A device for detecting the sealing quality of gas drainage boreholes and a method for evaluating the sealing quality

Abstract

The present invention discloses a device for detecting the sealing quality of gas drainage boreholes, which includes a detection host, a detection tube, a seal and a tee. Above the detection host, there are multiple air inlets and multiple air outlets. Inside the detection host, there is a negative pressure ejector. The detection host is also provided with a quick connector and a control switch. The quick connector is used to connect to the air duct underground, and the air duct underground is additionally connected to the underground compressed air pipeline. The control switch is used to start and stop the negative pressure ejector inside the detection host. The present invention also provides a method for evaluating the sealing quality of gas drainage boreholes. The quality detection device of the present invention effectively avoids the problem that the gas concentration in the borehole changes due to the time difference, which ultimately leads to the detection result deviating from the actual situation. The present invention has the advantages of simple operation and high precision, and can quantitatively evaluate the sealing quality of gas drainage boreholes.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mine gas drainage, and particularly relates to a device for detecting the sealing quality of gas drainage boreholes and a method for evaluating the sealing quality. Background Art

[0002] As one of the fundamental measures for treating coal mine gas problems, the gas drainage technology has been widely applied in many coal mines at home and abroad. The sealing quality of gas drainage boreholes is one of the key factors to ensure the gas drainage effect. Therefore, to ensure the gas drainage effect of gas drainage boreholes, the sealing quality of gas drainage boreholes must be guaranteed. The sealing quality of gas drainage boreholes generally refers to the degree to which the sealed section can effectively resist air leakage from the borehole wall, surrounding rock, etc. into the borehole, as well as its timeliness and stability. The factors affecting the sealing quality are mainly related to the borehole, surrounding rock, sealing material, retention of the sealing process, and personnel operation, etc. At present, the main methods for detecting the sealing quality of gas drainage boreholes are as follows: (1) Judging the sealing quality of gas drainage boreholes and the air leakage position by detecting and comparing the gas drainage concentration at different positions inside the borehole (patent publication number: CN102900428B). This device can detect and judge the air leakage position inside the borehole under negative pressure drainage conditions, but it is necessary to continuously adjust the length of the detection tube to detect the gas concentration at different positions inside the borehole. The detection time between the first measurement point and the last measurement point is relatively long, which may seriously affect the detection effect and lead to misjudgment of the sealing quality of gas drainage boreholes; (2) Pressurizing air into the gas drainage borehole and judging the sealing quality by observing the pressure change inside the borehole (patent publication number: CN102680187A). This judgment method can only roughly classify the sealing quality of the drainage borehole according to the pressure change, and cannot accurately analyze the air leakage position; (3) Injecting water into the borehole and detecting the sealing quality with the help of an ultrasonic detector (patent publication number: CN110985106A). This method is relatively cumbersome to operate, and the resolution of the ultrasonic reflection signal is relatively low, and it is affected by many factors; (4) Judging the sealing quality of gas drainage boreholes according to the change of gas drainage concentration and with the help of tracer gas (patent publication number: CN113107466A). This method is complex to operate, has a high cost, and can only judge whether there is air leakage in the whole sealed section, and cannot accurately judge the air leakage position; (5) Classifying the gas drainage concentration, pure gas drainage volume, attenuation coefficient, and abnormal phenomena of the drainage borehole, and comprehensively evaluating the sealing quality of the gas drainage borehole according to the weights of various indicators (patent publication number: CN110424948A). The accuracy of this method of judgment is very limited, and there are many factors that can affect the on-site drainage, such as drainage negative pressure, drainage pipe diameter, etc. Therefore, a device and method that are simple to operate, have high precision, and can quantitatively evaluate the sealing quality of gas drainage boreholes are needed. Summary of the Invention

[0003] To solve the above technical problems, the object of the present invention is to provide a device for detecting the sealing quality of a gas drainage borehole and a method for evaluating the sealing quality.

[0004] To achieve the above object, the present invention provides the following technical solution: A device for detecting the sealing quality of a gas drainage borehole includes a detection host, a detection pipe, a sealing member and a tee. There are multiple air inlets and multiple air outlets above the detection host. A negative pressure ejector is provided inside the detection host. A quick connector and a control switch are also provided on the detection host. The quick connector is used to connect to the air pipe underground, and the air pipe underground is additionally connected to the underground compressed air pipeline. The control switch is used to start and stop the negative pressure ejector inside the detection host. The second interface of the tee is connected to the extraction pipe, the extraction pipe is placed in the gas drainage borehole, the third interface of the tee is connected to the extraction pipeline, one end of the detection pipe is connected to the air inlet of the detection host, and the other end of the detection pipe passes through the first interface of the tee and then passes out from the second interface and is placed in the extraction pipe and the gas drainage borehole. A sealing member is provided at the connection between the detection pipe and the first interface of the tee, and the sealing member is used to seal the gap between the detection pipe and the first interface of the tee;

[0005] The detection pipe includes a hollow pipe body, multiple air suction ports, a support skeleton, and multiple air suction pipes. Multiple air suction ports are provided on the hollow pipe body at intervals. A support skeleton is provided inside the hollow pipe body. Multiple through holes for the air suction pipes to pass through are provided on the support skeleton. One air suction pipe can pass through each through hole. One end of each of the multiple air suction pipes passes through the through hole on the support skeleton and is respectively connected to the air suction port on the hollow pipe body one-to-one. One end of each air suction pipe is placed outside the hollow pipe body and is connected to the air inlet on the detection host one-to-one during use.

