Construction method for forced caving of carbon dioxide fracturing device

Abstract

The invention relates to the technical field of construction methods for forced caving, and provides a construction method for forced caving of a carbon dioxide fracturing device, the carbon dioxide fracturing technology is different from traditional explosives, and carbon dioxide fracturing does not generate open fire and heat sources, so that the major potential safety hazard of gas explosion in the fracturing process is completely eradicated, and the construction efficiency is improved. In the using process, the safety and reliability are higher, the carbon dioxide fracturing process is a physical change, various poisonous and harmful gases generated due to chemical reaction cannot be generated, guarantee is provided for health of workers, no shock wave is generated during carbon dioxide fracturing, vibration is small, the influence on roadway supporting is small, and the safety and reliability are high. Not only is the probability of inducing gas outburst greatly reduced, but also the safety in construction is improved, and the method comprises the following steps of preparation before construction, site preparation, drilling construction, fracturing device installation, detonation and top caving aftertreatment, and the preparation before construction comprises technical preparation, equipment material preparation and site preparation.

Description

Technical Field

[0001] The invention relates to the technical field of forced top caving construction methods, and in particular to a carbon dioxide fracturing device forced top caving construction method. Background Art

[0002] As we all know, a carbon dioxide fracturing device is a device that uses liquid carbon dioxide to rapidly gasify and expand when heated to generate powerful thrust. Forced roof caving is a measure that uses certain technical means to artificially cause unstable rock strata above the goaf or at the top of the tunnel to collapse in time, so as to reduce roof pressure and ensure the safety of the working space. Applying a carbon dioxide fracturing device to the forced roof caving process is called forced roof caving by a carbon dioxide fracturing device. Forced roof caving by a carbon dioxide fracturing device is a roof control technology used in mines, tunnels and other projects.

[0003] During the advancement of the coal mining face, the two air inlet and return tunnels will have hanging ceilings. There are two major hazards after the hanging ceiling is generated. First, it is very easy for toxic and harmful gases such as gas to accumulate at the rear of the working face. Second, the sudden collapse of a large area of ​​hanging ceiling is likely to produce shock waves, which will cause great harm to the equipment and personnel in the tunnel. In order to eliminate the hanging ceiling phenomenon in the two tunnels of the working face, it is generally adopted to drill holes behind the hanging ceiling of the tunnel (in the direction of advancement of the working face), and then use explosives to blast them to cut off the hanging ceiling and make it collapse in time.

[0004] Although the existing blasting with explosives can cut off the hanging roof and achieve the purpose of timely collapse of the hanging roof, there are great safety hazards in the use of blasting with explosives. First, blasting with explosives is prone to produce open flames, which can cause gas or coal dust explosions. Second, the management of explosives is very strict (once they flow into society, serious consequences will occur), and the management cost far exceeds the cost of use. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a construction method for forced roof release using a carbon dioxide fracturing device. The carbon dioxide fracturing technology is different from traditional explosives. Carbon dioxide fracturing does not produce open flames and heat sources, thereby eliminating the major safety hazard of gas explosion during the fracturing process. The safety and reliability are higher during use. The carbon dioxide fracturing process is a physical change and will not produce various toxic and harmful gases generated by chemical reactions, thus providing a guarantee for the health of workers. Carbon dioxide fracturing does not produce shock waves and has little vibration, and has little effect on tunnel support. It not only greatly reduces the probability of inducing gas outbursts, but also improves the safety during construction.

[0006] To achieve the above object, the present invention provides the following technical solution: a construction method for forced top caving of a carbon dioxide fracturing device, comprising the following steps:

[0007] S1. Preparation before construction

[0008] S11. Technical preparation: Be familiar with the geological conditions and rock structure of the construction site, formulate a detailed construction plan, and clarify the fracturing parameters and construction process;

[0009] Provide technical briefing and safety training to construction personnel to ensure they understand the working principle, operation method and safety precautions of the carbon dioxide fracturing device;

[0010] S12. Equipment and material preparation

[0011] Prepare sufficient number of carbon dioxide fracturing devices and check whether their quality and performance meet the requirements. The fracturing devices should have certificates of conformity and test reports;

