Method for determining length of negative temperature zone of tunnel portal section in cold region

Abstract

The present application relates to a kind of cold region tunnel portal section negative temperature zone length determination method.The existing cold region tunnel portal section negative temperature zone length determination method is insufficient to consider factor, and tunnel is prone to freeze injury.The present application obtains the air temperature correction value influenced by tunnel portal microtopography condition according to the azimuth of the slope where the portal is located, the slope angle, the geographic latitude and the portal shielding coefficient;The portal air temperature calculation value is calculated according to the altitude, the average temperature of the coldest month, the extreme minimum temperature, the altitude of the tunnel portal, the air temperature correction value;The length of the negative temperature zone of the tunnel portal section is calculated according to the portal air temperature calculation value.The present application is aimed at the characteristics that the length of the negative temperature zone of the tunnel portal section in cold region is easily influenced by the altitude of the tunnel site, the microtopography condition of the portal and the extreme minimum temperature, and the result obtained by multi-factor analysis and calculation has more guiding significance for optimizing the selection of cold region tunnel cold prevention and drainage measures and the length setting, and can improve the accuracy of the cold prevention measure setting of the tunnel portal section in cold region.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, specifically to a method for determining the length of the negative temperature zone at the entrance section of a tunnel in a cold region. Background Technology

[0002] Currently, in the design of railway tunnels in frigid and cold regions, the temperature value at the tunnel entrance is usually based on the average temperature of the coldest month from a nearby meteorological station. However, this often leads to frost damage during operation, severely impacting the construction and operation of the tunnels. Surveys of completed railway tunnels show that, on the one hand, differences in tunnel site altitude and micro-topographical conditions at the tunnel entrance result in significant differences between the actual entrance temperature and the temperature at nearby meteorological stations; on the other hand, the use of the average temperature of the coldest month in the design does not account for the impact of extreme minimum temperatures, frequently leading to insufficient insulation length and subsequent frost damage.

[0003] Therefore, there is an urgent need to propose a new method for determining the length of the negative temperature zone at the tunnel entrance in cold regions. This method should be based on data from nearby meteorological stations, taking into account the elevation of the tunnel site, the micro-topographical conditions at the tunnel entrance, and the influence of extreme minimum temperatures. This would allow for a more reasonable calculation of the tunnel entrance temperature, which in turn would determine the length of the negative temperature zone at the tunnel entrance. This would overcome the shortcomings of existing methods that fail to consider sufficient factors, leading to frost damage in tunnels. This approach would optimize the selection and length setting of frost protection and drainage measures for tunnels in cold regions. Summary of the Invention

[0004] The purpose of this invention is to provide a method for determining the length of the negative temperature zone at the entrance of a tunnel in a cold region, so as to at least solve the problems of insufficient consideration of factors and easy frost damage to tunnels in existing methods.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for determining the length of the negative temperature zone at the entrance section of a tunnel in a cold region, the method comprising:

[0007] Based on four influencing factors—the azimuth of the slope at the tunnel entrance, the slope angle, the geographical latitude, and the tunnel entrance obstruction coefficient—the temperature correction value affected by the micro-topographic conditions at the tunnel entrance is obtained.

[0008] The calculated temperature value at the tunnel entrance is obtained based on the altitude of the nearby meteorological station, the average temperature of the coldest month measured by the meteorological station, the extreme minimum temperature, the altitude of the tunnel entrance, and the aforementioned temperature correction value.

[0009] Based on the calculated air temperature at the tunnel entrance, the length of the negative temperature zone at the tunnel entrance is calculated.

[0010] Furthermore, based on four influencing factors—the azimuth of the slope at the tunnel entrance, the slope angle, the geographical latitude, and the tunnel entrance shading coefficient—the temperature correction value for the influence of the tunnel entrance micro-topographic conditions is obtained, including:

[0011] The temperature correction value affected by the micro-topographic conditions at the tunnel entrance. The calculation process is as follows:

[0012]

[0013] in:

[0014] λ is the obstruction coefficient of the opening;

[0015] I θ The solar radiation value of the inclined surface of the tunnel entrance;

[0016] I H This represents the solar radiation value at the horizontal plane of the tunnel entrance.

