Calculation method of compensation air volume parameter of natural ventilation during multi-face tunnel construction period

Abstract

The application provides a kind of compensation air volume parameter calculation method of multi-working face tunnel construction period natural ventilation, comprising: the calculation of natural wind pressure under the condition of natural ventilation of multi-working face tunnel construction period shaft, the calculation of each working face required air volume and the calculation of total required air volume of multi-working face, the determination of each branch air volume through ventilation network solution, the direction of air flow in the complex construction ventilation of long and large tunnel with shaft is clarified, the required compensation air volume of mechanical ventilation is obtained, so as to install corresponding fan in the tunnel to realize the compensation of mechanical ventilation to natural ventilation under the condition of multi-shaft during tunnel construction period, thereby solving the problem of serious energy waste caused by considering natural wind as ventilation resistance in the existing tunnel construction ventilation process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of tunnel construction ventilation in civil engineering, and particularly relates to a method for calculating compensation air volume parameters of natural ventilation in multi-working-face tunnel construction period. BACKGROUND

[0002] Under the background of western development, China's transportation construction is constantly flowing into Sichuan, Tibet, Xinjiang and other places. Compared with the plain areas in the east, these western regions have complex terrain and numerous highland valleys, which brings great challenges to transportation construction. The traditional method of building bridges by cutting mountains is not only extremely difficult to construct but also costly, and tunnel engineering is undoubtedly the best choice for crossing mountains. During tunnel construction, tunnel construction ventilation is undoubtedly a "lifeline" and a "safety belt" for engineering construction, especially in the construction of long tunnels in high-cold and high-altitude areas. Due to the low oxygen content and poor ventilation effect in high-altitude areas, it brings great challenges to tunnel construction ventilation. Good construction ventilation not only ensures the health of construction personnel but also determines the length of tunnel construction and auxiliary tunnel construction. China has a vast territory, and the current transportation construction often needs to pass through mountains and ridges. The degree of mechanization is not high, and the most commonly used is the traditional drilling and blasting method and TBM construction method. A large amount of smoke and polluted gas is generated during construction, especially when explosives are used in drilling and blasting method, which will form harmful gases such as carbon monoxide, sulfur dioxide, and nitrogen oxides. If these polluted gases cannot be quickly and effectively discharged from the tunnel, it will seriously affect the health of construction personnel. Nowadays, tunnels are getting longer and longer, and the construction altitude is getting higher and higher, which makes the originally difficult construction ventilation more severe and brings greater challenges to the construction of long tunnels in high-cold and high-altitude areas.

[0003] Therefore, long tunnels often have many problems in the construction ventilation link, such as: tunnel construction ventilation usually designs the ventilation scheme according to the method of general plain tunnels, considering or not considering natural wind as ventilation resistance, which will lead to serious energy waste, and lack of effective use of natural wind in construction ventilation; the ventilation shaft plays a crucial role in construction ventilation. In the construction ventilation process of long tunnels with vertical shafts, the natural ventilation function of the vertical shaft is not effectively utilized, mainly relying on mechanical ventilation, without combining mechanical ventilation with natural ventilation. Therefore, a method for calculating compensation air volume parameters of natural ventilation in multi-working-face tunnel construction period is needed to combine mechanical ventilation with natural ventilation in tunnel construction period, which greatly reduces energy waste. SUMMARY

[0004] The present application aims to provide a kind of multi-working face tunnel construction period natural ventilation compensation air volume parameter calculation method, can significantly reduce energy waste, and solve the air volume of each branch in complex ventilation network, combine mechanical ventilation and natural ventilation together, instead of considering or not considering natural wind as ventilation resistance, avoid energy waste.

[0005] The technical solutions of the present application are as follows:

[0006] A kind of multi-working face tunnel construction period natural ventilation compensation air volume parameter calculation method, characterized in that, it includes the following steps:

[0007] Step 1: determine the tunnel site meteorological condition by field measurement, so that the superatmospheric pressure difference Δp between each section is calculated 超 , thermal head difference Δp 热 , wind wall pressure difference Δp 墙 , so that the total natural wind pressure of all vertical shafts is obtained;

[0008] Step 2: establish tunnel ventilation network diagram and mathematical model, and use Scott-Hinsley to solve complex ventilation network, obtain the ventilation volume of each ventilation branch of tunnel, and the ventilation vertical shaft is one of the ventilation branches, so that the vertical shaft air supply / exhaust volume is obtained;

[0009] Step 3: single face air requirement calculation under each condition, so as to determine the total air requirement of multi-working face construction face according to the site construction condition;

[0010] Step 4: the air supply / exhaust volume of vertical shaft obtained by solving the above steps and the calculated air requirement can be used to calculate the air volume and air pressure that need to be compensated by mechanical ventilation;

[0011] Step 5: control the parameters of fan according to the calculated compensation air volume;

[0012] In the above multi-working face tunnel construction period natural ventilation compensation air volume parameter calculation method, the tunnel site meteorological monitoring in step 1 obtains the hole temperature T0;The atmospheric pressure p1, p3 at the hole and vertical shaft, the air temperature T1, T3, the atmospheric natural wind speed v1, v3 outside the hole and vertical shaft, so that the density ρ of each node can be calculated i ;

[0013] The superatmospheric pressure difference between tunnel entrance and tunnel vertical shaft under single vertical shaft condition:

[0014] Δp 超 =p1-p3-ρ0gH 3-1

[0015] Where, Δp 超is the overpressure difference between the tunnel entrance and the shaft entrance, ρ0 is the average density of air outside the tunnel, g is the acceleration of gravity in the region, H 3-1 is the height difference between points 3 and 1.