[0006] Further, the number of the air suction ports is 12, and the number of the air suction pipes is 12.

[0007] Further, the hollow pipe body and the support skeleton are made of aluminum-plastic material, and the air suction pipes are made of flame-retardant PE material.

[0008] Further, multiple waterproof devices are also installed on the detection pipe. The waterproof devices are sleeved on the hollow pipe body and are placed behind each air suction port.

[0009] Further, the waterproof device includes a casing body, a first nut and a second nut. The casing body includes a first hollow cylindrical section, and a second hollow cylindrical section and a third hollow cylindrical section are respectively provided at both ends of the first hollow cylindrical section. A first external thread and a first square tooth are provided on the outer peripheral surface of the second hollow cylindrical section, and a second external thread and a second square tooth are provided on the outer peripheral surface of the third hollow cylindrical section. The casing body is sleeved outside the hollow tube body. By respectively installing the first nut and the second nut on the second hollow cylindrical section and the third hollow cylindrical section, the first nut and the second nut are respectively screwed tightly at the first external thread and the second external thread, and the casing body is fixed outside the hollow tube body.

[0010] The present invention also provides a method for evaluating the sealing quality of gas drainage boreholes, which is realized by using the gas drainage borehole sealing quality detection device, and includes the following steps:

[0011] Step 1: First, it is necessary to investigate the actual sealing section depth L1 of the gas drainage borehole, the sealing method, and the total length L2 of the extraction pipes used in the gas drainage borehole; and detect the positions before and after the connection between the extraction pipes, within the width of the roadway loose circle, and other possible air leakage positions to determine the number and positions of the measuring points that need to be detected. Each measuring point is respectively denoted as JC1, JC2... JC along the gas flow direction. n ;

[0012] Step 2: Use a gas flow detection device to detect the mixed gas volume Q of the extracted gas of the gas drainage borehole that needs to be detected.

[0013] Step 3: Assemble the gas drainage borehole sealing quality detection device: First, connect the second interface and the third interface of the tee to the extraction pipe and the extraction pipeline respectively. Then, according to the number and positions of the measuring points determined in Step 1, leave the corresponding positions and numbers of suction ports for detection on the hollow tube body of the detection pipe, and block other suction ports. Mark the suction pipes connected to the blocked suction ports and do not connect them to the air inlet during detection. At the same time, install a waterproof device beside each suction port for detection used. Quickly put the detection pipe with the waterproof device installed into the gas drainage borehole from the first interface of the tee, and install a seal at the connection between the first interface of the tee and the detection pipe. At this time, the gas drainage borehole will enter the normal extraction state. Connect the other ends of the suction pipes for detection to the air inlet of the detection host in sequence. After the connection is completed, connect the detection host to the underground compressed air pipeline with an air duct to provide power for the negative pressure ejector inside the detection host.

[0014] Step 4: After the assembly is completed, start the control switch to conduct a pre-test on the gas drainage borehole sealing quality detection device. Under normal circumstances, under the action of the negative pressure ejector, each suction port and each exhaust port on the detection host will work simultaneously.

[0015] Step 5: After the test, turn off the control switch, connect each exhaust port on the detection host used to the rubber bladder for collecting gas, then turn on the control switch. The gas in the gas drainage borehole will enter each suction pipe in the detection pipe through each suction port on the detection pipe simultaneously, and finally enter each rubber bladder through the corresponding exhaust port of the detection host. After the gas to be detected is collected in each rubber bladder, turn off the control switch, and then use the underground gas detection equipment to measure the gas concentration of the gas in each rubber bladder, or take each rubber bladder to the ground and use devices such as chromatographs to measure the gas concentration of the gas, and obtain the gas concentration ND1, ND2... ND of each measuring point n ;

[0016] Step 6: Repeat Step 5 in this cycle until the sealing quality of all gas drainage boreholes is completely measured;

[0017] Step 7: Use the total leakage rate K of a single borehole to evaluate the sealing quality of each gas drainage borehole.

[0018] Furthermore, the specific steps for evaluating the sealing quality of each gas drainage borehole in Step 7 are as follows:

[0019] According to the mixed gas volume Q value of the gas drained from the gas drainage borehole obtained in Step 2 and ND1, ND2... ND obtained in Step 5 n , based on the principle that the pure gas volume of gas at each place in the gas drainage borehole is the same, the pure gas volume CL of gas at each place in the gas drainage borehole is Q×ND n , based on Q i =CL / ND i (i = 1, 2,... n) to calculate the mixed gas volume Q of the gas drained at each measuring point i , then the total leakage air volume Q L =Q - Q1 = Q n -Q1, the total leakage rate of the borehole or

[0020] Furthermore, the evaluation method for the sealing quality of the gas drainage borehole also includes performing Step 8 after Step 7. Step 8 is specifically as follows:

[0021] According to the value of the total leakage rate K of the borehole, divide the grade of the sealing quality of the gas drainage borehole and put forward corresponding treatment suggestions. The sealing quality grades and recommended treatment measures are specifically shown in Table 1:

[0022] Table 1 Sealing quality grades and recommended treatment measures

[0023] Total air leakage rate K (%) of the borehole Sealing quality grade Suggested treatment measures 0 Tight borehole sealing Normal use 0～10 Minor air leakage Control negative pressure 10～50 Substantial air leakage Secondary borehole sealing ≥50 Serious air leakage Demolition, isolation 。

[0024] Further, step 7 further includes evaluating the sealing quality of different drilling groups. When a drilling group consists of multiple gas drainage boreholes, the evaluation is carried out by the leakage borehole ratio λ and the average leakage rate η of the drilling group;

[0025] Wherein: the leakage borehole ratio λ is the ratio of the number m of gas drainage boreholes with air leakage to the total number N of the entire evaluated boreholes, that is

[0026] The average leakage rate η is the ratio of the sum K of the total leakage rates of all the boreholes with air leakage among the entire evaluated boreholes to the number m of the gas drainage boreholes with air leakage, that is

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The gas drainage borehole sealing quality detection device of the present invention can be used under the normal gas drainage conditions of gas drainage boreholes; it can simultaneously collect gas at multiple measurement points (the number of measurement points n ≤ 12) in the drainage borehole, effectively avoiding the problem that the gas concentration in the borehole changes due to the time difference and finally leading to the detection result deviating from the actual situation; at the same time, the waterproof device of the device can effectively prevent small streams of water in the drainage borehole from entering the interior of the detection device; in addition, the detection tube of the device has strong plasticity and certain strength, which is convenient for carrying and using; furthermore, the power of the device can be provided by the underground compressed air pipeline, without the need for electronic equipment, which is safe and reliable. The sealing quality evaluation method of the present invention can quantitatively evaluate the sealing quality of a single borehole and compare the overall sealing quality of different drilling groups by calculating the leakage rate, and further can compare the sealing quality between different sealing methods. The present invention has the advantages of simple operation and high precision, and can quantitatively evaluate the sealing quality of gas drainage boreholes. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic structural diagram of the gas drainage borehole sealing quality detection device in the embodiment of the present invention;

[0030] Figure 2 is Figure 1 a schematic cross-sectional structure diagram at A-A in

[0031] Figure 3 is a schematic diagram of the distribution of the air suction ports on the detection tube of the gas drainage borehole sealing quality detection device in the embodiment of the present invention;

[0032] Figure 4 is a schematic structural diagram of the waterproof device of the gas drainage borehole sealing quality detection device in the embodiment of the present invention;

[0033] Figure 5Schematic diagram of the overall appearance structure of the waterproof device of the gas drainage borehole sealing quality detection device in the embodiment of the present invention;

[0034] Figure 6 Schematic diagram of the determination of the mixed gas volume of the gas extracted from the extraction borehole by the pitot tube in the gas drainage borehole sealing quality evaluation method in the embodiment of the present invention;

[0035] In the figure:

[0036] 1. Detection host; 101. Quick joint; 102. Control switch; 103. Exhaust port; 104. Intake port; 2. Detection tube; 201. Suction tube; 202. Suction port; 203. Support skeleton; 2031. Through hole; 204. Hollow tube body; 3. Waterproof device; 301. Sleeve body; 3011. First hollow cylindrical section; 3012. Second hollow cylindrical section; 3013. Third hollow cylindrical section; 3014. First external thread; 3015. First square tooth; 3016. Second external thread; 3017. Second square tooth; 302. First nut; 303. Second nut; 4. Three-way joint; 5. Sealing element; 6. Extraction pipeline; 7. Gas drainage borehole; 8. Coal seam; 9. Extraction pipe; 10. Sealing material; 11. Air duct; 12. Underground compressed air pipeline; 13. Pitot tube; 14. U-shaped differential pressure gauge; 15. Elbow; 16. Hose. Detailed implementation manners

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] Construct a gas drainage borehole 7 in the coal seam 8. After the construction is completed, place an extraction pipe 9 in the gas drainage borehole 7, and then grout for sealing. Use the sealing material 10 to seal the gap between the extraction pipe 9 and the gas drainage borehole 7. The gas drainage borehole sealing quality detection device and the sealing quality evaluation method of the present invention are used to detect and evaluate the sealing quality of the gas drainage borehole 7 in the coal seam 8.

