Abstract
It is meaningful to study the issues of CO migration and its concentration distribution in a blind gallery to provide a basis for CO monitoring and calculation of fume-drainage time, which is of a great
significance to prevent fume-poisoning accidents and improve efficiency of an excavation cycle. Based on a theoretical analysis of a differential change of CO mass concentration and the CO dispersion model
in a fixed site, this paper presents several blasting fume monitoring test experiments, carried out with the
test location to the head LP in arrange of 40-140 m. Studies have been done by arranging multiple sensors
in the arch cross-section of the blind gallery, located at the Guilaizhuang Gold Mine, Shandong Province,
China. The findings indicate that CO concentrations in the axial directions are quadratic functions with
the Y and Z coordinate values of the cross-section of the blind gallery in an ascending stage of CO time-
-concentration curve, with the maximum CO concentrations in Y = 150 cm and Z = 150 cm. Also, the
gradients of CO concentration in the gallery are symmetrical with the Y = 150 cm and Z = 150 cm. In the
descending stage of CO time-concentration curve, gradients of CO concentration decrease in lateral sides
and increase in the middle, then gradually decrease at last. The rules of CO concentration distribution in the
cross-section are that airflow triggers the turbulent change of the CO distribution volume concentration and
make the CO volume concentration even gradually in the fixed position of the gallery. Moreover, the CO
volume concentrations decrease gradually, as well as volume concentration gradients in the cross-section.
The uniformity coefficients of CO concentration with duct airflow velocities of 12.5 m/s, 17.7 m/s and
23.2 m/s reach near 0.9 at 100-140 m from the heading to the monitoring spot. The theoretical model of
a one-dimensional migration law of CO basically coincides with the negative exponential decay, which
is verified via fitting. The average effective turbulent diffusion coefficient of CO in the blind gallery is
approximate to 0.108 m2/s. There are strong linear relationships between CO initial concentration, CO
peak concentrations and mass of explosive agent, which indicates that the CO initial concentration and
the CO peak concentration can be predicted, based on the given range of the charging mass. The above
findings can provide reliable references to the selection, installation of CO sensors and prediction of the
fume-drainage time after blasting.
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