[0016] Thermal head difference between the tunnel entrance and the shaft of the tunnel under single-shaft condition

[0017]

[0018] where Δp 热 represents the thermal head difference between the tunnel entrance and the shaft entrance; H 3-1 is the height difference between points 3 and 1; ρ0, ρ1, ρ3 are the air densities inside the tunnel, at the tunnel entrance and at the shaft entrance;

[0019] Wind wall pressure difference between the tunnel entrance and the shaft of the tunnel under single-shaft condition:

[0020] Δp 墙 = 0.35 · [ρ1(v1·cosα1) 2 - ρ3(v3·cosα3) 2 ]

[0021] where v1, v3 are the natural wind speeds outside the tunnel entrance and the shaft entrance, and α1, α3 are the angles between the natural wind direction and the tunnel center line at the tunnel entrance and the shaft entrance;

[0022] Comprehensive pressure difference Δp 总i between the tunnel entrance and the shaft of the tunnel under single-shaft condition:

[0023] Δp 总i = Δp 超i + Δp 热i + Δp 墙i

[0024] Total wind pressure of all shafts

[0025] where Δp sum is the sum of the natural wind pressures of all shafts, and n is the number of shafts.

[0026] In the above method for calculating the compensation air volume parameters of natural ventilation during the construction period of a multi-working-face tunnel, step 2: a tunnel ventilation network diagram and a mathematical model are established, and Scott-Hinsley is used to solve a complex ventilation network. For a ventilation network with m nodes and n branches, a set of independent loop air volumes is selected as M y1 , y2 , y1 , yb b = n - m + 1. Taking M y as a variable, a nonlinear equation group can be obtained from the pressure balance equations of each independent loop.

[0027]

[0028] Wherein, fi is the i-th ventilation circuit equation; Rmj is the j-branch wind resistance, Mys is the wind volume of the loop residual chord, s = 1 ~ b; Cij is the i-th row and j-th column element of the loop matrix; Csj is the s-th row and j-th column element of the loop matrix; Pj self is the natural wind pressure of the j-branch; Pj wind is the pressure provided by the j-branch fan; because there are b equations in the formula, which contains b unknowns (My1, My2, …, Myb), which means that the equation has a definite solution.

[0029] The equation is expanded by Taylor series using the approximate value of the set of roots of the equation, the wind volume correction value calculation formula is obtained by simplifying, the approximate true value of the wind volume is obtained by successive iteration calculation and based on the natural wind pressure of the shaft calculated in step 1, and the ventilation volume of each ventilation branch of the tunnel is solved, the ventilation shaft is one of the ventilation branches, so that the shaft supply / exhaust air volume is obtained;

[0030] In the above-mentioned method for calculating the compensation air volume parameters of natural ventilation of the multi-working-face tunnel during construction period, step 3: calculating the required air volume of each working face, the air volume is calculated according to the maximum number of people working in the tunnel at the same time, the maximum amount of explosives blasting at the same time, the minimum air speed for smoke exhaust after tunnel blasting, and the amount of toxic and harmful gas emission;

[0031] The air volume Q1 is calculated according to the maximum number of people working in the tunnel at the same time:

[0032] Q1 = kmq

[0033] Wherein, k is the air volume standby coefficient, Q1 is the required air volume according to the maximum number of people working in the tunnel at the same time, m is the maximum number of people working in the tunnel at the same time, and q is the amount of fresh air required by each person in the tunnel per minute;

[0034] The air volume calculated according to the maximum amount of explosives blasting at the same time is divided into pressure-in type ventilation and mixed type ventilation, the difference is that the value of L in the formula is different, and the air volume Q2 calculated according to the maximum amount of explosives blasting at the same time:

[0035]

[0036] Wherein, A is the amount of explosives blasting at the same time, S is the cross-sectional area of the tunnel, t is the ventilation time after blasting, L is the length of ventilation improvement required after blasting when the construction ventilation is pressure-in type ventilation; L is the distance from the pressure-in air inlet to the working face when the construction ventilation is mixed type ventilation;

[0037] The air volume Q3 is calculated according to the minimum air speed for smoke exhaust after tunnel blasting:

[0038] Q3 = 60 × v × S

[0039] Wherein, v is the minimum wind speed of hole internal explosion smoke exhaust.

