A tunnel absolute gas emission calculation method and device based on a survey hole

Abstract

The present application relates to the in-situ testing technology field of railway tunnel survey, in particular to a tunnel absolute gas emission calculation method and device based on a survey hole. The present application carries out pressure ventilation on the survey hole, measures the ventilation volume and the maximum gas concentration in the return air flow near the hole, calculates the tunnel absolute gas emission according to the relationship between the survey hole and the tunnel gas emission section, so as to ensure that the tunnel absolute gas emission index is obtained in the survey stage, solves the problem that the gas emission index is difficult to obtain in the current survey stage, and brings great difficulty to accurately determine the gas work area. Thus, the tunnel gas work area grade can be accurately determined, the railway harmful gas tunnel survey quality is greatly improved, the survey cost is reduced, the survey period is saved, and the economy and rationality of the project are realized.

Description

Technical Field

[0001] This invention relates to the field of in-situ testing technology for railway tunnel exploration, and in particular to a method and apparatus for calculating the absolute gas emission rate of a tunnel based on exploration boreholes. Background Technology

[0002] Methane gas, primarily composed of methane (CH4), is a harmful gas found or released from underground strata. Excavation of tunnels and other underground projects often encounters various harmful gases that can poison people and even cause combustion and explosions, leading to serious accidents. Methane-prone work areas can be categorized based on absolute methane emission (Q). 绝 The tunnels are divided into non-gas, micro-gas, low-gas, and high-gas work areas (as shown in the table below) to determine the gas tunnel category and carry out tunnel structure protection design, construction ventilation, gas detection and monitoring.

[0003] Table of Indicators for Determining Absolute Gas Emission in Gas-Containing Work Areas

[0004]

[0005] Absolute gas emission (Q) 绝 Gas is the amount of gas emitted (or released) from coal seams, rock strata, and excavated coal (rock) bodies per unit time, expressed in meters (m). 3 / min measurement. It is generally determined during railway tunnel construction by calculating the maximum gas concentration in the return airflow based on the measured ventilation volume near the excavation face. However, it is difficult to obtain gas emission indicators in the early exploration stage, which makes it impossible to accurately determine the gas-prone area during the exploration stage, resulting in a significant risk of misjudgment and omission.

[0006] Therefore, it is necessary to propose a calculation method for determining the absolute gas emission of a tunnel during the exploration stage by utilizing the in-situ measured absolute gas emission from the exploration boreholes and based on the relationship between the exploration boreholes and the tunnel cross-section. This method aims to accurately determine the gas zone level of the tunnel in advance and reduce the impact of harmful gases on the tunnel project. Summary of the Invention

[0007] The purpose of this invention is to overcome the problem in the prior art that it is impossible to accurately determine the gas zone level in tunnels in advance, and to provide a method and device for calculating the absolute gas emission of tunnels based on exploration boreholes.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0009] A method for calculating absolute gas emission from tunnels based on exploration boreholes includes the following steps:

[0010] S1. An exploration hole is arranged on the ground at the location to be inspected in the tunnel, and the bottom of the exploration hole extends to the location of the gas bladder or gas-rich mass in the tunnel.

[0011] S2. After the exploration holes are arranged, the openings of the exploration holes are sealed, and the gas concentration inside the exploration holes is detected;

[0012] When the gas concentration is less than the preset safety threshold, the calculation of the absolute gas emission in the tunnel ends and a safety signal is output; otherwise, proceed to step S3.

[0013] S3. Forced ventilation is introduced into the exploration borehole. After the wind speed stabilizes, the ventilation volume and maximum gas concentration passing through the wind measurement section are obtained.

[0014] S4. Determine the absolute gas emission rate of the exploration borehole based on the ventilation volume and the maximum gas concentration of the wind measurement section;

[0015] S5. Calculate the absolute gas emission rate of the tunnel based on the absolute gas emission rate of the exploration borehole.

[0016] As a preferred embodiment of the present invention, when the exploration hole is arranged in step S1, the upper soil layer is isolated and sealed using a casing.

[0017] As a preferred embodiment of the present invention, the preset safety threshold in S2 is 10000ppm.