[0012] Prepare electrical equipment such as detonators and wires, and ensure their reliable performance;

[0013] Prepare protective equipment, such as hard hats, protective glasses and earplugs;

[0014] S13. Site preparation

[0015] Clean up the construction site to ensure there are no obstacles and flammable and explosive items;

[0016] Set up cordons and warning signs around the construction area to prohibit unauthorized personnel from entering;

[0017] S2. Drilling construction

[0018] Determine the drilling location and parameters according to the construction plan, use a drilling rig to drill, and the drilling diameter and depth should meet the requirements of the fracturing device;

[0019] During the drilling process, the verticality and smoothness of the hole wall must be ensured to avoid bending or hole collapse;

[0020] After drilling is completed, the cuttings in the hole are cleaned up with high-pressure air and water;

[0021] S3. Installation of the cracking device

[0022] Carefully place the carbon dioxide fracturing device into the borehole, making sure that the release tube of the fracturing device faces the predetermined top-dropping direction;

[0023] According to the model and specifications of the cracker, select the appropriate detonation method and connect the detonator with the cracker;

[0024] Fill a certain thickness of taphole mud around the fracturing device to increase the fracturing effect and reduce flying rocks;

[0025] S4, Detonation

[0026] Check the detonation circuit and equipment again to ensure that the connection is correct and reliable;

[0027] After all personnel have evacuated to a safe area, a dedicated person will be responsible for detonation. Detonation must be carried out strictly in accordance with the operating procedures to ensure safety;

[0028] S5, post-top processing

[0029] After detonation, wait for a while to allow the rock to fully break and collapse, then ventilate to remove blasting smoke and harmful gases;

[0030] Inspect the site after roofing and clean up loose rocks and debris;

[0031] Evaluate the effect of roof caving. If the expected effect is not achieved, additional blasting and further adjustment of the construction plan are required;

[0032] Preferably, in step S2, the drilling depth is 10m-15m, ensuring that the blasting section is located in the roof rock layer, the hole diameter is Ф89mm, the drilling direction is along the slot to the outside of the working face, the drilling inclination is generally 20-30°, and the distance between the hole mouth and the bottom plate is not less than 1.5m. Before drilling, it must be ensured that the roof and the two sides of the surrounding rock are stable, otherwise reliable support should be carried out first to ensure the safety of the work site. When drilling, it is not allowed to try to hold the drill rod with a gloved hand, and each pipe joint must use a matching regular U-shaped pin to ensure that the drilling rig is not short of oil, otherwise the drilling rig shall not be operated. During operation, the personnel must tighten their cuffs to prevent accidental injury due to entanglement in clothes.

[0033] Preferably, the fracturing device in step S3 is made of 6 sections of ZL250-63 / 1200 carbon dioxide fracturing devices connected in series, each section of the fracturing device is injected with 1.5 kg of carbon dioxide, and its blasting equivalent is equivalent to 3 kg of ordinary fracturing devices. During the installation process, the remaining uncharged sections of the blasthole are connected with a Φ63 fracturing device connecting rod, and the hole is sealed and fixed with wooden wedges at the hole mouth, and the number of sealing wooden wedges is not less than 4.

[0034] Preferably, in step S4, the requirements for the seismic wave velocity measurement of the microseismic monitoring system of the entire mine must be met, and the normal monitoring operation of the microseismic monitoring system must be ensured during blasting. The "XYZ" of the artificial blasting explosion source position must be the precise position of the fracturing device placement point, and its coordinate system is the same as that of each sensor.

[0035] Preferably, in step S4, all connections must be carefully checked before blasting, and the busbar connection leg wires can only be blasted after confirmation, and a blasting signal must be issued before blasting and at least 5 seconds must be waited before detonation.

[0036] Preferably, after the blasting in step S5, a comprehensive inspection of the support conditions of the surrounding tunnels must be carried out when entering the blasting site. If broken beams, bent columns and roof collapse are found, re-support must be carried out. After the blasting, the fracturing devices are removed one by one and lifted to the well for next use.

