Methods for determining ventilation and exhaust patterns in tunnel construction using natural ventilation in vertical shafts

Abstract

This invention discloses a tunnel construction ventilation method and exhaust mode determination method using natural exhaust from vertical shafts. The ultra-long tunnel includes a main tunnel, a central guide tunnel, a first vertical shaft, and a second vertical shaft. A first fan, a second fan, and a third fan are respectively installed at the entrances of the right tunnel, the left tunnel, and the central guide tunnel. Fresh air is delivered to the working faces of these tunnels via ducts. Polluted air from the working faces is either discharged independently from the vertical shafts or mixed with other airflow within the shafts. This invention utilizes existing vertical shafts for ventilation during tunnel construction. On one hand, it reduces the length of the exhaust path for polluted air, lowers the frictional resistance encountered, and thus allows for control of the wind pressure and power of the fans at the tunnel entrances, improving tunnel construction ventilation and achieving energy saving and cost reduction. On the other hand, the complete or partial discharge of polluted air from the vertical shafts facilitates on-site scheduling of personnel and vehicles, and reduces the impact on personnel health.

Description

Technical Field

[0001] This invention belongs to the technical field of tunnel ventilation systems, specifically relating to a tunnel construction ventilation method and exhaust mode determination method that utilizes natural ventilation through vertical shafts in the construction of ultra-long tunnels at high altitudes. Background Technology

[0002] The construction of long highway tunnels at high altitudes is an important component of my country's tunnel engineering development, playing an irreplaceable role in the highway transportation system. Ventilation during the construction of high-altitude tunnels is not merely a technical means of removing dust and harmful gases. It directly impacts tunnel route surveying, engineering design, construction plans, the selection of construction machinery and equipment, and even has a significant influence on the entire tunnel engineering industry chain.

[0003] In conventional tunnels, polluted air from the tunnel face is discharged along the main tunnel to the tunnel entrance. On the one hand, because the tunnel is very long, the wind resistance caused by the discharge path is large, so high-energy-consuming fans need to be installed at the tunnel entrance to discharge the polluted air. On the other hand, when the polluted air is discharged along the tunnel, it also affects the entry and exit of construction personnel and vehicles, which affects the health protection of personnel. Summary of the Invention

[0004] This invention addresses the high energy consumption and impact on vehicles and personnel during ventilation in the construction of long highway tunnels at high altitudes. By using existing vertical shafts as ventilation channels before the tunnel is opened, the length of the exhaust path for polluted air is reduced, thereby achieving energy conservation.

[0005] The technical solution of the present invention is as follows:

[0006] A tunnel construction ventilation method using natural exhaust ventilation in vertical shafts, wherein the extra-long tunnel includes a main tunnel, a central guide tunnel, a first vertical shaft, and a second vertical shaft. The main tunnel includes a left tunnel and a right tunnel. The central guide tunnel is located between the left and right tunnels. The first and second vertical shafts are located along the middle section of the tunnel and are connected to the right and left tunnels respectively via connecting ventilation ducts. The method is characterized in that: a first fan, a second fan, and a third fan are respectively installed at the entrances of the right tunnel, the left tunnel, and the central guide tunnel, and fresh air is delivered to the working faces of the right tunnel, the left tunnel, and the central guide tunnel via ventilation ducts. Polluted air at the working faces is discharged independently by the vertical shafts or mixed with the shaft bodies.

[0007] In the tunnel construction ventilation method of natural exhaust ventilation of the above-mentioned vertical shaft, in the independent exhaust mode of the vertical shaft, the polluted air from the right tunnel face is discharged through the first vertical shaft, the polluted air from the left tunnel face is discharged through the second vertical shaft, and the polluted air from the middle guide tunnel face is divided into two parts. One part reaches the left tunnel through the first horizontal passage and is discharged through the second vertical shaft, and the other part reaches the right tunnel through the second horizontal passage and is discharged through the first vertical shaft.

[0008] In the tunnel construction ventilation method of natural exhaust ventilation through vertical shafts, in the mixed exhaust mode of the vertical shafts, part of the polluted air from the right tunnel face is discharged through the tunnel body of the right tunnel, and the other part is discharged through the first vertical shaft; part of the polluted air from the left tunnel face is discharged through the tunnel body of the left tunnel, and the other part is discharged through the second vertical shaft; the polluted air from the middle guide tunnel face is divided into three parts: the first part is discharged through the middle guide tunnel; the second part reaches the left tunnel through the first transverse passage and is discharged through the second vertical shaft; the third part reaches the right tunnel through the second transverse passage and is discharged through the first vertical shaft.

[0009] A method for determining the exhaust mode in a tunnel construction ventilation method using natural exhaust in a vertical shaft includes the following steps:

[0010] [1] The exhaust pressure P at the tunnel exhaust outlet is calculated based on the exhaust path and required air volume parameters at the tunnel face during tunnel construction.

[0011] [2] The natural wind pressure P0′ at the tunnel exhaust outlet was calculated based on the elevation of the shaft and the local atmospheric pressure.

[0012] [3] Based on the calculated exhaust wind pressure P and natural wind pressure P0′ at the tunnel exhaust outlet, the critical conditions for polluted wind to be discharged independently through the vertical shaft or mixed with the vertical shaft cavity are calculated; where the tunnel exhaust outlet is the connection between the vertical shaft and the tunnel.

