A method for determining nighttime ventilation strategies for subway tunnel sections in the long term of operation

Abstract

This invention relates to a method for determining nighttime ventilation strategies for subway tunnel sections in the long term of operation, relating to the field of subway tunnels. The method includes: Step 1, simulating on a monthly cycle, using soil temperatures from year 1 to year N-1 as boundary conditions to obtain temperature distribution; Step 2, designing ventilation conditions for the non-air-conditioned seasons of the tunnel section; conducting simulation studies for different ventilation measures; Step 3, using the soil temperature at the end of December of year N-1 as the initial boundary condition, and using the simulation results of each month as the boundary condition for the next month to obtain the temperature distribution; Step 4, integrating the end-of-month temperature curves for each month with and without nighttime ventilation conditions, transforming the soil temperature distribution characteristics under different conditions into soil heat storage characteristics to obtain the incremental heat storage capacity; Step 5, determining the optimal nighttime ventilation and cooling strategy for the non-air-conditioned seasons of the subway in the long term of operation. This invention is beneficial for proposing an effective cooling measure to alleviate energy consumption and safety problems caused by the harsh thermal environment of the tunnel section.

Description

Technical Field

[0001] This invention relates to the field of subway tunnel sections, and more particularly to a method for determining a nighttime ventilation strategy for subway tunnel sections in the long term of operation. Background Technology

[0002] With the rapid development of urban construction in my country, the country's rail transit has also entered a period of rapid development, and subways have become an important choice for people's daily travel. However, subway trains release a lot of heat when running in tunnels, which leads to many problems as the subway ages. On the one hand, the temperature rise in the tunnels affects the station platforms through heat transfer and air infiltration through the platform screen doors, resulting in increased energy consumption of the station's environmental control system during the summer air-conditioning season. On the other hand, the temperature rise also increases the energy consumption of the subway train's air conditioning. Tunnel temperatures exceeding 40°C can even cause malfunctions in the subway train's environmental control system equipment, especially the condensers in the train carriages, affecting the cooling effect inside the carriages and reducing the thermal comfort of passengers.

[0003] Current research on nighttime ventilation strategies includes studies on air quality in tunnels under different ventilation strategies throughout the day, such as temperature, humidity, CO2, and particulate matter; however, the study timeframes are relatively short. For other types of buildings, nighttime ventilation strategies have also been explored, but most studies investigate natural temperature changes under different operating conditions by varying the number of air exchanges during nighttime ventilation and combining this with wall heat storage and release. Currently, there are no research studies, domestically or internationally, on strategies for cooling subway tunnel sections using nighttime ventilation applicable to long-term operational use. Summary of the Invention

[0004] The problem this invention aims to solve is to propose an effective cooling measure for the air temperature in subway tunnels during long-term operation, thereby alleviating the energy consumption and safety issues caused by the harsh thermal environment in the tunnel sections.

[0005] To achieve the above objectives, the present invention provides a method for determining a nighttime ventilation strategy for subway tunnel sections in the long term of operation, comprising the following steps:

[0006] Step 1: Simulate on a monthly cycle, using the temperature of the tunnel surrounding rock and soil from year 1 to year N-1 (the year before long-term operation) as the boundary condition, to obtain the temperature distribution of the tunnel surrounding rock and soil in the monthly intervals from the end of December of year N-1 to January to September of year N.

[0007] Step 2: Design the nighttime ventilation conditions for the non-air-conditioned season in the interval; conduct simulation studies on the optimal months for starting nighttime ventilation measures for different lengths of nighttime operation, respectively.

[0008] Step 3: Using the soil temperature at the end of December of year N-1 as the initial boundary condition for soil temperature, the simulation results of soil temperature for each month are used as the boundary condition for soil temperature in the next month, so as to obtain the temperature distribution of surrounding rock and soil in the interval of the end of June, July, August and September in summer under different working conditions of nighttime ventilation.

[0009] Step 4: Integrate the temperature curves of the surrounding rock and soil in the tunnel at the end of each month in summer with and without nighttime ventilation, and transform the soil temperature distribution characteristics under different conditions into soil heat storage characteristics to obtain the increase in the heat storage capacity of the subway tunnel in the long term under nighttime ventilation in the non-air-conditioned season compared with the case without nighttime ventilation in July, August and September.

