| Dust lung complications such as pneumoconiosis due to dust occurring in tunnel construction has become a matter of grave concern. In the tunnel construction, a large quantity of dust is often generated especially at the time of spraying of concrete or machine digging.A study was conducted using a full-scaled tunnel simulation at our Construction Environment Laboratory (100 meter-long, cross-sectional area 80 square meters). In this Laboratory, various countermeasure techniques were applied and it evaluated about those effectiveness.In the result of the experiments, the following things became clear.(1) By the air-less spraying system using a liquid quick setting admixture, the dust concentration decreased greatly as compared with traditional spraying systems.(2) Using a dust reducer or a low dust quick setting admixture, slurry shot system, and partial dust collecting system can also reduce a considerable quantity of dusts.(3) The more the rock mass strength is, the more dust produced.(4) The air blower set at 1,500 cubic meters/min. reduced the dust particle size less than 5 μm which is said to cause pneumoconiosis.(5) The more water sprayed, the more it reduced the dust. However, it didn’t help reduce the grain size distribution under 5 μm. (6) By the dust collection system using the elastic ventilation ducting, the dust concentration decreased greatly. |