[0040] The air volume Q4 is calculated according to the amount of toxic and harmful gas emission:

[0041]

[0042] Wherein, t is the ventilation time, L1 is the distance between the air pipe and the tunnel face, L2 is the ventilation length, S is the tunnel cross-sectional area, C0 is the initial concentration of harmful gas, C max is the maximum allowable concentration of harmful gas.

[0043] After calculating the required air volume of a single tunnel face, the required air volume of all tunnel faces is summed up to calculate the total required air volume Q req .

[0044] In the above-mentioned method for calculating the compensation air volume parameters of natural ventilation of multi-working-face tunnel construction period, step 4: the theoretical air volume Q p / s of each branch when the vertical shaft is used for air supply and exhaust is obtained respectively by using the Scott-Hinsley method to theoretically solve the ventilation volume of each branch under the vertical shaft natural exhaust mode, and α% of the unit time air supply / exhaust volume of the vertical shaft is taken as the effective fresh air / polluted air supply / exhaust efficiency.

[0045] Then the theoretical air volume Q sup compensated by the natural ventilation of the tunnel mechanical ventilation when the vertical shaft is naturally ventilated is:

[0046] Q sup = Q req - α% Q p / s

[0047] According to the total air volume required by the tunnel, the theoretical value of the compensation air pressure when the vertical shaft is naturally exhausted / supplied can be calculated, and the mechanical air pressure compensation can be performed by installing a fan in the main hole or the vertical shaft.

[0048] The relationship between pressure and wind speed is:

[0049]

[0050] The compensation air pressure from the fan in the main hole is calculated as:

[0051]

[0052] Wherein, P sup is the theoretical value of the compensation air pressure required when the vertical shaft is naturally ventilated, P p / s is the theoretical air pressure when the vertical shaft is supplied or exhausted, P req is the required air pressure of the tunnel face, ρ is the air density, and v req is the total required air speed of the tunnel face, The average natural wind speed in the tunnel when the vertical shaft is naturally ventilated;

[0053] The compensation wind pressure from the fan in the vertical shaft needs to consider the efficiency of the vertical shaft exhaust and supply air, and the required compensation wind pressure of the vertical shaft when the vertical shaft is exhausted is:

[0054]

[0055] The total required wind speed v of the tunnel face req is:

[0056]

[0057] The natural wind speed in the tunnel when the vertical shaft is naturally ventilated:

[0058]

[0059] Wherein, S is the area of the tunnel section.

[0060] According to the calculated required compensation mechanical wind pressure and the selected jet fan parameters, the number of fans is optimized.

[0061]

[0062] Wherein, n 射 is the number of jet fans required to be increased in the main hole, P 射 is the pressure of a single jet fan; and the obtained n 射 is the number of jet fans required to be increased in the main hole.

[0063] The present application provides a kind of compensation air volume parameter calculation method of natural ventilation of multi-working face tunnel construction period, and the air volume distributed in each branch in complex ventilation network is solved by Scott-Hinsley method, avoid the problem that the gathering of pollutants in tunnel internal and the problem that pollutants cannot be quickly and effectively discharged caused by not considering the continuous change of natural wind in mechanical ventilation process. Simultaneously based on the branch air volume parameters obtained by calculation, mechanical ventilation compensation natural ventilation is realized under the condition of single vertical shaft in tunnel construction period by installing fan in tunnel, effectively combines natural ventilation and mechanical ventilation, thereby solve the energy waste problem caused by ignoring natural wind or considering natural wind as ventilation resistance in tunnel construction ventilation process. DETAILED DESCRIPTION

[0064] Figure 1 is the flow chart of the present application;

[0065] Figure 2 is the schematic diagram of face, vertical shaft ventilation branch and other branches;

[0066] Figure 3The schematic diagram of natural wind pressure flow for single vertical shaft;

[0067] Figure 4 The ventilation diagram for multiple working faces

[0068] Figure 5 The tunnel construction ventilation network diagram when the vertical shaft exhausts air in the embodiment of the application;

[0069] Figure 6 The tunnel construction ventilation network diagram when the vertical shaft supplies air in the embodiment of the application;

[0070] Figure 7 The single ventilation network loop diagram in the embodiment of the application;

[0071] Figure 8 The independent loop matrix C of the vertical shaft exhaust ventilation network p ;

[0072] Figure 9 The independent loop matrix C of the vertical shaft supply ventilation network s . DETAILED DESCRIPTION

[0073] The implementation scheme of the application is introduced below by taking the Tianshan Victory Tunnel as an example.

[0074] As shown in Figures 1 to 4 , the embodiment is a high-altitude super-long highway tunnel, and a "2 main holes + service tunnel" simultaneous construction method is used during construction, and a calculation flowchart of the wind pressure and air volume required for mechanical wind compensation of natural wind is calculated. The construction ventilation uses the "vertical shaft + main hole + service tunnel" mode for ventilation. This ventilation mode has the problems of great ventilation difficulty, fuzzy ventilation organization and unclear ventilation network, which brings severe challenges to the construction ventilation.