[0017] I Dθ This represents the direct solar radiation value on the inclined surface. ;

[0018] I dθ This represents the solar diffuse radiation value on the inclined surface. ;

[0019] I Rθ The ground reflected radiation value obtained on the inclined surface. ;

[0020] I DH This represents the value of direct solar radiation on a horizontal plane. ;

[0021] I dH This represents the value of solar radiation scattered across a horizontal surface. ;

[0022] I DN This is the normal solar radiation value. ;

[0023] h is the solar altitude angle. ;

[0024] i is the angle of incidence of the sun. ;

[0025] θ is the slope angle of the slope where the tunnel entrance is located;

[0026] The azimuth of the slope where the tunnel entrance is located is the angle between the horizontal projection of the slope normal and the due south direction, with eastward deviation being positive and westward deviation being negative.

[0027] δ is the declination angle;

[0028] φ represents the geographical latitude of the cave entrance;

[0029] The surface reflectance of the slope at the tunnel entrance;

[0030] I0 is the solar constant, taken as I0 = 1367 W / m 2 ;

[0031] m is the mass of the atmosphere. ;

[0032] P is the atmospheric transparency coefficient.

[0033] Furthermore, the process of determining the value of the opening obstruction coefficient λ is as follows:

[0034] If the tunnel entrance is on a shady slope, i.e., 90° < γ < 180° or -180° < γ < -90°, then λ = 1.0;

[0035] If the tunnel entrance is on a sunny slope and the nearby mountains do not affect the sunlight reaching the entrance, i.e., -90° < γ < 90° and Ψ ≤ h, then λ = 1.0;

[0036] If the tunnel entrance is on a sunny slope, but the adjacent mountain is steep and close to the entrance (i.e., -90° < γ < 90° and Ψ > h), the adjacent mountain will affect the lighting conditions at the tunnel entrance. ;

[0037] in:

[0038] Ψ is the angle between the line connecting the tunnel entrance and the ridgeline of the adjacent mountain and the horizontal plane.

[0039] Furthermore, based on the altitude of the nearby meteorological station, the average temperature of the coldest month measured by the meteorological station, the extreme minimum temperature, the altitude of the tunnel entrance, and the aforementioned temperature correction value, the calculated temperature value at the tunnel entrance is obtained, including:

[0040] The calculated temperature T at the tunnel entrance d The calculation process is as follows:

[0041]

[0042] in:

[0043] T u T m These are the average temperature of the coldest month at the cave entrance and the extreme minimum temperature, respectively.

[0044] ρ is the correction factor for the extreme minimum temperature of the coldest month;

[0045] T u0 T m0 These are the average temperature of the coldest month and the extreme minimum temperature measured by the meteorological station, respectively.

[0046] H0 represents the altitude of the nearest weather station;

[0047] H represents the elevation of the tunnel entrance;

[0048] β is the decreasing temperature gradient along the altitude, which is taken as 0.6.

[0049] Furthermore, based on the calculated air temperature at the tunnel entrance, the length of the negative temperature zone at the tunnel entrance is calculated, including:

[0050] The method for calculating the length L0 of the negative temperature zone at the tunnel entrance is as follows:

[0051]

[0052] We derive that:

[0053]

[0054] In the formula, α is the longitudinal temperature gradient factor of the tunnel.

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0056] The method of this invention addresses the characteristic that air temperature at the tunnel entrance is easily affected by the altitude of the tunnel site, the micro-topography of the tunnel entrance, and the extreme minimum temperature. It analyzes four influencing factors—the azimuth angle of the slope at the tunnel entrance, the slope angle, the latitude, and the tunnel entrance shading coefficient—to obtain a temperature correction value influenced by the micro-topography of the tunnel entrance. Based on the altitude of nearby meteorological stations, the average temperature of the coldest month measured by the meteorological stations, the extreme minimum temperature, and the altitude of the tunnel entrance, a calculated temperature value for the tunnel entrance is obtained. Based on the calculated temperature value at the tunnel entrance, the length of the negative temperature zone at the tunnel entrance is calculated. Compared to existing methods that only refer to the average temperature of the coldest month from nearby meteorological stations, the results obtained are more instructive for optimizing the selection and length setting of cold-weather protection and drainage measures for tunnels in cold regions.

[0057] The method of this invention comprehensively considers the altitude of the tunnel site, the micro-topographical conditions at the tunnel entrance, and the length of the negative temperature zone at the tunnel entrance in cold regions under the influence of extreme minimum temperatures, thereby improving the accuracy of setting up cold-proof measures for the tunnel entrance in cold regions. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained from these drawings without creative effort.

