Method for air supply of vertical shaft in super-long tunnel construction and calculation method for fan parameters

Abstract

The application discloses a vertical shaft air supply method and a fan parameter calculation method in super-long tunnel construction, wherein the super-long tunnel comprises a main hole, a middle pilot hole, a first vertical shaft and a second vertical shaft; first and second fans are arranged in the main hole corresponding to the first and second vertical shafts respectively; fresh air is pumped through the vertical shafts and is delivered to the tunnel face of the left hole, the middle pilot hole and the right hole of the tunnel through air pipes; and contaminated air is discharged from the tunnel mouth along the hole body of the left hole, the middle pilot hole and the right hole of the tunnel. The application proposes a tunnel construction ventilation method based on vertical shaft air supply according to the ventilation demand of the tunnel face in high-altitude super-long tunnel construction. Since the length of the air pipe required by the vertical shaft air supply is shorter than that required by the tunnel mouth air supply, the air resistance during air supply is relatively reduced, energy saving is achieved, and the application has important significance for guiding the construction ventilation of high-altitude super-long highway tunnels.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of tunnel ventilation system, and particularly relates to a control method of a vertical shaft air supply system in tunnel construction. BACKGROUND

[0002] When a tunnel is built in a high-cold and high-elevation area, construction ventilation organization design is a fundamental guarantee for tunnel construction. Especially in a plateau environment with low pressure and oxygen deficiency, long excavation length and poor construction conditions, construction ventilation technology has become a technical problem for high-elevation highway tunnel construction. However, before the tunnel is opened, there is rarely a vertical shaft used as a channel for construction ventilation. The use of a vertical shaft for air supply during construction ventilation can reduce the length of the air pipe and lower the air resistance. In addition, compared with single-head air supply, this mode only needs two air fans, which greatly reduces energy consumption. According to the above problems, it is necessary to theoretically deduce and calculate the construction period vertical shaft air supply ventilation network according to relevant specifications and in combination with the related theory of aerodynamics, and to combine with the actual construction to improve the tunnel construction ventilation effect and reduce the tunnel construction ventilation cost. SUMMARY

[0003] The present application is to solve the problem of controlling the power of the fan during the construction ventilation of the high-elevation super-long highway tunnel, and to achieve the purpose of energy saving.

[0004] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0005] A vertical shaft air supply method in super-long tunnel construction, the super-long tunnel comprises a main hole, a middle pilot hole, a first vertical shaft and a second vertical shaft, the main hole comprises a tunnel left hole and a tunnel right hole, the middle pilot hole is located between the tunnel left hole and the tunnel right hole, the first vertical shaft and the second vertical shaft are located in the middle part of the whole tunnel and are respectively communicated with the tunnel right hole and the tunnel left hole through the connecting air duct; characterized in that: a first fan and a second fan are respectively arranged in the tunnel main hole corresponding to the first vertical shaft and the second vertical shaft, fresh air is sucked and supplied through the vertical shaft, and is transported to the tunnel left hole, the middle pilot hole and the tunnel right hole through the air pipe, and the contaminated air is discharged from the tunnel opening along the tunnel left hole, the middle pilot hole and the tunnel right hole.

[0006] In the above-mentioned vertical shaft air supply method in super-long tunnel construction, the first fan divides the fresh air coming from the first vertical shaft into two paths, one path passes through the tunnel right hole to the right hole face, and the contaminated air is discharged from the tunnel opening through the tunnel right hole; the other path passes through the tunnel right hole, the second horizontal passage and the middle pilot hole in turn, enters the middle pilot hole face, and the contaminated air is discharged from the tunnel opening through the middle pilot hole.

[0007] In the above-mentioned vertical shaft ventilation method for the construction of super-long tunnels, the second fan splits the fresh air coming in from the second vertical shaft into two paths. One path passes through the left tunnel to the working face of the left tunnel, while the polluted air is discharged to the tunnel entrance through the left tunnel. The other path passes through the left tunnel, the first transverse passage and the central guide tunnel in sequence, enters the working face of the central guide tunnel, and the polluted air is discharged to the tunnel entrance through the central guide tunnel.

[0008] A method for calculating the parameters of the vertical shaft ventilation fan in the construction of ultra-long tunnels includes the following steps:

[0009] [1] Based on the air supply path and required air volume parameters at the tunnel face during tunnel construction, the required air pressure at the tunnel air supply outlet where the fan is located is calculated.