[0075] The specific scheme of the application is as follows:

[0076] Step 1: Perform tunnel site meteorological monitoring to obtain the air temperature T0 in the hole, the atmospheric pressures p1 and p3 at the hole and the vertical shaft, the air temperatures T1 and T3, and the natural wind speeds v1 and v3 outside the hole and the vertical shaft.

[0077] The density of each point ρ m :

[0078]

[0079] Among them, ρ m is the density of each node, p m is the atmospheric pressure at each node, and T m is the temperature at each node.

[0080] The excess static pressure difference between the tunnel entrance and the tunnel vertical shaft under the condition of a single vertical shaft:

[0081] Δp 超 =p1-p3-ρ0gH 3-1

[0082] Where, Δp 超 The static pressure difference between the tunnel entrance and the shaft opening is given by ρ0, where ρ is the average density of air outside the tunnel, g is the gravitational acceleration in that region, and H is the static pressure difference between the tunnel entrance and the shaft opening. 3-1 The difference in elevation between points 3 and 1.

[0083] Thermal potential difference Δp between tunnel entrance and tunnel shaft under single shaft conditions 热 :

[0084]

[0085] Where, Δp 热 H represents the thermal potential difference between the opening and the shaft opening; 3-1 ρ0, ρ1, and ρ3 represent the elevation difference between points 3 and 1; ρ0, ρ1, and ρ3 represent the air density inside the tunnel, at the tunnel entrance, and at the shaft opening, respectively.

[0086] Pressure difference between the tunnel entrance and the tunnel shaft under single shaft conditions:

[0087] Δp 墙 =0.35·[ρ1(v1·cosα1) 2 -ρ3(v3·cosα3) 2 ]

[0088] Where v1 and v3 are the natural wind speeds outside the tunnel entrance and shaft opening, and α1 and α3 are the angles between the natural wind direction at the tunnel entrance and shaft opening and the tunnel centerline.

[0089] Therefore, the overall pressure difference Δp 总 :

[0090] Δp 总 =Δp 超 +Δp 热 +Δp 墙

[0091] The tunnel exit section is still closed and not yet completed. Ventilation monitoring revealed that the wind direction at the tunnel entrance is mostly perpendicular to the tunnel's orientation. Furthermore, due to the ongoing construction, buildings obstruct the entrance, making it difficult for natural wind to enter the tunnel. Therefore, Δp can be considered... 墙 =0, the natural wind inside the cave is mainly caused by the excess static pressure difference and thermal potential difference.

[0092] Step 2: Now analyze the ventilation network in this mode, establish the mathematical model of the ventilation network, and draw the ventilation network during construction according to the construction ventilation conditions of the tunnel site. Correctly label the serial number, direction, nodes, and related attributes of each branch. And combine with the actual calculation requirements to simplify and merge the ventilation network reasonably, reduce the calculation amount, and improve the calculation speed. According to the actual situation, draw the ventilation network diagram and mathematical model of the vertical shaft exhaust and supply air.

[0093] (1) Tunnel ventilation resistance calculation model

[0094] The tunnel construction period ventilation resistance can be divided into two types, one is the along-the-way resistance loss, that is, the along-the-way resistance; the other is the local resistance loss, that is, the local resistance. The along-the-way resistance loss h fj and the local resistance loss h ξj of the branch in the ventilation network diagram can be calculated as follows:

[0095]

[0096] Where, M j is the mass flow of j branch, p j is the air density of j branch, l is the tunnel wall friction loss coefficient, v r is the tunnel wind speed, A r is the tunnel cross-sectional area, D r is the equivalent diameter of the tunnel cross section, L j is the length of j branch, and R mj is the along-the-way loss wind resistance of the branch.

[0097]

[0098] ξ is the local loss coefficient of the tunnel, and R mξ is the local loss wind resistance of the branch.

[0099] As mentioned above, the branch ventilation resistance h

[0100]

[0101] (2) Calculation model of jet (axial) flow fan pressure

[0102] Calculate the wind pressure of jet flow fan and axial flow fan. According to the current "Highway Tunnel Ventilation Design Details" (JTGT D70 / 2-02-2014), the pressure P 射 of a single jet flow fan:

[0103]

[0104] Where, P 射 is the pressure of jet flow fan, v sV is the outlet air speed of the jet fan r A is the air speed in the tunnel s A is the outlet area of the jet fan r M is the cross-sectional area of the tunnel s M is the outlet mass flow of the jet fan r M is the cross-sectional flow of the tunnel η is the position friction loss reduction coefficient of the jet fan, which can be taken as 0.85-0.91.

[0105] In the jth ventilation branch of the ventilation network diagram during the tunnel construction period, the total pressure boosting of k jet fans P j射 :

[0106]

[0107] The air pressure of the axial flow fan is used to overcome the resistance of the air flow through the air pipe along the path, which is the sum of the resistance along the path and the local resistance of the air pipe. Therefore, the air pressure of the axial flow fan needs to satisfy P 风机 ≥P 沿程阻力 +P 局部阻力 P 动力 .