[0059] Figure 1 This is a schematic diagram showing the values ​​of the inclination angle θ of the slope where the tunnel entrance is located;

[0060] Figure 2This is a schematic diagram showing the values ​​of the angle ψ between the line connecting the tunnel entrance and the ridgeline of the adjacent mountain and the horizontal plane. Detailed Implementation

[0061] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0062] It should be noted that similar labels and letters indicate similar items; therefore, once an item is defined in one embodiment, it does not need to be further defined and explained in subsequent embodiments. The values ​​for certain parameters are based on suggested values ​​from existing standards and other sources, so specific calculation processes are not required.

[0063] It should also be noted that although the order of steps is mentioned in the method description, in some cases, steps may be performed in a different order than that described here, and this should not be interpreted as a restriction on the order of steps.

[0064] This invention provides a method for determining the length of the negative temperature zone at the entrance section of a tunnel in a cold region. It not only considers the average temperature of the coldest month at a nearby weather station, but also integrates and corrects multiple influencing factors to obtain a more instructive result. The method includes:

[0065] Step 1: Based on four influencing factors—azimuth of the slope at the tunnel entrance, slope inclination, geographical latitude, and tunnel entrance obstruction coefficient—observe the temperature correction value affected by the micro-topographical conditions at the tunnel entrance.

[0066] The air temperature at the tunnel entrance is easily affected by the altitude of the tunnel site, the micro-topography of the entrance, and the extreme minimum temperature. Therefore, the calculation process for the entrance temperature needs to be corrected to obtain accurate and objective results. This method introduces a temperature correction value for the influence of the tunnel entrance micro-topography into the calculation process, focusing on four factors: the azimuth of the slope where the entrance is located, the slope angle, the geographical latitude, and the tunnel entrance shading coefficient. The specific process is as follows:

[0067] Calculate the temperature correction value for the influence of micro-topographic conditions at the tunnel entrance. :

[0068]

[0069] in:

[0070] λ is the obstruction coefficient of the opening;

[0071] I θThe solar radiation value on the inclined surface of the tunnel entrance, in W / m² 2 ;

[0072] I H The solar radiation value at the horizontal plane of the tunnel entrance, in W / m² 2 ;

[0073] I Dθ This represents the direct solar radiation value on the inclined surface. ;

[0074] I dθ This represents the solar diffuse radiation value on the inclined surface. ;

[0075] I Rθ The ground reflected radiation value obtained on the inclined surface. ;

[0076] I DH This represents the value of direct solar radiation on a horizontal plane. ;

[0077] I dH This represents the value of solar radiation scattered across a horizontal surface. ;

[0078] I DN This is the normal solar radiation value. ;

[0079] h is the solar altitude angle. ;

[0080] i is the angle of incidence of the sun. ;

[0081] θ is the slope angle of the slope where the tunnel entrance is located;

[0082] γ is the azimuth angle of the slope where the tunnel entrance is located. It is the angle between the horizontal projection of the slope normal and the due south direction. Eastward deviation is positive and westward deviation is negative.

[0083] δ is the declination angle; in the Northern Hemisphere, δ = -23.26° is taken on the winter solstice.

[0084] φ represents the geographical latitude of the cave entrance;

[0085] The surface reflectance of the cave entrance slope is denoted as 0.1 to 0.2, which can be taken as a reference for the surface reflectance of a typical surface. When the surface of the cave entrance slope is bare, the reflectance can be taken as 0.15 to 0.25, and when the surface of the cave entrance slope is densely vegetated, the reflectance can be taken as 0.15 to 0.25.

[0086] I0 is the solar constant, taken as I0 = 1367 W / m 2 ;

[0087] m is the mass of the atmosphere. ;

[0088] P is the atmospheric transparency coefficient, which can be selected based on atmospheric transparency coefficient data from various regions in my country.

[0089] The slope angle θ where the cave entrance is located is the angle between the plane formed by the cave entrance and the ridgeline of the mountain and the horizontal plane of the earth. Figure 1 As shown.

[0090] The process of determining the value of the opening obstruction coefficient λ is as follows:

[0091] If the tunnel entrance is on a shady slope, i.e., 90° < γ < 180° or -180° < γ < -90°, then λ = 1.0;

[0092] If the tunnel entrance is on a sunny slope and the nearby mountains do not affect the sunlight reaching the entrance, i.e., -90° < γ < 90° and Ψ ≤ h, then λ = 1.0;

[0093] If the tunnel entrance is on a sunny slope, but the adjacent mountain is steep and close to the entrance (i.e., -90° < γ < 90° and Ψ > h), the adjacent mountain will affect the lighting conditions at the tunnel entrance, and λ is not taken as 1.0. ;

[0094] In summary:

[0095]

[0096] in:

[0097] ψ is the angle between the line connecting the tunnel entrance and the ridgeline of the adjacent mountain and the horizontal plane, such as... Figure 2 As shown.

