A safe and efficient construction method for gas tunnel

Abstract

The present invention discloses a safe and efficient construction method for a gas tunnel, including the steps of blasting scheme optimization, calculation of gas outflow after blasting, gas migration law and time-space distribution characteristics, and ventilation network optimization and ventilation volume adjustment based on the above research. The present invention proposes a more accurate blasting construction scheme for the gas geological section of the tunnel, which is different from the blasting construction in the non-gas geological section, thereby making the blasting construction of the gas tunnel safer, simpler and more efficient. At the same time, the migration law of gas after blasting and its distribution characteristics in time and space are clarified, the gas accumulation area can be further clarified and targeted monitoring can be carried out, and the ventilation network optimization and dynamic adjustment can be fed back to optimize the ventilation, which provides a beneficial guarantee for the safe and efficient construction of the gas tunnel and can provide a reference for similar gas tunnel blasting construction and ventilation optimization.

Description

Technical Field

[0001] The invention relates to a safe and efficient construction method for a gas tunnel. Background Art

[0002] In recent years, my country's tunnel and underground engineering construction has developed rapidly, and the number and total mileage of tunnels have shown an increasing trend year by year. By the end of 2022, the total mileage of tunnels in my country reached 48,762 kilometers, an increase of 3,008.1 kilometers from 2021. Among them, the mileage of highway tunnels accounts for 54.93% of the total mileage of tunnels in the country; the mileage of railway tunnels accounts for 45.07% of the total mileage of tunnels in the country. In addition, there have been breakthroughs not only in the number and length of tunnels, but also in the technology and process of tunnel construction. However, gas over-limit and gas explosion accidents still occur from time to time. Good gas monitoring and emission work is an important guarantee for ensuring safe tunnel construction. Summary of the invention

[0003] In order to study the diffusion and migration characteristics and diffusion laws of gas in a gas tunnel after blasting, and then optimize the ventilation plan according to the research conclusions to achieve safe ventilation of the gas tunnel, the present invention provides a safe and efficient construction method for a gas tunnel.

[0004] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0005] A safe and efficient construction method for a gas tunnel, characterized by comprising the following steps:

[0006] (a) Optimization of blasting scheme in gas geological section;

[0007] (b) Calculation of gas outflow after explosion;

[0008] (c) gas migration patterns and time-space distribution characteristics;

[0009] (d) Ventilation network optimization and ventilation volume adjustment.

[0010] Preferably, the step (a) of optimizing the blasting scheme for the gas geological section comprises: optimizing the blasthole spacing, row spacing, hole depth, drilling angle and uncoupled charging coefficient by using an orthogonal test method on the basis of a conventional blasting scheme, so as to form a blasting scheme suitable for the gas geological section.

[0011] Preferably, the post-explosion gas outflow in step (b) is calculated according to the following formula:

[0012]

[0013] in is the absolute gas outflow in the tunnel (m 3 / min); Q is the total construction ventilation volume (m3 / min); ω is the average gas concentration (%); K is the gas outburst unevenness coefficient, which is between 1.5 and 2.0.

[0014] Preferably, the total construction ventilation volume is calculated according to the following conditions and the maximum value is selected as the control design ventilation volume:

[0015] Q = max {Q 1 ,Q 2 ,Q 3 ,Q 4} (2)

[0016] In formula (2), Q 1 Calculated based on the maximum number of people working in the cave at the same time:

[0017] Q 1 =q·k·m (3)

[0018] In formula (3), q is the fresh air required per person per minute, m 3 / min; k is the air volume reserve coefficient, k≥1; m is the maximum number of people working in the tunnel at the same time;

[0019] In formula (2), Q 2 Calculated based on blasting smoke exhaust:

[0020]

[0021] In formula (4), t is the ventilation time, which is generally 20 to 30 minutes; A is the amount of explosives used per blasting cycle, kg; S is the cross-sectional area of ​​the tunnel, m 2 ; L is the tunnel length or critical length, m; p is the air leakage coefficient, which is selected according to the performance of the wind tube and relevant specifications; b is the amount of harmful gas generated when 1 kg of explosives explodes, L / kg; k is the water spray coefficient; C is the allowable concentration of CO;

[0022] In formula (2), Q 3 Calculated based on minimum wind speed:

[0023] Q 3 =V·S·60 (5)

[0024] In formula (5), V is the minimum allowable wind speed in the tunnel, m / s; S is the cross-sectional area of ​​the tunnel, m 2 ;

[0025] In formula (2), Q 4 Calculated by internal combustion engine operation:

[0026]

[0027] In formula (6), k is the air volume per unit power of the internal combustion engine, m 3 / (min·kW); is the total power of the internal combustion equipment operating simultaneously in the tunnel (kW); N i is the rated power (kW) of each internal combustion equipment.

