A construction method for advanced gas detection under special geological conditions

Abstract

The present invention provides a method for advanced gas detection under special geological conditions. The method comprises the following steps: Step 1: drilling an advanced borehole on the tunnel face, the advanced borehole being used to detect whether there is a special geological condition such as a coal seam or goaf ahead of the tunnel face; Step 2: removing rock dust and stone chips from the borehole to prevent the stone chips from affecting gas detection during the detection process; Step 3: installing an advanced gas detection auxiliary device in the borehole, the advanced gas detection auxiliary device being used to displace gas from the bottom of the borehole to the orifice for easy detection; and installing a gas detection device at the orifice of the borehole, the gas detection device being used to detect harmful gases; Step 4: activating the advanced gas detection auxiliary device, continuously collecting harmful gas data through the gas detection device, and processing the collected detection data to obtain the absolute emission volume of the harmful gas. The method is cost-effective and highly adaptable.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunnel gas detection, and in particular relates to an advanced gas detection construction method under special geological conditions. Background Art

[0002] During tunnel construction, unique geological environments are often encountered. For example, tunnels must pass through goafs, some water-rich strata, and spontaneously combustible strata, among other special geological conditions. This often requires advanced gas detection to detect harmful gases ahead of the tunnel and take appropriate action based on the results. Currently, all advanced gas detection equipment in this field requires deep-drilling testing, is not waterproof, and is not heat-resistant. This makes it unsuitable for testing under various hydrogeological conditions and special geological conditions.

[0003] Therefore, it is necessary to provide an improved technical solution to the above-mentioned deficiencies in the prior art. Summary of the Invention

[0004] The purpose of the present invention is to provide a construction method for advanced gas detection under special geological conditions, so as to at least solve the problem that the current advanced gas detection equipment cannot adapt to special geological conditions.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for advanced gas detection construction under special geological conditions, the detection construction method comprising the following steps:

[0007] Step 1: Drilling advance holes on the tunnel face to detect whether there are special geological conditions such as coal seams and goafs ahead of the tunnel face.

[0008] Step 2: Remove rock dust and stone chips from the borehole to prevent the stone chips from affecting gas detection during the detection process.

[0009] Step 3: Installing an advanced gas detection auxiliary device in the borehole, wherein the advanced gas detection auxiliary device is used to displace the gas at the bottom of the borehole to the orifice position for easy detection;

[0010] Installing a gas detection device at the orifice of the drill hole, wherein the gas detection device is used to detect harmful gases;

[0011] Step 4: Turn on the advanced gas detection auxiliary device, and continuously collect harmful gas data through the gas detection equipment, and process the collected detection data to obtain the absolute outflow volume of the harmful gas.

[0012] In the advanced gas detection construction method as described above, preferably, in step 1, an advanced borehole is set in the non-coal-uncovering section of the gas tunnel, and the front and rear advanced boreholes have overlapping parts in the drilling direction.

[0013] In the advanced gas detection construction method described above, preferably, when the advance drilling reveals the presence of special geological conditions such as coal seams and goafs, at least one advance positioning hole is drilled at a minimum normal distance of 15-25 m from the special geological conditions based on the detected locations of the coal seams, goafs, etc., and the advance positioning hole penetrates the floor rock layer by no less than 0.5 m.

[0014] Both the advanced positioning holes and the advanced drilling holes are used as holes to be tested for advanced harmful gas detection.

[0015] In the advanced gas detection construction method as described above, preferably, in step 2, after the advanced drilling or advanced positioning hole is completed, the original hole position is repeatedly drilled by the drilling rig to clear the rock powder and stone chips in the hole; after the hole is cleaned, the next hole position is constructed.

[0016] In the advanced gas detection construction method as described above, preferably, the advanced gas detection auxiliary device includes an air pump and an air supply pipe, and the diameter of the air supply pipe is smaller than the inner diameter of the hole to be detected, so that the air supply pipe can be inserted into the hole to be detected;

[0017] One end of the air supply pipe extends into the bottom of the hole to be detected, and the other end of the air supply pipe extends out of the hole to be detected and is used to be connected to the air pump.