[0013] In the above method for determining the exhaust mode, the calculation steps for the exhaust pressure P at the tunnel exhaust outlet are as follows:

[0014] 【1.1】Calculation of duct resistance during ventilation and tunnel resistance during exhaust:

[0015] Measure the length l of the ventilation duct inside the tunnel respectively f The distance l between the working face of the main tunnel and the intermediate pilot tunnel and the tunnel ventilation outlet p And calculate the laminar flow resistance h in the duct according to steps [1.2] and [1.3] respectively. cf Turbulent resistance h wf Local resistance h x and the frictional resistance P along the tunnel λ Local resistance P ξ ;

[0016] 【1.2】Calculate the laminar flow resistance, turbulent flow resistance, and local resistance of the duct based on its length.

[0017] h wf =R cf Q

[0018]

[0019]

[0020] R cf laminar frictional resistance N·S 2 / m 3 λ is Darcy's coefficient, dimensionless; L is the length of the ventilation duct, m; D is the diameter of the ventilation duct, m; ρ is the fluid density, kg / m³. 3 V is the average air velocity in the ventilation duct, m / s; Q is the required air volume, m³ / s. 3 F represents the cross-sectional area of ​​the duct, in meters. 2 ;

[0021] 【1.3】Calculate the friction resistance and local resistance based on the distance from the tunnel face to the ventilation outlet, whereby...

[0022]

[0023]

[0024] Q = v e A; P λ For friction resistance, Pa; v e R represents the average wind speed across the tunnel cross section, in m / s. λ Frictional wind resistance, kg / m 7 A represents the cross-sectional area of ​​the tunnel, in meters. 2 P ξ R is the local resistance, Pa; ξ is the local resistance coefficient; ξ For local wind resistance, kg / m 7 L r ρ is the duct length, in meters; ρ is the air density, in kilograms per cubic meter of air. 3 ;

[0025] 【1.4】Calculation of exhaust air pressure at the tunnel ventilation outlet:

[0026] P = P k ′-P λ1 -P ξ1

[0027] Where P k ′ is the air pressure at the air outlet of the duct, which can be obtained based on the air pressure supplied by the fan and the resistance of the duct:

[0028] P′ k =P0+nP J -h cf -h wf -h x

[0029] P JPn is the wind pressure generated by a single fan, in Pa; n is the number of fans required, dimensionless; P0 is the natural wind pressure at the tunnel entrance, in Pa; Pn λ1 The frictional resistance along the tunnel face to the exhaust vent, Pa; P ξ1 The value is Pa, which represents the local resistance from the tunnel face to the ventilation outlet.

[0030] In the above method for determining the ventilation mode, the calculation steps for the natural wind pressure resistance of the tunnel ventilation outlet are as follows:

[0031] Calculate the natural wind pressure at the exhaust vent based on its elevation and that of the local weather station.

[0032]

[0033] In particular, when exhausting air through a vertical shaft, the pressure difference caused by the height difference between the shaft and the exhaust outlet in the tunnel needs to be considered.

[0034]

[0035] Furthermore, after simplifying and rearranging the above two equations, we obtain...

[0036]

[0037] In the formula P H P is the air pressure at an altitude of H, in Pa; 气 The air pressure at the local weather station, in Pa; g p For the pressure gradient, g p = 800~1067Pa / 100mm; ΔH is the pressure difference between the altitude H and the local meteorological station; P0′ is the exhaust vent pressure, Pa; M is the molar mass; R is a constant (constant in ideal gases, approximately 8.3144); T is the absolute temperature; P0′ is the air pressure at an altitude difference of Δh, Pa; Δh is the altitude difference, m.

[0038] In the above method for determining the exhaust mode, in step [3], when P + ΔP - P λ2 -P ξ2 When ≤P0, the polluted air is discharged in a vertical shaft independent discharge mode, where all polluted air is discharged from the vertical shaft; where ΔP=P0′-P H The pressure difference generated between the upper and lower ends of the shaft;

[0039] When P + ΔP - P λ2 -P ξ2 When the value is greater than P0, the emission of polluted wind is a mixed emission mode of vertical shaft and tunnel, and only a portion of the polluted wind is discharged from the vertical shaft.

[0040] The beneficial technical effects of this invention are as follows:

[0041] I. This invention combines specific construction specifications and relevant theories of fluid mechanics, and innovatively proposes a ventilation method using existing vertical shafts during tunnel construction to address the current problem of energy conservation in ventilation during the construction of long highway tunnels at high altitudes. On the one hand, this reduces the length of the exhaust path for polluted air and lowers the frictional resistance encountered by the polluted air, thereby controlling the air pressure and power of the ventilation fans at the tunnel entrance, improving the ventilation effect during tunnel construction, and achieving the goals of energy conservation and cost reduction. On the other hand, the fact that all or part of the polluted air is discharged from the vertical shaft facilitates the on-site scheduling of personnel and vehicles and reduces the impact on personnel health.

[0042] Second, this invention theoretically derives the ventilation network under the vertical shaft exhaust mode, and obtains the influencing factors of natural exhaust in vertical shafts and the calculation formulas for exhaust pressure and wind speed by combining relevant aerodynamic theories, providing theoretical conditions for the full utilization of vertical shafts; at the same time, it calculates the critical conditions for two modes of independent exhaust in vertical shafts or mixed exhaust in the vertical shaft cavity during tunnel construction, providing guidance for response plans and personnel and vehicle protection at tunnel construction sites, and is of great significance for guiding the construction ventilation of high-altitude extra-long highway tunnels.

