Matters to be noted in tunnel blasting
Excavation:
1. Tunnel excavation should formulate corresponding safety and technical measures according to various construction methods and geological conditions.
2. Drilling operations should comply with the following regulations:
(1) Before drilling, the safety status of the working environment should be checked, and drilling operations should be carried out only after the excavation surface has been cleared of floating stones and blind blasting has been dealt with.
(2) When drilling holes on the ballast pile, the support of the rock drill should keep the ballast pile stable. If necessary, step on the support to prevent it from moving back and forth.
(3) When drilling holes with an electric drill, do not guide the rotating drill bit by hand or use the electric drill to deal with the clamped drill bit.
(4) Do not drill holes in residual holes.
Blasting operations should comply with the following regulations:
1. Blasting operations must be carried out in accordance with the requirements of the current national standard "Safety Regulations for Blasting" (GB6722), and blasting design plans and corresponding technical measures must be formulated.
2. Blasting operations should take corresponding protective measures based on the specific conditions of the terrain, geology and construction area environment.
3. The blasting materials should be extracted by the person in charge of loading according to the amount needed at one time and taken as needed. The remaining materials after blasting should be returned to the warehouse in time after inspection and verification by a dedicated person.
4. The blasting material processing room should be 50m away from the tunnel entrance. If the distance between the tunnel entrance and the excavation surface is greater than 1000m, a processing room can be set up at an appropriate location in the tunnel, but it should comply with the following regulations:
(1) The amount of stored explosives is limited to the amount used during the shift.
(2) The tunnel depth should be greater than 10m, and it should have an angle of 60 degrees with the center line of the tunnel, and it should be equipped with two outward-opening doors.
(3) Obvious signs should be set up and a dedicated person should be on guard.
(4) The processing room should be located in solid surrounding rock and should be equipped with railings. Unauthorized personnel are strictly prohibited from entering.
5. Charging should comply with the following regulations:
(1) Before charging, non-charging personnel should evacuate the charging site; fireworks are prohibited in the charging area; after charging is completed, the number and location of the guns should be checked and recorded;
(2) Metal utensils and PVC pipes should not be used for charging; bamboo poles or wooden sticks should be used for charging, and the tamping force should be moderate.
(3) The detonating charge should be made when charging on site.
(4) Charging and blasting are strictly prohibited in the following situations: A. Insufficient lighting B. The surrounding rock of the excavation surface is broken and has not been supported. C. Quicksand and mud are not treated. D. A large amount of cave water and high-pressure water are gushing out and have not been treated. E. There is no good warning.
6. Blasting should not be carried out in foggy days, dusk and at night. If blasting is really necessary at night, effective safety measures should be taken. Blasting operations should be stopped in thunderstorms and the danger zone should be evacuated quickly.
7. The following protective measures should be taken before detonation:
(1) Detonation should be supervised and commanded by the on-duty personnel;
(2) Guards must be posted around the warning area; Warning range: small-volume blasting should be 200m away from the blasting site, and the warning distance for blasting with a large amount of explosives should be determined by calculation;
(3) People and animals in the warning area should be evacuated, and construction machinery and equipment that cannot be evacuated should be reliably protected;
(4) In construction areas where vehicles and ships pass, the blasting time should be determined in advance with the relevant transportation department.
(5) When blasting in the tunnel, all personnel must evacuate, and the safe evacuation distance should be: A. not less than 200m in a dead-end tunnel; B. not less than 100m in adjacent upper and lower tunnels; C. not less than 50m between adjacent tunnels, cross passages and cross tunnels; D. not less than 400m when excavating the upper section of a double line; E. not less than 500m when excavating the full section of a double line.
8. Detonation shall comply with the following provisions:
(1) When there is lightning and thunder nearby or when there is a possibility of sudden lightning due to clouds and rain, it is strictly forbidden to use electric detonators for detonation.
(2) When there are several work sites blasting at the same time in the same construction area, unified command must be implemented. Detonation at any site is strictly prohibited before all warning and protection work is completed.
(3) When using digital electronic detonators for detonation, network detection needs to be far away from the working face. For long tunnels, the distance is generally 200m. The tunnel entrance should generally be in a safe place outside the tunnel. During network detection, there should be no personnel or equipment on the blasting working face.
(4) The digital electronic detonator initiator should always be kept by the blasting team leader.
9. The handling of blind shots shall comply with the following provisions:
(1) The original explosives should be handled on the spot; when handling blind shots, the warning shall not be removed; in special circumstances, with the permission of the construction manager, it can be handled during the next blasting or rest; the blind shot location should be marked with obvious signs, and no one is allowed to pass within 5m around it.
(2) When the blasting line, fuse, detonating cord, etc. in the blasthole are checked and found to be intact, the lead or wire can be reconnected and detonation can be carried out again. Digital electronic detonators need to be tested one by one. If the electronic detonators are found to be safe and reliable, they can be re-networked for detection and detonation.
