What safety issues should be paid attention to during grouting construction behind coal mine walls?

1. Purpose and significance: This tunnel is a major project. In the later stage, it is susceptible to shrinkage and deformation of the scaffolding and cracking of the pulp skin due to mining, which affects the safety of waiting workers. In order to increase the service life of the waiting room and reduce the amount of tunnel maintenance , after the mine research, it was decided to set up a surrounding rock reinforcement test team. In accordance with the learning concept of going out and inviting in, the test team was arranged to go to the No. 4 Mine to learn the behind-the-wall grouting reinforcement technology. The fourth coal bottom waiting room reinforced in this test is about 18m long. In order to ensure safe construction, the following safety technical measures have been specially formulated: 2. Project Overview The fourth coal bottom waiting room is located on the east wing of the bottom of the Si 3 Coal I mining area and is connected to the No. 4 coal track. Going down the mountain is a -250m single-track lane with an elevation of -245m. It is mainly used for workers to take people's cars to and from get off work and wait for a rest. The waiting room is located in the 43 coal seam. Due to the emergence of mine pressure, the tunnel has become severely deformed and needs to be repaired before it can continue to be used. The tunnel has just been repaired. The support uses 36U-shaped steel arches and concrete shotcrete support. The tunnel has a net width of 3.5 m, a net height of 2.85 m, a shed spacing of 0.6 m, and a shotcrete thickness of 150 mm. Grouting reinforcement technology is used during repairs. 3. Construction methods and sequence: 1. On-site equipment, two YT28 air leg rock drills (one for use and one for backup) and supporting drill pipe drill bits, two MQT-120/3.0 pneumatic anchor (anchor cable) drilling rigs (one for use and one for backup) Equipment) and supporting drill pipe bits, one grouting pump, two slurry containers (volume not less than 0.4m3), four high-pressure pipes, sufficient No. 425 cement and grouting anchors, etc. 2. Equipment installation, disassembly and transportation of equipment into the well, and operation in strict accordance with the underground operating procedures.

3. Mark the grouting holes. The first row is marked 1-1, 1-2 from bottom to top, left to right, and so on to facilitate observation and recording. First construct 1-1, 1-3, 1-5...then construct 7-1, 7-3, 7-5...and so on. The row spacing is 1.0 meters and the spacing is 1.5 meters. Drill a row of holes and grout one row. 4. Drill the grouting hole, use a pneumatic drill to drill the grouting hole (2.5 meters deep), and clean the hole. 5. According to the conditions of the tunnel, grouting rows will be tentatively spaced 3 meters apart. In order to prevent grouting from running out, specific adjustments will be made based on the actual situation. 6. Grouting steps: ① Connecting equipment: The grouting pump is connected to an external pressure gauge and high-pressure pipe. One of the high-pressure pipes is the outlet pipe, and the outlet high-pressure pipe is connected to the high-pressure valve on the casing at the outer end of the borehole; the other is connected to the Containers for slurry are connected. In addition, it is required to use intact U-shaped pins when connecting, and ensure that all parts of the equipment are firmly connected. The connection between the grouting pump and the power supply must be safe and reliable, and must be connected by certified professionals. Failure to explode is strictly prohibited. ② Mixing materials: After the equipment is connected, mix cement and water into the container according to the proportion determined on site, and stir thoroughly. ③ Turn on the grouting pump, the slurry enters the grouting pump from the container, and then enters the borehole through the high-pressure pipe. ④Grouting will stop when the final grouting pressure is reached. The grouting pressure in the later stage should be appropriately adjusted according to the changes in the surrounding rock during grouting. ⑤ Observe the grouting equipment carefully during the grouting process to ensure the safety and normal operation of the equipment. After completion, first close the high-pressure valve, and then remove the high-pressure pipe connected to the grouting pump outside the high-pressure valve. It is strictly forbidden to disassemble the grouting pump under pressure for maintenance and cleaning. 7. Hole sealing: After careful analysis, the grouting holes that have indeed completed the grouting task will be sealed as required. 8. Inspection of grouting effect: Set up observation points in the tunnel to ① check the changes in the tunnel before and after grouting, such as width and height; ② observe the deformation of the tunnel in the next six months and beyond after grouting. 9. Construction of grouting effect inspection holes: After the grouting project is basically completed, observe the tunnel conditions and construct inspection holes to analyze the inspection hole data and analyze the tunnel grouting transformation effect. 10. Personnel arrangement: work in three shifts: two people for drilling grouting holes and cleaning them, two people for grouting and sealing holes, two people for grouting and mixing, and one electrician for mountain observation and recording. There are 7 people on duty in one shift, 21 people in the third shift, and 3 people on alternate days. A total of 24 people are needed. Four: Mechanical and electrical management 1. All mechanical and electrical equipment used must have product certificates, coal mine product safety signs, and explosion-proof certificates, otherwise they shall not be used. 2. All equipment must be in good condition, with complete safety protection devices, sensitive and reliable. 3. Establish a shift handover system for electromechanical equipment and an inspection, maintenance and maintenance system for each shift, fill in electrical and mechanical fault records, discover hidden dangers and deal with them in a timely manner. 4. The power supply method and line laying must comply with the safety technical equipment serialization standards and hanging standards. 5. Set up a full-time electrician to manage electrical explosion-proofing, check the electromechanical equipment in the tunnel every day and keep records to prevent electrical explosions. 6. When performing maintenance on electrical equipment, a designated person must be designated to stop the power supply, and others are strictly prohibited from stopping the power supply. 7. Maintenance personnel must carry portable gas detectors.