[0039] Embodiment 1

[0040] Please refer to Figure 1 - Figure 5, a device for detecting the sealing quality of gas drainage boreholes, comprising a detection host 1, a detection pipe 2, a seal 5 and a tee 4. Above the detection host 1, there are multiple air inlets 104 and multiple air outlets 103 (in this embodiment, 12 air inlets 104 and 12 air outlets 103 are provided in total), and their arrangement and distribution can be adjusted according to the actual shape of the detection host 1. Inside the detection host 1, there is a negative pressure ejector. On the detection host 1, there are also a quick connector 101 and a control switch 102. The quick connector 101 is used to connect with the air pipe 11 underground, and the air pipe 11 underground is additionally connected to the underground compressed air pipeline 12. The control switch 102 is used to start and stop the negative pressure ejector inside the detection host 1. The second interface of the tee 4 is connected to the extraction pipe 9, and the extraction pipe 9 is placed inside the gas drainage borehole 7. The third interface of the tee 4 is connected to the extraction pipeline 6. One end of the detection pipe 2 is connected to the air inlet of the detection host 1, and the other end of the detection pipe 2 passes through the first interface of the tee 4 and then passes out from the second interface and is placed inside the extraction pipe 9 and the gas drainage borehole 7. At the connection between the detection pipe 2 and the first interface of the tee 4, there is a seal 5, and the seal 5 is used to seal the gap between the detection pipe 2 and the first interface of the tee 4 to prevent the air in the roadway from entering the gas drainage borehole 7, thereby affecting the detection result. The aperture of the first interface of the tee 4 connected to the seal 5 is fixed, generally The apertures of the second interface and the third interface can be adjusted according to the diameters of the extraction pipeline 6 and the extraction pipe 9 actually used on site, generally The tee 4 is a flame-retardant PVC pipe fitting or PE pipe fitting. The structure of the seal 5 is similar to that of the waterproof device 3, both being hollow tubes. One end of it can be directly connected to the first interface of the tee 4, and the other end is also tightly connected to the detection pipe 2 by tightening the nut and squeezing the square teeth.

[0041] Refer to Figure 3The detection tube 2 includes a hollow tube body 204, multiple air intake ports 202, a support frame 203, and multiple air intake pipes 201. Multiple air intake ports 202 are arranged at intervals on the hollow tube body 204. The hollow tube body 204 is in the shape of a hollow cylinder. The front end of the hollow tube body 204 is designed to be conical, which is convenient for effectively reducing the propulsion resistance when it is advanced in the gas extraction borehole 7. A support frame 203 is provided inside the hollow tube body 204. The support frame 203 is provided with multiple through holes 2031 for the air intake pipes 201 to pass through. Each through hole 2031 can pass through an air intake pipe 201. One end of the multiple air intake pipes 201 passes through the through hole 2031 on the support frame 203 and is respectively connected one-to-one with the air intake ports 202 on the hollow tube body 204. A section of the other end of each air intake pipe 201 is placed outside the hollow tube body 204 and is connected one-to-one with the air inlet 104 on the detection host 1 when in use. The number of the air inlets 202 is 12, and the number of the air inlets 201 is 12. That is, the lengths of the 12 air inlets 201 inside the detection tube 2 are different. Considering that the sealing length of the current gas extraction borehole 7 is generally between 10-20m, the total length L3 of the hollow tube body 204 of the detection tube 2 provided in this embodiment is 35m, and the length L5 of the exposed part of all the air inlets 201 at the end of the hollow tube body 204 is 5m. In this embodiment, the 12 air inlets 202 are distributed as follows: one air inlet 202 is provided at a distance L6 of 1m between the front end of the hollow tube body 204 and the front end of the tapered end, and the other 11 air inlets 202 are evenly distributed on the hollow tube body 204 at a spacing H of 1.8m, and the distance L4 between the last air inlet 202 and the end surface of the hollow tube body 204 is 4.5m.

[0042] The hollow tube body 204 and the support frame 203 are made of aluminum-plastic material that is easy to bend, light in weight, highly corrosion-resistant and flame-retardant. The air intake pipe 201 is made of flame-retardant PE material that is easy to bend, light in weight and not easily deflated under negative pressure.

[0043] See also Figure 2 The support frame 203 of the present invention includes a plurality of cross beams and a plurality of longitudinal beams, which are fixed perpendicularly to each other to form a plurality of through holes 2031 for the air intake pipe 201 to pass through, and the ends of the plurality of cross beams and the plurality of longitudinal beams are respectively fixed on the inner wall surface of the hollow tube body 204 of the detection tube 2. The length of the support frame 203 is the distance from the end of the hollow tube body 204 to the center of the first air intake port 202 at the front end of the hollow tube body 204, that is, L3-L6. In this embodiment, L3-L6=(35-1)m=34m.

[0044] A plurality of waterproof devices 3 are also installed on the detection tube. The waterproof device 3 is sleeved on the hollow tube body 204 and is placed behind each air suction port 202. By setting the waterproof device 3, the position of each air suction port 202 can be raised, thereby avoiding the direct contact of the air suction port 202 with water, and further preventing the water in the gas drainage borehole 7 from being sucked into the air suction pipe 201, resulting in detection errors or damage to the instrument.

[0045] The waterproof device 3 includes a sleeve body 301, a first nut 302 and a second nut 303. The sleeve body 301 includes a first hollow cylindrical section 3011. At both ends of the first hollow cylindrical section 3011, a second hollow cylindrical section 3012 and a third hollow cylindrical section 3013 are respectively provided. On the outer peripheral surface of the second hollow cylindrical section 3012, a first external thread 3014 and a first square tooth 3015 are provided. On the outer peripheral surface of the third hollow cylindrical section 3013, a second external thread 3016 and a second square tooth 3017 are provided. The sleeve body 301 is sleeved outside the hollow tube body 204. By respectively installing the first nut 302 and the second nut 303 on the second hollow cylindrical section 3012 and the third hollow cylindrical section 3013, the first nut 302 and the second nut 303 are respectively screwed tightly at the first external thread 3014 and the second external thread 3016. During the screwing process, the first square tooth 3015 and the second square tooth 3017 are continuously squeezed, so as to realize clamping and fixing the sleeve body 301 outside the hollow tube body 204. The sleeve body 301, the first nut 302 and the second nut 303 are all made of flame-retardant plastic materials.

