Tunnel advance drilling harmful gas detection device and method

Abstract

The application discloses a tunnel advanced drilling harmful gas detection device and method, and relates to the technical field of tunnel construction. The tunnel advanced drilling harmful gas detection device comprises a sleeve pipe; a laser monitoring module is arranged on the sleeve pipe; the laser monitoring module is used for emitting laser along the axial direction of the sleeve pipe in the sleeve pipe, and is used for distance measurement and harmful gas concentration monitoring; a shielding module is arranged on the sleeve pipe; the shielding module is used for periodically shielding the laser emitted by the laser monitoring module; a gas flow speed monitoring module is arranged on the sleeve pipe; and the gas flow speed monitoring module is used for monitoring the harmful gas flow speed in the sleeve pipe. The application can accurately detect the harmful gas concentration at the bottom of the advanced drilling hole, and provides an accurate basis for the tunnel harmful gas risk evaluation.

Description

Technical Field

[0001] This application relates to the field of tunnel construction technology, specifically to a device and method for detecting harmful gases in tunnel pre-drilling. Background Technology

[0002] During tunnel construction, harmful gases often escape or gush out from the tunnel face or unsupported tunnel walls. When the concentration of harmful gases in the tunnel reaches a certain level, it can cause a series of disasters, threaten the personal safety of workers, delay the construction period, and even cause major engineering accidents.

[0003] To reduce the risk of harmful gases during tunnel construction, advanced geological forecasting is typically used to determine the danger of harmful gases in the tunnel before the formal excavation of the tunnel face.

[0004] Existing methods for advanced detection of hazardous gases in tunnels mainly include two types: one is to place sensors at the borehole opening to detect the concentration of hazardous gases; however, this method cannot accurately detect the concentration of hazardous gases inside the borehole. The second method is to seal the borehole for 24 hours after advanced drilling, and then measure the concentration of hazardous gases inside the borehole after 24 hours; however, this method cannot determine the actual concentration of hazardous gases inside the borehole during excavation, and it has low construction efficiency, affecting the normal excavation progress of the tunnel. Summary of the Invention

[0005] The purpose of this application is to provide a device and method for detecting harmful gases in tunnel pre-drilling, so as to solve the problem of inaccurate detection of the concentration of harmful gases in pre-drilling.

[0006] The technical solution adopted by this application to solve its technical problem is:

[0007] In a first aspect, a device for detecting harmful gases in tunnel pre-drilling is provided, comprising a casing; a laser monitoring module is provided on the casing, the laser monitoring module being used to emit laser along the axial direction of the casing inside the casing and to perform ranging and monitor the concentration of harmful gases; a shielding module is provided on the casing, the shielding module being used to periodically shield the laser emitted by the laser monitoring module; and a gas flow rate monitoring module is provided on the casing, the gas flow rate monitoring module being used to monitor the flow rate of harmful gases inside the casing.

[0008] Furthermore, the laser monitoring module includes a laser gas sensor, a laser rangefinder, and a reflecting prism disposed outside the sleeve. The sleeve has a laser hole on its wall, and the reflecting prism is used to reflect the laser emitted by the laser gas sensor and the laser rangefinder through the laser hole into the sleeve and propagate along the axial direction of the sleeve.

[0009] Furthermore, the laser monitoring module also includes a monitoring box connected to the sleeve, and the laser gas sensor, the laser rangefinder, and the reflecting prism are disposed inside the monitoring box.

[0010] Furthermore, the shielding module includes a driving component disposed outside the sleeve and a shielding component connected to the driving component. The sleeve wall is provided with a clearance hole to avoid the shielding component. The driving component is used to drive the shielding component to move and periodically shield the laser within the sleeve.

[0011] Furthermore, the gas flow rate monitoring module includes a flow rate monitoring box disposed outside the sleeve and a gas flow rate sensor disposed inside the flow rate monitoring box, the flow rate monitoring box being in communication with the inner cavity of the sleeve.

[0012] Furthermore, it also includes a control module, which is connected to the laser monitoring module, the shielding module and the gas flow rate monitoring module respectively.