[0108]

[0109] Wherein, ρ is the air density, v is the outlet speed of the last section pipe, d is the diameter of the air pipe, β is the air leakage rate, L is the ventilation length of the main hole tunnel, Q0 is the required air volume of the main hole construction, ξ is the local resistance coefficient, v r is the air speed in the pipe.

[0110] The ventilation network diagram of the tunnel construction is respectively established when the vertical shaft is used for air supply and air exhaust, Figure 5 is the ventilation network diagram when the vertical shaft is used for air exhaust, Figure 6 is the ventilation network diagram when the vertical shaft is used for air supply, and then the air pressure balance equation of each loop is established, for example, the axial flow fan is installed on the branch 13 in the embodiment, so the ventilation network loop diagram thereof is as shown in Figure 7 The air pressure balance equation thereof is

[0111] R m21 M 21 |M 21 |-R m36 M 36 |M 36 |-R m13 M 13 |M 13 |+R m35 M 35 |M 35 |+P 13风 =0

[0112] The air flow of each node in the ventilation network diagram during the tunnel construction period follows the law of conservation of mass, so the air flow into each node is equal to the air flow out of it, for example Figure 5 Node 2 in

[0113] M2+M 24 =M1

[0114] The air velocity v j in each branch:

[0115]

[0116] The Scott-Hinsley method is used to solve complex ventilation networks. For a ventilation network with m nodes and n branches, a set of independent loop air flows is selected as the air flows of the remaining tree branches, denoted as M y1 , M y2 , …, M yb , and b = n-m+1. Taking M y as the variable, the nonlinear equation set can be obtained from the air pressure balance equation of each independent loop:

[0117]

[0118] where R mj is the air resistance of branch j, M j is the air flow of branch j, and M y1 , M y2 , …, M yb are the air flows of the remaining tree branches. Because there are b equations in the equation set, and there are b unknowns (M y1 , M y2 , …, M yb ) in the equations, it means that the equation set has a definite solution.

[0119] Suppose that the ventilation network air pressure nonlinear equation set is solved after k iterations, and the approximate air flow value of the kth iteration is:

[0120]

[0121] The ventilation network air pressure nonlinear equation set can be expanded using the Taylor formula to obtain:

[0122]

[0123] where ΔM is the kth iteration air flow correction value of loop i.

[0124] Neglecting the high-order infinitesimal of the second order and above in the expanded equation, the k+1th linearized approximation equation is:

[0125]

[0126] Write it as a matrix form:

[0127]

[0128] To simplify the calculation, make the following assumptions for the above formula:

[0129]

[0130] That is, assume that the coefficient matrix of the formula (the first derivative matrix, called the Jacobi matrix) has a dominant diagonal line. Neglect the same order of small quantities, that is, neglect each item on the non-diagonal line in the matrix formula, then the matrix formula becomes:

[0131]

[0132] The above formula can be written as:

[0133]

[0134] That is:

[0135]

[0136] Where, is the partial derivative of the i-th equation with respect to the i-th residual tree branch air volume.

[0137] Let the nodes of the ventilation network diagram be n, the branches be m, and the number of independent loops be m-n+1=x. The correction formula for the i-th independent loop air volume of the ventilation network can be obtained:

[0138]

[0139] Because:

[0140]

[0141] We can get:

[0142]

[0143] Where, C sj is the element in the s-th row and j-th column of the loop matrix, M ys is the residual tree branch air volume column vector.

[0144] For

[0145]

[0146] Taking the derivative gives:

[0147]

[0148] Because the size of the branch natural wind pressure in the ventilation network is independent of the branch air volume, it can be known that in the above formula:

[0149]

[0150] Also:

[0151]

[0152] Since s = i, the derivative of yi is not zero.

[0153] Also:

[0154]

[0155] Also from equation

[0156]

[0157] We can get:

[0158]

[0159] Therefore:

[0160]

[0161] Thus we get:

[0162]

[0163] In the above equation is the slope of the equation of the fan pressure in the loop with respect to the air volume at point , which is negative when the fan is working normally. The fan pressure can be represented by a quadratic equation or a characteristic curve of the fan. Since the axial flow fan and the jet flow fan inside the tunnel are generally set to a constant value during the construction period, we have:

[0164]

[0165] Therefore, the above equation can be written as:

[0166]

[0167] The above equation is the calculation formula of the independent loop air volume correction value ΔM y in the tunnel shaft natural ventilation network. The numerator is the pressure imbalance value when the progressive air volume M y flows through the independent loop. When the value of ΔM y is zero, the branch air volume does not need to be corrected, which is the true air volume.