[0010] Step 5: For long-term operation, the actual change value of tunnel temperature under nighttime ventilation can be obtained based on the effective air exchange rate of the tunnel piston ventilation shaft, thus converting the increase in soil heat storage into the decrease in temperature between different months in summer; based on different ventilation durations, the result that nighttime ventilation measures can reduce the average monthly temperature of the tunnel in summer can be obtained; based on the decrease in tunnel temperature between different summer periods, the optimal nighttime ventilation and cooling strategy for the non-air-conditioned season of the subway in the long-term operation period can be finally determined.

[0011] Preferably, when designing the ventilation conditions at night during non-air-conditioned seasons in the tunnel section, factors such as the temperature difference between the inside and outside of the tunnel and the time distance from the hottest month are taken into account.

[0012] Preferably, the soil temperature characteristics are converted into soil heat storage characteristics; the fitted soil temperature curve is integrated to obtain the soil temperature curve integral at the end of June under the condition that there are no nighttime ventilation measures in the subway tunnel in the long term.

[0013] Preferably, the soil temperature in June, July, August and the end of September of summer is integrated under different working conditions of nighttime ventilation measures. The integral values ​​of the curves and the integral differences of the curves under different working conditions of nighttime ventilation measures can be obtained, that is, the heat absorbed by the tunnel temperature by the nighttime ventilation measures under different working conditions in each month of summer.

[0014] Preferably, the heat storage characteristics of the soil are transformed into the temperature drop characteristics of each month in summer; for the variable working condition study of nighttime ventilation, the heat generation of trains and equipment, the heat dissipation of piston ventilation shafts and the heat storage and release of surrounding rock and soil are considered to establish the heat balance equation of the tunnel section, thereby deriving the tunnel air cooling formula for each month in summer.

[0015] Preferably, for long-term operating conditions, the effective ventilation volume obtained from the actual measurement needs to be corrected to obtain the effective ventilation volume of the piston ventilation shaft of the tunnel in the long term. Based on the effective ventilation volume, the correction coefficient of the tunnel temperature is calculated to obtain the true change value of the tunnel temperature under nighttime ventilation.

[0016] Preferably, CHAMPS-BES simulation software is used.

[0017] In summary, the present invention has the following beneficial technical effects:

[0018] Current research on nighttime ventilation strategies includes studies on air quality in tunnels under different ventilation strategies throughout the day, such as temperature, humidity, CO2, and particulate matter; however, the time spans studied are relatively short. In contrast, this invention explores the temperature drop in summer tunnel sections under nighttime ventilation measures during the non-air-conditioned season over a longer period, focusing on the impact of nighttime ventilation strategies on the temperature drop in subway tunnel sections during long-term operation.

[0019] For other types of buildings, there have been discussions on nighttime ventilation strategies, but most of these studies explore natural room temperature changes under different operating conditions by changing the number of air exchanges during nighttime ventilation and combining this with the heat storage and release of the walls. This invention, however, studies the temperature drop of tunnels in summer air-conditioned seasons during non-air-conditioned seasons by changing the duration of nighttime ventilation (per month). From a time perspective, this is a delayed effect, not an immediate one.

[0020] Currently, there are no research studies on strategies for cooling subway tunnels during the long term of operation, both domestically and internationally. Therefore, a method for determining the nighttime ventilation and cooling strategy for subway tunnels during the long term of operation has been designed. By ventilating subway tunnels at night during the non-air-conditioned season, the heat storage capacity of the surrounding rock and soil can be increased, and the air temperature of the tunnels in summer can be reduced. This can effectively solve the energy consumption and safety problems such as train stoppages caused by excessively high temperatures in summer. Attached Figure Description

[0021] Appendix Figure 1 This is a schematic diagram of the temperature change curve of the surrounding rock and soil in the first year;

[0022] Appendix Figure 2 This is a schematic diagram of the temperature change curve of the surrounding rock and soil in the 14th year.