[0043] Third, the ventilation theory derivation of this invention is easy to understand, and the letters in the derived formulas for wind pressure, wind speed, and intermediate process formulas have clear meanings. The relevant parameters are easy to obtain and have strong operability. Attached Figure Description

[0044] Figure 1 This is a schematic diagram illustrating the principle of the traditional single-head ventilation mode in tunnel construction in an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram illustrating the principle of independent ventilation in vertical shafts during tunnel construction, as described in this embodiment of the invention.

[0046] Figure 3 This is a schematic diagram illustrating the principle of mixed ventilation in the vertical shaft during tunnel construction, as described in this embodiment of the invention.

[0047] The attached diagram is labeled as follows: 1-Left tunnel; 2-Central pilot tunnel; 3-Right tunnel; 4-Left tunnel ventilation duct; 5-Central pilot tunnel ventilation duct; 6-Right tunnel ventilation duct; 7-Left tunnel face; 8-Central pilot tunnel face; 9-Right tunnel face; 12-First transverse passage; 13-Second transverse passage; 14-First vertical shaft; 15-Second vertical shaft; 16-Second fan; 17-First fan; 18-Contaminated air; 19-Fresh air; 21-Connecting ventilation duct; 23-Third fan. Detailed Implementation

[0048] To make the objectives and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and engineering examples. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0049] like Figures 1 to 3 As shown, during the tunnel construction process, the entire tunnel includes the main tunnel (left and right tunnels) for traffic and the central pilot tunnel. During the construction process, the central pilot tunnel is constructed using a TBM hard rock tunnel boring machine, while the main tunnels on both sides are constructed using the drill and blast method. The TBM can quickly tunnel in hard rock, enabling TBM advanced construction. Therefore, it is reasonable to open cross passages from the central pilot tunnel to the main tunnels on both sides, increasing the working face of the left and right main tunnels and achieving the goal of shortening the construction period.

[0050] Traditional ventilation methods used in tunnel construction Figure 1 The single-head ventilation system shown places a second fan 16, a third fan 23, and a first fan 17 at the entrances of the left tunnel 1, the middle guide tunnel 2, and the right tunnel 3, respectively. Fresh air 19 is introduced through ducts to the corresponding working faces 7, 8, and 9 of the left tunnel, the middle guide tunnel, and the right tunnel, respectively, while polluted air 18 is discharged through the tunnel entrances. In the construction of ultra-long tunnels at high altitudes, due to the length of the tunnel, the long ducts create significant wind resistance when construction reaches deeper areas, thus placing higher demands on the power of the fans.

[0051] In the construction of ultra-long tunnels at high altitudes, vertical shafts are required in the middle section of the tunnel for ventilation during normal operation. However, these shafts are constructed along with the tunnel and are not opened for use during construction. If these shafts, located in the middle sections of the long tunnel, could be used for ventilation during construction, the length of the ventilation ducts could be saved, wind resistance reduced, and energy conservation achieved.

[0052] The following uses the construction of a tunnel in western China as an example to illustrate the implementation of the present invention.

[0053] like Figure 2 In the independent discharge mode of the vertical shaft, after the vertical shaft is built, during construction, the second fan 16, the first fan 17, and the third fan 23 are placed at the entrances of the left tunnel 1, the right tunnel 3, and the central guide tunnel 2, respectively. Fresh air from the entrances is delivered to the working faces of the left tunnel 1, the central guide tunnel 2, and the right tunnel 3 through ducts. Polluted air from the working face 9 of the right tunnel is discharged through the first vertical shaft 14, polluted air from the working face 7 of the left tunnel is discharged through the second vertical shaft 15, and polluted air from the working face 8 of the central guide tunnel is divided into two parts: one part reaches the left tunnel 1 through the first horizontal passage 12 and is discharged through the second vertical shaft 15, and the other part reaches the right tunnel 3 through the second horizontal passage 13 and is discharged through the first vertical shaft 14.

[0054] like Figure 3In the mixed discharge mode of the vertical shaft, part of the polluted air from the right tunnel face 9 is discharged through the tunnel body of the right tunnel 3, and the other part is discharged through the first vertical shaft 14; part of the polluted air from the left tunnel face 7 is discharged through the tunnel body of the left tunnel 1, and the other part is discharged through the second vertical shaft 15; the polluted air from the middle guide tunnel face 8 is divided into three parts: the first part is discharged through the middle guide tunnel 2; the second part reaches the left tunnel 1 through the first transverse passage 12 and is discharged through the second vertical shaft 15; the third part reaches the right tunnel 3 through the second transverse passage 13 and is discharged through the first vertical shaft 14.

[0055] Compared to the single-head air supply method where the fan is placed at the tunnel entrance, the required duct length is shorter, the air resistance during air supply is also relatively reduced, and the vertical shaft can create negative pressure, i.e. the chimney effect, so the vertical shaft participates in the exhaust and achieves the effect of energy saving.

[0056] The critical conditions for vertical shaft exhaust parameters, independent vertical shaft exhaust mode, and mixed vertical shaft exhaust mode are calculated below.

[0057] [1] Draw a tunnel ventilation model for "vertical shaft ventilation". Based on the ventilation path and required air volume parameters at the tunnel face during tunnel construction, calculate the ventilation pressure P at the tunnel ventilation outlet.

[0058] 【1.1】:The polluted air in the tunnel is discharged simultaneously from the vertical shaft and the main tunnel.