[0168] For each independent loop in the ventilation network, a set of air volume correction values ΔM y(i = 1, 2,..., x), the air flow of each branch of the wind network after the kth and (k+1)th iteration can be obtained from equation (2.74):

[0169]

[0170] The difference between the two is:

[0171]

[0172] Thus, the approximate air flow of each branch of the wind network after the (k+1)th iteration is obtained

[0173]

[0174] Repeat

[0175]

[0176] Until the correction value of the air flow of each independent loop is less than the predetermined precision ε, i.e.:

[0177] max | ΔM yi | < ε (i = 1, 2,..., x)

[0178] When the above equation is satisfied, the air flow of each branch obtained from

[0179]

[0180] is the approximate natural air distribution value of the natural ventilation of the vertical shaft of the Tianshan Victory Tunnel.

[0181] According to the remaining tree branches in the exhaust ventilation network of the vertical shaft and the above equation, the independent loop matrix Cp of the ventilation network is listed. Since there are 16 independent loops and 42 branches in the ventilation network, the matrix is 16 rows

[0182] × 42 columns, as shown in the attached Figure 8 .

[0183] It is known that the ventilation network of the natural exhaust mode of the vertical shaft has 16 remaining tree branches, which are 1, 2, 3, 4, 5, 6, 7, 16, 17, 18, 19, 20, 21, 22, 23, and 39. The remaining tree branch vector is:

[0184] M yi = (M y1 , M y2 , M y3 , M y4 , M y5 , M y6 , M y7 , M y16 , M y17 , My18 M y19 M y20 M y21 M y22 M y23 M y39 As can be seen, each branch can be represented by a branch of the tree; therefore, calculate M. yi ×C p We can obtain:

[0185]

[0186] The theoretical air volume solution for branch 39 is obtained as 250.04761 kg / s, or 15160.7 m³. 3 / min, theoretical wind speed is

[0187] 5.83664 m / s. Since branch 39 is the actual vertical shaft in the tunnel, and the air discharged from this shaft mainly comes from two parts: polluted air flowing out of the tunnel and natural air entering from the tunnel entrance, based on the on-site measurement results and to meet the safety requirements of construction ventilation calculations, 50% of the shaft's exhaust volume per unit time is taken as its polluted air discharge efficiency, i.e., the effective rate of polluted air discharged from the shaft is 7580.35 m / s.

[0188] m 3 / min.

[0189] The number of branches and nodes in the ventilation network under the natural air supply mode of the vertical shaft is different from that under the natural exhaust mode of the vertical shaft.

[0190] Similarly, Cs has 16 independent loops and 42 branches, so the matrix is ​​16 rows × 42 columns, as shown in the attached diagram. Figure 9

[0191] As shown.

[0192] Given that the ventilation network of the natural air supply mode in the vertical shaft has 16 secondary branches, namely 1, 2, 3, 4, 5, 6, 7, 16, 17, 18, 19, 20, 21, 22, 23, and 39, the vector of the secondary branches is:

[0193] M yi =(M y1 M y2 M y3 M y4 M y5 M y6 M y7 M y16 M y17 M y18 M y19 M y20 M y21M y22 ,M y23 ,M y39 ) can be expressed by the surplus tree branch, so the M yi ×C s can be obtained:

[0194]

[0195] The theoretical air flow of the branch 39 is 243.23332 kg / s, i.e. 14750.4 m 3 / min, and the theoretical air speed is

[0196] 5.67758 m / s. The branch 39 in the ventilation network represents a vertical shaft of the tunnel. When air is supplied, it enters the inside of the tunnel and is divided into two parts, one of which enters the inside of the tunnel, and the other directly exhausts out of the tunnel through the right hole of the tunnel. According to the on-site measurement results and in order to meet the requirements of safety of construction ventilation calculation, 50% of the exhaust air quantity of the vertical shaft per unit time is taken as the efficiency of the air supply, i.e. the effective rate of the air supply of the vertical shaft is 7375.2 m 3 / min.

[0197] Step 3: Calculate the air quantity required by each working face. The air quantity is calculated according to the maximum number of people working simultaneously in the hole, the maximum explosive for simultaneous blasting, the minimum air speed for tunnel blasting smoke exhaust, and the outflow of toxic and harmful gases.

[0198] The air quantity Q1 is calculated according to the maximum number of people working simultaneously in the hole:

[0199] Q1 = kmq

[0200] wherein k is a ventilation reserve coefficient, Q1 is the air quantity required according to the maximum number of people working simultaneously in the hole, m is the maximum number of people working simultaneously in the hole, and q is the amount of fresh air required by each person in the hole per minute.

[0201] The air quantity calculated according to the maximum explosive for simultaneous blasting is divided into pressure-in type ventilation and mixed type ventilation, the difference being that L in the formula is different. The air quantity Q2 calculated according to the maximum explosive for simultaneous blasting is:

[0202]

[0203] wherein A is the amount of explosive for simultaneous blasting, S is the cross-sectional area of the tunnel, t is the ventilation time after blasting, L1 is taken when the construction ventilation is pressure-in type ventilation, and L2 is taken when the construction ventilation is mixed type ventilation. L1 is the length of ventilation to be improved after blasting, and L2 is the distance from the pressure-in air inlet to the working face.

