can exist.
5. The fire disaster temperature field estimation method in the wall thickness direction of the fire-proof plate protection immersed tube tunnel according to claim 4, characterized in that: the S4 specifically includes:
in order to solve the second problem in S1, the boundary condition of the bottom of the tunnel tube wall is given according to the temperature of the back fire surface of the fireproof plate and the cavity attenuation coefficient, the boundary condition of the top of the tunnel tube wall is given according to the underwater earthing, and the initial condition and the one-dimensional transient heat conduction differential equation are combined to solve.
6. The fire disaster temperature field estimation method in the wall thickness direction of the fire-proof plate protection immersed tube tunnel according to claim 5, characterized in that: the S5 specifically includes:
establishing a fire curve equation according to fire combustion curves of different vehicles in a fire scene, substituting thermal parameters and sizes of a pipe wall and a fire-proof plate and a cavity heat flow attenuation coefficient expression in S3 into a transient temperature field solving model in S4, and solving a temperature value at any position in the pipe wall thickness direction at any time; wherein the more accurate the fire combustion curve and cavity heat flow attenuation coefficient measurements are, the more accurate the temperature estimation in the concrete pipe wall is.
7. The fire disaster temperature field estimation method in the wall thickness direction of the fire-proof plate protection immersed tube tunnel according to claim 2, characterized in that: in the S1, the fire source function T is applied to the bottom of the fire-proof platef(t) the outer wall of the concrete of the tunnel pipe joint is contacted with the underwater earth covering, and the convection heat exchange effect is generated; the temperature of the underwater covering soil is TwThe initial temperature in the concrete wall of the pipe section is T0(y) initial temperature in the fire protection plate is Ta(ii) a A cavity with a certain height is formed between the pipe joint and the fireproof plate, and the heat transfer mode between the fireproof plate and the concrete wall is the comprehensive action of thermal radiation and thermal convection.
8. The fire disaster temperature field estimation method in the wall thickness direction of the fire-proof plate protection immersed tube tunnel according to claim 3, characterized in that: the function T of the fire-proof plate in the fire source in S2f(T) Back-fire surface temperature function Tb(t) the flame-retardant board is obtained through a fire-retardant test before installation of the flame-retardant board, and the test is realized through an infrared thermometer or a thermocouple and other temperature measuring elements arranged on the back fire surface of the flame-retardant board; function of fire source Tf(t) the actual conditions of the fire scene are different according to the type of the vehicle; considering that the tunnel space is small, the fire source function is assumed to directly act on the fire-resisting surface of the fire-resisting plate, namely the temperature of the boundary of the fire-resisting surface of the fire-resisting plate is equal to the temperature of the fire source.
9. The fire disaster temperature field estimation method in the wall thickness direction of the fire-proof plate protection immersed tube tunnel according to claim 4, characterized in that: in S3, the expression of the cavity attenuation function is defined as the cavity heat flow loss qcA function of the positive correlation is determined,
η＝qc/qb (1)
cavity heat flow lossqcValue q at the boundary with the back-fire surface of the fire-proof platebMeasured using a heat flow meter, wherein qcTaking the value of the position 5cm outside the center of the side wall of the cavity, or symmetrically taking points around the position 5cm outside the center of the side wall for measurement, and then obtaining the arithmetic mean value; and (3) taking the boundary central value of the back fire surface of the fire-proof plate or symmetrically taking points around the boundary center for measurement, and then obtaining an arithmetic mean value.
10. The fire disaster temperature field estimation method in the wall thickness direction of the fire-proof plate protection immersed tube tunnel according to claim 5, characterized in that: in the step S4, the transient heat conduction of the immersed tube wall under the combined action of the back fire surface temperature of the fire-proof plate and the cavity attenuation is solved by the following mathematical model:
the differential equation is as follows:
boundary conditions:
initial conditions:
Ti(y,0)＝T0(y)0≤y≤d1 (4)
wherein, T1(y, T) is the transient temperature at the y position in the concrete pipe wall at the time T after the fire occurs, T1(0, T) is the temperature of the concrete outer wall of the pipe section at time T, T1(d1And t) is the temperature of the inner wall of the pipe joint concrete at the moment t; eta is a cavity heat flow attenuation function after the fire disaster occurs; d1The total thickness of the concrete layer on the wall of the tunnel pipe is the total thickness of the concrete layer; neglecting the height of the cavity and the thickness of the fireproof plate;
temperature value T of any position at any time in the pipe wall thickness direction of immersed tube tunnel in S51(y, t) is solved by:
in the formula:
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