[0013] Furthermore, the sleeve is used to fit over the drill pipe, and the sleeve is movable along the axial direction of the drill pipe.

[0014] Furthermore, a water tank communicating with its inner cavity is provided below the sleeve; the bottom of the inner cavity of the water tank has an upwardly extending baffle plate, forming a water outlet cavity and a sampling cavity located on both sides of the baffle plate; the lower end of the water tank is provided with a water outlet pipe communicating with the water outlet cavity, and the lower end of the water tank is provided with a sampling pipe communicating with the sampling cavity.

[0015] Furthermore, the water tank has a horizontally arranged filter element located above the water-separating plate, and the water tank is provided with a slag discharge door for opening and closing the chamber above the filter element.

[0016] Secondly, a method for detecting harmful gases in tunnel pre-drilling is provided, employing the harmful gas detection equipment for tunnel pre-drilling provided in the first aspect. The method includes:

[0017] S1. Connect one end of the casing to the opening of the pre-drilled hole;

[0018] S2. The laser monitoring module emits a laser to the bottom of the pre-drilled hole to obtain the concentration of harmful gas c1 from the laser monitoring module to the bottom of the pre-drilled hole.

[0019] S3. After time t1, the shielding module shields the laser inside the sleeve, the laser monitoring module emits a laser to the shielding module, and obtains the concentration of harmful gas c2 from the laser monitoring module to the shielding module and the distance d2 from the laser monitoring module to the shielding module. The gas flow rate monitoring module monitors the flow rate v of harmful gas inside the sleeve.

[0020] S4. After time t2, the shielding module releases the laser inside the casing, and the laser monitoring module emits the laser towards the bottom of the pre-drilled hole to obtain the concentration of harmful gas c3 from the laser monitoring module to the bottom of the pre-drilled hole.

[0021] S5. Based on the data obtained in steps S2, S3, and S4, calculate the concentration of harmful gases at the bottom of the advanced borehole.

[0022] The beneficial effects of this application are:

[0023] The tunnel pre-drilling hazardous gas detection equipment and method provided in this application can accurately detect the concentration of hazardous gases at the bottom of the pre-drilled hole in real time with the drilling rig, thereby improving construction efficiency and providing an accurate basis for the assessment of the hazardous gas hazard in tunnels. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a perspective view of the tunnel pre-drilling hazardous gas detection device provided in the embodiments of this application;

[0026] Figure 2 This is a cross-sectional view of the tunnel pre-drilling hazardous gas detection device provided in the embodiments of this application;

[0027] Figure 3 This is a partial enlarged view of the tunnel pre-drilling hazardous gas detection device provided in the embodiments of this application;

[0028] Figure 4 This is a state diagram of the tunnel pre-drilling hazardous gas detection equipment provided in the embodiments of this application during detection.

[0029] Figure label:

[0030] 10-Casing;

[0031] 101 - Laser aperture; 102 - Clearance hole; 103 - Connecting hole;

[0032] 11-Laser monitoring module;

[0033] 111-Laser gas sensor; 112-Laser rangefinder sensor; 113-Reflecting prism; 114-Monitoring box; 115-Power supply;

[0034] 12-Obscuration module;

[0035] 121-Driver component; 122-Shielding component;

[0036] 13-Gas flow rate monitoring module;

[0037] 131 - Flow rate monitoring box; 132 - Gas flow rate sensor;

[0038] 14-Control Module;

[0039] 15-Drill pipe;

[0040] 16-Water tank;

[0041] 161 - Water outlet chamber; 162 - Sampling chamber;

[0042] 17-Waterproof board;

[0043] 18-Water outlet pipe;

[0044] 19-Sampling tube;

[0045] 20 - Filter element;

[0046] 21-Slag Removal Gate;

[0047] 22-Flow meter;

[0048] 23-Sampling valve;

[0049] 24-Working face;

[0050] 25-Advanced drilling;

[0051] 26-Flange assembly. Detailed Implementation

[0052] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0053] In the description of this application, the terms "upper," "lower," "left," "right," "front," "rear," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Unless otherwise specified, the above-mentioned orientational descriptions can be flexibly set in actual application, provided that the relative positional relationships shown in the accompanying drawings are satisfied.