[0018] In the advanced gas detection construction method as described above, preferably, colored corn powder is arranged inside the air supply pipe near the bottom of the hole to be detected. As the air pump blows air into the hole to be detected, the colored corn powder is blown out from the bottom of the hole to be detected to the mouth of the hole to be detected along with the air flow.

[0019] In the advanced gas detection construction method as described above, preferably, the air supply pipe includes a plurality of pipe units with terminal connections, and each of the pipe units is made of a PVC pipe with a length of 1 m and a diameter of 10 mm.

[0020] In the advanced gas detection construction method as described above, preferably, the gas detection equipment includes a gas detection system, wherein the gas detection system includes a methane sensor; the methane sensor is arranged above the orifice of the hole to be detected;

[0021] The gas detection equipment also includes a portable gas detector and an anemometer; the portable gas detector and the anemometer are fixedly arranged at the orifice position of the hole to be detected.

[0022] The advanced gas detection construction method as described above is preferably performed by processing the data obtained by wind speed measurement, harmful gas concentration measurement, and borehole diameter measurement to obtain the average wind speed V, the maximum concentration of harmful gas ω max , the air volume Q in the hole is:

[0023] Q=S*V*60

[0024] Where: Q - ventilation volume, unit: m 3 / min;

[0025] S——Drilling cross-sectional area after deducting the duct cross-sectional area, S=S 总 -S 送 , S 总 is the cross-sectional area of ​​the hole to be tested, S 送 is the cross-sectional area of ​​the air supply pipe, unit: m 2

[0026] V——average wind speed, unit: m / s.

[0027] In the advanced gas detection construction method as described above, preferably, the absolute outflow volume Q of harmful gas is 害 =Q*ω max ;

[0028] Where: Q 害 ——Absolute outflow of harmful gases, unit: m 3 / min;

[0029] Q——ventilation volume, unit: m 3 / min

[0030] ω max ——The maximum concentration of harmful gases measured in stable wind flow.

[0031] Beneficial Effects: This application's detection and construction method not only effectively reduces project teams' advanced gas detection costs, but also verifies the accuracy of detection data through the use of various detection methods. This detection and construction method and the equipment used meet detection requirements and avoid blind spots. It provides technical support for tunnel construction safety and hazardous gas detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings and the accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. Among them:

[0033] Figure 1 Schematic diagram of the process of the advanced gas detection construction method in an embodiment of the present invention;

[0034] Figure 2Schematic diagram of the installation structure of the advanced gas detection auxiliary device and the gas detection equipment in an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of colored corn flour disposed at the bottom of the air supply pipe in an embodiment of the present invention.

[0036] In the figure: 1. Hole to be tested; 2. Air supply pipe; 3. Air pump; 4. Methane sensor; 5. Colored corn flour. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0038] In the description of the present invention, the terms "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention. The terms "connected" and "connected" used in the present invention should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be a direct connection or an indirect connection through an intermediate component. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0039] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other.

[0040] According to a specific embodiment of the present invention, Figure 1-3 As shown, the present invention provides a method for advanced gas detection construction under special geological conditions, and the detection construction method includes the following steps:

[0041] Step 1: Drilling an advance borehole on the tunnel face. This advance borehole is used to detect the presence of special geological conditions, such as coal seams or goaf, ahead of the tunnel face. In Step 1, an advance borehole is set in the non-coal-excavating section of the gas tunnel, with the two advance boreholes overlapping in the drilling direction.

[0042] In this embodiment, the diameter of the advance borehole is φ89mm, the borehole length is 30m, and the front and rear advance boreholes overlap each other by 5m. That is, after excavating 25m from the tunnel face, a 30m long advance borehole is first drilled on the tunnel face, and then drilling is continued so that the intersection of the borehole and the coal seam roof is controlled within 5m of the lining excavation contour line.

