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(II) Preventive measures 1. Technical measures to reduce the effect of blasting vibration (1) Use millisecond delay blasting to limit the maximum dose of one blast. Practice has proved that the average vibration reduction rate is 50% compared with the use of instant burst blasting. The more the number of millisecond delays, the better the vibration reduction effect.
(2) Using pre-split blasting or excavation damping groove, or drilling a single-row or double-row anti-vibration hole between the blasting body and the protected body, the vibration reduction rate can reach 30%~50% . The anti-vibration hole diameter can be selected from 35 to 65 mm, and the hole spacing is not more than 25 mm.
(3) As holes, slits and grooves for pre-cracking, care should be taken to prevent water filling, otherwise the effect of vibration reduction will be affected.
(4) In the blasting design, the direction of the minimum resistance line can be selected, the dispersibility of the cloth and the air surface can be increased, the explosives with low detonation speed, low density or the selection of reasonable charging structure, and the monitoring of blasting vibration can be adopted. To control the vibration effect of blasting, ensure the safety of the protected object, and provide scientific data for litigation or claims that may be caused by blasting vibration.
2. Technical measures to reduce the impact of explosion air and noise The protection measures for air shock waves are as follows:
(1) The millisecond delay blasting technique is used to weaken the intensity of the air shock wave.
(2) The detonating cord of the bare ground is covered with sand and soil. Strengthening the filling of the orifice section and ensuring the quality of the packing can reduce the impact of the shock wave.
(3) Strictly designed to resist line construction to prevent the generation of strong shock waves.
(4) Reinforce the geological weak side of the rock mass to suppress the generation of shock waves.
(5) Pay attention to the weather and weather conditions during the blasting operation; control the blasting direction and select a reasonable blasting time.
(6) Preset blocking wall, including hydraulic blocking wall, sandbag blocking wall, anti-wave row column, wooden chopping block wall, etc.
For the control of blasting noise, measures must be taken from the three sources of sound source, transmission route and receiver. Reducing the noise source is the most effective and direct measure to control noise. The multi-segment charge blasting method is adopted to minimize the amount of the blasting dose, thereby reducing the initial energy of the blasting noise. From the way of transmission, by setting up the shelter or making full use of the topography and attention, and paying attention to the direction effect, that is, in the practice of blasting, try to avoid the direction of the radiation source and noise of the sound source to avoid the quiet place.
3. Control and protection measures for blasting individual flying stones (flying objects) (1) Reasonably determine the airfront surface, reasonably select the direction of the resistance line, so that the protected object avoids the main direction of the flying stone, thereby maximizing the protected object. Flying stone damage.
(2) Reasonable design of the charge structure, blasting parameters and row detonation time. In general, the delay time between adjacent rows is preferably controlled at 20~50ms.
(3) Do a good job in handling special terrain and geological conditions. Care should be taken to avoid the pack being located on the weak interlayer of the rock or the base of the joint to avoid escaping from these weak surfaces.
(4) Guarantee the quality of the packing. Not only to ensure the length of the packing, but also to ensure that the packing is dense, and the packing is to avoid inclusion of gravel.
(5) The use of low explosive explosives, non-consumer charge, extrusion blasting and millisecond delay blasting, etc., can play a role in controlling scattered objects.
(6) Covering the blasting body and taking protective measures against the protected object.
4. Measures to reduce the damage of rock mass by blasting (1) Before blasting, it is necessary to pay attention to the investigation of geological conditions (such as lithology, geological structure, hydrogeology, ground stress, landslide, etc.) in the explosion area to avoid the geological environment that is not conducive to blasting. Inappropriate blasting design and construction schemes are used.
(2) Carefully designed, the drug package should be arranged strictly according to the excavation contour range, the dose should be calculated, the total scale of one blasting should be controlled, or the millisecond millisecond blasting should be adopted to control the dose of the adjacent excavation profile drug room (gun L). .