[0204] The air quantity Q3 calculated according to the minimum air speed for tunnel blasting smoke exhaust is:

[0205] Q3=60xv x S

[0206] Wherein, v is the minimum wind speed of the hole.

[0207] The air volume Q4 is calculated according to the amount of toxic and harmful gas emission:

[0208]

[0209] Wherein, t is the ventilation time, L1 is the distance between the air pipe and the tunnel face, L2 is the ventilation length, S is the tunnel cross-sectional area, C0 is the initial concentration of harmful gas, C max is the maximum allowable concentration of harmful gas.

[0210] Step 4: In order to ensure the safety of the tunnel construction ventilation, the maximum air volume required for the main hole drilling and blasting method construction needs to be calculated, that is, the minimum wind speed of the hole is calculated. 1980m 3 / min; and the maximum air volume required for the TBM construction of the middle guide hole is 1500m 3 / min. When the tunnel face of the main hole is only constructed by workers without blasting, slagging and large-scale mechanical work, the required air volume is 105.6m 3 / min. The required air volume of the tunnel face working at the same time is summed up to obtain the total required air volume Q req of the tunnel construction. The tunnel construction organization is according to the most working face, that is, seven working faces are constructed at the same time, and one of the tunnel faces of the left and right holes is only constructed by workers. At this time, the required air volume is calculated according to the maximum number of workers working at the same time, and the required air volume is 105.6m 3 / min; the required air volume of the main hole is 1980m 3 / min; and the required air volume of the middle guide hole is 1500m 3 / min. Therefore, the total air volume required by the tunnel is 9631.2m 3 / min.

[0211] The theoretical value of the required compensation exhaust air volume is:

[0212] Q sup =Q req -α%Q p =9631.2-50%×15160.7=2050.9m 3 / min

[0213] The relationship between pressure and wind speed is:

[0214]

[0215] In this embodiment, the main hole of the tunnel is selected to mechanically ventilate the tunnel face, and the theoretical value of the compensation air pressure when the vertical shaft is naturally ventilated is:

[0216]

[0217] The compensation air volume theoretical value required is:

[0218] Q sup = Q req - α%Q s = 9631.2 - 50% x 14750.4 = 2256 m 3 / min

[0219] The compensation air pressure theoretical value when the shaft is naturally ventilated is:

[0220]

[0221] wherein P p / s is the compensation air pressure theoretical value when the shaft is naturally ventilated, P req is the air pressure required by the working face, p is the air density, v req is the total air speed required by the working face, is the average natural air speed in the tunnel.

[0222] Step 5: According to the calculated compensation air pressure theoretical value 0.976 Pa when the shaft is naturally ventilated and the compensation air pressure theoretical value 1.061 Pa when the shaft is naturally ventilated, the working face is compensated for ventilation by installing a fan in the main hole, two jet fans with a boost pressure of 0.5 Pa are selected to be added in the main hole, so as to realize the utilization of natural wind and reduce the waste of natural resources.