[0037] Preferably, the evaluation of the caving effect in step S5 includes wave velocity calculation and positioning accuracy analysis. During the wave velocity calculation process, since the positioning calculation is performed in a small-scale space, the propagation velocity of the elastic wave is considered to be a constant. Therefore, the propagation velocity of the elastic wave under coal-rock conditions is determined to be the distance difference from any detector to the blasting point divided by the corresponding inverse time difference, which is the propagation velocity of the elastic wave. The calculation formula is:

[0038] V=Δs / Δt

[0039] In this way, a series of velocity values ​​can be obtained. Using the above data, the average value can be used to obtain the average propagation velocity of microseismic waves in coal mines. During the positioning accuracy analysis, the positioning accuracy of the calibration gun (measured value m / millisecond) is calibrated according to the measured propagation velocity of seismic waves in the mine strata. The wave velocity of the monitoring software is set to the measured analysis wave velocity, and the calibration gun is implemented again. The positioning result is compared with the actual coordinates, and the wave velocity is corrected again to achieve the positioning accuracy.

[0040] Compared with the prior art, the present invention provides a construction method for forced top caving of a carbon dioxide fracturing device, which has the following beneficial effects:

[0041] In the present invention, the formulation of a construction method for forced roof caving by a carbon dioxide fracturing device not only introduces a safer method of forced roof caving construction, but also carbon dioxide fracturing does not produce open flames and heat sources, thereby eliminating the major safety hazard of gas explosion during the fracturing process, and the safety and reliability are higher during use. The carbon dioxide fracturing process is a physical change and will not produce various toxic and harmful gases generated by chemical reactions, which provides a guarantee for the health of workers. Carbon dioxide fracturing does not produce shock waves and vibrations, and has little effect on tunnel support. It not only greatly reduces the probability of inducing gas outbursts, but also improves the safety during construction. In addition, a specification document is formulated to match the construction process, which ensures the construction specifications while further improving the construction safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the design of calibrated gun borehole parameters of the present invention. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example

[0045] See also Figure 1The construction method of forced top caving of a carbon dioxide fracturing device comprises the following steps:

[0046] S1. Preparation before construction

[0047] S11. Technical preparation: Be familiar with the geological conditions and rock structure of the construction site, develop a detailed construction plan, clarify the fracturing parameters and construction process, conduct technical briefings and safety training for construction personnel, and ensure that they understand the working principle, operation method and safety precautions of the carbon dioxide fracturing device.

[0048] S12. Equipment and material preparation

[0049] Prepare a sufficient number of carbon dioxide fracturing devices and check whether their quality and performance meet the requirements. The fracturing devices should have certificates of conformity and test reports. Prepare electrical equipment such as detonators and wires and ensure their reliable performance. Prepare protective equipment such as safety helmets, protective glasses and earplugs.

[0050] S13. Site preparation

[0051] Clean up the construction site, ensure there are no obstacles and flammable and explosive items, set up cordons and warning signs around the construction area, and prohibit unauthorized personnel from entering.

[0052] S2. Drilling construction

[0053] The drilling position and parameters are determined according to the construction plan, and a drilling rig is used for drilling. The diameter and depth of the drilling hole should meet the requirements of the fracturer. The verticality and smoothness of the hole wall should be ensured during the drilling process to avoid bending or hole collapse. After the drilling is completed, the rock chips in the hole are cleaned with high-pressure wind and water. The drilling depth is 10m~15m, and the blasting section is ensured to be located in the roof rock layer. The hole diameter is Ф89mm, and the drilling direction is along the slot to the outside of the working face. The drilling inclination is generally 20~30°, and the distance between the hole mouth and the bottom plate is not less than 1.5m. Before drilling, it is necessary to ensure that the roof and the surrounding rocks on both sides are stable, otherwise reliable support should be carried out first to ensure the safety of the work site. When drilling, it is not allowed to try to hold the drill rod with gloved hands. Each pipe joint must use a matching regular U-shaped pin to ensure that the drilling rig is not short of oil, otherwise the drilling rig shall not be operated. During operation, the personnel must tighten their cuffs to prevent accidental injury due to entanglement in clothes.

