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威远煤矿是一座有50余年开采历史的老矿,解放前是小煤窑手工采掘。1957年以后为干式作业,并下岩尘浓度高达187.5～795.0mg/m~3,1964年以后实施水风钻打眼,岩尘浓度降至5.56mg/m~3。采煤一直是机式干采,仅1986年的粉尘平均浓度高达133mg/m~3。历年采掘工作面粉尘浓度合格率为0。岩尘中游离二氧化硅含量波动在6.43～70.5%之间,煤尘中游离二氧化硅含量波动在2
Weiyuan Coal Mine is an old mine with more than 50 years of mining history and was liberated by hand before the small coal mines were excavated. After 1957 dry operation, and under the rock dust concentration as high as 187.5 ~ 795.0mg / m ~ 3, 1964 after the implementation of water drilling, drilling, rock dust concentration dropped to 5.56mg / m3. Coal mining has been dry-type machines, only the average dust concentration in 1986 up to 133mg / m ~ 3. Over the years mining face dust concentration pass rate of 0. The content of free silica in rock dust fluctuated between 6.43% and 70.5%, the content of free silica in coal dust fluctuated between 2