[0059] 【1.2】: The length of the ventilation pipe in the left tunnel is l1, the cross-sectional area of ​​the ventilation pipe is F1, the cross-sectional area of ​​the tunnel is A1, the required air volume is Q′1 (i.e. the required air volume of the working face, which can be calculated based on the actual maximum number of workers in the tunnel, the required air volume for blasting, and the required air volume for machinery), and the distance from the working face to the exhaust port of the vertical shaft is l′1.

[0060] 【1.3】: The length of the ventilation pipe in the right tunnel is l3, the cross-sectional area of ​​the ventilation pipe is F3, the cross-sectional area of ​​the tunnel is A3, the required air volume is Q′3 (i.e. the required air volume of the working face, which can be calculated based on the actual maximum number of workers in the tunnel, the required air volume for blasting, and the required air volume for machinery), and the distance from the working face to the vertical shaft exhaust port is l′3.

[0061] 【1.4】: The length of the ventilation pipe in the central tunnel is l2, the cross-sectional area of ​​the ventilation pipe is F2, the cross-sectional area of ​​the tunnel is A2, the required air volume is Q′2 (i.e. the required air volume of the working face, which can be calculated based on the actual maximum number of workers in the tunnel, the required air volume for blasting, and the required air volume for machinery), and the distance from the working face to the No. 2 cross passage is l′2.

[0062] 【1.5】: The laminar flow resistance inside the duct is calculated based on the required air volume at the tunnel face:

[0063] h cf =R cf Q (1)

[0064] In the formula R cf laminar frictional resistance N·S 2 / m 3 .

[0065] 【1.6】:The turbulent flow resistance inside the tunnel duct is:

[0066]

[0067] In the formula, λ is Darcy's coefficient, dimensionless; L is the length of the ventilation duct, m; D is the diameter of the ventilation duct, m; and ρ is the fluid density, kg / m³. 3 V represents the average wind speed in the ventilation duct, in m / s.

[0068] 【1.7】:The local resistance inside the tunnel duct is:

[0069]

[0070] In the formula h x ξ is the local resistance of the ventilation duct, Pa; v1 is the wind speed at a certain cross-section of the ventilation duct, m / s; ρ is the air density, kg / m³. 3 Q represents the airflow through a local cross-section, in meters (m). 3 / s. F is the cross-sectional area of ​​the ventilation duct, in meters. 2 .

[0071] [1.8]: The relationship between altitude and air pressure is as follows:

[0072]

[0073] In the formula P H P is the air pressure at an altitude of H, in Pa; 气 The air pressure at the local weather station, in Pa; g p For the pressure gradient, g p =800~1067Pa / 100mm; ΔH is the pressure-altitude difference between the location at altitude H and the local meteorological station.

[0074] 【1.9】:When the temperature T is constant, the relationship between air pressure and altitude is:

[0075]

[0076] In the formula, M is the molar mass.

[0077] 【1.10】:The relationship between wind speed and wind pressure in tunnels or ventilation ducts is as follows:

[0078]

[0079] In the formula, P is the pressure at a certain cross section, Pa; v is the wind speed at a certain cross section, m / s.

[0080] 【1.11】:The relationship between wind speed and air volume in a tunnel or ventilation duct is as follows:

[0081]

[0082] In the formula, Q represents the air volume in the tunnel or duct, in meters. 3 / s; A(F) is the cross-sectional area of ​​the tunnel or ventilation duct, m 2 .

[0083] 【1.12】:The frictional resistance along the tunnel is:

[0084]

[0085]

[0086] Q = v·A (10)

[0087] In the formula P λ R is the frictional resistance along the tunnel, Pa; v is the average wind speed across the tunnel cross section, m / s; λ Frictional wind resistance, kg / m 7 A represents the cross-sectional area of ​​the tunnel, in meters. 2 L r d is the tunnel exhaust distance, in meters; d is the equivalent diameter of the tunnel cross-section, in meters; Q is the air volume in the tunnel or duct, in meters. 3 / s; A is the tunnel cross-sectional area, m 2 .

[0088] 【1.13】:The local resistance within the tunnel is:

[0089]

[0090]

[0091] In the formula P ζ R is the local resistance, Pa; ξ is the local resistance coefficient; ξ For local wind resistance, kg / m 7 Q represents the air volume in the tunnel or duct, in meters. 3 / s; A is the tunnel cross-sectional area, m 2 .

[0092] [1.14]: Based on step [1.1], the ventilation network under this condition is theoretically derived to clarify the relationship between air volume, wind speed, and wind pressure. The specific ventilation mode is as follows: Figure 1 As shown.

[0093] 【1.15】: Based on the laminar flow resistance, turbulent flow resistance, and local resistance within the duct in steps 【1.5】, 【1.6】, and 【1.7】, the outlet air pressure of the left duct can be calculated as follows:

[0094] P′ k1 =P0+n1P J -h cf1 -h wf1 -h x1 (7)

[0095] Similarly, the outlet air pressure of the central tunnel duct can be calculated as follows:

[0096] P′ k2 =P0+n2P J -h cf2 -h wf2 -h x2 (8)

[0097] In the formula P J P0 is the wind pressure generated by a single fan, Pa; P' is the natural wind pressure in the tunnel, Pa; k1 The air pressure at the outlet of the left duct is measured in Pa and h. cf1 The laminar flow resistance of the left duct is given in Pa and h. wf1 The turbulent flow resistance of the left duct is given in Pa and h. x1 Let n1 be the local resistance of the left duct, Pa; n1 be the number of fans required for the left duct. k ′2 is the outlet air pressure of the central tunnel duct, Pa; h cf2 The laminar flow resistance of the central tunnel duct is given in Pa; h. wf2 The turbulent flow resistance of the central tunnel duct is given in Pa; h. x2 n1 represents the local resistance of the central tunnel duct, Pa; n2 represents the number of fans required for the central tunnel.