[0043] When advance drilling reveals the presence of special geological conditions such as coal seams and goafs ahead, at least one advance positioning hole shall be drilled at a minimum normal distance of 15-25m from the special geological conditions based on the locations of the detected coal seams, goafs and other special geological conditions. The advance positioning hole shall penetrate into the bottom rock layer by no less than 0.5m. Both the advance positioning hole and the advance drilling hole shall be used as the hole to be detected 1 for advance harmful gas detection.

[0044] In this embodiment, based on the preliminary detection of special geological positions, the special geology in this embodiment is coal seams and goafs; two advance positioning holes are drilled at a minimum normal distance of 20m from the initially explored coal seams and goafs, plus one advance drilling hole, for a total of three holes. The advance positioning holes are drilled into the bottom rock layer by no less than 0.5m, and relevant parameter tests are carried out. Coring is carried out on one of the advance positioning holes, and the core data are recorded in detail. The drill cuttings method is used for indicators. When the excavation working face is 5m away from the coal seam roof in a vertical distance, a full-thickness prediction hole is drilled through the coal seam. All drill cuttings are collected for every meter of coal hole drilled. Relevant indicators are tested in accordance with the "Detailed Rules for Preventing and Controlling Coal and Gas Outbursts", gas is predicted, the position, thickness, occurrence, and coal quality of the coal seam are explored, the position and size of the goaf are explored, and the gas content, pressure, and outburst volume are measured by gas detection equipment to determine the danger of outburst.

[0045] Step 2: Clear the rock powder and stone chips in the borehole to avoid the stone chips in the hole affecting gas detection during the detection process.

[0046] In step 2, after the advance drilling or the advance positioning hole is completed, the original hole position is repeatedly drilled by the drilling rig to clear the rock powder and stone chips in the hole; after the hole is cleared, the next hole position is constructed.

[0047] After drilling is complete, the site must be cleaned and no unauthorized personnel or machinery should be allowed near the hole opening. This prevents stone chips from affecting the inspection process.

[0048] Step 3: Install an advanced gas detection auxiliary device in the borehole. The advanced gas detection auxiliary device is used to displace the gas at the bottom of the borehole to the orifice position for easy detection. A gas detection device is installed at the orifice position of the borehole to detect harmful gases.

[0049] The advanced gas detection auxiliary device includes an air pump 3 and an air supply pipe 2. The diameter of the air supply pipe 2 is smaller than the inner diameter of the hole to be detected 1, so that the air supply pipe 2 can be inserted into the hole to be detected 1; one end of the air supply pipe 2 is inserted into the bottom of the hole to be detected 1, and the other end of the air supply pipe 2 is extended outside the hole to be detected 1 for connection with the air pump 3.

[0050] The air pump 3 blows gas through the air supply pipe 2 toward the bottom of the hole 1 to be inspected, displacing the gas at the bottom of the hole 1 to the hole's opening, allowing the gas detection equipment to detect harmful gases within the hole 1. In this embodiment, the air supply pipe 2 is exposed within 1 meter of the hole's opening. The end of the air supply pipe 2 is connected to a 10 mm diameter hose, which is connected to the air pump 3. All connections are checked for tightness to prevent air leaks.

[0051] Colored corn powder 5 is arranged inside the air supply pipe 2 near the bottom of the hole 1 to be detected. As the air pump 3 blows air into the hole 1 to be detected, the colored corn powder 5 is blown out from the bottom of the hole 1 to be detected to the orifice of the hole 1 to be detected along with the air flow. When the colored corn powder 5 is seen at the orifice, it means that the gas at the bottom of the hole 1 to be detected has been replaced to the orifice. If the air pump 3 continues to blow air, the harmful gas at the bottom of the hole 1 to be detected can be continuously replaced to the orifice for easy detection.