[0046] The negative pressure ejector in the detection host 1 of the present invention can simultaneously generate negative pressure and suction on the air suction pipes 201 connected to 12 air inlet ports 104. The functions of the air inlet port 104 and the exhaust port 103 are respectively to suck the gas in the gas drainage borehole 7 into the detection host 1 by connecting the air suction pipe 201 to the air inlet port 104, and to discharge it to the outside of the detection host 1 or the gas collection device through the corresponding exhaust port 103. The function of the quick connector 101 is to quickly connect with the air duct 11 underground, and convert the positive pressure wind energy into the power of the negative pressure ejector through the device inside the detection host 1 for the negative pressure ejector to work. The function of the control switch 102 is to start and close the negative pressure ejector inside the detection host 1. The main function of the detection tube 2 is to extend into the gas drainage borehole 7 to provide a flow channel for collecting the gas inside the borehole.

[0047] Embodiment 2

[0048] A method for evaluating the sealing quality of a gas drainage borehole is realized by using the gas drainage borehole sealing quality detection device in Embodiment 1, and includes the following steps:

[0049] Step 1: First, it is necessary to investigate the actual sealed hole section depth L1 of the gas drainage borehole 7, the sealing method, and the total length L2 of the drainage pipe 9 used in the gas drainage borehole 7; and detect the positions before and after the connection between the drainage pipes 9, within the width of the roadway loose circle, and other possible air leakage positions to determine the number and positions of the measuring points to be detected (the number of measuring points is n, n ≤ 12). Each measuring point is respectively denoted as JC1, JC2... JC along the gas flow direction n ;

[0050] Step 2: Use a gas flow detection device to detect the mixed gas volume Q of the gas drained from the gas drainage borehole 7 to be detected;

[0051] The detection method can select an orifice plate, a relevant detector, or a pitot tube 13 to detect the mixed gas volume Q of the drained gas. Refer to Figure 6 , taking the detection by the pitot tube 13 as an example. During detection, through the detection hole reserved on the drainage pipe 9 (located at the orifice of the gas drainage borehole 7), put the detection end of the pitot tube 13 into the drainage pipe 9. The drainage pipe 9 is connected to the drainage pipeline 6 through an elbow 15, and the connection port at the tail of the pitot tube 13 is connected to a U-shaped differential pressure gauge 14 through a hose 16. Keep the drainage state and record the pressure difference value Δh and the velocity pressure value H displayed by the U-shaped differential pressure gauge 14 v (The hand-held end of the pitot tube 13 is connected to the U-shaped differential pressure gauge 14 through 2 hoses 16. When detecting, when both hoses 16 are connected to the pitot tube 13, the measured value is the pressure difference value Δh; when the hose 16 on the right side of the hand-held end of the pitot tube 13 is disconnected, the right side of the hand-held end of the pitot tube 13 and the right side of the U-shaped differential pressure gauge 14 connected to it are both connected to the atmosphere, and only the hose 16 on the left side of the hand-held end of the pitot tube 13 is connected to the left side of the U-shaped differential pressure gauge 14. At this time, the measured value is the velocity pressure value H v ), and calculate the value of the mixed gas volume Q of the gas drained in the gas drainage borehole 7 according to the following calculation formula:

[0052]

[0053] In the formula, K p is the flow coefficient of the pitot tube 13, Pa -0.5 m / min; Y is a function of the maximum Reynolds number R of the center of the drainage pipe 9 ∞ , and the value can be referred to Table 2; D is the diameter of the drainage pipe 9, m

[0054]

[0055] In the formula, D is the diameter of the drainage pipe 9, m; μ is the kinematic viscosity coefficient of the gas, which can be taken as 1.51×10 -5 m 2 / s; ν is the flow velocity at the center point inside the drainage pipe 9, m / s, and ν can be obtained from the following formula:

[0056]

[0057] where ρ is the density of the gas, kg / m 3 ; H v is the velocity pressure value at the center point of the extraction pipe 9, Pa.

[0058] Table 2 Relationship between the maximum Reynolds number R at the center of the gas extraction pipe and the Y value ∞ and the Y value

[0059]

[0060] After the measurement of the pressure difference Δh is completed, the Pitot tube 13 and the U-tube manometer 14 are recovered, and the reserved detection holes on the extraction pipe 9 are sealed. The elbow is disassembled from the extraction pipe 9 and the extraction pipeline 6, and the connection of the hole sealing quality detection device is started;

[0061] Step 3, Assemble the hole sealing quality detection device for the gas extraction borehole: First, connect the second interface and the third interface of the tee 4 to the extraction pipe 9 and the extraction pipeline 6 respectively. Then, according to the number and positions of the measuring points determined in Step 1, corresponding positions and numbers of suction ports 202 for detection are left on the hollow tube body 204 of the detection tube 2, and other suction ports 202 are blocked. The suction pipes 201 connected to the blocked suction ports 202 are marked and will not be connected to the air inlet 104 during detection. At the same time, waterproof devices 3 are installed beside each suction port 202 for detection used. The detection tube 2 with the waterproof device 3 installed is quickly inserted into the gas extraction borehole 7 from the first interface of the tee 4, and a seal 5 is installed at the connection between the first interface of the tee 4 and the detection tube 2. At this time, the gas extraction borehole 7 will enter the normal extraction state. The other ends of the suction pipes 201 for detection are respectively connected to the air inlet 104 of the detection host 1 in sequence. After the connection is completed, the detection host 1 is connected to the underground compressed air pipeline 12 by the air duct 11 to provide power for the negative pressure ejector inside the detection host 1;