[0018] As a preferred embodiment of the present invention, S3 uses an axial flow fan or an industrial-grade blower for forced ventilation.

[0019] As a preferred embodiment of the present invention, the air outlet of the forced ventilation in S3 is less than or equal to 10m from the bottom of the exploration hole, and the wind measurement section is selected near the ground hole opening.

[0020] In a preferred embodiment of the present invention, in step S3, the ventilation volume of the wind measuring section is calculated based on the average wind speed and the area of ​​the wind measuring section, and the calculation formula is as follows:

[0021] Q 孔 =S 孔 ×ν 孔 ×60,

[0022] S 孔 =πr 2 ,

[0023] Among them, Q 孔 S represents the ventilation volume passing through the wind measurement section. 孔 ν is the area of ​​the wind measurement section. 孔 denoted as the average wind speed at the wind measurement section, and r as the borehole radius.

[0024] As a preferred embodiment of the present invention, the maximum gas concentration in S3 is the maximum value obtained by continuously detecting the gas concentration in the exploration hole several times after the wind speed stabilizes.

[0025] As a preferred embodiment of the present invention, the formula for calculating the absolute gas emission rate of the exploration borehole in step S4 is as follows:

[0026] Q 孔绝 =Q 孔 ×ω 孔 ,

[0027] Among them, Q 孔绝 For absolute gas emission, ω 孔 For the maximum gas concentration, Q 孔 The ventilation volume passing through the wind measurement section.

[0028] As a preferred embodiment of the present invention, the formula for calculating the absolute gas emission volume of the tunnel in step S5 is as follows:

[0029] Q 绝 =Q 孔绝 ·S 隧 / (S 孔 +C 孔 ·H 孔 )

[0030] In the formula: Q 绝 Q represents the absolute gas emission rate in the tunnel. 孔绝 S is the absolute gas emission rate. 隧 S represents the cross-sectional area of ​​the tunnel. 孔 C is the area of ​​the wind measurement section; 孔 H is the perimeter of the wind measurement section; 孔 The distance between the air inlet and the bottom of the hole for forced ventilation.

[0031] A device for calculating absolute gas emission from a tunnel based on a borehole includes at least one processor and a memory communicatively connected to the at least one processor; the memory stores instructions executable by the at least one processor, which, when executed by the at least one processor, enable the at least one processor to perform any of the methods described above.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] This invention utilizes forced ventilation in exploration boreholes, measuring the ventilation volume and maximum methane concentration in the return airflow near the borehole opening. Based on the relationship between the exploration borehole and the tunnel's methane emission cross-section, the absolute methane emission rate of the tunnel is calculated. This ensures that the absolute methane emission rate index is obtained during the exploration phase, solving the current problem of difficulty in obtaining methane emission rate indicators during exploration, which greatly hinders the accurate determination of methane-prone areas. Therefore, it enables accurate determination of the methane-prone area level in tunnels, significantly improving the quality of railway hazardous gas tunnel exploration, reducing exploration costs, and saving exploration time, thus achieving both economic efficiency and rationality in the project. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating a method for calculating absolute gas emission from a tunnel based on exploration boreholes, as described in Embodiment 1 of the present invention.

[0035] Figure 2 This is a schematic diagram of the detection site in the method for calculating the absolute gas emission of a tunnel based on exploration holes, as described in Embodiment 2 of the present invention.

[0036] Figure 3 This is a schematic diagram of a tunnel absolute gas emission calculation device based on an exploration borehole, which utilizes the tunnel absolute gas emission calculation method based on an exploration borehole as described in Embodiment 4 of the present invention.

[0037] Markings in the diagram: 1-Exploration hole, 2-Ventilation pipe, 3-Distance between air outlet and bottom of hole, 4-Bottom of hole, 5-Tunnel, 6-Gas measurement section, 7-Gas bag or gas-rich mass, 8-Fan, 9-Anemometer, 10-Gas detector. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to experimental examples and specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0039] Example 1

[0040] like Figure 1 As shown, a method for calculating the absolute gas emission rate in a tunnel based on exploration boreholes includes the following steps:

[0041] S1. Exploration holes are arranged on the ground at the location to be inspected in the tunnel, and the bottom of the exploration holes extends to the location of the gas bladder or gas-rich mass in the tunnel.