[0052] Before the corn powder was observed, the concentration of harmful gases and wind speed were measured to calculate and analyze the difference in harmful gas outflow at different depths. After the colored corn powder was observed for 5 minutes, the measurement was continued for 5 minutes, and the absolute harmful gas outflow was calculated based on the wind speed and concentration.

[0053] Colored corn powder 5 is stable in nature and will not react with the harmful gases to be detected, so it is convenient to observe wind speed changes and air supply effects without affecting the composition of harmful gases. When detecting other gases, it is also necessary to detect harmful gases such as carbon monoxide, carbon dioxide, methane, sulfur dioxide, and hydrogen sulfide. Other colored mist generators may react with harmful gases and affect the content of the gas to be detected in the hole. Therefore, colored corn powder 5 was selected during construction.

[0054] The air supply duct 2 consists of multiple connected tube units, each made of 1-meter-long, 10-mm-diameter PVC pipe. The size of the tube units can be selected based on the required ventilation volume. In this embodiment, PVC pipe is stable and does not react with harmful gases. In other embodiments, the tube units can also be made of stainless steel, iron, or other materials.

[0055] In this embodiment, the first tube unit is the first to enter the hole. When the last tube unit is connected, the first tube unit has already reached the bottom of the hole. Therefore, colored corn powder 5 is provided near the bottom of the hole in the first tube unit. Figure 3 As shown, the colored corn flour 5 is fixed to the bottom of the tube unit through a net bag, and as the gas flows, the gas can blow the colored corn flour 5 out of the net bag.

[0056] The gas detection equipment includes a gas detection system, which has a methane sensor 4; the methane sensor 4 is arranged at the upper part of the orifice of the hole to be detected 1; the gas detection equipment also includes a portable gas detector and an anemometer; the portable gas detector and anemometer are fixedly arranged at the orifice position of the hole to be detected 1.

[0057] In this embodiment, the gas detection system uses harmful gas detection sensors for data acquisition, achieving high frequency and accuracy. Because the pre-drilled hole opening is relatively narrow, sensor placement should be adjusted based on specific circumstances. Since methane density is generally approximately 0.6 times that of air and is primarily concentrated at the top, the system's sensor is positioned above the hole opening (1) to more accurately measure methane concentration.

[0058] In this embodiment, in order to prevent abnormal detection data of the gas detection system, portable gas detectors, anemometers and other portable devices are fixed at the hole position during the construction process, and the portable devices are compared with the automatic monitoring data to eliminate mutation data, making the detection results more accurate.

[0059] The harmful gas detection process is: turn on the power to supply air → observe the colored powder at the orifice → record the time when the colored powder is observed → continue to supply air for 5 minutes → collect data.

[0060] 1) Power on and supply air: After the air supply pipe 2 has been inspected and the detection equipment has been fixed, connect the power supply to the air pump 3 and start the air supply mode.

[0061] 2) Observe the colored powder at the orifice: After the air supply starts, record the detection data of the portable device in real time and observe the dispersion of the colored powder. When colored powder floats out of the orifice, it proves that all the gas in the hole has been blown out.

[0062] 3) Record the time when colored powder is observed: When colored powder is observed, the corresponding time needs to be recorded so as to facilitate comparison with the monitoring data of the automatic monitoring system (i.e., gas detection system).

[0063] 4) Continue ventilation for 5 minutes: Observation of colored powder confirms that the gas in the hole has been completely replaced. Subsequent test data indicates the real-time emission of harmful gases. By measuring the harmful gas concentration and wind speed, the absolute emission volume of harmful gases can be calculated. Continuous ventilation for 5 minutes is used to observe the changes in harmful gas concentration during this period. The absolute emission volume of harmful gases at different depths is calculated based on wind speed and harmful gas concentration.

[0064] 5) Collect data: During the testing process, data collection should be done well. The test results of fixed time points and portable equipment need to be recorded in a timely manner to facilitate data analysis and collation.

[0065] Step 4: Turn on the advanced gas detection auxiliary device, and continuously collect harmful gas data through the gas detection equipment, and process the collected detection data to obtain the absolute outflow volume of the harmful gas.