[0010] [2] The natural wind pressure at the tunnel air supply outlet of the shaft is calculated based on the elevation of the shaft and the atmospheric pressure.

[0011] [3] Based on the calculated required air pressure at the air outlet and the natural air pressure at the air outlet of the shaft in the tunnel, the required air pressure value to be supplied by the fan is obtained, and the corresponding fan parameters are set.

[0012] In the above-mentioned calculation method for the parameters of the vertical shaft ventilation fan during the construction of ultra-long tunnels, the formula for calculating the natural air pressure at the vertical shaft ventilation outlet in the tunnel is as follows:

[0013]

[0014] In the formula, P0′ is the natural wind pressure at the tunnel air supply outlet of the vertical shaft, 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; Pa; M is the molar mass of air; g is the acceleration due to gravity, m / s² 2 R is a constant, approximately 8.3144; T is the absolute temperature; Δh is the height difference, in meters.

[0015] In the above-mentioned calculation method for the parameters of the vertical shaft ventilation fan during the construction of ultra-long tunnels, the calculation steps for the required air pressure at the tunnel air inlet where the fan is located are as follows:

[0016] 【1.1】Measure the length l of the ventilation duct inside the tunnel respectively. f , Shaft bottom air pressure P sd And calculate the laminar flow resistance h in the duct. cf Turbulent resistance h wf Local resistance h x ;

[0017] h wf =Rcf Q

[0018]

[0019]

[0020] R cf is the laminar friction resistance N·S 2 / m 3 ; λ is the Darcy coefficient, dimensionless; L is the length of the ventilation pipe, m; D is the diameter of the ventilation pipe, m; ρ is the fluid density, kg / m 3 V is the average wind speed of the ventilation pipe, m / s; Q is the air volume passing through the air pipe, m 3 .

[0021] 【1.2】According to the required fresh air volume Q during tunnel construction, the required air supply pressure P is calculated in combination with the air pipe diameter F:

[0022] the outlet air speed v'

[0023]

[0024] the outlet air pressure P'

[0025]

[0026] then the required air pressure P of the tunnel air supply outlet where the fan is located:

[0027] P = P' + h cf +h wf +h x

[0028] wherein P' is the air outlet pressure of the air pipe, Pa.

[0029] In the above-mentioned parameter calculation method of the vertical shaft air supply fan in the super-long tunnel construction, the required air pressure provided by the fan is P j

[0030] P j = P - (P0' - P0)

[0031] wherein P0 is the natural air pressure in the tunnel.

[0032] The present application has the following beneficial technical effects:

[0033] I. The present application is directed to the demand of the face ventilation in the construction of the super-long tunnel at high altitude, and proposes a tunnel construction ventilation method based on the vertical shaft air supply. Since the length of the air pipe required by the vertical shaft air supply is shorter than that required by the tunnel portal air supply, the air resistance during the air supply is relatively reduced, the energy saving effect is achieved, and the already built but not yet used vertical shaft plays a role in advance in the construction, which has important significance for guiding the construction ventilation of the super-long tunnel at high altitude.

[0034] II. The present application gives the calculation of the vertical shaft air supply fan parameters in the construction of the super-long tunnel, fully considers the effect caused by the natural wind pressure of the vertical shaft, analyzes the theoretical conditions of the natural air supply of the vertical shaft, obtains the relationship between the fan wind pressure and the natural wind pressure of the vertical shaft during the natural air supply, and finally controls the fan power in combination with the actual engineering, which has important significance for guiding the construction ventilation of the super-long tunnel at high altitude.