[0042] S2. After the exploration holes are arranged, the openings of the exploration holes are sealed, and the gas concentration inside the exploration holes is detected.

[0043] When the gas concentration is less than the preset safety threshold, the calculation of the absolute gas emission in the tunnel ends and a safety signal is output; otherwise, proceed to step S3.

[0044] S3. Forced ventilation is introduced into the exploration borehole. After the wind speed stabilizes, the ventilation volume and maximum gas concentration passing through the wind measurement section are obtained.

[0045] S4. Determine the absolute gas emission rate of the exploration borehole based on the ventilation volume and the maximum gas concentration of the wind measurement section.

[0046] S5. Calculate the absolute gas emission rate of the tunnel based on the absolute gas emission rate of the exploration borehole.

[0047] Example 2

[0048] like Figure 2 As shown, this embodiment is a specific implementation of the method for calculating the absolute gas emission of a tunnel based on exploration boreholes described in Embodiment 1, and includes the following steps:

[0049] S1. An exploration hole 1 is arranged on the ground at the location to be tested in tunnel 5, and the bottom 4 of the exploration hole 1 extends to the location of the gas bladder or gas-rich mass 7 in the tunnel.

[0050] When arranging the exploration borehole 1, the upper soil layer can also be isolated and sealed with a casing to prevent soil pore water from seeping downwards.

[0051] S2. After the exploration borehole 1 is arranged, the opening of the exploration borehole 1 is sealed, and the gas concentration inside the exploration borehole 1 is detected.

[0052] When the methane concentration is less than the preset safety threshold, the hazard of the harmful gas is low, the calculation of the absolute methane emission in the tunnel ends, and a safety signal is output; otherwise, it indicates that the hazard of the harmful gas is high, and a harmful gas test needs to be carried out, proceeding to step S3. The preset safety threshold mentioned in this embodiment is preferably 10000 ppm.

[0053] S3. Forced ventilation is introduced into the exploration borehole 1 via the fan 8. After the wind speed stabilizes, the ventilation volume and maximum gas concentration at the wind measurement section 6 are obtained. In this embodiment, forced ventilation is performed using an axial flow fan or an industrial-grade blower. Simultaneously, during forced ventilation, the distance between the air outlet of the ventilation pipe 2 and the bottom 4 of the exploration borehole 1 is less than or equal to 10m, and the wind measurement section 6 is selected near the ground opening.

[0054] The ventilation volume of the wind measuring section 6 is calculated based on the average wind speed and the area of ​​the wind measuring section 6, and the calculation formula is as follows:

[0055] Q 孔 =S 孔 ×ν 孔 ×60,

[0056] S 孔 =πr 2 ,

[0057] Among them, Q 孔 The ventilation volume passing through the wind measurement section 6; S 孔 ν is the area of ​​the wind measurement section 6. 孔The average wind speed at the wind measurement section 6 (which can be measured by an anemometer 9, such as a mechanical anemometer, electromechanical anemometer, electronic anemometer, or wind speed sensor, etc.) is r, and the borehole radius is r.

[0058] The maximum gas concentration is determined by taking the maximum value after the wind speed stabilizes and the gas concentration is continuously measured several times in the exploration hole 1 by the gas detector 10.

[0059] S4. Determine the absolute gas emission rate of borehole 1 based on the ventilation volume and the maximum gas concentration at the wind measurement section 6. The formula for calculating the absolute gas emission rate of borehole 1 is:

[0060] Q 孔绝 =Q 孔 ×ω 孔 ,

[0061] Among them, Q 孔绝 For absolute gas emission, ω 孔 For the maximum gas concentration, Q 孔 The ventilation volume is measured through the wind measurement section 6.

[0062] S5. Calculate the absolute gas emission rate of the tunnel based on the absolute gas emission rate of the exploration borehole 1.

