1 Formation of hidden dangers of gas and coal dust explosion accidents when the roadway runs through
(1) When the roadway runs through, only one work face is allowed to face the front, but some mines only take care of the head of the excavation, neglect the other end, stop the supply of the end of the excavation, or do not pay attention to the ventilation and safety management at the end of the work. The formation of gas accumulation has caused a gas explosion that caused a stoppage and a stoppage. A major gas explosion accident in a coal mine in Guizhou is a case.
(2) Downhole ventilation system is a network structure composed of many wells and ventilation facilities, which has certain independence, integrity and stability in a certain production period. The passage of the roadway will destroy the original balance and stability. The wind direction, wind speed and air volume of some wells will be abruptly changed. It is very likely that the wind speed will exceed the limit and the coal dust will fly, due to the large amount of gas in the goaf or the closed area. Due to the formation of circulating wind and unreasonable series ventilation, the emergence of windless or breeze shafts and other reasons, there is a serious hidden danger of gas rapid overrun. On January 21, 1995, after the 508 lane and the 408 dark inclined shaft yard of the 7# layer of a coal mine in Datong were connected, the air volume of the 1030 main road was reduced due to the lack of timely wind control measures, and the closed inner gas was leaked and accumulated nearby. When the line motor car runs near the airtight, the electric spark causes a gas explosion.
(3) Due to the adjustment of the position of the local ventilator, the wind control measures are not timely or incorrect, which may cause hidden dangers of gas explosion accidents. As shown in Figure 1, when the double lanes are simultaneously excavated, the local ventilator is originally in position A. After the lane 2 is connected, the fan is moved forward to position B. If the lane 1 is not closed beforehand, the wind flow is short-circuited at 1 place, local ventilation The air volume of the roadway where the machine is located is likely to be smaller than the suction volume of the local ventilation, thus forming a circulating wind. Such accident cases are numerous in China.
2 Formation of fire accidents when the roadway runs through
Old mines that are severely ignited in nature. The fire area is dotted. In the long-term production, it is very likely that some pressure equalization measures have been taken artificially to control the natural fire. In addition, some of the fire areas are likely to be directly discharged along the return air without being noticed. After the tunnel is connected, the change of the ventilation system will cause the wind pressure in the underground wind network to be redistributed. The original pressure equalization state may be destroyed, and the possibility of re-ignition or combustion in the fire zone is greater. If the wind control measures are not strong, the pole is not strong. It is easy to produce fires. In gas mines, explosion hazards can be formed at any time.
3 Formation of hidden dangers of coal and gas outburst accidents when the roadway runs through
Coal and gas outburst are the result of the combined effects of ground stress, gas pressure and coal structure performance. Due to the influence of mining activities, the ground stress will be more concentrated at the roadway penetration point, and the risk of coal and gas outburst will increase. And the difficulty increases, the handling is not easy to produce coal and gas outburst accidents.
4 Several problems should be paid attention to when selecting the roadway penetration location
(1) Try to select the location of the through-site in a mine with no danger of prominent or low risk in the mine with danger of coal and gas outburst. The superposition of the stress at the passage of the roadway increases the risk of protrusion. When selecting the location of the roadway, Efforts should be made to select areas where there is no significant risk or less risk. During the excavation of the returning wind tunnel of Fengying Mine 24061 working face of Jiaozuo Mining Bureau, the obvious signs are not obvious, but when the distance is 10m, the prediction index is obviously over-limit and there are coal gun sounds and top drilling and card drilling. The main reason is It is the point of penetration that is just in the prominent danger zone affected by the fault. During the tunneling of the 24081 working face, it was found that the gas content and prediction index had obvious regional and stripe characteristics. There was no obvious warning during the tunneling from 0 to 200 m in the inlet of the wind inlet, 200-350 m. Some kinetic phenomena appear, and the prominent signs are most obvious in the range of 350 to 400 m. The harbinger is gradually weakened in the future, and there is basically no outstanding danger in the range of 500 to 585 m. In order to absorb the experience of tunneling during the tunneling of the 24061 working face, it was decided to dig the return air duct of 24081. The connecting point of the return air duct and the air inlet lane was selected near the open cut (the trapped open eye was just in the absence of protrusion). Dangerous area), there is no outstanding danger when it penetrates.
(2) Try to avoid the passing point before the roadway between the main intake and return air systems. The coal pillars that are penetrated in the ventilation system are equivalent to the damper to control the wind flow in the wind network. The measure is equivalent to the opening of the damper. If the through location is between the main intake and return air systems, the influence of the Xiao pole will be intensified.
5 Wind control measures when the roadway is connected
(1) Strengthen the local ventilation management of the through-site. Only one work is allowed to be connected forward. The working face that has been stopped must be kept properly ventilated. Check whether there is a hidden danger in local ventilation, and check the gas concentration to ensure that the gas concentration in the two working faces and their return air passages does not exceed 1%. The local ventilation system must be safe, stable and reliable, to prevent circulating wind and unreasonable series ventilation, and the air volume and wind speed of each well must meet the requirements. In mines with coal and gas outburst danger, when the inclined roadway is connected with the upper roadway, the upper roadway must have a lead distance of at least 5m, and ensure that the return air system of each head is unblocked to prevent other areas from being prominently affected.
(2) The ventilation system should be adjusted before and after the completion of the preparation work for controlling the wind. When the through point itself is between the main inlet and return air systems, the wind pressure difference between the two sides is large, and the coal pillar is crossed. The control effect of the system is large, and direct penetration is potentially dangerous. In this case, the ventilation system must be adjusted in advance to minimize the air pressure difference between the two sides of the coal pillar. The damper is not placed at each of the two ends. The damper is closed at the moment of penetration. Make systematic adjustments. The more complicated the ventilation system is, the more difficult it is to adjust the airflow during the penetration. Sometimes the ventilation conditions of the branches in the wind network are difficult to accurately predict. It is necessary to use a computer to solve the simulation beforehand. The ventilation and gas conditions of the inner shafts are carefully checked and analyzed to prevent the shortage of air volume and gas out of limits, and also to avoid excessive wind speed in some wells and cause coal dust to fly. Here again, special emphasis should be placed on strengthening local ventilation management, preventing circulating winds and unreasonable series ventilation, and strengthening observations in closed areas and fire areas to prevent gas leakage and re-ignition of fire areas.
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