[0054] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0055] During tunnel construction, harmful gases often escape or gush out from the tunnel face or unsupported tunnel walls. When the concentration of harmful gases in the tunnel reaches a certain level, it can cause a series of disasters, such as explosions caused by methane and hydrogen, poisoning caused by carbon monoxide, hydrogen sulfide, and sulfur dioxide, and asphyxiation caused by carbon dioxide. These threats threaten the personal safety of workers, cause delays in the construction period, and may even lead to major engineering accidents.

[0056] To reduce the risk of harmful gases during tunnel construction, advanced geological forecasting is typically used to determine the danger of harmful gases in the tunnel before the formal excavation of the tunnel face.

[0057] Existing methods for advanced detection of hazardous gases in tunnels mainly involve deploying sensors at the borehole opening to detect the concentration of hazardous gases. These sensors primarily fall into two categories: contact sensors and laser sensors based on laser absorption spectroscopy.

[0058] Because the pre-drilling depth is quite deep, with the deepest holes reaching hundreds of meters, the concentration of harmful gases emerging from the newly revealed strata at the borehole opening differs significantly from the concentration at the bottom of the borehole. This results in a large error when using contact sensors to detect the gas concentration at the borehole opening.

[0059] Although laser sensors based on laser absorption spectroscopy can solve the problem of long-distance detection of harmful gases, the concentration of harmful gases detected by these sensors is the average concentration per meter, in ppm·m. This means that even if the concentration of harmful gases at the bottom of the hole is very high, the detection result may not be high after averaging over a distance of hundreds of meters, thus making its accuracy low.

[0060] Another existing method for advanced detection of harmful gases in tunnels involves sealing the borehole for 24 hours after advanced drilling is completed, and then measuring the concentration of harmful gases inside the borehole after 24 hours. However, this method cannot measure the actual concentration of harmful gases inside the borehole during excavation, and it has low construction efficiency, which affects the normal excavation and progress of the tunnel.

[0061] Based on this, embodiments of this application provide a device and method for detecting harmful gases in tunnel pre-drilling, used to accurately detect the concentration of harmful gases at the bottom of the pre-drilled borehole, providing an accurate basis for assessing the hazard of harmful gases in tunnels. The harmful gases include, but are not limited to, methane, hydrogen, carbon monoxide, hydrogen sulfide, sulfur dioxide, and carbon dioxide.

[0062] See Figure 1 , Figure 2 , Figure 3 This application provides a tunnel pre-drilling hazardous gas detection device, including a casing 10; a laser monitoring module 11 is provided on the casing 10, which is used to emit laser along the axial direction of the casing 10 and to measure distance and monitor the concentration of hazardous gases; a shielding module 12 is provided on the casing 10, which is used to periodically shield the laser emitted by the laser monitoring module 11; and a gas flow rate monitoring module 13 is provided on the casing 10, which is used to monitor the flow rate of hazardous gases inside the casing 10.

[0063] See Figure 1 , Figure 2 The casing 10 has a closed left end and an open right end. In use, the open end of the casing 10 is connected to the opening of the pre-drilled hole 25 to guide harmful gases and groundwater from the pre-drilled hole 25 into the casing 10. Of course, the casing 10 can also have an open-end structure; this is not a limitation.

[0064] For example, the casing 10 is used to fit over the drill pipe 15, and the casing 10 is movable along the axial direction of the drill pipe 15. For instance, the casing 10 can be connected to the drill pipe 15 via a flange assembly 26 to allow the drill pipe 15 to be used for installation and support of the casing 10.

[0065] See Figure 1 , Figure 2 The laser monitoring module 11 and the shielding module 12 are arranged at intervals along the axial direction of the sleeve 10 on the sleeve 10.