[0063] When tunnel 5 was constructed, it passed through gas-filled chambers or high-abundance areas. The tunnel walls were supported, and the gas mainly escaped from the tunnel face. However, the rock faces of the exploration boreholes were exposed, and the gas mainly escaped from the bottom of the borehole and a certain area around it. The absolute gas emission rate Q of tunnel 5 is... 绝 Absolute gas emission Q from the exploration borehole 孔绝 The ratio is the ratio of the gas outflow section.

[0064] Q 绝 / Q 孔绝 =S 隧 / (S 孔 +C 孔 ·H 孔 )

[0065] The formula for calculating the absolute gas emission rate of the tunnel is:

[0066] Q 绝 =Q 孔绝 ·S 隧 / (S 孔 +C 孔 ·H 孔 ) = 60·S 孔 ·S 隧 ·ν 孔 ·ω 孔 / (S 孔 +C 孔 ·H 孔)

[0067] In the formula: Q 绝 Q represents the absolute gas emission rate in the tunnel. 孔绝 S is the absolute gas emission rate. 隧 S represents the cross-sectional area of ​​the tunnel. 孔 C is the area of ​​the wind measurement section 6; 孔 H is the perimeter of the wind measurement section 6; 孔 The distance 3 between the air outlet and the bottom of the hole 4 is generally taken as 2 to 5 meters.

[0068] Example 3

[0069] This embodiment is a specific application example of using the method described in this invention to test and calculate the absolute gas emission rate when a high-speed railway tunnel passes through the Xindu gas field.

[0070] A high-speed railway tunnel is located in the Sichuan Basin, passing through the Xindu Gas Field. The main industrial extraction layers in the Xindu Gas Field are the Penglaizhen Formation, Suining Formation, and Shaximiao Formation. The tunnel is constructed using the shield tunneling method, adopts a circular structure, and has a cross-sectional area of ​​S. 隧 92m 2 The tunnel's maximum burial depth is approximately 49m. To assess the hazard posed by shallow natural gas to the tunnel, field measurements were conducted during the exploration phase using a PDZ-29-109 borehole. A small axial flow fan was used, along with an SL-808A gas detector and a mechanical anemometer. The PDZ-29-109 borehole reached a depth of 59m and a diameter of 0.13m. After drilling, the ventilation duct's outlet was approximately 5m from the bottom of the borehole, with a stable wind speed. 孔 At a wind speed of 5 m / s, the methane concentrations measured at the wind measuring section were 0.45%, 0.5%, and 0.48% in three separate measurements. The maximum measured methane concentration at the wind measuring section was ω. 孔 The value is 0.5%, and the parameters are as follows:

[0071] 1. Cross-sectional area S of the wind measurement borehole 孔 =πr 2 =3.14 × 0.065 2 =0.0132(m) 2 );

[0072] 2. Perimeter C of the wind measurement section of the exploration borehole 孔 =2πr=2×3.14×0.065=0.41(m);

[0073] 3. Tunnel cross-sectional area S 隧 =92(m) 2 );

[0074] 4. Average wind speed ν at the borehole wind measurement section 孔 =5 (m / s);

[0075] 5. Measured maximum methane concentration ω at the wind measurement section of the exploration borehole 孔 =0.5%.

[0076] Q 绝 =60·S 孔 ·S 隧 ·ν 孔 ·ω 孔 / (S 孔 +C 孔 ·H 孔 )

[0077] =60×0.0132×92×5×0.005 / (0.0132+0.41×2)=2.19m 3 / min

[0078] According to the "Indicator Table for Determining Absolute Gas Emission in Gas-Conducting Areas", Q 绝 >1.5m 3 / min indicates a high-gas work area.

[0079] Example 4

[0080] like Figure 3 As shown, a device for calculating absolute tunnel gas emission based on boreholes includes at least one processor, a memory communicatively connected to the at least one processor, and at least one input / output interface communicatively connected to the at least one processor. The memory stores instructions executable by the at least one processor, which, when executed, enables the at least one processor to perform the method for calculating absolute tunnel gas emission based on boreholes as described in the foregoing embodiments. The input / output interface may include a display, keyboard, mouse, and USB interface for inputting and outputting data.