[0098] 【1.16】: Based on the air pressure at the outlet of the left tunnel duct calculated in step 【1.15】, the air volume delivered to the working face can be calculated:

[0099]

[0100] Similarly, the air volume delivered to the working face from the pilot tunnel can be calculated:

[0101]

[0102] In the formula, Q1 represents the air volume delivered to the working face from the left tunnel, in meters. 3 / s; Cross-sectional area of ​​the left duct of F1, m 2 ;P′ k1 Q1 is the air pressure at the outlet of the left tunnel duct, Pa; Q2 is the air volume delivered to the working face from the middle tunnel, m³. 3 / s; Cross-sectional area of ​​the F2 central tunnel ventilation duct, m 2;P′ k2 The air pressure at the outlet of the central tunnel duct is Pa;

[0103] [2] The natural wind pressure resistance P0′ of the tunnel exhaust outlet was calculated based on the elevation of the shaft and the local atmospheric pressure.

[0104] 【2.1】:According to formula (4) in step 【1.8】, the atmospheric pressure at the second shaft opening can be calculated as follows:

[0105]

[0106] In the formula, ΔH is the pressure-elevation difference between the second shaft opening and the local meteorological station, in meters; P 气 P represents the air pressure at the local weather station, in Pa. H The air pressure at an altitude of H is expressed in Pa and g. p For the pressure gradient, g p =800~1067Pa / 100mm;

[0107] 【2.2】:According to formula (5) in step 【1.9】, the natural wind pressure P0′ at the ventilation outlet of the left tunnel of the second vertical shaft can be calculated as follows:

[0108]

[0109] In the formula, M is the molar mass; R is a constant (a constant in an ideal gas, approximately 8.3144); T is the absolute temperature; and Δh2 is the height of the second shaft, in meters.

[0110] 【2.3】:Solving the equations (23) in step 【2.1】 and (24) in step 【2.2】 simultaneously, we obtain the natural wind pressure P0′ at the ventilation outlet of the left tunnel of the second vertical shaft as follows:

[0111]

[0112] In the formula, Δh2 is the height of the second vertical shaft, in meters; P H P is the air pressure at an altitude of H, in Pa; 气 The air pressure at the local weather station, in Pa; g p For the pressure gradient, g p =800~1067Pa / 100mm;

[0113] 【2.4】: Due to the large burial depth of the shaft, a temperature difference will occur between the upper end of the shaft and the inside of the tunnel. In summer, the temperature at the upper end of the shaft is high and the air pressure is low; the temperature inside the tunnel is relatively low and the air pressure is high. Therefore, a pressure difference is generated between the upper and lower ends of the shaft, forming a chimney effect, and the polluted air inside the tunnel will be drawn out of the tunnel from the shaft. According to formula (17) in step 【2.1】, formula (18) in step 【2.2】 and formula (19) in step 【2.3】, the pressure difference generated by the second shaft connecting the left tunnel can be calculated and denoted as ΔP1=P′. 01 -P H .

[0114] 【2.5】: Half of the polluted air from the central tunnel enters the left tunnel through the cross passage. Therefore, when calculating the air pressure at the exhaust vent of the left tunnel, the air pressure generated by the polluted air from the central tunnel at the exhaust vent of the left tunnel must be considered. Since the air volume is halved, the air pressure generated by the polluted air from the central tunnel at the exhaust vent of the left tunnel is 1 / 4 of the original air pressure. Therefore, the air pressure P1 at the exhaust vent of the left tunnel is calculated according to formula (8) in step 【1.12】, formula (11) in step 【1.13】, and formula (13) in step 【1.15】:

[0115]

[0116] When the pressure difference ΔP1 generated by the vertical shaft is large, most of the polluted air in the tunnel will be discharged from the second vertical shaft, which satisfies the following:

[0117] P1+ΔP1-P λz2 -P ζz2 ≤P0 (13)

[0118] At that time, all the polluted air was discharged from the second vertical shaft. The air volume discharged from the shaft at this time...

[0119] When the pressure difference ΔP1 generated by the vertical shaft is small, part of the polluted air in the tunnel is discharged from the second vertical shaft, and the other part is discharged from the left tunnel entrance, which satisfies the following:

[0120] P1+ΔP1-P λz2 -P ξz2 >P0 (22)

[0121] According to formula (6) in step [1.10] and step [1.12] (10), the air volume discharged through the left tunnel opening and the second vertical shaft at this time can be calculated as follows:

[0122]

[0123]

[0124] Similarly, the wind pressure P2 at the right exhaust vent can be obtained:

[0125]

[0126] When the pressure difference ΔP2 generated by the first vertical shaft connecting the right tunnel is large, most of the polluted air in the tunnel will be discharged from the first vertical shaft, that is, the following condition is met:

[0127] P3+ΔP2-P λy2 -P ξy2 ≤P0 (26)

[0128] At that time, all the polluted air was discharged from the first vertical shaft. The air volume discharged from the shaft at this time...