(3) Sometimes it is necessary to remove the blockage and reload the detonating charge.
(4) Do not continue drilling in the residual hole.
(5) A parallel blasthole can be drilled at a distance of not less than 0.6m from the blind shot to induce explosion.
(6) Ammonium nitrate explosives can be diluted with water.
10. Explosives that produce a large amount of harmful gases shall not be used for blasting in the cave.
11. Open flame detonation shall not be used for blasting in the cave.
12. Ventilation and smoke exhaust must be carried out after blasting. Inspectors can enter the excavation surface for inspection only after 15 minutes. The inspection content includes: whether there is a blind shot; whether there is residual explosives or detonators; whether there is loose surrounding rock on the roof and both sides; whether the support is damaged and deformed.
13. During blasting, blasters should carry flashlights with them and provide fault lighting.
14. Charging and drilling should not be performed in parallel.
15. When the distance between two excavation faces that are excavated in opposite directions is only 15m, only one excavation face is allowed to be excavated and penetrated. The other end should stop working and remove personnel and machinery and equipment. Warning signs should be set up at a safe distance.
The transportation of blasting materials should comply with the following regulations:
(1) The transportation of blasting materials in the cave and auxiliary tunnels should meet the following requirements: a. It should be escorted by a special person and other personnel should not be allowed to take it. b. Detonators and explosives should be transported separately, and electric detonators should be transported in insulating boxes. c. The winch driver and the liaison personnel above and below the wellhead should be notified before transportation underground. d. It should not be transported during the time when the shift change personnel go up and down the well. e. Explosive materials should not be placed in the wellhead room, the well bottom parking lot or other tunnels.
(2) Explosive materials should not be transported by belt conveyors.
(3) When transporting blasting equipment by car, the following provisions shall be met: a. Explosives and detonators shall be transported separately in two vehicles. The transportation distance between the two vehicles shall be greater than 50m, and a special person shall be assigned to transport them; b. A red light or red flag shall be displayed during operation; c. A fireproof cover shall be added to the exhaust port of the car.
Construction requirements for unfavorable geological conditions:
1. Tunnel construction in unfavorable geological and special rock areas shall comply with the following provisions:
(1) Before construction, advance drilling shall be used to explore the geological conditions and take preventive measures.
(2) During construction, the monitoring and measurement of the surrounding rock and support system shall be strengthened. When the rate of change of the surrounding rock and support system is abnormal, effective measures shall be taken immediately. In serious cases, all personnel shall be evacuated from the dangerous area.
(3) There shall be sufficient emergency and first aid supplies during construction.
(4) If a collapse occurs, it shall be actively handled and rescued. The collapse shall be handled after the collapse situation is ascertained and safety measures are formulated.
2. When constructing tunnels in soft, broken, and water-rich surrounding rocks, comprehensive waterproofing measures such as interception, drainage, and blocking should be adopted, and measures should be formulated to deal with sudden large-scale water inrush.
3. The construction of karst geological tunnels should comply with the following provisions: (1) During construction, the advanced prediction and forecasting of geological conditions should be strengthened, and corresponding preventive measures should be taken to prevent sudden water inrush, sand inrush, and mudslides. (2) Excavation and support should take corresponding safety measures according to the specific conditions such as the size of the karst, the filling conditions, and the relative position of the tunnel. (3) For the cleaning of karst filling materials and the treatment of karst surrounding rocks, special safety measures should be formulated in accordance with the requirements of the design documents and the actual situation on site.
4. The construction of expansive rock geological tunnels should comply with the following provisions: (1) The support should be close to the surrounding rock, and the deformation of the surrounding rock should be strictly controlled. (2) Measures such as strict drainage, less movement, and dry closure should be adopted. (3) During construction, there should be dedicated personnel to monitor; when the deformation of the surrounding rock accelerates, personnel should be evacuated immediately.
5. Construction in rockburst geology shall comply with the following provisions: (1) There shall be a dedicated person to observe in the rockburst area. If a sound is detected on the rock wall, an alarm shall be given immediately to evacuate personnel. (2) In case of rockburst, personnel shall be evacuated first and then equipment. (3) Personnel shall not stay in the rockburst area. (4) After the rockburst, the top search shall be strengthened and the ventilation time shall be extended.
6. Construction in extrusion-type geological tunnels shall comply with the following provisions: (1) Excavation shall adopt the full-section method. (2) Lining shall preferably adopt integral lining, or adopt the partial lining with the invert leading the wall first and the arch later; lining and construction shall be carried out after the deformation rate of the surrounding rock is less than 0.5 mm/d. (3) The monitoring of the surrounding rock deformation rate shall be strengthened during construction; when abnormal deformation is found, corresponding safety measures shall be taken.