During maintenance, first cut off the power supply, lock the switch, and put up a power outage for maintenance or power supply prohibited sign. Always check for gas near electrical equipment before turning it on. When opening electrical equipment, it is necessary to check the electricity, discharge it to the ground, and hang a safety short-circuit grounding wire. 8. All electrical equipment must have three nos (no chicken feet, no sheep tails, no open joints) and four haves (overcurrent and leakage protection devices, screws and spring washers, seals and baffles, and grounding) installation), two things (cables are hung neatly, equipment rooms are clean and tidy), and three insistences (insist on using leak detection relays, insist on using coal-electric drills, lighting and signal comprehensive protection devices, insist on using gas electricity and wind power locks). 9. It is strictly prohibited to conduct maintenance and transportation of electrical equipment while powered on. 10. When all electrical equipment is not in use, turn the switch handle to the zero position and lock it. 11. Mechanical and electrical equipment implements a chartered flight listing system and a dedicated chartered flight maintenance system. The installation location is reasonable and hygienic. Five: Safety Technical Measures 1. During construction, the construction shall be carried out strictly in accordance with the design of the main office. 2. Strictly implement the system of knocking for help and asking for help and having dedicated people to observe the mountain during construction. 3. Before and after construction, debris and random materials at the construction site should be cleared away to keep the retreat route clear. 4. Set up a strong and reliable workbench as needed. To set up the workbench, use steel pipes with a diameter of not less than 50mm. First, erect two 2.5-meter-long steel pipes on each side of the tunnel, leaning against the side of the tunnel at an angle of 75°. At 1.0m of the four steel pipes, connect two 3m long steel pipes horizontally and two 3m long steel pipes longitudinally. Use 8# steel wire to cross-tie the overlapping areas, and lay them along the formed frame. The wooden board has a specification of 3000mmx200mmx50mm. The board surface should be flat. The wooden board and the frame are connected with iron wire to prevent slipping. The workbench should be firmly overlapped to ensure that personnel can work safely. The operating platform can only be used after it has been checked by the attendant. 5. When constructing near the track, personnel should adhere to the regulations of driving and not pedestrians and pedestrians and not driving. 6. Cables and feng shui pipelines must be protected before construction. Use old belts to wrap and protect the 10 meters of cables and pipelines before and after the repair site. Construction can only be carried out after confirmation by the attendants. 7. During the construction process, each shift will spray water and flush dust near the construction site. Install a roadway spray barrier on the return air flow below the construction site. 8. When a sledge hammer is required for maintenance and construction work, the operator should pay attention to the fact that no one is in front of the hammer head to prevent the hammer head from falling off and injuring people. 9. Portable and suspended in the wind flow of the construction site, check the gas concentration before construction. Construction can only be carried out when the gas concentration is below 0.5%. 6. Safety technical measures for using pneumatic tools 1. Qualified U-shaped cards must be used when connecting the wind and water pipes used in pneumatic tools. It is strictly forbidden to use other items instead. The connection of the wind and water pipes must be firm and reliable. 2. Before using a drilling rig, a comprehensive inspection of the drilling tools must be carried out to ensure that there are no safety hazards. When drilling, a dedicated person must be arranged to monitor the safety conditions of the working site and pay attention to the drilling situation to ensure construction safety. 3. Before drilling, first check the safety of the drilling location and ensure there is sufficient operating space. 4. It is strictly prohibited to drill holes along cracks and in residual holes. 5. When using a pneumatic drill, the wind pressure must not exceed its rated wind pressure. 6. Drilling personnel are strictly prohibited from wearing gloves when holding the drill rod, and fastening their clothes, collars and cuffs (it is strictly forbidden to hold or hold the twist drill rod with their hands); during normal drilling, no one is allowed to hold the drill rod with their hands. 7. When the drill bit alloy piece is found to fall off or the drill rod is bent in the drilling hole, the drill bit or drill rod must be replaced in time. 8. During the drilling process, if any abnormality is found in the parts, facilities, etc. of the drilling machine, drilling must be stopped and the wind must be stopped in a timely manner. 9. When drilling holes, do not swing the drill pipe up, down, left or right to maintain the drilling direction. Do not stand in front of the drilling machine or under the drill pipe to prevent the drill pipe from breaking and injuring people. 10. If you find that the drill is stuck, stopped or the drill pipe is bent during drilling, you should retract it immediately and readjust the advancement speed. 11. If there is flying dust in the drilling hole, stop drilling, check whether there is water in the water pipe, whether the center hole of the drill bit and drill pipe is clear, and then drill the hole again after processing. 7. Grouting safety technical measures 1. The purpose of grouting is to grout the surrounding rock of the tunnel, use the slurry to cement and break the loose rock strata, fill the loose rock strata and open spaces, and form a complete grouting zone around the periphery together with the surrounding rock** *It can also bear the mine pressure and prevent the deformation of the tunnel caused by the pressure from around the tunnel. 2. Grouting method and sequence (1) Grouting according to the principle from bottom to top, first low and then high. (2) During grouting, if grout leakage is found, the grouting must be stopped in time and sealed with fast cement to prevent the grout from continuing to leak. When the cement solidifies, grouting can be continued. 3. The arrangement and requirements of grouting holes. The grouting holes should be arranged in rows.