[0129] When the pressure difference ΔP2 generated by the first vertical shaft connecting the right tunnel is small, part of the polluted air in the tunnel will be discharged from the first vertical shaft, and the other part will be discharged from the right tunnel entrance, which satisfies the following:

[0130] P3+ΔP2-P λy2 -P ξy2 >P0 (27)

[0131] At this time, the air volumes discharged through the left tunnel entrance and the first vertical shaft are respectively:

[0132]

[0133]

[0134] In the formula Q s1 The volume of air discharged from the left tunnel entrance per unit time, in meters. 3 / s;Q s3 The volume of air discharged from the right tunnel entrance per unit time is expressed in meters (m). 3 / s;Q j1 The air volume discharged per unit time from the second vertical shaft, in meters (m). 3 / s;Q j3 The air volume discharged per unit time from the second vertical shaft, in meters (m). 3 / s; Q is the required air volume of the tunnel per unit time, in meters. 3 / s;Q j1 The air volume discharged from the second vertical shaft, in meters. 3 / s;;Q j3 The air volume discharged from the first vertical shaft, in m 3 / s;Q z The required air volume for the left tunnel is m 3 / s;Q y The required air volume for the right tunnel is m 3 / s;Q m The required air volume for the pilot tunnel is m 3 / s;P λz1 The frictional resistance along the path from the left tunnel face to the exhaust outlet is expressed in Pa; P ξz1 P represents the local resistance from the left tunnel face to the exhaust vent, measured in Pa. λy1The frictional resistance along the path from the right tunnel face to the exhaust outlet is expressed in Pa; P ξy1 P represents the local resistance from the right tunnel face to the exhaust vent, expressed in Pa. λmz The frictional resistance along the path from the working face of the central tunnel to the exhaust outlet of the left tunnel is expressed in Pa; P ξmz The local resistance from the tunnel face to the left tunnel exhaust outlet is expressed in Pa; P λmy The frictional resistance along the path from the working face of the central tunnel to the exhaust outlet of the right tunnel is expressed in Pa; P ξmy The local resistance from the tunnel face to the right tunnel exhaust outlet is expressed in Pa; P λz2 P is the frictional resistance along the route from the left ventilation outlet to the tunnel entrance, expressed in Pa. ξz2 P represents the local resistance from the left ventilation outlet to the tunnel entrance, expressed in Pa. λy2 P is the frictional resistance along the route from the right tunnel exhaust outlet to the tunnel entrance, in Pa; ξy2 P0 is the local resistance from the right tunnel exhaust vent to the tunnel entrance, Pa; P0 is the natural wind pressure outside the tunnel, Pa; A is the tunnel cross-sectional area, m2. 2 P1 is the air pressure at the left exhaust vent, Pa; P3 is the air pressure at the right exhaust vent, Pa; P k1 ′ represents the air pressure at the outlet of the left duct, in Pa; P k2 ′ represents the air pressure at the outlet of the central tunnel duct, in Pa; P k3 ΔP1 is the air pressure at the outlet of the right tunnel duct, Pa; ΔP2 is the pressure difference of the second vertical shaft connected to the left tunnel, Pa; ΔP3 is the pressure difference of the first vertical shaft connected to the right tunnel, Pa.

[0135] [3] Calculate the number of fans required when there is a vertical shaft and the number of fans required in the case of traditional single-head air supply based on the wind pressure relationship obtained in [2], and compare the two.

[0136] 【3.1】When the polluted air is simultaneously discharged through the second vertical shaft and the left tunnel entrance, the number of fans n required for the left tunnel is as follows: z :

[0137] P0+n z P J -(h cf1 +h wf1 +h x1 )-(P λz1 +P ξz1 )+ΔP1-(P λz2 +P ξz2 )=P0 (30)

[0138] Solving for:

[0139]

[0140] Similarly, the number of fans n required for the pilot tunnel can be calculated. m :

[0141]

[0142] Solving for:

[0143]

[0144] Similarly, the number of fans n required for the right tunnel can be calculated. y :

[0145] P0+n y P J -(h cf3 +h wf3 +h x3 )-(P λy1 +P ξy1 )+ΔP2-(P λy2 +P ξy2 )=P0 (34)

[0146] Solving for:

[0147]

[0148] The total number of fans required for the left tunnel, right tunnel, and central guide tunnel is n. ∑ :

[0149] n ∑ =n z +n m +n y (18)

[0150] [3.2] When the waste air is discharged only through the vertical shaft, the formula for calculating the number of fans required is the same as in [3.1]. When the pressure difference ΔP of the vertical shaft increases, the tunnel entrance will no longer discharge air, and ventilation will only be provided through the vertical shaft. According to the formula in [3.1], as ΔP increases, n decreases, which means that the number of fans required decreases, making it more energy-efficient than discharging air through both the vertical shaft and the tunnel entrance at the same time.