[0066] The laser emitted by the laser monitoring module 11 can propagate inside the sleeve 10, and the propagation direction of the laser inside the sleeve 10 is parallel to the axis of the sleeve 10. The laser can not only be used to measure distance, but also to monitor the concentration of harmful gases based on the principle of laser absorption spectrum.

[0067] The blocking module 12 can periodically block the laser along its propagation path within the sleeve 10. That is, the blocking module 12 can periodically and regularly block the laser, so that the laser is completely blocked within a specific time interval.

[0068] A gas flow rate monitoring module 13 is installed on the sleeve 10 to monitor the flow rate of harmful gases flowing into the sleeve 10. The gas flow rate monitoring module 13 can be positioned between the laser monitoring module 11 and the shielding module 12.

[0069] The laser monitoring module 11 may include a laser gas sensor 111 and a laser rangefinder 112 disposed within the sleeve 10; the laser gas sensor 111 is used to emit laser along the axial direction of the sleeve 10 to monitor the concentration of harmful gases; the laser rangefinder 112 is used to emit laser along the axial direction of the sleeve 10 to achieve distance measurement.

[0070] See Figure 3 The laser monitoring module 11 includes a laser gas sensor 111, a laser rangefinder 112, and a reflecting prism 113 disposed outside the sleeve 10. A laser aperture 101 is provided on the wall of the sleeve 10. The reflecting prism 113 reflects the laser emitted by the laser gas sensor 111 and the laser rangefinder 112 through the laser aperture 101 into the sleeve 10, where it propagates along the axial direction of the sleeve 10. The laser gas sensor 111 is used to monitor the concentration of harmful gases, and the laser rangefinder 112 is used for distance measurement. The laser gas sensor 111 and the laser rangefinder 112 are positioned axially on the sleeve 10. Figure 3 The dashed line in the image represents the propagation path of the laser.

[0071] Correspondingly, by setting a laser gas sensor 111, a laser rangefinder 112, and a reflective prism 113 outside the casing 10, and setting a laser hole 101 on the pipe wall of the casing 10, not only is the entire laser monitoring module 11 easy to install and maintain, but it also avoids occupying the installation space inside the casing 10, prevents groundwater and debris flowing into the casing 10 during drilling from contacting the sensor and damaging it, and improves the service life of the laser monitoring module 11.

[0072] See Figure 3 The laser monitoring module 11 also includes a monitoring box 114 connected to the sleeve 10, and the laser gas sensor 111, the laser range sensor 112 and the reflecting prism 113 are installed in the monitoring box 114.

[0073] Correspondingly, the monitoring box 114 provides physical protection for the laser gas sensor 111, laser rangefinder sensor 112, and reflecting prism 113, preventing damage to the equipment from dust, moisture, vibration, and other environmental factors, thereby extending their service life. The monitoring box 114 also reduces external electromagnetic and optical interference, ensuring the measurement accuracy and stability of the sensors. Integrating all components into a single monitoring box 114 makes the entire laser monitoring module 11 more compact, facilitating installation and maintenance, and reducing the complexity and time required for on-site installation.

[0074] See Figure 3 The laser monitoring module 11 also includes a power supply 115 installed in the monitoring box 114, which is connected to the laser gas sensor 111 and the laser rangefinder 112 respectively.

[0075] Correspondingly, integrating the power supply 115 into the monitoring box 114 can reduce the complexity of external power supply lines, simplify the wiring and installation process, and avoid the wiring problems of multiple power supply lines in the external environment. The integrated power supply 115 design makes the expansion of the laser monitoring module 11 more flexible. If more sensors or other components need to be added, they can be connected and coordinated in the monitoring box 114 without rewiring and installing an external power supply.

[0076] The shielding module 12 can be installed inside the sleeve 10, and the periodic shielding of the laser can be achieved by using the flipping, moving, and rotating functions of the shielding module 12.

[0077] See Figure 3 The shielding module 12 includes a drive member 121 disposed outside the sleeve 10 and a shielding member 122 connected to the drive member 121. The sleeve 10 has a clearance hole 102 on its wall to avoid the shielding member 122. The drive member 121 is used to drive the shielding member 122 to move and periodically shield the laser within the sleeve 10. The movement of the shielding member 122 can be moving, rotating, etc., and is not specifically limited here.