[0035] III. The ventilation theory of the present application is easy to understand, and the derived wind pressure, wind speed formula and the meaning of the letters in the intermediate process formula are clear, the related parameters are easy to obtain, and the present application has strong operability. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is a schematic diagram of the principle of the traditional tunnel construction in the single-head air supply mode;

[0037] Figure 2 It is a schematic diagram of the principle of the tunnel construction in the vertical shaft air supply in the embodiment of the present application;

[0038] The reference signs are: 1 - left tunnel; 2 - middle pilot hole; 3 - right tunnel; 4 - left tunnel air pipe; 5 - middle pilot hole air pipe; 6 - right tunnel air pipe; 7 - left tunnel face; 8 - middle pilot hole face; 9 - right tunnel face; 12 - first horizontal passage; 13 - second horizontal passage; 14 - first vertical shaft; 15 - second vertical shaft; 16 - second fan; 17 - first fan; 18 - contaminated air; 19 - fresh air; 21 - communication air duct; 23 - third fan. DETAILED DESCRIPTION

[0039] In order to make the purpose and advantages of the present application more clear and explicit, the present application is further described in detail below in combination with the drawings and engineering examples. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0040] As Figure 1 and Figure 2As shown, in the tunnel construction process, the whole tunnel includes the main hole (left hole and right hole) for traffic and the middle pilot hole in the middle, the pilot hole is constructed by TBM hard rock tunneling machine in the construction process, the main hole on both sides is constructed by drilling and blasting method, TBM can quickly tunnel in hard rock, realize the advanced construction of TBM, therefore, the horizontal passage can be reasonably opened from the pilot hole to the main hole on both sides, the working face of the left and right main hole is increased, and the purpose of shortening the construction period is achieved.

[0041] The traditional ventilation in the tunnel construction process adopts the mode of Figure 1 As shown, the mode of single-head air supply, the second fan 16, the third fan 23 and the first fan 17 are respectively placed at the hole openings of the tunnel left hole 1, the pilot hole 2 and the tunnel right hole 3, the fresh air 19 is introduced into the corresponding left hole working face 7, the pilot hole working face 8 and the right hole working face 9 through the air pipe, and the contaminated air 18 is discharged from the hole opening along the hole body. In the construction of the super-long tunnel at high altitude, because the tunnel is very long, when the construction reaches the deep area, the longer air pipe will bring greater air resistance, and therefore a higher requirement is put forward for the power of the fan.

[0042] In the construction of the super-long tunnel at high altitude, the vertical shaft in the middle part of the tunnel needs to be constructed to support the ventilation in the normal operation of the tunnel, because the vertical shaft is constructed together with the tunnel, and is not used during the construction of the tunnel. If the vertical shaft in the middle part of the long tunnel can be used for air supply during the construction, the length of the air pipe can be saved, the air resistance can be reduced, and the energy saving effect can be achieved.

[0043] Next, the embodiment of the present application will be described taking the construction of XX tunnel as an example.

[0044] As shown in the figure, Figure 2 As shown, after the construction of the vertical shaft, the second fan 16 and the first fan 17 originally reserved at the hole openings of the tunnel left hole 1 and the tunnel right hole 3 are respectively moved to the vicinity of the second vertical shaft 15 and the first vertical shaft 14, and are connected through the connecting air duct 21, so that the two vertical shafts supply air to the working faces of the tunnel left hole 1, the pilot hole 2 and the tunnel right hole 3.

[0045] Figure 1 The first fan 17 divides the fresh air 19 coming from the first vertical shaft 14 into two paths, one path passes through the tunnel right hole 3 to the right hole working face 9, and the contaminated air 18 is discharged to the hole opening through the tunnel right hole 3; the other path passes through the tunnel right hole 3, the second horizontal passage 13 and the pilot hole 2 in sequence, enters the pilot hole working face 8, and the contaminated air 18 is discharged to the hole opening through the pilot hole 2;

[0046] The second fan 16 divides the fresh air 19 from the second shaft 15 into two paths, one of which passes through the left tunnel 1 to the left tunnel face 7, and the contaminated air 18 is discharged to the tunnel entrance through the left tunnel 1; the other passes through the left tunnel 1, the first horizontal passage 12 and the middle drift 2 in turn, enters the middle drift face 8, and the contaminated air 18 is discharged to the tunnel entrance through the middle drift 2;

[0047] Compared with the single-head air supply mode in which the fan is arranged at the tunnel entrance, the required length of the air pipe is shorter than that required for air supply at the tunnel entrance, the air resistance during air supply is relatively reduced, and the energy-saving effect is achieved.

[0048] The air flow direction during tunnel construction is shown in the schematic diagram, fresh air reaches the tunnel through the shaft, and then enters the air pipe after being pressurized by the fan. The air pipe is divided into two parts at the horizontal passage connecting the main hole and the middle drift, and is supplied to each face.