[0098] Step 2: Based on the altitude of the nearby meteorological station, the average temperature of the coldest month measured by the meteorological station, the extreme minimum temperature, the altitude of the tunnel entrance, and the aforementioned temperature correction value, the calculated temperature value at the tunnel entrance is obtained. The specific process is as follows:

[0099] The calculated temperature T at the tunnel entrance d The calculation process is as follows:

[0100]

[0101] in:

[0102] T u T m These are the average temperature and extreme minimum temperature of the coldest month at the cave entrance, respectively, in °C;

[0103] ρ is the correction factor for the extreme minimum temperature of the coldest month, which can be taken as 0.2~0.4 based on experience;

[0104] T u0 Tm0 These are the average temperature of the coldest month and the extreme minimum temperature measured by the meteorological station, respectively, in °C;

[0105] H0 represents the altitude of the nearest weather station, in meters;

[0106] H represents the elevation of the tunnel entrance, in meters;

[0107] β is the decreasing temperature gradient along the altitude, usually taken as 0.6.

[0108] Step 3: Calculate the air temperature T at the tunnel entrance. d The length L0 of the negative temperature zone at the tunnel entrance was calculated as follows:

[0109] Depend on

[0110] We derive that:

[0111] In the formula, α is the temperature gradient factor, which is affected by the natural wind inside the cave; it is generally taken as 1.15~1.20, with a higher value for the lower end of the cave entrance and a lower value for the higher end of the cave entrance.

[0112] The method of this invention aims to solve the problem that current tunnel cold protection design only considers the average temperature of the coldest month at the nearest meteorological station, resulting in insufficient length of cold protection measures at the tunnel entrance. It proposes a method for determining the length of the negative temperature zone at the tunnel entrance of cold-region tunnels by comprehensively considering the altitude of the tunnel site, the micro-topographic conditions at the tunnel entrance, and the influence of extreme minimum temperatures, thereby improving the accuracy of the length of tunnel cold protection measures.

[0113] Example:

[0114] Taking an existing operational tunnel in a high-altitude region of Northwest my country as an example, the tunnel is located at a latitude of φ=38°. According to data from nearby meteorological stations: the average temperature of the coldest month is T u0 =-10.3℃, extreme minimum temperature T m0 = -31.5℃, the altitude of the nearby meteorological station is H0=3150m.

[0115] The tunnel entrance has an elevation of H=3380m, a slope orientation of 20° east of south (i.e., azimuth γ=20°), a slope inclination angle of θ=35°, and an angle ψ=40° between the tunnel entrance and the ridgeline of the adjacent mountain to the south. The lighting conditions at the tunnel entrance are affected by the obstruction of the adjacent mountain. The exit has an elevation of H=3300m, a slope orientation of 8° west of north (i.e., azimuth γ=-172°), a slope inclination angle of θ=18°, and a λ=1.0 for the shady slope entrance.

[0116] Based on the above information, the calculation process for the length of the negative temperature zone at the tunnel entrance is as follows:

[0117] (1) Calculate the temperature correction value ∆T due to the influence of micro-topographic conditions at the tunnel entrance.I

[0118] Data on atmospheric transparency coefficients from various parts of my country show that the atmospheric transparency coefficient at the tunnel site in January, the coldest month, is P=0.738; the surface vegetation at the tunnel entrance is dense, and the surface reflectance is taken as... =0.2; The surface at the exit end of the tunnel is exposed, and the surface reflectance is taken as... =0.15; the correction factor for the extreme minimum temperature of the coldest month is ρ=0.2.

[0119] Tunnel entrance end:

[0120]

[0121]

[0122]

[0123]

[0124]

[0125]

[0126]

[0127]

[0128]

[0129] Tunnel exit end:

[0130]

[0131]

[0132]

[0133]

[0134]

[0135]

[0136]

[0137]

[0138] (2) Calculate the calculated value of the air temperature T at the tunnel entrance. d

[0139] Tunnel entrance end:

[0140]

[0141]

[0142]

[0143] Tunnel exit end:

[0144]

[0145]

[0146]

[0147] (3) Calculate the length L0 of the negative temperature zone at the tunnel entrance.