[0078] For example, the driving component 121 may include a motor, and the blocking component 122 may include a blocking plate, with the output shaft of the motor connected to the blocking plate. In use, the output shaft of the motor drives the blocking plate to rotate, thereby periodically blocking the laser within the sleeve 10. The driving component 121 may also include a linear actuator, and the blocking component may include the blocking plate, with the piston rod of the linear actuator connected to the blocking plate. In use, the piston rod of the linear actuator extends and retracts to drive the blocking plate to reciprocate, thereby periodically blocking the laser within the sleeve 10.

[0079] Correspondingly, the shielding module 12 is integrated outside the sleeve 10, which not only makes the entire shielding module 12 easy to install and maintain, but also avoids occupying the installation space inside the sleeve 10.

[0080] The gas flow rate monitoring module 13 may include a gas flow rate sensor disposed within the sleeve 10. When harmful gas flows into the sleeve 10, the gas flow rate sensor is used to monitor the flow rate of the harmful gas.

[0081] See Figure 3 The gas flow rate monitoring module 13 includes a flow rate monitoring box 131 disposed outside the sleeve 10 and a gas flow rate sensor 132 disposed inside the flow rate monitoring box 131. The flow rate monitoring box 131 is connected to the inner cavity of the sleeve 10. For example, the top of the sleeve wall of the sleeve 10 is provided with a connecting hole 103, and the flow rate monitoring box 131 is connected to the inner cavity of the sleeve 10 through the connecting hole 103. The top of the flow rate monitoring box 131 may be provided with several overflow holes so that harmful gases inside the sleeve 10 can overflow from the overflow holes.

[0082] Correspondingly, the gas velocity sensor 132 can monitor the flow rate of harmful gases entering the casing 10. By placing the gas velocity sensor 132 outside the casing 10, it not only facilitates installation and maintenance but also avoids occupying installation space inside the casing 10. This prevents groundwater and debris flowing into the casing 10 during drilling from contacting the sensor and causing damage, thus extending the service life of the gas velocity sensor 132. The flow rate monitoring box 131 also provides physical protection for the gas velocity sensor 132, reducing interference from the external environment and ensuring the stability and reliability of the measurement.

[0083] In some embodiments, see Figure 1 The detection device of this application also includes a control module 14, which is connected to the laser monitoring module 11, the shielding module 12, and the gas flow rate monitoring module 13. An exemplary control module 14 may include a PLC controller, a computer, a control center, etc.

[0084] Correspondingly, the control module 14 can centrally control the laser monitoring module 11, the shielding module 12, and the gas flow rate monitoring module 13, achieving automatic control, unified management, and coordinated operation of the entire detection equipment. This simplifies operation and reduces complexity and the probability of errors. The control module 14 can also execute precise control algorithms based on sensor feedback data, achieving high-precision control. Furthermore, the control module 14 can integrate measurement data from various sensors, perform unified data processing and analysis, and generate comprehensive monitoring reports. For example, through control algorithms, it can accurately calculate the concentration of harmful gases at the bottom of the borehole and generate a hazardous gas hazard assessment report.

[0085] In some embodiments, see Figure 1 , Figure 2Below the sleeve 10, there is a water tank 16 communicating with its inner cavity; the bottom of the inner cavity of the water tank 16 has an upwardly extending baffle plate 17, forming an outlet cavity 161 and a sampling cavity 162 located on both sides of the baffle plate 17. The lower end of the water tank 16 is provided with an outlet pipe 18 communicating with the outlet cavity 161, and the lower end of the water tank 16 is provided with a sampling pipe 19 communicating with the sampling cavity 162. For example, the top of the water tank 16 is connected to the bottom of the sleeve 10, a flow meter 22 is provided on the outlet pipe 18, and a sampling valve 23 is provided on the sampling pipe 19.