[0049] 【1】Draw a tunnel ventilation model for shaft air supply, calculate the required air pressure P at the tunnel air supply port according to the air supply path and the required air volume parameters of the face during tunnel construction.

[0050] 【1.1】The tunnel is supplied with air only from the shaft.

[0051] 【1.2】The length of the ventilation pipe from the left hole fan to the first horizontal passage 12 is l1, the cross-sectional area of the ventilation pipe is F1, the required air volume is Q1 (i.e. the required air volume of the working face, which can be calculated according to 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 first horizontal passage 12 to the air pipe exhaust port is l2.

[0052] 【1.3】The length of the ventilation pipe from the right hole fan to the second horizontal passage 13 is l5, the cross-sectional area of the ventilation pipe is F3, the required air volume is Q3 (i.e. the required air volume of the working face, which can be calculated according to 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 second horizontal passage 13 to the air pipe exhaust port is l2.

[0053] 【1.4】The length of the ventilation pipe at the first horizontal passage and the second horizontal passage of the middle drift hole fan is l4, the cross-sectional area of the ventilation pipe is F2, the required air volume is Q2 (i.e. the required air volume of the working face, which can be calculated according to 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 first horizontal passage and the second horizontal passage to the air pipe exhaust port is l4.

[0054] 【1.5】The laminar flow resistance in the air pipe is calculated according to the required air volume of the tunnel face as follows:

[0055] h cf =R cf Q (1)

[0056] Where R cfThe laminar flow friction resistance N·S 2 / m 3 .

[0057] 【1.6】The turbulent flow resistance in the tunnel duct is:

[0058]

[0059] where λ is the Darcy coefficient, dimensionless; L is the length of the duct, m; D is the diameter of the duct, m; ρ is the fluid density, kg / m 3 V is the average wind speed in the duct, m / s.

[0060] 【1.7】The local resistance in the tunnel duct is:

[0061]

[0062] where h x is the local resistance in the duct, Pa; ξ is the local resistance coefficient; v1 is the wind speed at a certain section of the duct, m / s; ρ is the air density, kg / m 3 ; Q is the air volume passing through the local section, m 3 / s. F is the cross-sectional area of the duct, m 2 .

[0063] 【1.8】The relationship between the altitude and the air pressure is:

[0064]

[0065] where P H is the air pressure at an altitude of H, Pa; P 气 is the air pressure at the local weather station, Pa; g p is the air pressure gradient, g p = 800-1067 Pa / 100 mm; ΔH is the difference in altitude between the altitude of H and the altitude of the local weather station.

[0066] 【1.9】When the temperature T is constant, the relationship between the air pressure and the altitude is:

[0067]

[0068] where M is the molar mass.

[0069] 【1.10】The relationship between the wind speed and the air pressure in the tunnel or duct is:

[0070]

[0071] where P is the pressure at a certain section, Pa; v is the wind speed at a certain section, m / s.

[0072] 【1.11】The relationship between the wind speed and the wind volume in the tunnel or air duct is:

[0073]

[0074] where Q is the wind volume in the tunnel or air duct, m 3 / s; A(F) is the cross-sectional area of the tunnel or air duct, m 2 .

[0075] 【1.12】The air duct resistance P of the left-line air duct branch in the middle pilot hole is calculated according to the formula (1), (2), (3) in steps 【1.5】、【1.6】、【1.7】: Zz

[0076] Laminar flow resistance:

[0077]

[0078] Turbulent flow resistance:

[0079]

[0080] Local resistance:

[0081]

[0082]

[0083] where Q2 is the required wind volume during the construction of the middle pilot hole, m 3 ; V2 is the average wind speed in the air duct, m / s; F2 is the cross-sectional area of the air duct in the middle pilot hole, m 2 .

[0084] Similarly, the air duct resistance P of the right-line air duct branch in the middle pilot hole is: Yy

[0085] Laminar flow resistance:

[0086]

[0087] Turbulent flow resistance:

[0088]

[0089] Local resistance:

[0090]

[0091]

[0092] 【1.13】The air duct resistance P1 of the first horizontal passage to the air duct outlet of the left line is calculated according to the formula (1), (2), (3) in steps 【1.5】、【1.6】、【1.7】:​​

[0093] Laminar resistance:

[0094] h 1cf = R 1cf · Q1 (16)

[0095] Turbulent resistance:

[0096]

[0097] Local resistance:

[0098]

[0099]

[0100] where Q1 is the required air volume during left tunnel construction, m 3 ; V1 is the average air speed in the air duct, m / s; F1 is the cross-sectional area of the air duct in the middle pilot tunnel, m 2 .