[0062] Step 4, After the assembly is completed, start the control switch 102 to conduct a pre-test on the hole sealing quality detection device for the gas extraction borehole. Under normal circumstances, under the action of the negative pressure ejector, each suction port 202 and each exhaust port 103 on the detection host 1 will work simultaneously;

[0063] Step 5, after the test, turn off the control switch 102, connect each exhaust port 103 on the used detection host 1 to a rubber balloon for collecting gas, then turn on the control switch 102. The gas in the gas drainage borehole 7 will enter each suction pipe 201 in the detection pipe 2 simultaneously through each suction port 202 on the detection pipe 2, and finally enter each rubber balloon through the corresponding exhaust port 103 from each air inlet 104 on the detection host 1. After the predicted quantitative gas is collected in each rubber balloon, turn off the control switch 102, and then use the underground gas detection equipment (optical gas detector) to measure the gas concentration in each rubber balloon, or take each rubber balloon to the ground and use devices such as chromatographs to measure the gas concentration, so as to obtain the gas concentrations ND1, ND2... ND at each measuring point n ;

[0064] Step 6, repeat Step 5, and cycle in this way until the sealing quality of all the gas drainage boreholes 7 is completely measured;

[0065] Step 7, use the total leakage rate K of a single borehole to evaluate the sealing quality of each gas drainage borehole 7. The specific steps are as follows:

[0066] According to the mixed gas volume Q value of the extracted gas in the gas drainage borehole 7 obtained in Step 2 and ND1, ND2... ND obtained in Step 5 n , based on the principle that the pure gas volume of gas at each place in the gas drainage borehole 7 is the same, the pure gas volume CL at each place in the gas drainage borehole 7 is Q×ND n , and the mixed gas volume Q of the extracted gas at each measuring point i is: Q i =CL / ND i (i = 1, 2,... n), then the total leakage volume Q of the gas drainage borehole L =Q - Q1 = Q n -Q1 (the distance between the position of the detection hole for detecting the mixed gas volume Q value and the position of the nth detection point JC at the hole mouth is small, and the gases detected at both positions are in the same section of the extraction pipe 9. Therefore, the mixed gas volume Q value can be regarded as the mixed gas volume Q of the extracted gas at the JC n measuring point, that is, Q = Q n ), that is, Q = Q n ), and the total leakage rate of the borehole n ), or or

[0067] Taking the example that 6 detection points are arranged in sequence in the gas drainage borehole 7 (the deepest detection point in the gas drainage borehole 7 is JC1, and the hole mouth is JC6), that is, 6 suction ports 202 are used on the detection pipe 2. The gas concentrations and the measured values of the mixed gas volume Q of the extracted gas at each measuring point are shown in Table 3.

[0068] Table 3 Detection values of gas concentration and mixed gas volume Q of extracted gas at each measuring point

[0069]

[0070] According to the principle that the pure gas volume of gas at each point in the gas extraction borehole 7 is the same, the pure gas volume CL of gas at each point in the gas extraction borehole 7 is Q×ND n , then CL = Q×ND6 = 1.2×60% = 0.72m 3 / min; Based on this, the mixed gas volume Q of the extracted gas at each measuring point can be calculated i , Q i = CL / ND i (i = 1, 2,... n), as shown in Table 4

[0071] Table 4 Mixed gas volume Q of extracted gas at each measuring point i value

[0072]

[0073] Then the total air leakage volume Q of the gas extraction borehole 7 L is the mixed gas volume of the extracted gas at measuring point 6 (JC6) minus the mixed gas volume of the extracted gas at measuring point 1 (JC1), that is, Q L = Q6 - Q1 = 1.2 - 0.9 = 0.3m 3 / min; Furthermore, the total air leakage rate K of the borehole is as follows

[0074]

[0075] According to the value of the total air leakage rate K of the borehole, the sealing quality grade of the gas extraction borehole 7 is classified, and corresponding treatment suggestions are put forward. The sealing quality grade and recommended treatment measures are specifically shown in Table 1

[0076] Table 1 Sealing quality grade and recommended treatment measures

[0077] Total air leakage rate K (%) of the borehole Sealing quality grade Suggested treatment measures 0 Tight borehole sealing Normal use 0～10 Minor air leakage Control negative pressure 10～50 Substantial air leakage Secondary borehole sealing ≥50 Serious air leakage Demolition, isolation

[0078] According to Table 1, the total air leakage rate K of the borehole is 25%, and the sealing quality grade of the borehole belongs to large air leakage. To ensure the overall extraction effect of all gas extraction boreholes 7 in the working area, it is recommended to perform secondary sealing on them

[0079] Step 7 also includes evaluating the sealing quality of different borehole groups. When a borehole group consists of multiple gas extraction boreholes 7, the evaluation is carried out through the air leakage borehole ratio λ and the average air leakage rate η of the borehole group

[0080] Among them: the air leakage borehole ratio λ is the ratio of the number m of gas extraction boreholes 7 with air leakage to the total number N of the evaluated boreholes, that is

[0081] The average air leakage rate η is the ratio of the sum of the total air leakage rates K of the gas drainage boreholes 7 with air leakage in the entire evaluation boreholes to the number m of the gas drainage boreholes 7 with air leakage, that is

[0082] The evaluation of the sealing quality of the borehole group is carried out based on the single-borehole evaluation, by means of the air leakage borehole ratio λ and the average air leakage rate η of each borehole group. The sealing quality of the borehole group is mostly used for the comparison of the sealing quality between different sealing methods.