[0023] Appendix Figure 3 A schematic diagram illustrating the increase in soil heat storage caused by only opening nighttime ventilation for one month;

[0024] Appendix Figure 4 A schematic diagram illustrating the increase in soil heat storage due to two months of nighttime ventilation;

[0025] Appendix Figure 5 A schematic diagram illustrating the increase in soil heat storage due to three months of nighttime ventilation;

[0026] Appendix Figure 6 A schematic diagram showing the cooling effect of nighttime ventilation measures for different durations in summer (cooling value of tunnel air after one month of nighttime ventilation);

[0027] Appendix Figure 7A schematic diagram showing the cooling effect of nighttime ventilation measures for different durations in summer (cooling value of tunnel air after two months of nighttime ventilation);

[0028] Appendix Figure 8 A schematic diagram illustrating nighttime ventilation measures of different durations and their corresponding summer temperature reduction effects (temperature reduction of tunnel air after three months of nighttime ventilation). Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] This invention discloses a method for determining nighttime ventilation strategies for subway tunnels in the long term of operation. The main mechanism of the technical solution adopted by this invention lies in the fact that, during the non-air-conditioned season, the temperature difference between the tunnel air and the outdoor air is large. During the early morning hours when trains are not running in certain months, cooler air is introduced from the outside using tunnel emergency fans. This air exchanges heat fully with the surrounding rock and soil in the tunnel, reducing the internal temperature of the surrounding rock and soil and increasing its own heat storage capacity. The enhanced heat storage capacity of the surrounding rock and soil will absorb more heat from the tunnel during the hottest month of summer, thereby reducing the air temperature in the subway tunnels during the long-term air-conditioned season.

[0031] The technical solution of the present invention is implemented in the following way:

[0032] (1) Set the initial soil temperature for the first year and simulate it in a monthly cycle. The soil temperature of the next month is the soil temperature at the end of the previous month as the boundary condition. Ignore the temperature change along the tunnel length direction and only consider the temperature change along the depth direction of the surrounding rock and soil to simulate the monthly temperature change of the tunnel surrounding rock and soil in the year before the long-term operation, i.e., the N-1th year.

[0033] (2) The surrounding rock and soil of the tunnel exchange heat with the tunnel air. Nighttime ventilation during non-air conditioning seasons is a cooling measure for tunnel temperatures in July, August, and September. On the one hand, the greater the temperature difference between the outdoor and tunnel temperatures, the more heat is exchanged in the same amount of time, and the better the heat exchange effect. On the other hand, for the summer of that year, starting nighttime ventilation too early may result in the coldness in the soil being consumed during the transition season due to the temperature difference, leading to a less significant drop in tunnel temperature in summer. Therefore, when designing nighttime ventilation for non-air conditioning seasons, the temperature difference between the inside and outside of the tunnel and the time distance from the hottest month should be considered.

[0034] (3) The soil temperature at the end of year N-1 is used as the initial boundary condition of the soil side. Based on the original air boundary condition of the tunnel, the air boundary condition for nighttime ventilation is set. Then, the simulation results of the soil temperature in each month are used as the boundary condition of the soil temperature in the next month. The temperature distribution characteristics of the surrounding rock soil of the subway tunnel in summer June, July, August and September under different working conditions of nighttime ventilation measures in the long term of non-air-conditioned season operation are obtained.

[0035] (4) By solving the integral difference of the soil temperature fitting curve, the soil temperature distribution characteristics are transformed into soil heat storage characteristics. The increase in the heat storage capacity of the soil in July, August and September of summer when there is no night ventilation is obtained compared with the non-air-conditioned season. Thus, the amount of temperature reduction of the surrounding rock soil by night ventilation measures under different working conditions in the non-air-conditioned season is obtained.

[0036] (5) Based on the principle of thermal balance in tunnel sections, formulas for tunnel air cooling in each month of summer can be derived. It can be seen that the monthly average cooling value of tunnel air due to nighttime ventilation during non-air-conditioned seasons is related to two factors: the effective air exchange rate of the piston ventilation shaft and the heat storage and release of the soil. The effective air exchange rate affects the temperature drop because the actual change in tunnel air temperature is obtained by multiplying the air temperature drop formula by a correction factor, which is related to the effective air exchange rate of the piston ventilation shaft. For long-term operating conditions, the measured effective air exchange rate is corrected to obtain the effective air exchange rate of the piston ventilation shaft in the long-term tunnel. Based on the effective air exchange rate, the correction factor for tunnel air temperature is calculated, and the actual change in tunnel air temperature under nighttime ventilation can be obtained, thus converting the increase in heat storage in the soil of the subway tunnel section into the decrease in tunnel air temperature. Based on the decrease in air temperature, the optimal nighttime ventilation and cooling strategy for the non-air-conditioned season of the subway in the long-term operation period is finally determined.