A grouting pipe is installed in each hole, and the grouting pipe is exposed by 30 to 50 mm. When making the grouting hole at the bottom corner, drill the hole at an angle of -15°. The primary grouting pressure is 1.0~2.0Mpa, and the secondary reinforcing grouting pressure is 2~3Mpa. The specific conditions can be adjusted according to the site conditions. 4. Grouting materials: 425# ordinary mineral Portland cement is used for grouting, clean water is used, and the water-cement ratio is 1:0.8. 5. Construction method (1) Water and compressed air pipelines should be connected to the construction site nearby. (2) In order to ensure the safety of grouting work, grout storage barrels, grouting machines and grouting pipelines are installed on one side of the tunnel. When grouting holes in rows 3, 4 and 5, a workbench must be set up to facilitate the installation of grouting anchors and grouting anchors. Connect the high pressure pipe. 6. Anchor injection hole construction and grouting (1) First mark the anchor injection hole position, and use Φ32mm and Φ28mm drill bits to drill holes strictly according to the design. (2) Each grouting pipe must seal the grouting orifice tightly, and use a wrench to tighten the expansion sleeve of the grouting anchor so that grout will not leak and the grouting pipe will not be flushed out by high pressure during grouting. Grouting can be done only after tightening to ensure sufficient grouting pressure during grouting. (3) Prepare the grout according to the designed water-cement ratio, and only start grouting after everything is normal. (4) When the pressure of the grouting machine reaches the maximum and the shutdown pressure does not drop, close the grouting orifice valve and use the pressure relief valve to relieve the pressure in time, and then remove the quick connector. Wait 4 hours before removing the orifice valve. (5) If grouting is suspended for some reason during grouting, a certain amount of clean water can be injected into the hole to ensure that the grouting passage is smooth. (6) When grouting this hole, rags or woven bags or gate valves can be used to seal the adjacent holes when the grout comes out of the adjacent holes. (7) During grouting, no one is allowed within 3m around the grouting hole. (8) During the grouting process, it is necessary to observe the operation of the grouting pump and the grout discharge. After each grouting, the pipelines and machinery must be rinsed immediately with clean water, and the machinery and equipment must be inspected and repaired at the same time (9) Clean water should be available when grouting to prepare for cleaning when the grout is sprayed or enters the eyes. 8. Safety precautions 1. If you need to deal with a pipeline failure during the grouting process, you must stop the machine and relieve the pressure before proceeding. During the process, the grouting pipe mouth is strictly prohibited from facing personnel. 2. During the grouting process, it is necessary to strengthen monitoring of the roof of the tunnel. If any abnormal phenomena such as noise, vibration of the roof, cracking of the skin, etc. are found, the work must be stopped immediately, evacuated to a safe location, reported in time, and effective measures taken for construction. 3. Grouting must be performed strictly according to the design pressure, and over-pressure grouting is strictly prohibited. 4. During grouting, ensure that the pressure gauge is intact and protect the pressure gauge during construction. Grouting without a pressure gauge is strictly prohibited. 5. When the prepared slurry is used up during the shift, the storage time of the slurry should be shortened as much as possible. When injection is stopped after get off work, the grouting equipment and utensils should be cleaned in time. 6. During the grouting process, personnel must frequently stir the grout storage barrel to reduce condensation. 7. During the grouting period, you must abide by the rules and disciplines and obey the instructions. Each grouting shift must allow time to clean up the leaked grout, pay attention to keeping the construction site clean, and achieve civilized construction. 8. Check the tools used in detail before work, and promptly detect any damage. Repair, otherwise it may not be used. 9. Materials should be stacked neatly and should not affect the tunnel environment and safe retreat. 10. All personnel must take good care of construction machines and tools, put them away promptly after injection, and are not allowed to drop, smash, or bump them at will. 9. Disaster avoidance route: Working surface → Four coal transporters go down the mountain → 20m ventilation stone gate → Auxiliary inclined shaft → Ground 10. Other matters not covered shall be strictly implemented in accordance with the "Coal Mine Safety Regulations" and other relevant safety production regulations.

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