[0101] Similarly, the air duct resistance P3 of the second transverse passage of the right line to the air duct outlet is:

[0102] Laminar resistance:

[0103] h 3cf = R 3cf · Q3 (20)

[0104] Turbulent resistance:

[0105]

[0106] Local resistance:

[0107]

[0108]

[0109] where Q3 is the required air volume during left tunnel construction, m 3 ; V3 is the average air speed in the air duct, m / s; F3 is the cross-sectional area of the air duct in the middle pilot tunnel, m 2 .

[0110] 【1.14】The air duct resistance P 1z of the left line fan to the first transverse passage is calculated according to the formulas (1), (2), and (3) in steps 【1.5】, 【1.6】, and 【1.7】 as follows:

[0111] Laminar resistance:

[0112]

[0113] Turbulent resistance:

[0114]

[0115] Local resistance:

[0116]

[0117]

[0118] Similarly, the resistance of the air pipe from the right-line fan to the second cross passage P 3y is:

[0119] Laminar flow resistance:

[0120]

[0121] Turbulent flow resistance:

[0122]

[0123] Local resistance:

[0124]

[0125]

[0126] 【1.15】The air supply pressure P Z , P Y of the left and right lines can be calculated according to the formulas (11), (15), (19), (23), (27), (31) in steps 【1.12】, 【1.13】, 【1.14】 respectively.

[0127] Left-line air supply pressure:

[0128]

[0129] Right-line air supply pressure:

[0130]

[0131] 【2】According to the altitude of the shaft and the local atmospheric pressure, the natural wind pressure P0' of the shaft at the tunnel air supply outlet is calculated.

[0132] The main factor considered here is that the shaft, similar to the chimney on the upper part of the boiler room, usually functions as a natural air extractor (air exhaust to the outside) for the tunnel, and this natural air extraction will eventually affect the parameter calculation of the fan, so the mechanism and conditions of shaft air exhaust need to be studied.

[0133] 【2.1】Calculate the natural wind pressure P0′ at the air supply outlet of the tunnel shaft according to formulas (4) and (5) in steps 【1.8】 and 【1.9】:

[0134]

[0135] 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 air pressure at the air supply outlet of the shaft in the tunnel, Pa; M is the molar mass; R is a constant (constant in ideal gases, approximately 8.3144); T is the absolute temperature; Δh is the altitude difference, m.

[0136] [3] Based on the calculated required air pressure at the air outlet and the natural air pressure at the air outlet of the shaft in the tunnel, set the air pressure of fans #1 and #2.

[0137] 【3.1】Assume the natural wind pressure inside the tunnel is P0.

[0138] 【3.2】Based on formulas (32), (33), and (34) in steps 【1.15】 and 【2.1】, the wind pressure P of the left and right line fans can be calculated respectively. jZ and P jY for:

[0139] The air pressure of fan #1 on the left is:

[0140]

[0141] The air pressure of fan #2 on the left is:

[0142]

[0143] Therefore, the air pressure of the fan is related to the required air volume, the length of the duct, and the pressure difference within the shaft. Since the duct length required for air supply from the shaft is shorter than that required for air supply from the tunnel entrance, the air resistance during air supply is relatively reduced. Even under normal conditions of natural exhaust from the shaft, the fan power should be increased. For ultra-long tunnels, compared to... Figure 1 The single-head air supply mode shown in this invention can still achieve energy saving because the length of the air duct required for vertical shaft air supply is much shorter than that required for tunnel entrance air supply, the air resistance during air supply is also relatively reduced, and one less fan is required.