[0151] 【3.3】Number of fans required in traditional single-head air supply cases:

[0152] The number of fans required for the left tunnel, n cz :

[0153] P0+n cz P J -(h cf1 +h wf1 +h x1 )-(P λz1 +P ξz1 )-(P λz2 +P ξz2 )=P0 (37)

[0154] Solving for:

[0155]

[0156] Therefore, it can be seen that the number of fans saved when using a vertical shaft for exhaust ventilation in the left tunnel compared to traditional single-head ventilation is:

[0157]

[0158] Similarly, the number of fans n required for the right tunnel can be calculated. cy :

[0159] P0+n cy P J -(h cf3 +h wf3 +h x3 )-(P λy1 +P ξy1 )-(P λy2 +P ξy2 )=P0 (40)

[0160] Solving for:

[0161]

[0162] Therefore, it can be seen that the number of fans saved when using a vertical shaft for ventilation in the right tunnel is compared to the traditional single-head ventilation:

[0163]

[0164] Number of fans required for the pilot tunnel n cm :

[0165] P0+n cm P J -(h cf2 +h wf2 +h x2 )-(P λm +P ξm )=P0 (19)

[0166] Solving for:

[0167]

[0168] This shows that the number of fans saved when the central guide tunnel connects to the second and first vertical shafts via the transverse passage to the left and right tunnels is:

[0169]

[0170] When using a traditional single-head air supply, the total number of fans required is n. ∑ ′:

[0171] n ∑ ′=ncz +n cm +n cy (46)

[0172] The total number of fans saved Δn when using vertical shaft exhaust compared to traditional single-head air supply Σ :

[0173]

[0174] In the formula n z n represents the number of fans required for the left tunnel. m n is the number of fans required for the pilot tunnel; y n represents the number of fans required for the right tunnel. ∑ n is the total number of ventilation fans required for the left tunnel, right tunnel, and central pilot tunnel. cz n represents the number of fans required for the left duct in a traditional single-head ventilation system. cy n represents the number of fans required for the right duct in a traditional single-head ventilation system. cm The number of fans required for the central tunnel in the traditional single-head ventilation system; Δn z The number of fans saved when using a vertical shaft for exhaust ventilation in the left tunnel compared to traditional single-head ventilation; Δn m The number of fans saved when using vertical shafts for ventilation in the pilot tunnel compared to traditional single-head ventilation; Δn y The number of fans saved when using a vertical shaft for exhaust ventilation in the right tunnel compared to traditional single-head ventilation; P λm The frictional resistance generated by the polluted air from the tunnel face to the tunnel entrance is expressed in Pa; P ξm The local resistance generated by the polluted air from the tunnel face to the tunnel entrance is Pa; n ∑ ′ represents the total number of fans required when using traditional single-head air supply; Δn ∑ This refers to the total number of fans saved when using vertical shaft exhaust compared to traditional single-head ventilation.

[0175] The above theoretical calculations show that:

[0176] Both exhaust modes can achieve energy saving.

[0177] Calculations show that regardless of whether the polluted air is discharged simultaneously through the vertical shaft and the main tunnel, or only through the vertical shaft, the number of fans required is less than that required for traditional single-head ventilation. Therefore, using existing vertical shafts for ventilation during the construction of ultra-long tunnels can effectively reduce the number of fans, resulting in significant energy savings and reducing construction costs. In the construction of high-altitude ultra-long tunnels, using existing vertical shafts for ventilation can effectively save energy and reduce the concentration of pollutants within the tunnel. This ventilation mode can guide ventilation schemes in different tunnel designs.

[0178] II. The calculation of critical values ​​for the two exhaust modes is of great significance to the construction site.

[0179] Whether using independent vertical shaft exhaust or a combined vertical shaft and tunnel entrance exhaust, vertical shaft ventilation reduces or eliminates all or part of the polluted air discharged through the main tunnel, effectively lowering the concentration of pollutants inside the tunnel. This provides guidance for on-site vehicle scheduling and personnel protection when entering and exiting the tunnel. Furthermore, as the tunnel continues to advance, the distance to the shaft and tunnel entrance increases, leading to greater resistance to polluted air within the tunnel, thus favoring independent vertical shaft exhaust. Compared to tunnel entrance exhaust, this method is more energy-efficient, reduces the distribution range of pollutants within the tunnel, and is beneficial to the health and safety of construction workers inside the tunnel.

Claims

1. A tunnel construction ventilation method using natural exhaust ventilation in vertical shafts, wherein the tunnel is a high-altitude, ultra-long tunnel, comprising a main tunnel, a central guide tunnel (2), a first vertical shaft (14), and a second vertical shaft (15), the main tunnel comprising a left tunnel (1) and a right tunnel (3), the central guide tunnel (2) being located between the left tunnel (1) and the right tunnel (3), and the first vertical shaft (14) and the second vertical shaft (15) being located in the middle of the entire tunnel and connected to the right tunnel (3) and the left tunnel (1) respectively via connecting ventilation ducts (21); characterized in that: At the entrances of the right tunnel (3), left tunnel (1) and central guide tunnel (2), a first fan (17), a second fan (16) and a third fan (23) are respectively installed, and fresh air is delivered to the working faces of the right tunnel (3), left tunnel (1) and central guide tunnel (2) through air ducts. The polluted air at the working faces is discharged independently by the vertical shaft or mixed with the vertical shaft body. In the independent vertical shaft discharge mode, the polluted air from the right tunnel face (9) is discharged through the first vertical shaft (14), the polluted air from the left tunnel face (7) is discharged through the second vertical shaft (15), and the polluted air from the middle guide tunnel face (8) is divided into two parts. One part reaches the left tunnel (1) through the first horizontal passage (12) and is discharged through the second vertical shaft (15), while the other part reaches the right tunnel (3) through the second horizontal passage (13) and is discharged through the first vertical shaft (14). In the mixed discharge mode of the vertical shaft, part of the polluted air from the right tunnel face (9) is discharged through the tunnel body of the right tunnel (3), and the other part is discharged through the first vertical shaft (14); part of the polluted air from the left tunnel face (7) is discharged through the tunnel body of the left tunnel (1), and the other part is discharged through the second vertical shaft (15); the polluted air from the middle guide tunnel face (8) is divided into three parts: the first part is discharged through the middle guide tunnel (2); the second part reaches the left tunnel (1) through the first transverse passage (12) and is discharged through the second vertical shaft (15); the third part reaches the right tunnel (3) through the second transverse passage (13) and is discharged through the first vertical shaft (14). The method for determining the two modes of independent discharge from vertical shafts and mixed discharge from vertical shaft caverns includes the following steps: [1] The exhaust pressure P at the tunnel exhaust outlet is calculated based on the exhaust path and required air volume parameters at the tunnel face during tunnel construction. [2] The natural wind pressure P0′ at the tunnel exhaust outlet was calculated based on the elevation of the shaft and the local atmospheric pressure. [3] Based on the calculated exhaust wind pressure P and natural wind pressure P0′ at the tunnel exhaust outlet, the critical conditions for polluted wind to be discharged independently through the vertical shaft or mixed with the vertical shaft cavity are calculated; where the tunnel exhaust outlet is the connection between the vertical shaft and the tunnel.