[0054] S3. Installation of the cracking device

[0055] Carefully place the carbon dioxide fracturing device into the borehole, ensuring that the release tube of the fracturing device faces the predetermined top release direction. According to the model and specification of the fracturing device, select the appropriate detonation method, connect the detonator to the fracturing device, and fill a certain thickness of gun mud around the fracturing device to increase the fracturing effect and reduce flying rocks. The fracturing device uses 6 sections of ZL250-63 / 1200 carbon dioxide fracturing devices in series, and each section of the fracturing device is injected with 1.5kg of carbon dioxide, and its blasting equivalent is equivalent to 3kg of ordinary fracturing devices. During the installation process, the remaining uncharged sections of the blasthole are connected with a Φ63 fracturing device connecting rod, and the hole is sealed and fixed with wooden wedges at the hole mouth. There should be no less than 4 sealing wooden wedges.

[0056] S4, Detonation

[0057] Check the blasting lines and equipment again to ensure that the connection is correct and reliable. After all personnel have evacuated to a safe area, a dedicated person will be responsible for detonation. Detonation must be carried out in strict accordance with the operating procedures to ensure safety. The requirements for the seismic wave velocity measurement of the microseismic monitoring system for the entire mine must be met. The normal monitoring and operation of the microseismic monitoring system must be ensured during blasting. The "XYZ" of the artificial blasting explosion source position must be the precise location of the fracturing device placement point, and its coordinate system must be the same as that of each sensor. All connections must be carefully checked before blasting, and the busbar connection leg lines can only be blasted after confirmation. A blasting signal must be issued before blasting and at least 5 seconds must be waited before detonation.

[0058] S5, post-processing

[0059] After detonation, wait for a while to allow the rock to fully break and collapse, then ventilate, remove blasting smoke and harmful gases, inspect the site after roof release, and clean up loose rocks and debris. After blasting, enter the blasting site and conduct a comprehensive inspection of the support conditions of the surrounding tunnels. If broken beams, broken columns and roof collapse are found, they must be re-supported. After blasting, remove the fracturers one by one and lift them to the well for next use. Evaluate the roof release effect. If the expected effect is not achieved, supplementary blasting and further adjustment of the construction plan are required. Evaluation of the roof release effect includes wave velocity calculation and positioning accuracy analysis. During the wave velocity calculation process, since the positioning calculation is performed in a small-scale space, it is determined that the propagation speed of elastic waves is a constant. Therefore, the propagation speed of elastic waves under coal and rock conditions is determined to be the distance difference from any detector to the blasting point divided by the corresponding inverse time difference, which is the propagation speed of elastic waves. The calculation formula is:

[0060] V=Δs / Δt

[0061] In this way, a series of velocity values ​​can be obtained. Using the above data, the average value can be used to obtain the average propagation velocity of microseismic waves in coal mines. During the positioning accuracy analysis, the positioning accuracy of the calibration gun (measured value m / millisecond) is calibrated according to the measured propagation velocity of seismic waves in the mine strata. The wave velocity of the monitoring software is set to the measured analysis wave velocity, and the calibration gun is implemented again. The positioning result is compared with the actual coordinates, and the wave velocity is corrected again to achieve the positioning accuracy.

[0062] In summary: The specific safety measures are as follows:

[0063] 1) Before blasting, the equipment, pipelines, cables, etc. on site must be well protected to prevent damage caused by blasting.

[0064] 2) The tunnels at the blasting site must be reinforced; before each charging and after blasting, the support conditions within a radius of 30m must be carefully checked. Only after confirmation can the next step of operation be carried out. Any problems found must be dealt with immediately.

[0065] 3) Before charging, the surrounding rock and hanging gangue must be removed. The blaster must be in a safe place when making the blast head to prevent coal from falling from the top and hitting the blast head.

[0066] 4) Before charging, three warnings must be set up for blasting, namely, warning personnel, warning ropes, and warning signs. If the warning personnel do not hear the evacuation order from the blaster or safety officer, they are strictly prohibited from evacuating the warning post at will.

[0067] 5) When setting off fireworks, the “three inspections for one shot” and three-person chain firing system must be strictly followed.

[0068] 6) It is strictly forbidden to smash, bump or hit the cracker. Only blasters are allowed to assemble the cracker, and no one else is allowed to replace it. The distance of the cordon is at least 300m, and the time to avoid the blast is not less than 40 minutes.