Claims

1. A method for vertical shaft ventilation during the construction of an ultra-long tunnel, wherein the ultra-long tunnel includes a main tunnel, a central pilot tunnel (2), a first vertical shaft (14), and a second vertical shaft (15), the main tunnel includes a left tunnel (1) and a right tunnel (3), the central pilot tunnel (2) is located between the left tunnel (1) and the right tunnel (3), and the first vertical shaft (14) and the second vertical shaft (15) are located in the middle of the entire tunnel and are respectively connected to the right tunnel (3) and the left tunnel (1) through connecting ventilation ducts (21); characterized in that: In the main tunnels corresponding to the first shaft (14) and the second shaft (15), the first fan (17) and the second fan (16) are respectively installed to draw fresh air through the shafts and deliver it to the working faces of the left tunnel (1), the middle guide tunnel (2) and the right tunnel (3) through the air ducts. The polluted air is discharged from the tunnel entrance along the tunnel body of the left tunnel (1), the middle guide tunnel (2) and the right tunnel (3); The first fan (17) splits the fresh air (19) coming in from the first vertical shaft (14) into two paths. One path passes through the right tunnel (3) to the working face (9) of the right tunnel, while the polluted air (18) is discharged through the right tunnel (3) to the tunnel entrance. The other path passes through the right tunnel (3), the second transverse passage (13) and the central guide tunnel (2) in sequence, and enters the working face (8) of the central guide tunnel. The polluted air (18) is discharged through the central guide tunnel (2) to the tunnel entrance. The second fan (16) splits the fresh air (19) coming in from the second shaft (15) into two paths. One path passes through the left tunnel (1) to the working face (7) of the left tunnel, while the polluted air (18) is discharged to the tunnel entrance through the left tunnel (1). The other path passes through the left tunnel (1), the first transverse passage (12) and the central guide tunnel (2) in sequence, and enters the working face (8) of the central guide tunnel. The polluted air (18) is discharged to the tunnel entrance through the central guide tunnel (2).

2. The method for vertical shaft ventilation in the construction of ultra-long tunnels according to claim 1, characterized in that, The calculation method for fan parameters in vertical shaft ventilation systems includes the following steps: [1] Based on the air supply path and required air volume parameters at the tunnel face during tunnel construction, the required air pressure at the tunnel air supply outlet where the fan is located is calculated. [2] The natural wind pressure at the tunnel air supply outlet of the shaft is calculated based on the elevation of the shaft and the atmospheric pressure. [3] Based on the calculated required air pressure at the air outlet and the natural air pressure at the air outlet of the shaft in the tunnel, the required air pressure value to be supplied by the fan is obtained, and the corresponding fan parameters are set.

3. The method for vertical shaft ventilation during the construction of ultra-long tunnels according to claim 2, characterized in that: The formula for calculating the natural wind pressure at the tunnel ventilation outlet of the vertical shaft is: ； In the formula This refers to the natural wind pressure at the tunnel ventilation outlet of the vertical shaft. The air pressure at an altitude of H is in Pa; The air pressure at the local weather station, in Pa; For pressure gradient, ; This represents the pressure-altitude difference between a location at altitude H and the local weather station. The molar mass of air; It is the acceleration due to gravity. R is a constant, approximately 8.3144; T is the absolute temperature. The height difference is in meters (m).

4. The method for vertical shaft ventilation in the construction of ultra-long tunnels according to claim 2, characterized in that, The calculation steps for the required air pressure at the tunnel air supply outlet where the fan is located are as follows: 【1.1】Measure the length of the ventilation ducts inside the tunnel respectively. Shaft bottom air pressure And calculate the laminar flow resistance in the duct. Turbulent resistance Local resistance ; ； ； ； Laminar frictional resistance ; Darcy's coefficient is dimensionless. The length of the ventilation duct is in meters (m). The diameter of the ventilation duct is in meters (m). For fluid density, ; The average wind speed in the ventilation duct. ; Q This refers to the airflow rate through the duct. ; This is the local drag coefficient; F The cross-sectional area of ​​the ventilation duct is in meters. 2 ; 【1.2】Based on the required fresh air volume Q during tunnel construction, combined with the cross-sectional area of ​​the ventilation duct. F Calculate the required supply air pressure P: Air outlet wind speed ； Air pressure at the air outlet ； The required air pressure P at the tunnel air outlet where the fan is located: ； In the formula The air pressure at the air outlet of the duct is measured in Pa.

5. The method for vertical shaft ventilation during the construction of ultra-long tunnels according to claim 2, characterized in that: The required air pressure for the fan is ； in This refers to the natural wind pressure inside the tunnel.

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