[0086] Correspondingly, the water tank 16 can collect the groundwater gushing from the pre-drilled borehole. The water tank 16 is divided into an outlet chamber 161 and a sampling chamber 162 by a baffle plate 17, preventing interference between the water outlet and sampling processes. Water outlet 161 discharges directly through the outlet pipe 18, ensuring a smooth and efficient water discharge process. The flow rate of the groundwater can be measured using a flow meter 22. The sampling chamber 162 is dedicated to sampling. By opening the sampling valve 23, samples can be taken through the sampling pipe 19 for analyzing the content of soluble harmful gases in the groundwater.

[0087] See Figure 1 , Figure 2 The water tank 16 has a horizontally arranged filter element 20 located above the baffle plate 17. The water tank 16 is provided with a slag discharge door 21 for opening and closing the chamber above the filter element 20. For example, the filter element 20 can be a bar screen, filter mesh, etc.

[0088] Correspondingly, the filter element 20 can filter the drilling cuttings that enter the water tank 16 with the groundwater, preventing the drilling cuttings from entering the water outlet chamber 161 and the sampling chamber 162 and clogging the water outlet pipe 18 and the sampling pipe 19. The design of the cuttings outlet door 21 allows the chamber above the filter element 20 to be easily opened, facilitating the regular cleaning of impurities and deposits on the filter element 20, reducing maintenance time and costs.

[0089] See Figure 4 This application also provides a method for detecting harmful gases in tunnel pre-drilling, using a tunnel pre-drilling harmful gas detection device, the method comprising:

[0090] S1. Connect one end of the casing 10 to the opening of the pre-drilled hole 25.

[0091] For example, after drilling according to the advanced geological drilling design requirements, the casing 10 is fitted onto the drill pipe 15 and positioned between the working face 24 and the drilling rig. The right end of the casing 10 is connected to the opening of the advanced borehole 25, and the left end of the casing 10 is connected to the drill pipe 15 via a flange assembly 26. This allows groundwater and harmful gases from the advanced borehole 25 to be guided into the casing 10. (For simplified illustration,...) Figure 4 The structure of the drilling rig is not shown.

[0092] S2. The laser monitoring module 11 emits a laser to the bottom of the pre-drilled hole 25 to obtain the concentration of harmful gas c1 from the laser monitoring module 11 to the bottom of the pre-drilled hole 25.

[0093] For example, a laser gas sensor 111 emits a laser beam towards the bottom of the pre-drilled hole 25 to obtain the concentration of harmful gas c1 from the laser gas sensor 111 to the bottom of the pre-drilled hole 25, where c1 is in ppm·m. Alternatively, a laser rangefinder 112 can also emit a laser beam towards the bottom of the pre-drilled hole 25 to obtain the distance d1 from the laser rangefinder 112 to the bottom of the pre-drilled hole 25, where d1 is in meters.

[0094] S3. After time t1, the shielding module 12 shields the laser inside the sleeve 10. The laser monitoring module 11 emits a laser to the shielding module 12 to obtain the concentration of harmful gas c2 between the laser monitoring module 11 and the shielding module 12 and the distance d2 between the laser monitoring module 11 and the shielding module 12. The gas flow rate monitoring module 13 monitors the flow rate v of harmful gas inside the sleeve 10.

[0095] For example, after time t1, the shielding module 12 blocks the laser, preventing it from propagating to the bottom of the pre-drilled hole 25. The laser gas sensor 111 emits a laser towards the shielding module 12 to obtain the concentration of harmful gas c2 between the laser gas sensor 111 and the shielding module 12, where c2 is in ppm·m. The laser rangefinder 112 emits a laser towards the shielding module 12 to obtain the distance d2 between the laser rangefinder 112 and the shielding module 12, where d2 is in meters. The gas flow rate sensor 132 measures the flow rate v of the harmful gas inside the casing 10, where v is in m / s.

[0096] S4. After time t2, the shielding module 12 releases the laser inside the sleeve 10, and the laser monitoring module 11 emits a laser towards the bottom of the advanced drilling hole 25 to obtain the concentration of harmful gas c3 from the laser monitoring module 11 to the bottom of the advanced drilling hole 25.