[0037] This invention primarily focuses on subway tunnel sections in the long term of operation. Because the air temperature in subway tunnel sections is affected by various heat dissipation factors, and the cooling effect of track heat dissipation is not ideal in the long term of operation, the air temperature in subway tunnel sections in the long term of operation will increase year by year. Excessive temperature in the tunnel sections will increase the energy consumption of the station and subway train environmental control systems, and may even cause the train's condenser to stop, affecting the cooling effect inside the carriages and reducing the thermal comfort of passengers.

[0038] The specific research method of this invention is as follows:

[0039] First, CHAMPS-BES software was used to simulate the monthly temperature changes of the surrounding rock and soil in the tunnel from a depth of 10m to the wall surface during the early and mid-term operation, obtaining the internal temperature distribution of the surrounding rock and soil at the end of the previous year for the long-term period. Second, when designing the nighttime ventilation measures for non-air-conditioned seasons, the variable-condition scheme for nighttime ventilation needed to be determined by considering two factors: the temperature difference between the inside and outside of the tunnel and the time distance from the hottest month. Simultaneously, to explore the cooling effect of nighttime ventilation measures under different conditions, numerical simulations were used to obtain the temperature distribution characteristics of the surrounding rock and soil at the end of June, July, August, and September of the current summer under different nighttime ventilation conditions and without nighttime ventilation measures. Based on the soil heat transfer formula, the soil temperature distribution characteristics under different conditions can be converted into soil heat storage characteristics, obtaining the increase in the soil's heat storage capacity in July, August, and September of the summer under nighttime ventilation conditions compared to without nighttime ventilation. Finally, based on the principle of thermal balance in tunnel sections, the increase in soil heat storage can be converted into the decrease in tunnel temperature in each month of summer, yielding the tunnel air temperature reduction values ​​in July, August, and September under different operating conditions with nighttime ventilation. Based on the summer tunnel temperature reduction, the optimal nighttime ventilation and cooling strategy for the long-term operation of the metro during the non-air-conditioned season is finally determined.

[0040] The significance of this invention lies in its ability to reduce the ambient temperature inside subway tunnels during long-term operation, thereby ensuring the safe operation of the train's air conditioning system; at the same time, it utilizes the heat storage characteristics of the soil surrounding the station to reduce the energy consumption of the air conditioning environmental control system in summer.

[0041] This invention discloses a method for determining nighttime ventilation strategies for subway tunnel sections in the long term of operation, which specifically includes the following steps:

[0042] (1) In the simulation study from year 1 to 14, a model of the surrounding rock and soil of the tunnel was established using CHAMPS-BES software. The surrounding rock and soil from a depth of 10m to the wall was divided into 5 layers. The initial soil temperature in year 1 was set to 17℃. The simulation was conducted on a monthly cycle, with the soil temperature of the following month being the soil temperature at the end of the previous month as the boundary condition. Temperature changes along the tunnel length were ignored, and only temperature changes along the depth of the surrounding rock and soil were considered. The soil temperature at the end of December of year 1 was used as the boundary condition at the beginning of January of year 2 to simulate the internal temperature changes of the soil in January of year 2. This process was repeated to simulate the monthly temperature changes of the surrounding rock and soil of the tunnel from year 2 to 14. Monthly soil temperature change curves were plotted for comparison between year 1 and year 14, as shown in the figure. Figure 1 , 2 It can be seen that the surrounding rock and soil of the tunnel absorbed a large amount of heat from the tunnel over 14 years, causing the internal temperature of the surrounding rock and soil to rise.

[0043] (2) The surrounding rock and soil of the tunnel exchange heat with the tunnel air. Nighttime ventilation during non-air-conditioning seasons is a cooling measure for tunnel temperatures in July, August, and September. On the one hand, the greater the temperature difference between the outdoor and tunnel temperatures, the more heat is exchanged within the same time period, resulting in a better heat exchange effect. On the other hand, for the summer of that year, starting nighttime ventilation too early may result in the coldness in the soil being consumed during the transition season due to the temperature difference, leading to a less significant drop in tunnel temperature during the summer. Therefore, when designing nighttime ventilation for non-air-conditioning seasons, the temperature difference between the inside and outside of the tunnel and the time distance from the hottest month should be considered. Simulation studies were conducted to determine the optimal month for starting nighttime ventilation measures for different lengths of nighttime ventilation, specifically for one-month, two-month, and three-month periods.