[0081] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above method embodiments. The aforementioned storage medium includes various media that can store program code, such as mobile storage devices, read-only memory (ROM), magnetic disks, or optical disks.

[0082] When the integrated units of this invention are implemented as software functional units and sold or used as independent products, they can also be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the embodiments of this invention, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, ROMs, magnetic disks, or optical disks.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating the absolute gas emission rate in tunnels based on exploration boreholes, characterized in that, Includes the following steps: S1. An exploration hole is arranged on the ground at the location to be inspected in the tunnel, and the bottom of the exploration hole extends to the location of the gas bladder or gas-rich mass in the tunnel. S2. After the exploration holes are arranged, the openings of the exploration holes are sealed, and the gas concentration inside the exploration holes is detected; When the gas concentration is less than the preset safety threshold, the calculation of the absolute gas emission in the tunnel ends and a safety signal is output; otherwise, proceed to step S3. S3. Forced ventilation is introduced into the exploration borehole. After the wind speed stabilizes, the ventilation volume and maximum gas concentration passing through the wind measurement section are obtained. S4. Determine the absolute gas emission rate of the exploration borehole based on the ventilation volume and the maximum gas concentration of the wind measurement section; S5. Calculate the absolute gas emission rate of the tunnel based on the absolute gas emission rate of the exploration borehole; The formula for calculating the absolute gas emission rate of the tunnel is as follows: Q 绝 =Q 孔绝 ·S 隧 / (S 孔 +C 孔 ·H 孔 ) In the formula: Q 绝 Q represents the absolute gas emission rate in the tunnel. 孔绝 S represents absolute gas emission; 隧 S represents the cross-sectional area of ​​the tunnel. 孔 C is the area of ​​the wind measurement section; 孔 H is the perimeter of the wind measurement section; 孔 The distance between the air outlet and the bottom of the hole for forced ventilation.

2. The method for calculating absolute gas emission from tunnels based on exploration boreholes according to claim 1, characterized in that, When the exploration hole is arranged in S1, the upper soil layer is isolated and sealed with a casing.

3. The method for calculating absolute gas emission from tunnels based on exploration boreholes according to claim 1, characterized in that, The preset safety threshold in S2 is 10000ppm.

4. The method for calculating absolute gas emission from tunnels based on exploration boreholes according to claim 1, characterized in that, The S3 uses an axial flow fan or an industrial-grade blower for forced ventilation.

5. The method for calculating absolute gas emission from tunnels based on exploration boreholes according to claim 1, characterized in that, The air outlet of the forced ventilation in S3 is less than or equal to 10m from the bottom of the exploration hole, and the wind measurement section is selected near the ground hole opening.

6. The method for calculating absolute gas emission from tunnels based on exploration boreholes according to claim 1, characterized in that, In step S3, the ventilation volume of the wind measurement section is calculated based on the average wind speed and the area of ​​the wind measurement section, and the calculation formula is as follows: Q 孔 =S 孔 ×ν 孔 ×60, S 孔 ＝πr 2 ， Among them, Q 孔 S represents the ventilation volume passing through the wind measurement section. 孔 ν is the area of ​​the wind measurement section. 孔 denoted as the average wind speed at the wind measurement section, and r as the borehole radius.

7. The method for calculating absolute gas emission from tunnels based on exploration boreholes according to claim 1, characterized in that, The maximum gas concentration mentioned in S3 is the maximum value obtained by continuously detecting the gas concentration in the exploration hole several times after the wind speed stabilizes.

8. The method for calculating absolute gas emission from tunnels based on exploration boreholes according to claim 1, characterized in that, The formula for calculating the absolute gas emission rate of the exploration borehole in S4 is as follows: Q 孔绝 =Q 孔 ×ω 孔 , Among them, Q 孔绝 For absolute gas emission, ω 孔 For the maximum gas concentration, Q 孔 The ventilation volume passing through the wind measurement section.

9. A device for calculating the absolute gas emission rate in tunnels based on exploration boreholes, characterized in that, It includes at least one processor and a memory communicatively connected to the at least one processor; The memory stores instructions that can be executed by the at least one processor to enable the at least one processor to perform the method of any one of claims 1 to 8.

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