Affiliation(s)
1. Department of Mining Engineering, Colorado School of Mines, Golden 80401, Colorado, USA
2. Earth Mechanics Institute Colorado School of Mines, Golden 80401, Colorado, USA
3. Department of Environmental Health and Industrial Hygiene, University of California Los Angeles, Los Angeles 90095, California, USA
4. Department of Statistics, University of British Columbia, Vancouver V6T 1Z4, Canada
ABSTRACT
Airborne rock dust poses serious long-term health effects to workers in
mining and tunneling underground rock environments. When inhaled, respirable
crystalline silica particles commonly found in quartz and other minerals will
scar sensitive lung tissue and cause irreversible lung diseases.
Characteristics such as concentration, type of mineral, particle size, and
particle shape can harm workers to various extents. Therefore, this study
characterizes airborne rock dust particles that are released from mechanically
cutting rock. Laboratory full scale linear cutting tests on samples of potash
rock were performed with radial picks to generate dust and were collected with
various instruments, including Dorr-Oliver cyclones. Three stages of pick wear
were tested: new, moderately worn, and severely worn. Comparisons between
different stages of pick wear to dust concentration, size distribution, and
particle shape characteristics are drawn from this preliminary study using
analytical methods, field-emission scanning electron microscope image capture
techniques, and laser diffraction. Although further testing needs to be
conducted to make viable and concrete conclusions, a review of the test results
reveals a strong tendency in generated airborne and deposited dust to be linked
to the bit tip wear, which was influenced by tip surface area geometry, such as
a sharp tip, blunt tip, or undulating sharp tips. The moderately worn pick, or
the pick with the bluntest tip, in these experiments released the highest
concentration of dust. The moderately worn (bluntest) pick also generated
particle shapes with the highest aspect ratio compared to the other two picks.
Additionally, in terms of the particle size distributions, all the picks
generated airborne particle size mean values between 0.7 and 1.2 µm in
aerodynamic diameter. As for deposited particle size distributions, all the
picks generated particles with the mode of particle aerodynamic diameter sizes
at 13 µm. In the end, the results of this preliminary study paired with future
testing can confirm and eventually provide the basis for optimum bit management
and maintenance systems to control airborne dust exposures.
KEYWORDS
Respirable rock dust, particle size distribution, particle shape, dust
concentration.
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