[0028] Preferably, the step (c) reveals the gas migration law and time-space distribution characteristics under unventilated and ventilated conditions through numerical simulation based on actual measurements.

[0029] Preferably, the numerical simulation in step (c) is performed based on the blasting scheme optimized in step (a).

[0030] Preferably, step (d) is determined comprehensively based on the conclusion of step (c) and the on-site monitoring results.

[0031] The present invention has the following beneficial effects:

[0032] (1) The present invention has clear objectives and a simple process, and effectively solves the problems of excessive disturbance of surrounding rocks by blasting, unclear gas diffusion and migration rules, and poor ventilation effect.

[0033] (2) The present invention can be used to accurately define gas accumulation blind areas, thereby achieving safe and efficient gas management.

[0034] (3) Based on the conclusions of numerical simulation research, the present invention further optimizes the ventilation network and adjusts the ventilation volume, so that the ventilation plan is more targeted and the ventilation effect is better. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a flow chart of a safe and efficient method for constructing a gas tunnel. DETAILED DESCRIPTION

[0036] In order to fully reflect the characteristics and advantages of the present invention, it is described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figure 1 As shown, a safe and efficient construction method for a gas tunnel is characterized by comprising the following steps:

[0038] (a) Optimization of blasting scheme in gas geological section;

[0039] (b) Calculation of gas outflow after explosion;

[0040] (c) gas migration patterns and time-space distribution characteristics;

[0041] (d) Ventilation network optimization and ventilation volume adjustment.

[0042] Preferably, the step (a) of optimizing the blasting scheme for the gas geological section comprises: optimizing the blasthole spacing, row spacing, hole depth, drilling angle and uncoupled charging coefficient by using an orthogonal test method on the basis of a conventional blasting scheme, so as to form a blasting scheme suitable for the gas geological section.

[0043] Preferably, the post-explosion gas emission in step (b) is calculated according to the following formula:

[0044]

[0045] in is the absolute gas outflow in the tunnel (m 3 / min); Q is the total construction ventilation volume (m 3 / min); ω is the average gas concentration (%); K is the gas outburst unevenness coefficient, which is between 1.5 and 2.0.

[0046] Preferably, the total construction ventilation volume is calculated according to the following conditions and the maximum value is selected as the control design ventilation volume:

[0047] Q = max {Q 1 ,Q 2 ,Q 3 ,Q 4} (2)

[0048] In formula (2), Q 1 Calculated based on the maximum number of people working in the cave at the same time:

[0049] Q 1 =q·k·m (3)

[0050] In formula (3), q is the fresh air required per person per minute, m 3 / min; k is the air volume reserve coefficient, k≥1; m is the maximum number of people working in the tunnel at the same time;

[0051] In formula (2), Q 2 Calculated based on blasting smoke exhaust:

[0052]

[0053] In formula (4), t is the ventilation time, which is generally 20 to 30 minutes; A is the amount of explosives used per blasting cycle, kg; S is the cross-sectional area of ​​the tunnel, m 2 ; L is the tunnel length or critical length, m; p is the air leakage coefficient, which is selected according to the performance of the wind tube and relevant specifications; b is the amount of harmful gas generated when 1 kg of explosives explodes, L / kg; k is the water spray coefficient; C is the allowable concentration of CO;

[0054] In formula (2), Q 3 Calculated based on minimum wind speed:

[0055] Q 3 =V·S·60 (5)

[0056] In formula (5), V is the minimum allowable wind speed in the tunnel, m / s; S is the cross-sectional area of ​​the tunnel, m 2 ;

[0057] In formula (2), Q 4 Calculated by internal combustion engine operation:

[0058]

[0059] In formula (6), k is the air volume per unit power of the internal combustion engine, m 3 / (min·kW); is the total power of the internal combustion equipment operating simultaneously in the tunnel (kW); N i is the rated power (kW) of each internal combustion equipment.

[0060] Preferably, the step (c) reveals the gas migration law and time-space distribution characteristics under unventilated and ventilated conditions through numerical simulation based on actual measurements.

[0061] Preferably, the numerical simulation in step (c) is performed based on the blasting scheme optimized in step (a).

[0062] Preferably, step (d) is determined comprehensively based on the conclusion of step (c) and the on-site monitoring results.

[0063] The operation flow of the present invention is: firstly, on the basis of conventional blasting scheme, a new combined detonation technology of "energy-gathering device + emulsion explosive" is used to blast the surrounding rock when blasting the gas geological section of the tunnel, so as to achieve the purpose of improving the half-hole trace rate, stabilizing the blasting footage, further controlling over-excavation and under-excavation, and reducing the disturbance range of the surrounding rock. The specific method is: using the orthogonal test method to optimize the blasthole spacing, row spacing, hole depth, drilling angle and uncoupled charge coefficient, and form a blasting scheme suitable for the gas geological section.