[0066] This method is suitable for advanced deep-hole hazardous gas detection in tunnels under various geological conditions and can also be applied to deep-hole advanced gas detection construction in various other projects. This detection method utilizes the principle of gas exchange to evenly and slowly blow deep-hole gas out of the hole. Wind speed and hazardous gas concentration are then measured at the hole mouth. The absolute amount of hazardous gas released is calculated using wind speed and concentration data.

[0067] The data obtained by wind speed measurement, harmful gas concentration measurement, and borehole diameter measurement are processed to obtain the average wind speed V and the maximum concentration of harmful gases ω. max , the air volume Q in the hole is:

[0068] Q=S*V*60

[0069] Where: Q - ventilation volume, unit: m 3 / min;

[0070] S——Drilling cross-sectional area after deducting the duct cross-sectional area, S=S 总 -S 送 , S 总 is the cross-sectional area of ​​the hole to be tested, S 送 is the cross-sectional area of ​​the air supply pipe, unit: m 2

[0071] V——average wind speed, unit: m / s.

[0072] Absolute outflow of harmful gases Q 害 =Q*ω max .

[0073] Where: Q 害 ——Absolute outflow of harmful gases, unit: m 3 / min;

[0074] Q——ventilation volume, unit: m 3 / min

[0075] ω max ——The maximum concentration of harmful gases measured in stable wind flow.

[0076] Example 1: This detection construction method can greatly save detection costs and labor costs; the following calculations are explained using the data of the detection construction method in actual construction as an example.

[0077] 1. Testing cost:

[0078] Through the practical application of this detection construction method, the project department effectively saved costs during the advanced gas detection process. The total length of the two tunnels is 3861 meters, and each test is 30 meters, with a 5-meter overlap. The cost of testing a standard test hole is 3000 yuan per hole. The project department used this independent detection construction method to conduct self-tests on two holes and outsourced one hole. The specific benefits are as follows:

[0079] The use of this inspection and construction method eliminates the cost of ordinary monitoring.

[0080] Number of tests: 3861m÷25m=155 (times)

[0081] Number of self-test holes: 155*2=310 (holes)

[0082] Cost savings: 310*3000=930000 (yuan)

[0083] 2. Save labor costs

[0084] By using this detection construction method for advanced gas detection, the detection time is greatly saved. The ordinary monitoring method takes an average of 40 minutes to detect a single hole, while this detection construction method takes an average of 20 minutes to detect a single hole; the detection efficiency is improved by 50%.

[0085] Since the workers (7 persons) on the working surface were unable to carry out construction during the inspection period, the labor cost per shift (8 hours) was RMB 400 per person.

[0086] Cost of common detection methods:

[0087] Cumulative detection time: 40 min / well * 310 wells ÷ 60 min / h = 207h

[0088] Cost: 207 hours ÷ 8 hours / shift * 400 yuan / person * 7 people = 72,450 yuan

[0089] Testing cost of the new method: Cumulative testing time: 20 min / well * 310 wells ÷ 60 min / h = 103.3 h Cost: 103.3 h ÷ 8 h / shift * 400 yuan / person * 7 people = 36,155 yuan

[0090] That is, the new method saves costs 72,450 yuan - 36,155 yuan = 36,300 yuan;

[0091] In summary, the total cost savings are RMB 930,000 + RMB 36,300 = RMB 966,300.

[0092] In summary, the detection construction method provided by the present invention not only effectively reduces the cost of advanced gas detection for project teams, but also verifies the accuracy of detection data through the application of different detection methods. This detection construction method can adapt to various geological conditions, such as water-rich strata and high geothermal strata, for detection. This detection construction method and the equipment used meet detection requirements and avoid detection blind spots. It provides technical support for tunnel construction safety and harmful gas detection, and this detection construction method has proven to be highly effective.

[0093] It will be understood that the above description is merely exemplary and the embodiments of the present application do not limit this.