[0097] For example, after time t2, the shielding module 12 is removed, allowing the laser to propagate to the bottom of the pre-drilled hole 25; the laser gas sensor 111 emits a laser to the bottom of the pre-drilled hole 25 to obtain the concentration of harmful gas c3 from the laser gas sensor 111 to the bottom of the pre-drilled hole 25, where the unit of c3 is ppm·m.

[0098] Since the blocking module 12 periodically blocks the laser, the blocking period is set to T, where the unit of T is seconds, then t = t1 + t2.

[0099] Since the harmful gas at the bottom of the pre-drilled hole 25 will flow along the borehole towards the opening, the distance d3 of the harmful gas flow within the hole during period T can be calculated by the following formula: d3 = v × T. Where d3 is in meters (m).

[0100] Because harmful gases continuously flow within the pre-drilled borehole 25, some of these gases will flow to the outside of the casing 10. The concentration of harmful gases c2 obtained by the laser gas sensor 111 from the laser monitoring module 11 to the shielding module 12 can be considered as the average concentration of harmful gases flowing out of the casing 10. Therefore, the concentration of harmful gases c4 flowing out of the casing 10 can be calculated by the following formula: c4=(c2 / d2)·d3. Wherein, the unit of c4 is ppm·m.

[0101] S5. Based on the data obtained in steps S2, S3, and S4, calculate the concentration of harmful gases at the bottom of the advanced borehole 25.

[0102] During cycle T, harmful gases are both released and replenished in the advanced borehole 25. By subtracting the harmful gas concentration obtained in step S3 from the harmful gas concentration obtained in step S1, and adding the harmful gas concentration released from the casing 10, the average concentration of harmful gases released from the newly revealed formation at the bottom of the advanced borehole 25 within a distance d3 can be obtained.

[0103] The concentration C of harmful gases emerging from the formation newly revealed at the bottom of borehole 25 can be calculated using the following formula: C = (c3 - c1 + c4) / d3 = [c3 - c1 + (vTc2 / d2)] / (vT). The unit of C is ppm.

[0104] The tunnel pre-drilling hazardous gas detection equipment and method provided in this application can accurately detect the concentration of hazardous gases at the bottom of the pre-drilled hole in real time, following the drill rod 15, and provide an accurate basis for the assessment of the hazardous gas hazard in tunnels.

[0105] Example:

[0106] Methane was discovered during the construction of a tunnel, and it is necessary to detect the methane concentration in the unconstructed sections for tunnel gas registration and hazardous gas hazard assessment.

[0107] The detection of harmful gases in tunnel pre-drilling was carried out using the tunnel pre-drilling harmful gas detection equipment provided in the embodiment of this application. The blocking period of the blocking module 12 was T = 2s. The detected data were: c1 = 200ppm·m, c2 = 100ppm·m, c3 = 220ppm·m, v = 0.1m / s, d2 = 0.2m.

[0108] The calculated concentration of methane gas emerging from the newly revealed formation at the bottom of borehole 25 is:

[0109] C=[220-200+(0.1×2×100) / (0.1×2)] / (0.1×2)=600ppm.

[0110] Traditional detection methods can only measure the average concentration of methane gas inside the borehole to be 200 ppm·m to 220 ppm·m. This demonstrates that traditional methods are inadequate for accurately detecting the concentration of harmful gases at the bottom of the borehole.

[0111] During the drilling process, groundwater and drilling rig cooling water enter the water tank 16 through the casing 10. The testing personnel collect the groundwater and drilling rig cooling water during drilling through the sampling tube 19, and test the collected water samples to analyze the content of soluble harmful gases in the groundwater.