[0069] 7) As this deep hole blasting is the first construction in the mine, the on-site construction procedures are complicated and the workload is relatively large. At the same time, there are technical instructors such as the anti-collision department. It is now planned that the number of on-site charging and auxiliary personnel will not exceed 9 people.

[0070] 8) When installing a fracturer, personnel must not face the mouth of the blast hole to prevent the fracturer or other objects from slipping out and injuring people.

[0071] 9) Before blasting, the production unit of the working face must be contacted and notified, and all personnel must evacuate the tunnel 300 meters away from the blasting site.

[0072] 10) During charging, no personnel not related to the blasting operation are allowed to be in the warning area.

[0073] 11) The fracturing device must reach the bottom of the hole and ensure that the fracturing device is conductive and insulated from the pipe body; and strict installation records must be kept, with clear records of the installation conditions, hole sealing conditions, and installers.

[0074] 12) The uncharged part of the blasthole must be connected to the hole mouth with a Φ63 cracker connecting rod, and the hole mouth must be sealed and compacted with wooden wedges.

[0075] 13) All line joints must be wrapped with waterproof tape and the wiring points must be suspended in the air to prevent them from contacting the bottom plate, the side of the lane or any conductive body.

[0076] 14) A dedicated gas inspector must be assigned to conduct gas detection. When the gas concentration exceeds 1%, charging and blasting are strictly prohibited.

[0077] 15) Strictly manage the detonator to ensure that the detonator is in good condition and its voltage meets the requirements;

[0078] 16) All connections must be carefully checked before blasting. The busbar connection legs can only be blasted after confirmation. A blasting signal must be given and then at least 5 seconds must pass before detonation.

[0079] 17) Pressure relief blasting must be managed by posting a signboard. Whoever performs the construction and supervision is responsible. Blasting workers and assistants must strictly control the quality and prevent man-made accidents.

[0080] 18) After the blasting, the team leader must conduct a comprehensive inspection of the support conditions of the surrounding tunnels when entering the blasting site. If any broken beams, columns, or roof collapse is found, re-support must be carried out.

[0081] 19) After the blasting, the fracturing devices are removed one by one and lifted out of the well for next use.

[0082] 20) All commanders and operators at the work site must strictly implement the "Coal Mine Safety Regulations", "Coal Mine Work Safety Technical Operation Regulations" and other special safety and technical measures in the work area.

[0083] 21) All operating personnel must hold valid job certificates and strictly implement various rules and regulations. It is strictly prohibited to give illegal commands, perform illegal operations, and violate labor discipline.

[0084] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A construction method for forced top caving of a carbon dioxide fracturing device, characterized in that: The following steps are involved: S1. Preparation before construction S11. Technical preparation: Be familiar with the geological conditions and rock structure of the construction site, formulate a detailed construction plan, and clarify the fracturing parameters and construction process; Provide technical briefing and safety training to construction personnel to ensure they understand the working principle, operation method and safety precautions of the carbon dioxide fracturing device; S12. Equipment and material preparation Prepare sufficient number of carbon dioxide fracturing devices and check whether their quality and performance meet the requirements. The fracturing devices should have certificates of conformity and test reports; Prepare electrical equipment such as detonators and wires, and ensure their reliable performance; Prepare protective equipment; S13. Site preparation Clean up the construction site to ensure there are no obstacles and flammable and explosive items; Set up cordons and warning signs around the construction area to prohibit unauthorized personnel from entering; S2. Drilling construction Determine the drilling location and parameters according to the construction plan, use a drilling rig to drill, and the drilling diameter and depth should meet the requirements of the fracturing device; During the drilling process, the verticality and smoothness of the hole wall must be ensured to avoid bending or hole collapse; After drilling is completed, the cuttings in the hole are cleaned up with high-pressure air and water; S3. Installation of the cracking device Carefully place the carbon dioxide fracturing device into the borehole, making sure that the release tube of the fracturing device faces the predetermined top-dropping direction; According to the model and specifications of the cracker, select the appropriate detonation method and connect the detonator with the cracker; Fill a certain thickness of taphole mud around the fracturing device to increase the fracturing effect and reduce flying rocks; S4, Detonation Check the detonation circuit and equipment again to ensure that the connection is correct and reliable; After all personnel have evacuated to a safe area, a dedicated person will be responsible for detonation. Detonation must be carried out strictly in accordance with the operating procedures to ensure safety; S5, post-top processing After detonation, wait for a while to allow the rock to fully break and collapse, then ventilate to remove blasting smoke and harmful gases; Inspect the site after roofing and clean up loose rocks and debris; Evaluate the effect of roof blasting. If the expected effect is not achieved, additional blasting and further adjustment of the construction plan are required.