[0064] Secondly, a gas outburst calculation model was constructed based on the on-site monitoring gas outburst data to prepare for further numerical simulation.

[0065] Then, the gas outburst volume and required air volume were further calculated, and the obtained parameters were input into the Fluent numerical simulation software to simulate the gas flow field during tunnel blasting excavation. The gas diffusion and migration conditions and time-space distribution characteristics under post-blasting ventilation and non-ventilation conditions were studied respectively, and the areas prone to gas accumulation were preliminarily obtained, supplemented by on-site monitoring to achieve accurate delineation of gas accumulation areas.

[0066] Finally, the ventilation network is optimized and adjusted dynamically to optimize ventilation and achieve safe and efficient construction of gas tunnels.

[0067] Of course, although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Technical personnel in the relevant field should understand that on the basis of the technical solution of the present invention, various modifications or deformations that can be made by technical personnel in this field without creative work are still within the scope of protection of the present invention.

Claims

1. A safe and efficient construction method for a gas tunnel, characterized in that: The following steps are involved: Step (a), optimizing the blasting scheme for the gas geological section; optimizing the blasthole spacing, row spacing, hole depth, drilling angle and uncoupled charge coefficient by using the orthogonal test method to form a blasting scheme suitable for the gas geological section; Step (b), calculating the gas emission after explosion; constructing a gas emission calculation model based on the on-site monitoring gas emission data to prepare for further numerical simulation; The gas outflow after explosion is calculated according to the following formula: In formula (1), q CH4 is the absolute gas outflow in the tunnel, m 3 / min; Q is the total construction ventilation volume, m 3 / min; ω is the average gas concentration, %; K is the gas outflow unevenness coefficient, which is 1.5 to 2.0; The total construction ventilation volume Q is calculated according to the following conditions and the maximum value is selected as the control design ventilation volume: Q=max{Q1, Q2, Q3, Q4} (2) In formula (2), Q1 is calculated based on the maximum number of people working in the tunnel at the same time: Q1=q·k·m (3) In formula (3), q is the fresh air required per person per minute, m 3 / min; k is the air volume reserve coefficient, k≥1; m is the maximum number of people working in the tunnel at the same time; In formula (2), Q2 is calculated based on blasting smoke exhaust: In formula (4), t is the ventilation time, which is generally 20 to 30 minutes; A is the amount of explosives used per blasting cycle, kg; S is the cross-sectional area of ​​the tunnel, m 2 ; L is the tunnel length or critical length, m; p is the air leakage coefficient, which is selected according to the performance of the wind tube and relevant specifications; b is the amount of harmful gas generated when 1 kg of explosives explodes, L / kg; k is the water spray coefficient; C is the allowable concentration of CO; In formula (2), Q3 is calculated based on the minimum wind speed: Q3=V·S·60 (5) In formula (5), V is the minimum allowable wind speed in the tunnel, m / s; S is the cross-sectional area of ​​the tunnel, m 2 ; In formula (2), Q4 is calculated based on the internal combustion engine operation: In formula (6), k is the air volume per unit power of the internal combustion engine, m 3 / (min·kW); is the total power of the internal combustion equipment operating simultaneously in the tunnel, kW; N i is the rated power of each internal combustion equipment, kW; Step (c), gas migration law and time-space distribution characteristics; further calculate the gas outflow and required air volume, input the obtained parameters into Fluent numerical simulation software, simulate the gas flow field during tunnel blasting excavation, and study the gas diffusion and migration conditions and time-space distribution characteristics under the two conditions of post-blast ventilation and no ventilation, preliminarily obtain the gas easy accumulation area, and realize the accurate delineation of the gas accumulation area with the help of on-site monitoring; Step (d), ventilation network optimization and ventilation volume adjustment; feedback ventilation network optimization and dynamic adjustment, optimize ventilation, and achieve safe and efficient construction of gas tunnels; The overall operation process is as follows: first, on the basis of the conventional blasting plan, the new combined detonation technology of "energy-gathering device + emulsion explosive" is used to carry out surrounding rock blasting when blasting the gas geological section of the tunnel, so as to achieve the purpose of increasing the half-hole mark rate, stabilizing the blasting footage, further controlling over-excavation and under-excavation, and reducing the range of surrounding rock disturbance.

2. A safe and efficient gas tunnel construction method according to claim 1, characterized in that: The numerical simulation in step (c) is performed on the basis of the blasting scheme optimized in step (a).

3. A safe and efficient gas tunnel construction method according to claim 1, characterized in that: The step (d) is determined comprehensively based on the conclusion of step (c) and the on-site monitoring results.

Images