[0044] (3) Establish the CHAMPS-BES surrounding rock and soil model for the 15th year. Use the soil temperature at the end of the 14th year as the initial boundary condition of the soil side. Set the air boundary condition for nighttime ventilation on the basis of the original air boundary condition of the tunnel. Then, use the simulation results of the soil temperature in each month as the boundary condition of the soil temperature in the next month. Iterate and simulate the nine nighttime variable working conditions in turn to obtain the temperature distribution characteristics of the surrounding rock and soil of the subway tunnel in June, July, August and September under different working conditions and nighttime ventilation measures.

[0045] (4) Soil heat exchange formula

[0046] Q = c·m·Δt Equation (1)

[0047] Based on the simulation and temperature distribution curves, we can obtain...

[0048] m=ρ·V=ρ·S·x Equation (2)

[0049] Δt=Δf(x) Equation (3)

[0050] Simplify to get

[0051]

[0052] In the formula: Q is the heat exchange of the soil, J; m is the mass of the soil, kg; V is the volume of the soil, m³. 3 c represents the specific heat capacity of the soil, J / (kg·℃); ρ represents the soil density, kg / m³. 3 S is the surface area of ​​the surrounding rock of a 1.2km subway tunnel, in m². 2 x is the distance of the soil along the depth direction, in meters; Δf(x) is the change in soil temperature. This represents the integral of the soil temperature curve between depths x1 and x2.

[0053] The above formula can be used to transform the soil temperature distribution characteristics into soil heat storage characteristics by solving the integral difference of the soil temperature fitting curve. This allows us to obtain the increase in soil heat storage capacity during the summer months of July, August, and September when there is nighttime ventilation compared to when there is no nighttime ventilation, such as... Figure 3 , 4 5. Thus, the amount of temperature reduction of the surrounding rock and soil due to nighttime ventilation measures under different working conditions can be obtained.

[0054] Analysis of the results shows that when nighttime ventilation is only operated for one month during the non-air-conditioning season, the increase in soil heat storage is greatest in January; when nighttime ventilation is operated for two months during the non-air-conditioning season, the increase in soil heat storage is greatest and the heat storage effect is best in January and February; and when nighttime ventilation is operated for three months during the non-air-conditioning season, the effect of nighttime ventilation on soil heat storage is better in January, February and March.

[0055] (5) Heat balance equation for no nighttime ventilation:

[0056] Q0 = Q 车 -(Q 井 +Q 土 Equation (5)

[0057] The heat balance equation for nighttime ventilation is as follows:

[0058] Q0′=Q 车 ′-(Q 井 ′+Q 土 Formula (6)

[0059] In the formula: Q0 and Q0′ are the air energy increments; Q 车 Q 车 ′ represents the heat dissipation of the train; Q 井 Q 井 ′ represents the heat dissipation of the ventilation shaft; Q 土 Q 土 ′ represents the heat stored in the soil.

[0060] The formula for calculating the coefficient is as follows:

[0061]

[0062] Based on the principle of thermal balance in tunnel sections, formulas for tunnel air cooling in various months of summer can be derived. It can be seen that the monthly average cooling value of tunnel air due to nighttime ventilation is related to two factors: the effective air exchange rate of the piston ventilation shaft and the heat storage and release in the soil. The effective air exchange rate affects the temperature drop because the actual change in tunnel air temperature is obtained by multiplying the air temperature drop formula by a correction factor, which is related to the effective air exchange rate of the piston ventilation shaft. For long-term operational conditions, the measured effective air exchange rate is corrected to obtain the effective air exchange rate of the piston ventilation shaft in the long-term tunnel. Based on the effective air exchange rate, the correction factor for tunnel air temperature is calculated, allowing the calculation of the actual change in tunnel air temperature under different nighttime ventilation conditions, thus converting the increase in soil heat storage into the decrease in tunnel air temperature in various months of summer. Based on the summer tunnel air temperature decrease, the optimal nighttime ventilation and cooling strategy for the long-term subway operation during the non-air-conditioned season is finally determined, as shown in the following results. Figure 6 , 7 8.

[0063] As can be seen from the table, if nighttime ventilation measures are implemented for one month outside of the air-conditioning season, choosing January to implement nighttime ventilation is most beneficial for reducing summer tunnel temperatures; if nighttime ventilation measures are implemented for only two months outside of the air-conditioning season, choosing January and February to implement nighttime ventilation is most beneficial for reducing summer tunnel temperatures; if nighttime ventilation measures are implemented for three months outside of the air-conditioning season, choosing January, February, and March to implement nighttime ventilation is most beneficial for reducing summer tunnel temperatures.