2. The construction method of forced caving of a carbon dioxide fracturing device according to claim 1, characterized in that: In step S2, the drilling depth is 10m-15m, ensuring that the blasting section is located in the roof rock layer, the hole diameter is Ф89mm, the drilling direction is along the slot to the outside of the working face, the drilling inclination is generally 20-30°, and the distance between the hole mouth and the bottom plate is not less than 1.5m. Before drilling, it must be ensured that the roof and the surrounding rocks on both sides are stable, otherwise reliable support should be carried out first to ensure the safety of the work site. When drilling, it is not allowed to try to hold the drill rod with a gloved hand, and each pipe joint must use a matching regular U-shaped pin to ensure that the drilling rig is not short of oil, otherwise the drilling rig shall not be operated. During operation, the personnel must tighten their cuffs to prevent accidental injury due to entanglement in clothes.

3. The construction method of forced caving of a carbon dioxide fracturing device according to claim 2, characterized in that: The fracturing device in step S3 is made of 6 sections of ZL250-63 / 1200 carbon dioxide fracturing devices connected in series, each section of the fracturing device is injected with 1.5kg of carbon dioxide, and its blasting equivalent is equivalent to 3kg of ordinary fracturing devices. During the installation process, the remaining uncharged sections of the blasthole are connected with Φ63 fracturing device connecting rods, and the hole is sealed and fixed with wooden wedges at the hole mouth, and the number of sealing wooden wedges is not less than 4.

4. The construction method of forced caving of a carbon dioxide fracturing device according to claim 3 is characterized in that: In step S4, the requirements for the seismic wave velocity measurement of the microseismic monitoring system of the entire mine must be met. The normal monitoring operation of the microseismic monitoring system must be ensured during blasting. The "XYZ" of the artificial blasting explosion source position must be the precise position of the fracturing device placement point, and its coordinate system is the same as that of each sensor.

5. The construction method of forced caving of a carbon dioxide fracturing device according to claim 4, characterized in that: In step S4, all connections must be carefully checked before blasting, and the busbar connection leg wires can only be blasted after confirmation. A blasting signal must be issued before blasting and at least 5 seconds must be waited before detonation.

6. The construction method of forced caving of a carbon dioxide fracturing device according to claim 5, characterized in that: After the blasting in step S5, a comprehensive inspection of the support conditions of the surrounding tunnels must be carried out when entering the blasting site. If broken beams, collapsed columns, and roof collapse are found, they must be re-supported. After the blasting, the fracturing devices are removed one by one and lifted to the well for next use.

7. The construction method of forced caving of a carbon dioxide fracturing device according to claim 6, characterized in that: The evaluation of the caving effect in step S5 includes wave velocity calculation and positioning accuracy analysis. In the wave velocity calculation process, since the positioning calculation is performed in a small-scale space, the propagation velocity of the elastic wave is considered to be a constant. Therefore, the propagation velocity of the elastic wave under coal and rock conditions is determined to be the distance difference from any detector to the blasting point divided by the corresponding inverse time difference, which is the propagation velocity of the elastic wave. The calculation formula is: V=Δs / Δt In this way, a series of velocity values ​​can be obtained. Using the above data, the average value can be used to obtain the average propagation velocity of microseismic waves in coal mines. During the positioning accuracy analysis, the positioning accuracy of the calibration gun is calibrated according to the measured propagation velocity of seismic waves in the mine strata. The wave velocity of the monitoring software is set to the measured analysis wave velocity, and the calibration gun is implemented again. The positioning result is compared with the actual coordinates, and the wave velocity is corrected again to achieve the positioning accuracy.

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