2. A method for determining the exhaust mode in the tunnel construction ventilation method for natural exhaust ventilation of vertical shafts as described in claim 1, characterized in that, The steps for calculating the exhaust air pressure P at the tunnel ventilation outlet are as follows: 【1.1】Calculation of duct resistance during ventilation and tunnel resistance during exhaust: 【1.1】Measure the length l of the ventilation duct inside the tunnel respectively. f The distance l between the working face of the main tunnel and the intermediate pilot tunnel and the tunnel ventilation outlet p And calculate the laminar flow resistance h in the duct according to steps [1.2] and [1.3] respectively. cf Turbulent resistance h wf Local resistance h x and the frictional resistance P along the tunnel λ Local resistance P ξ ; 【1.2】Calculate the laminar flow resistance, turbulent flow resistance, and local resistance of the duct based on its length. h cf =R cf Q R cf laminar frictional resistance N·S 2 / m 3 λ is Darcy's coefficient, dimensionless; L is the length of the ventilation duct, m; D is the diameter of the ventilation duct, m; ρ is the fluid density, kg / m³. 3 V is the average air velocity in the ventilation duct, m / s; Q is the required air volume, m³ / s. 3 F represents the cross-sectional area of ​​the duct, in meters. 2 ; 【1.3】Calculate the friction resistance and local resistance based on the distance from the tunnel face to the ventilation outlet, whereby... Q = v e A; P λ For friction resistance, Pa; v e R represents the average wind speed across the tunnel cross section, in m / s. λ Frictional wind resistance, kg / m 7 A represents the cross-sectional area of ​​the tunnel, in meters. 2 P ξ R is the local resistance, Pa; ξ is the local resistance coefficient; ξ For local wind resistance, kg / m 7 L r ρ is the duct length, in meters; ρ is the air density, in kilograms per cubic meter of air. 3 ; 【1.4】Calculation of exhaust air pressure at the tunnel ventilation outlet: P=P k ′-P λ1 -P ξ1 Where P k ′ is the air pressure at the air outlet of the duct, which can be obtained based on the air pressure supplied by the fan and the resistance of the duct: P′ k =P0+nP J -h cf -h wf -h x P J Pn is the wind pressure generated by a single fan, in Pa; n is the number of fans required, dimensionless; P0 is the natural wind pressure at the tunnel entrance, in Pa; Pn λ1 The frictional resistance along the tunnel face to the exhaust vent, Pa; P ξ1 The value is Pa, which represents the local resistance from the tunnel face to the ventilation outlet.

3. The method for determining the exhaust mode in the tunnel construction ventilation method using natural exhaust ventilation in vertical shafts according to claim 2, characterized in that, The calculation steps for the natural wind pressure resistance of the tunnel exhaust vent are as follows: Calculate the natural wind pressure at the exhaust vent based on its elevation and that of the local weather station. In particular, when exhausting air through a vertical shaft, the pressure difference caused by the height difference between the shaft and the exhaust outlet in the tunnel needs to be considered. Furthermore, after simplifying and rearranging the above two equations, we obtain... In the formula P H P is the air pressure at an altitude of H, in Pa; 气 The air pressure at the local weather station, in Pa; g p For the pressure gradient, g p = 800~1067Pa / 100mm; ΔH is the pressure difference between the altitude H and the local meteorological station; P′0 is the exhaust vent pressure, Pa; M is the molar mass; R is a constant (constant in ideal gases, approximately 8.3144); T is the absolute temperature; P′0 is the air pressure at an altitude difference of Δh, Pa; Δh is the altitude difference, m.

4. The method for determining the exhaust mode in the tunnel construction ventilation method using natural exhaust ventilation in vertical shafts according to claim 2, characterized in that: In step [3], when P + ΔP - P λ2 -P ξ2 When ≤P0, the polluted air is discharged in a vertical shaft independent discharge mode, where all polluted air is discharged from the vertical shaft; where ΔP=P′0-P H The pressure difference generated between the upper and lower ends of the shaft; When P + ΔP - P λ2 -P ξ2 When the value is greater than P0, the emission of polluted wind is a mixed emission mode of vertical shaft and tunnel, and only a portion of the polluted wind is discharged from the vertical shaft.

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