[0148] Tunnel entrance (α=1.17 for the high-end entrance):

[0149]

[0150] Tunnel exit end (lower tunnel entrance, α=1.18):

[0151]

[0152] Monitoring data from actual operation shows that the tunnel entrance suffered virtually no frost damage, while the exit suffered severe frost damage, and a mixture of ice and water was still observed at a depth of 4600m inside the tunnel. This demonstrates the greater rationality of the method described in this invention. Because this method comprehensively considers the altitude of the tunnel site, the micro-topographical conditions at the tunnel entrance, and the effects of extreme minimum temperatures, and through multi-factor analysis and calculation, it obtains more objective and accurate results, providing greater guidance for optimizing the selection and length setting of frost protection and drainage measures for tunnels in cold regions.

[0153] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A method for determining the length of the negative temperature zone at the entrance section of a tunnel in a cold region, characterized by: The method includes: Based on four influencing factors—azimuth of the slope at the tunnel entrance, slope angle, geographical latitude, and tunnel entrance obstruction coefficient—the temperature correction value for the influence of micro-topographical conditions at the tunnel entrance is obtained, including: The temperature correction value affected by the micro-topographic conditions at the tunnel entrance. The calculation process is as follows: in: λ is the obstruction coefficient of the opening; I θ The solar radiation value on the inclined surface of the tunnel entrance; I H This represents the solar radiation value at the horizontal plane of the tunnel entrance. I Dθ This represents the direct solar radiation value on the inclined surface. ; I dθ This represents the solar diffuse radiation value on the inclined surface. ; I Rθ The ground reflected radiation value obtained on the inclined surface. ; I DH This represents the value of direct solar radiation on a horizontal plane. ; I dH This represents the value of solar radiation scattered across a horizontal surface. ; I DN This is the normal solar radiation value. ; h is the solar altitude angle. ; i is the angle of incidence of the sun. ; θ is the slope angle of the slope where the tunnel entrance is located; The azimuth of the slope where the tunnel entrance is located is the angle between the horizontal projection of the slope normal and the due south direction, with eastward deviation being positive and westward deviation being negative. δ is the declination angle; φ represents the geographical latitude of the cave entrance; The surface reflectance of the slope at the tunnel entrance; I0 is the solar constant, taken as I0 = 1367 W / m 2 ; m is the mass of the atmosphere. ; P is the atmospheric transparency coefficient; Based on the altitude of the nearby meteorological station, the average temperature of the coldest month measured by the meteorological station, the extreme minimum temperature, the altitude of the tunnel entrance, and the aforementioned temperature correction value, the calculated temperature value at the tunnel entrance is obtained, including: The calculated temperature T at the tunnel entrance d The calculation process is as follows: in: T u T m These are the average temperature of the coldest month at the cave entrance and the extreme minimum temperature, respectively. ρ is the correction factor for the extreme minimum temperature of the coldest month; T u0 T m0 These are the average temperature of the coldest month and the extreme minimum temperature measured by the meteorological station, respectively. H0 represents the altitude of the nearest weather station; H represents the elevation of the tunnel entrance; β represents the decreasing temperature gradient along the altitude direction, and is taken as 0.6; Based on the calculated air temperature at the tunnel entrance, the length of the negative temperature zone at the tunnel entrance is calculated, including: The method for calculating the length L0 of the negative temperature zone at the tunnel entrance is as follows: We derive that: In the formula, a is the longitudinal temperature gradient factor of the tunnel.

2. The method for determining the length of the negative temperature zone at the entrance section of a cold-region tunnel according to claim 1, characterized in that: The process of determining the value of the opening obstruction coefficient λ is as follows: If the tunnel entrance is on a shady slope, i.e., 90° < γ < 180° or -180° < γ < -90°, then λ = 1.0; If the tunnel entrance is on a sunny slope and the nearby mountains do not affect the sunlight reaching the entrance, i.e., -90° < γ < 90° and Ψ ≤ h, then λ = 1.0; If the tunnel entrance is on a sunny slope, but the adjacent mountain is steep and close to the entrance (i.e., -90° < γ < 90° and Ψ > h), the adjacent mountain will affect the lighting conditions at the tunnel entrance. ; in: Ψ is the angle between the line connecting the tunnel entrance and the ridgeline of the adjacent mountain and the horizontal plane.

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