(3) Pre-splitting blasting, smooth blasting, or designing anti-vibration holes along the excavation profile, and the surrounding holes are made of low-explosive explosives or no accidental charges.
(4) After the blasting, the damage of the rock mass and other engineering geological problems caused by the blasting should be investigated in time, such as the stability of the slope, the stability of the landslide body, dangerous rock and dangerous slope.
(5) When blasting operations are carried out near the saturated sand (soil) foundation, experts should be invited to evaluate the possibility and degree of damage caused by blasting caused by blasting; and measures to prevent the soil layer from being blasted and vibrated and the pore water pressure is raised; Assess the hazards posed by the liquefaction of the body to the building and its foundation.
5. Measures to avoid gas explosion caused by blasting (1) Allow the use of safe explosives, allow the use of instant or millisecond delay detonators; ensure that the extension of the last paragraph does not exceed 130ms.
(2) Do not use detonating tube, Common detonating cord; the use of coal mine explosion-proof detonator.
(3) In the mining face with gas or coal dust explosion hazard, millisecond blasting shall be adopted; in the excavation working face, the full face shall be detonated once, and if the full section cannot be detonated once, safety measures shall be taken.
(4) The blasting operation must strictly implement the "one shot three inspections" system.
(5) The blasthole sealing mud is applied with water cannon mud. The remaining blast hole part of the 7K gun mud is sealed with the gunnery mud or the gun mud made of non-combustible and plastic loose material. It is strictly forbidden to use pulverized coal, block materials or other flammable materials for blasthole sealing. The length of the blasting hole should meet the following requirements: when the depth of the blasthole is less than 0.6 m, it should not be charged or blasted; when the depth of the blasthole is O. 6~lm, the length of the sealing mud should not be less than 1/2 of the length of the blasthole; When the depth of the blasthole exceeds 1m, the length of the sealing mud should not be less than 0.5m; when the depth of the blasthole exceeds 2.5m, the length of the sealing mud should not be less than 1m. When smooth blasting, the length of the peripheral eye seal mud shall not be less than 0.3 m. No lute, lute false or insufficient blast hole blasting is prohibited.
(6) Good ventilation to prevent gas accumulation.
6. Measures to prevent the explosion of harmful gases and blasting dust (1) Uniform pores, control single-volume consumption, single-pore dosage and one-time detonation dose, and improve the effective utilization rate of explosive energy.
(2) Using millisecond delay blasting technology.
(3) Use qualified explosives, try to make the explosive components achieve zero oxygen balance, and strictly prohibit the use of expired and deteriorated explosives; select the corresponding explosives according to the nature of the rock, and strive to achieve wave impedance matching.
(4) Do a good job of waterproofing the blasting equipment to ensure the quality of filling and filling, and avoid half-explosion and detonation.
(5) Adequate detonation energy should be ensured so that the explosive can quickly reach stable detonation and complete reaction.
(6) Spraying water before blasting, that is, installing a dust sprayer at 15~20m from the working surface, and opening the water spray device 2~3min before blasting, and close it about 30min after blasting.
(7) Strengthening ventilation before and after blasting in the well, measures should be taken to attract people to the dead zone.
(8) During mine and underground blasting, attention should be paid to prevent gas outburst and prevent gas explosion accidents.
(9) Wet rock drilling is used in underground blasting, spray dust is sprayed on the working surface to reduce blasting dust; before blasting, blasting body is sprayed in advance, and the "dust source " inside and around the blasting body may cause blasting dust in advance . .
Prevention of mine blasting hazards
(I) Main contents of mine blasting construction hazards The main hazards of mine blasting are seismic effects caused by blasting, blasting flying stones (individual scattered objects), blasting air shock waves and noise, shock waves in blasting water, gas explosion caused by blasting, and blasting. Damage to rock mass, blasting of harmful gases, blasting dust and blasting's damage and impact on the ecological environment.