Evolutionary mechanism and particle characterization analysis of dust produced by wet-mix shotcrete in tunnels.

Wet-mix shotcrete, an essential form of concrete support, has been widely applied in underground constructions such as tunnels and mines. This study analyzed the gas jet structure and particle velocity differential equations in the wet-mix shotcrete process and physicochemically characterized collected dust samples. Based on field measurements and laboratory analyses, we established an experimental platform and a numerical simulation model for wet-mix shotcrete to investigate dust generation characteristics. The results showed the following: 1) The particles generated during wet-mix shotcrete primarily consisted of cement particles, exhibiting a spherical and blocky shape with a relatively regular morphology. However, their surfaces possessed numerous burrs and pores, resulting in poor wettability. 2) Suspended aerosol particles mainly comprised particles below 10 µm, exhibiting a unimodal particle size distribution. Smaller particles showed a higher abundance, with particles below 2 µm accounting for over 95% of the total particles. 3) The dust generation during wet-mix shotcrete was significantly influenced by the compressed gas flow rate and material viscosity. An increase in the gas flow rate or material viscosity led to higher production of fine particles. This study elaborated the mechanisms underlying particle generation during wet-mix shotcrete, providing valuable insights for wet-mix shotcrete dust control techniques. • Constructed a similar experimental platform for wet-mix shotcrete. • The number of particles below 2 µm in the wet-mix shotcrete process was relatively large. • The dust particles generated by wet-mix shotcrete were mostly spherical or blocky. • Dust generation zones were mainly at the boundary layer of the sprayed material and in the area of material rebounding. • The compressed gas flow rate and the material viscosity influence the wet-mix shotcrete dust generation. [ABSTRACT FROM AUTHOR]