[0083] In this embodiment, it is assumed that there are two groups of borehole groups (the number of gas drainage boreholes 7 in each group of borehole groups is 5. The sealing method of each gas drainage borehole 7 in the first group of borehole groups is polyurethane, and the sealing method of each gas drainage borehole 7 in the second group of borehole groups is cement mortar). The sealing quality detection device for gas drainage boreholes of the present invention is used to evaluate the sealing quality of each gas drainage borehole 7 in each group of borehole groups. The total air leakage rate K values of each borehole in the two groups of borehole groups are shown in Table 5.

[0084] Table 5 Total air leakage rate K values of each gas drainage borehole in two groups of borehole groups

[0085] Gas drainage borehole 7 number of the first group of boreholes 1 2 3 4 5 Total air leakage rate K (%) of each borehole 15 0 0 20 0 Gas drainage borehole 7 number of the second group of boreholes 1 2 3 4 5 Total air leakage rate K (%) of each borehole 0 0 8 0 0

[0086] According to the data in the table and the calculation formulas of the air leakage borehole ratio λ and the average air leakage rate η, calculate

[0087] The air leakage borehole ratio of the first group of borehole groups The average air leakage rate of the first group of borehole groups

[0088] The air leakage borehole ratio of the second group of borehole groups The average air leakage rate of the second group of borehole groups

[0089] By comparing the air leakage borehole ratio λ and the average air leakage rate η of the two groups of borehole groups, it can be seen that both the air leakage borehole ratio λ and the average air leakage rate η of the second group of borehole groups are smaller than those of the first group of borehole groups. That is, the sealing quality of the boreholes with the cement mortar sealing method in the second group is significantly higher than that of the boreholes with the polyurethane sealing method in the first group.

[0090] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A device for detecting the sealing quality of gas drainage boreholes, characterized in that, It includes a detection host, a detection tube, a seal and a tee. There are multiple air inlets and multiple air outlets above the detection host. A negative pressure ejector is provided inside the detection host. A quick connector and a control switch are also provided on the detection host. The quick connector is used to connect with the air duct underground. The air duct underground is additionally connected to the compressed air pipeline underground. The control switch is used to start and stop the negative pressure ejector inside the detection host. The second interface of the tee is connected to the extraction pipe. The extraction pipe is placed in the gas extraction borehole. The third interface of the tee is connected to the extraction pipeline. One end of the detection tube is connected to the air inlet of the detection host. The other end of the detection tube passes through the first interface of the tee and then passes out from the second interface and is placed in the extraction pipe and the gas extraction borehole. A seal is provided at the connection between the detection tube and the first interface of the tee. The seal is used to seal the gap between the detection tube and the first interface of the tee; The detection tube includes a hollow tube body, multiple air suction ports, a support skeleton and multiple air suction pipes. There are multiple air suction ports arranged at intervals on the hollow tube body. A support skeleton is provided inside the hollow tube body. Multiple through holes for the air suction pipes to pass through are provided on the support skeleton. One air suction pipe can pass through each through hole. One ends of the multiple air suction pipes pass through the through holes on the support skeleton and are respectively connected to the air suction ports on the hollow tube body one by one. One section of the other end of each air suction pipe is placed outside the hollow tube body and is connected to the air inlet on the detection host one by one during use.

2. The gas drainage borehole sealing quality detection device according to claim 1, characterized in that The number of the air suction ports is 12, and the number of the air suction pipes is 12.

3. The gas drainage borehole sealing quality detection device according to claim 1, characterized in that, The hollow tube body and the support skeleton are made of aluminum-plastic material, and the air suction pipes are made of flame-retardant PE material.

4. The gas drainage borehole sealing quality detection device according to claim 1, characterized in that Multiple waterproof devices are also installed on the detection tube. The waterproof devices are sleeved on the hollow tube body and are placed behind each air suction port.

5. The gas drainage borehole sealing quality detection device according to claim 4, characterized in that, The waterproof device includes a sleeve body, a first nut and a second nut. The sleeve body includes a first hollow cylindrical section. A second hollow cylindrical section and a third hollow cylindrical section are respectively provided at both ends of the first hollow cylindrical section. A first external thread and a first square tooth are provided on the outer peripheral surface of the second hollow cylindrical section. A second external thread and a second square tooth are provided on the outer peripheral surface of the third hollow cylindrical section. The sleeve body is sleeved outside the hollow tube body. By respectively installing the first nut and the second nut on the second hollow cylindrical section and the third hollow cylindrical section, the first nut and the second nut are respectively screwed tightly at the first external thread and the second external thread, and the sleeve body is fixed outside the hollow tube body.