[0094] 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, improvements, etc. made within the spirit and principles of the present invention are within the scope of protection of the pending claims of the present invention.

Claims

1. A method for advanced gas detection construction under special geological conditions, characterized in that: The detection construction method comprises the following steps: Step 1: Drilling advance holes on the tunnel face to detect whether there are coal seams or special geology in the goaf ahead of the tunnel face. Step 2: Remove rock dust and stone chips from the borehole to prevent the stone chips from affecting gas detection during the detection process. Step 3: Installing an advanced gas detection auxiliary device in the borehole, wherein the advanced gas detection auxiliary device is used to displace the gas at the bottom of the borehole to the orifice position for easy detection; Installing a gas detection device at the orifice of the drill hole, wherein the gas detection device is used to detect harmful gases; Step 4: Turn on the advanced gas detection auxiliary device, and continuously collect harmful gas data through the gas detection equipment, and process the collected detection data to obtain the absolute outflow volume of the harmful gas; The advanced gas detection auxiliary device includes an air pump and an air supply pipe, wherein the diameter of the air supply pipe is smaller than the inner diameter of the hole to be detected so that the air supply pipe can be inserted into the hole to be detected; One end of the air supply pipe extends into the bottom of the hole to be detected, and the other end of the air supply pipe extends out of the hole to be detected for connection with the air pump; Colored corn powder is placed inside the air supply pipe near the bottom of the hole to be tested. As the air pump blows air into the hole to be tested, the colored corn powder is blown out from the bottom of the hole to be tested to the hole mouth along with the air flow. The air supply pipe includes a plurality of pipe units connected at the end, and each of the pipe units is made of a PVC pipe with a length of 1m and a diameter of 10mm.

2. The advanced gas detection construction method according to claim 1, characterized in that: In step 1, an advance borehole is set in the non-coal uncovering section of the gas tunnel, and the two front and rear advance boreholes have overlapping parts in the drilling direction.

3. The advanced gas detection construction method according to claim 2, characterized in that: When advance drilling reveals the presence of special geology in coal seams or goafs, at least one advance positioning hole shall be drilled at a minimum normal distance of 15-25m from the special geology according to the detected location of the coal seams or goafs, and the advance positioning hole shall penetrate into the floor rock layer by no less than 0.5m; Both the advanced positioning holes and the advanced drilling holes are used as holes to be tested for advanced harmful gas detection.

4. The advanced gas detection construction method according to claim 3, characterized in that: In step 2, after the advance drilling or the advance positioning hole is completed, the original hole position is repeatedly drilled by the drilling rig to clear the rock powder and stone chips in the hole; after the hole is cleared, the next hole position is constructed.

5. The advanced gas detection construction method according to claim 1, characterized in that: The gas detection device includes a gas detection system, wherein the gas detection system has a methane sensor; the methane sensor is arranged above the orifice of the hole to be detected; The gas detection equipment also includes a portable gas detector and an anemometer; the portable gas detector and the anemometer are fixedly arranged at the orifice position of the hole to be detected.

6. The advanced gas detection construction method according to claim 5, characterized in that: The data obtained by wind speed measurement, harmful gas concentration measurement, and borehole diameter measurement are processed to obtain the average wind speed V and the maximum concentration of harmful gases ω. max , the air volume Q in the hole is: Q=S*V*60 Where: Q - ventilation volume, unit: m³ / min; S——Drilling cross-sectional area after deducting the duct cross-sectional area, S=S 总 -S 送 , S 总 is the cross-sectional area of ​​the hole to be tested, S 送 is the cross-sectional area of ​​the air supply pipe, unit: m 2 V——average wind speed, unit: m / s.

7. The advanced gas detection construction method according to claim 6, characterized in that: Absolute outflow of harmful gases Q 害 =Q*ω max ; Where: Q 害 ——Absolute outflow of harmful gases, unit: m³ / min; Q——ventilation volume, unit: m³ / min ω max ——The maximum concentration of harmful gases measured in stable wind flow.

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