[0112] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A device for detecting harmful gases during tunnel pre-drilling, characterized in that, Includes a sleeve (10); the sleeve (10) is provided with a laser monitoring module (11), the laser monitoring module (11) is used to emit laser along the axial direction of the sleeve (10) inside the sleeve (10) and to perform distance measurement and monitor the concentration of harmful gases; The sleeve (10) is provided with a shielding module (12), which is used to periodically shield the laser emitted by the laser monitoring module (11); the sleeve (10) is provided with a gas flow rate monitoring module (13), which is used to monitor the flow rate of harmful gases inside the sleeve (10); The laser monitoring module (11) includes a laser gas sensor (111), a laser rangefinder (112), and a reflecting prism (113) disposed outside the sleeve (10). The sleeve (10) has a laser hole (101) on its wall. The reflecting prism (113) is used to reflect the laser emitted by the laser gas sensor (111) and the laser rangefinder (112) through the laser hole (101) into the sleeve (10) and propagate along the axial direction of the sleeve (10). The laser monitoring module (11) also includes a monitoring box (114) connected to the sleeve (10), and the laser gas sensor (111), the laser rangefinder (112) and the reflecting prism (113) are disposed in the monitoring box (114); The sleeve (10) is used to be fitted onto the drill pipe (15), and the sleeve (10) can move along the axial direction of the drill pipe (15); The sleeve (10) is provided with a water tank (16) communicating with its inner cavity below it; the bottom of the inner cavity of the water tank (16) has an upwardly extending baffle plate (17), and forms a water outlet cavity (161) and a sampling cavity (162) on both sides of the baffle plate (17). The lower end of the water tank (16) is provided with a water outlet pipe (18) communicating with the water outlet cavity (161), and the lower end of the water tank (16) is provided with a sampling pipe (19) communicating with the sampling cavity (162).

2. The tunnel pre-drilling hazardous gas detection equipment according to claim 1, characterized in that, The shielding module (12) includes a drive member (121) disposed outside the sleeve (10) and a shielding member (122) connected to the drive member (121). The sleeve (10) has a clearance hole (102) on its wall to avoid the shielding member (122). The drive member (121) is used to drive the shielding member (122) to move and periodically shield the laser inside the sleeve (10).

3. The tunnel pre-drilling hazardous gas detection equipment according to claim 1, characterized in that, The gas flow rate monitoring module (13) includes a flow rate monitoring box (131) disposed outside the sleeve (10) and a gas flow rate sensor (132) disposed inside the flow rate monitoring box (131), wherein the flow rate monitoring box (131) is connected to the inner cavity of the sleeve (10).

4. The tunnel pre-drilling hazardous gas detection equipment according to claim 1, characterized in that, It also includes a control module (14), which is connected to the laser monitoring module (11), the shielding module (12) and the gas flow rate monitoring module (13) respectively.

5. The tunnel pre-drilling hazardous gas detection equipment according to claim 1, characterized in that, The water tank (16) has a horizontally arranged filter element (20) located above the water baffle (17), and the water tank (16) is provided with a slag discharge door (21) for opening and closing the chamber above the filter element (20).

6. A method for detecting harmful gases in tunnel pre-drilling, characterized in that, The method using the tunnel pre-drilling hazardous gas detection equipment according to any one of claims 1 to 5 includes: S1. Connect one end of the casing (10) to the opening of the pre-drilled hole (25); S2. The laser monitoring module (11) emits a laser to the bottom of the pre-drilled hole (25) to obtain the concentration of harmful gases from the laser monitoring module (11) to the bottom of the pre-drilled hole (25). ; S3, in After a certain period of time, the shielding module (12) shields the laser inside the sleeve (10), and the laser monitoring module (11) emits a laser towards the shielding module (12) to obtain the concentration of harmful gases from the laser monitoring module (11) to the shielding module (12). The distance between the laser monitoring module (11) and the blocking module (12) The gas flow rate monitoring module (13) monitors the flow rate of harmful gases inside the sleeve (10). ; S4, in After a certain period of time, the shielding module (12) releases the laser inside the casing (10), and the laser monitoring module (11) emits a laser towards the bottom of the pre-drilled hole (25) to obtain the concentration of harmful gases from the laser monitoring module (11) to the bottom of the pre-drilled hole (25). ; S5. Based on the data obtained in steps S2, S3, and S4, calculate the concentration of harmful gases at the bottom of the advanced borehole (25).

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