6. A method for evaluating the sealing quality of gas drainage boreholes, which is realized by using the gas drainage borehole sealing quality detection device described in any one of claims 1-5, characterized in that, It includes the following steps: Step 1: First, it is necessary to investigate the actual sealing section depth L1 of the gas drainage borehole, the sealing method, and the total length L2 of the drainage pipes used in the gas drainage borehole; and detect the positions before and after the connection between the drainage pipes, within the width of the roadway loose circle, and other positions where air leakage may occur, to determine the number and positions of the measuring points to be detected. Each measuring point is respectively denoted as JC1, JC2... JC along the gas flow direction n ; Step 2, use a gas flow detection device to detect the mixed gas volume Q of the gas extracted from the gas extraction borehole to be detected; Step 3, assemble the device for detecting the sealing quality of gas drainage boreholes: First, connect the second interface and the third interface of the three-way joint to the gas drainage pipe and the gas drainage pipeline respectively. Then, according to the number and positions of the measuring points determined in Step 1, leave the corresponding positions and numbers of air inlets for detection on the hollow pipe body of the detection pipe, and block the other air inlets. Mark the air suction pipes connected to the blocked air inlets, and do not connect them to the air inlet during detection. At the same time, install waterproof devices beside each air inlet for detection in use. Quickly place the detection pipe with the installed waterproof device into the gas drainage borehole from the first interface of the three-way joint, and install a seal at the connection between the first interface of the three-way joint and the detection pipe. At this time, the gas drainage borehole will enter the normal drainage state. Connect the other ends of the air suction pipes for detection to the air inlets of the detection host in sequence. After the connection is completed, connect the detection host to the underground compressed air pipeline using an air duct to provide power for the negative pressure ejector inside the detection host; Step 4, after the assembly is completed, start the control switch to conduct a pre-test on the device for detecting the sealing quality of gas drainage boreholes. Under normal circumstances, under the action of the negative pressure ejector, all the air inlets and all the air outlets on the detection host will work simultaneously; Step 5, after the test is completed, turn off the control switch, connect each exhaust port on the detection host used to the rubber bladder for collecting gas, then turn on the control switch. The gas in the gas drainage borehole will enter each suction pipe in the detection tube through each suction port on the detection tube at the same time, and finally enter each rubber bladder through the corresponding exhaust port from each intake port on the detection host. After the gas to be detected is collected in each rubber bladder, turn off the control switch, and then use the underground gas detection equipment to measure the gas concentration in each rubber bladder, or take each rubber bladder to the ground and use devices such as chromatographs to measure the gas concentration, obtaining the gas concentration ND1, ND2... ND at each measurement point n ; Step 6, repeat Step 5, and cycle in this way until the sealing quality of all gas drainage boreholes is completely measured; Step 7, use the total leakage rate K of a single borehole to evaluate the sealing quality of each gas drainage borehole.

7. The quality evaluation method for gas drainage borehole sealing according to claim 6, characterized in that, The specific steps for evaluating the sealing quality of each gas drainage borehole in Step 7 are as follows: Based on the mixed gas volume Q value in the gas drainage borehole obtained in step 2 and ND1, ND2... ND obtained in step 5 n , according to the principle that the pure gas content of gas is the same at each location in the gas drainage borehole, the pure gas content CL at each location in the gas drainage borehole is Q×ND n , based on Q i =CL / ND i (i = 1, 2,... n), the mixed gas volume Q of the drained gas at each measuring point is calculated i , then the total air leakage volume Q L＝ Q - Q 1＝ Q n -Q1, the total air leakage rate of the borehole or 8. The quality evaluation method for gas drainage borehole sealing according to claim 6, characterized in that, The evaluation method for the sealing quality of gas drainage boreholes further includes, after Step 7, performing Step 8. Step 8 is specifically as follows: According to the value of the total leakage rate K of the borehole, divide the grade of the sealing quality of the gas drainage borehole, and put forward corresponding treatment suggestions. The sealing quality grades and recommended treatment measures are as follows: When the total leakage rate K of the borehole is 0, the sealing quality grade is tight sealing, and the recommended treatment measure is normal use; When the total leakage rate K of the borehole is 0 - 10%, the sealing quality grade is minor leakage, and the recommended treatment measure is to control the negative pressure; When the total leakage rate K of the borehole is 10% - 50%, the sealing quality grade is large leakage, and the recommended treatment measure is secondary sealing; When the total leakage rate K of the borehole ≥ 50%, the sealing quality grade is severe leakage, and the recommended treatment measure is to remove and isolate; 9. The quality evaluation method for gas drainage borehole sealing according to claim 6, characterized in that, Step 7 also includes evaluating the sealing quality of different borehole groups. When a borehole group consists of multiple gas drainage boreholes, evaluate it through the leakage borehole ratio λ and the average leakage rate η of the borehole group; Wherein: the air leakage borehole ratio λ is the ratio of the number m of air leakage gas drainage boreholes to the total number N of all evaluation boreholes, that is The average air leakage rate η is the ratio of the sum of the total air leakage rates K of the gas drainage boreholes with air leakage in the entire evaluation boreholes to the number m of the gas drainage boreholes with air leakage, that is

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