Claims

1. A method for calculating the compensation air volume parameter of natural ventilation in multi-working-face tunnel construction period, characterized in that, Includes the following steps: Step 1: Based on the actual meteorological conditions measured on site, calculate the excess static pressure difference, thermal potential difference, and wind wall pressure difference generated by a single shaft, and then sum them up to obtain the total natural wind pressure generated by all shafts; Step 2: Establish a tunnel ventilation network diagram and mathematical model, and based on the natural wind pressure of the shaft calculated in Step 1, use the Scott-Hinsley solution to solve the ventilation network and calculate the ventilation volume of each ventilation branch in the tunnel. Take the ventilation shaft as one of the ventilation branches to obtain the supply / exhaust air volume of the shaft. Step 3: Calculate the required air volume for a single working face based on the on-site construction conditions, and sum them up to obtain the total required air volume for all working faces; When calculating the required air volume for each working face, the air volume is calculated based on the maximum number of people working simultaneously in the tunnel, the maximum amount of explosives blasted simultaneously, the minimum wind speed for tunnel blasting smoke exhaust, and the amount of toxic and harmful gases emitted. Air volume in terms of the maximum number of people working in the hole at the same time : wherein, is the air volume reserve factor, is the air volume required for the maximum number of persons working simultaneously in the hole, is the maximum number of persons working simultaneously in the hole, is the amount of fresh air required per person per minute in the hole; The air volume for the maximum explosive in simultaneous blasting is divided into forced ventilation and mixed ventilation, the difference is in the formula L The air volume for the maximum explosive in simultaneous blasting is divided into forced ventilation and mixed ventilation, the difference is in the formula : wherein, is the explosive quantity for simultaneous blasting, S is the cross-sectional area of the tunnel, t is the ventilation time after blasting, when the construction ventilation is the pressure ventilation, L is the length of ventilation to be improved after blasting; when the construction ventilation is the mixed ventilation, L is the distance from the pressure inlet to the working face; Calculate the air volume based on the minimum wind speed for smoke extraction during tunnel blasting. : in, v The minimum wind speed for blasting and smoke extraction inside the tunnel; Calculate air volume based on the amount of toxic and harmful gases emitted. : Where t is the ventilation time. L 1 represents the distance from the duct outlet to the working face. L 2 represents the ventilation length. S The cross-sectional area of ​​the tunnel. C 0 represents the initial concentration of harmful gases. C max This refers to the maximum permissible concentration of harmful gases. After calculating the required air volume for a single working face, considering the scenario with the most working faces on site, sum the required air volumes for all working faces to calculate the total required air volume. ; Step 4: Based on the vertical shaft supply / exhaust air volume and the calculated air demand, calculate the air volume and air pressure that the mechanical ventilation needs to compensate for; The theoretical air volume for mechanical ventilation to compensate for natural ventilation in tunnels during natural ventilation in vertical shafts. Represented as: in, Q p / s The theoretical air volume for air supply / exhaust in each branch shaft. α % represents the effective fresh air / sewage air supply and exhaust efficiency of the vertical shaft; Step 5: Optimize the number of fans based on the calculated compensation air volume; The theoretical value of the compensating wind pressure during natural ventilation / supply in the shaft can be calculated based on the total air volume required for the tunnel. Mechanical wind pressure compensation can be achieved by installing fans from the main tunnel or shaft. The relationship between pressure and wind speed is as follows: Calculation based on the wind pressure compensation from the main tunnel's ventilation fans: in, This is the theoretical value of the compensating wind pressure required for natural ventilation in a vertical shaft. air density, For the working face, wind speed is always required. The average natural wind speed inside the tunnel when the shaft is naturally ventilated. To compensate for the air pressure from the fans in the shaft, the efficiency of the shaft's exhaust and supply air needs to be considered. The required compensation air pressure for natural ventilation in the shaft is: The wind speed required at the tunnel face for: Natural wind speed inside the tunnel during shaft natural ventilation: in, S The cross-sectional area of ​​the tunnel; The number of fans is optimized based on the calculated required compensation mechanical air pressure and the selected jet fan parameters. in, n 射 The number of additional jet fans required to compensate for tunnel mechanical ventilation. The boost pressure of a single jet fan.

2. The method for calculating the compensating air volume parameters for natural ventilation during the construction of multi-face tunnels according to claim 1, characterized in that, In step 1, the temperature inside the tunnel was obtained from on-site meteorological monitoring. Atmospheric pressure at the tunnel entrance and shaft Temperature ; Natural wind speed outside the tunnel entrance and shaft opening This allows us to calculate the density of each node. ; The excess static pressure difference between the tunnel entrance and the tunnel shaft under single shaft conditions: in, The excess static pressure difference between the tunnel entrance and the shaft opening. Let be the average air density outside the tunnel, and g be the gravitational acceleration in that region. The difference in elevation between points 3 and 1; The thermal potential difference Δp between the tunnel entrance and the tunnel shaft under single-shaft conditions 热 : ； in, This indicates the thermal potential difference between the opening and the shaft opening; The difference in elevation between points 3 and 1; The air density inside the tunnel, at the entrance, and at the shaft opening; Pressure difference between the tunnel entrance and the tunnel shaft under single shaft conditions: in, The natural wind speed outside the tunnel entrance and shaft opening. The angle between the natural wind direction at the tunnel entrance and shaft opening and the tunnel centerline; The overall pressure difference between the tunnel entrance and the tunnel shaft in a single vertical shaft : Total natural wind pressure of all shafts in, This is the sum of the natural wind pressure in all vertical shafts. This refers to the number of vertical shafts.

3. The method for calculating the compensating air volume parameters for natural ventilation during the construction of multi-face tunnels according to claim 1, characterized in that, The specific steps for step 2 are as follows: [2.1] A tunnel ventilation network diagram and mathematical model were established. The Scott-Hinsley method was used to solve complex ventilation networks. For a ventilation network with m nodes and n branches, a set of cochord airflow was selected as the independent loop airflow, denoted as... , b = n - m +1; 【2.2】with As variables, a set of nonlinear equations can be obtained from the wind pressure balance equations of each independent loop: in, f i Let i be the equation for the i-th ventilation loop; R mj For the j-branch air resistance, M ys For the air volume of the loop chord, s =1~ b C ij C is the element in the i-th row and j-th column of the loop matrix; sj The first loop matrix s The element in row j; P j自 The natural wind pressure of branch j; P j风 The pressure provided to the J branch fan; 【2.3】Using the approximate value of a set of roots in the equation, the equation is expanded by Taylor series. The formula for calculating the air volume correction value is obtained by simplification. Then, through successive iterations, and based on the natural wind pressure of the shaft calculated in step 1, the approximate true value of the air volume is obtained. The ventilation volume of each ventilation branch of the tunnel is calculated. The ventilation shaft is taken as one of the ventilation branches, so the air supply / exhaust volume of the shaft is obtained.

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