Three-dimensional spatial and temporal distributions of dust in roadway tunneling

Abstract

To study the three-dimensional spatial and temporal distributions of dust in tunneling roadways, and to solve the problems of inadequate time and limited number of monitoring points, this paper designs a device for the real-time monitoring and storage of data on the concentrations of dust at multiple measuring points in the same section of a tunnel. The proposed device can measure the total concentration of dust and that of respirable dust in real time at different instances and locations, and using different working procedures. These measurements are used to study the temporal and spatial migration of dust. The results show that there was a sharp fluctuation zone 0–25 m from the heading face, about 25–40 m was high speed subsidence, beyond 40 m was gentle subsidence, The change of respiratory dust is much smoother. At different distances from the heading face, the total dust concentration exhibited a process of “violent oscillation–rapid descent–stable descent,” while the respirable dust exhibited a process of “fluctuating ascent–gradual subsidence.” Changes in the concentrations of total dust and respirable dust dust were consistent at different positions in the same section of the tunnel. The concentration of dust near the wall was low, and those along the sidewalk and air duct of the roadway were slightly higher than in the middle. The concentration of dust farther down the air duct decreased more slowly than that in the remaining lines of measurement. Small amounts of dust featuring large particles settled quickly. High concentrations of dust were observed to be intermittent, and the background value of dust concentration within 100 m of heading face was between 0.5 and 3 mg/m3.