[0064] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining nighttime ventilation strategies for subway tunnel sections in the long term of operation, characterized in that, Includes the following steps: Step 1: Simulate on a monthly cycle, using the temperature of the tunnel surrounding rock and soil from year 1 to year N-1 (the year before long-term operation) as the boundary condition, to obtain the temperature distribution of the tunnel surrounding rock and soil in the monthly intervals from the end of December of year N-1 to January to September of year N. Step 2: Design the nighttime ventilation conditions for the non-air-conditioned season in the interval; conduct simulation studies on the optimal months for starting nighttime ventilation measures for different lengths of nighttime operation, respectively. Step 3: Using the soil temperature at the end of December of year N-1 as the initial boundary condition for soil temperature, the simulation results of soil temperature for each month are used as the boundary condition for soil temperature in the next month, so as to obtain the temperature distribution of surrounding rock and soil in the interval of the end of June, July, August and September in summer under different working conditions of nighttime ventilation. Step 4: Integrate the temperature curves of the surrounding rock and soil in the tunnel at the end of each month in summer with and without nighttime ventilation, and transform the soil temperature distribution characteristics under different conditions into soil heat storage characteristics to obtain the increase in the heat storage capacity of the subway tunnel in the long term under nighttime ventilation in the non-air-conditioned season compared with the case without nighttime ventilation in July, August and September. Step 5: For long-term operation, the actual change value of tunnel temperature under nighttime ventilation can be obtained based on the effective air exchange rate of the tunnel piston ventilation shaft, thus converting the increase in soil heat storage into the decrease in temperature between different months in summer; based on different ventilation durations, the result that nighttime ventilation measures can reduce the average monthly temperature of the tunnel in summer can be obtained; based on the decrease in tunnel temperature between different summer periods, the optimal nighttime ventilation and cooling strategy for the non-air-conditioned season of the subway in the long-term operation period can be finally determined.

2. The method for determining the nighttime ventilation strategy for subway tunnel sections in the long term of operation, as described in claim 1, is characterized in that... When designing the ventilation conditions for nighttime use during non-air-conditioned seasons in the tunnel section, factors such as the temperature difference between the inside and outside of the tunnel and the time distance from the hottest month should be taken into account.

3. The method for determining the nighttime ventilation strategy for subway tunnel sections in the long term of operation, as described in claim 1, is characterized in that... The soil temperature characteristics are transformed into soil heat storage characteristics; the fitted soil temperature curve is integrated to obtain the soil temperature curve integral at the end of June under the condition that there is no nighttime ventilation in the subway tunnel in the long term.

4. The method for determining the nighttime ventilation strategy for subway tunnel sections in the long term of operation, as described in claim 1, is characterized in that... By integrating the soil temperature under different working conditions of nighttime ventilation measures in June, July, August and the end of September in summer, the integral values ​​of the curves and the curve integral differences under different working conditions of nighttime ventilation measures can be obtained, that is, the heat absorbed by the nighttime ventilation measures under different working conditions on the tunnel air temperature in each month of summer.

5. The method for determining a nighttime ventilation strategy for subway tunnel sections in the long term of operation, as described in claim 1, is characterized in that... The heat storage characteristics of the soil are transformed into the temperature drop characteristics of the tunnel in each month of summer. For the variable working condition study of nighttime ventilation, the heat generated by the train and equipment, the heat dissipation of the piston ventilation shaft and the heat storage and release of the surrounding rock and soil are considered to establish the heat balance equation of the tunnel in each month of summer, thereby deriving the air cooling formula of the tunnel in each month of summer.

6. The method for determining the nighttime ventilation strategy for subway tunnel sections in the long term of operation, as described in claim 1, is characterized in that... For long-term operating conditions, it is necessary to make certain corrections to the effective ventilation volume obtained from the actual measurement, so as to obtain the effective ventilation volume of the piston ventilation shaft of the tunnel in the long term. Based on the effective ventilation volume, the correction coefficient of tunnel temperature is calculated to obtain the true change value of tunnel temperature under nighttime ventilation.

7. The method for determining the nighttime ventilation strategy for subway tunnel sections in the long term of operation, as described in claim 1, is characterized in that... The CHAMPS-BES simulation software was used.

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